Why aquatic mammals need to be big, but not too big

March 26, 2018

Sperm whales (above), which have teeth, don’t grow as large as baleen whales, which expend much less energy on feeding because they filter all their food. Efficiency in feeding allows baleen whales to grow larger than toothed whales. Credit: Getty Images

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Anyone who has witnessed majestic whales or lumbering elephant seals in person would be forgiven for associating ocean life with unlimited size in mammals, but new research reveals that mammal growth is actually more constrained in water than on land.

This finding by Stanford researchers is in contrast to previous theories suggesting that pressure on body size should be more relaxed in water, perhaps because of the large environment and ability for animals to float rather than have to support their body weight on legs.

Instead, the group found that aquatic mammal size is bounded at the small end by the need to retain heat and at the large end by difficulties getting enough food to survive. The group published their findings March 26 in Proceedings of the National Academy of Sciences.

“Many people have viewed going into the water as more freeing for mammals, but what we’re seeing is that it’s actually more constraining,” said co-author Jonathan Payne, a professor of geological sciences at Stanford’s School of Earth, Energy & Environmental Sciences (Stanford Earth). “It’s not that water allows you to be a big mammal, it’s that you have to be a big mammal in water — you don’t have any other options.”

Getting big, but not too big

Although mammals that live in water share a similarly oblong body shape, they are not closely related. Rather, seals and sea lions are closely related to dogs, manatees share ancestry with elephants, and whales and dolphins are related to hippos and other hoofed mammals.

To learn more about how these groups of land mammals took on their characteristic girth when they turned aquatic, the researchers compiled body masses for 3,859 living and 2,999 fossil mammal species from existing data sets. The analysis includes about 70 percent of living species and 25 percent of extinct species. They analyzed the data with a set of models developed in collaboration with Craig McClain of the Louisiana Universities Marine Consortium.

From this analysis, the group found that once land animals take to the water, they evolve very quickly toward their new size, converging at around 1,000 pounds. Smaller ancestors like dog relatives increased in size more than larger ancestors like hippos to reach that optimal weight, suggesting that bigger is better for aquatic life, but only up to a point. The group points out that otters, which took to the water more recently, don’t follow that trend, perhaps because many otter species still live much of their lives on land.

“The key is having a phylogenetic tree to understand how these species are related to one another and the amount of time that has taken place between different evolutionary branching events,” said lead author Will Gearty, a graduate student at Stanford Earth. “The tree of ancestral relationships allows us to build models based on data from modern species to predict what the ancestors’ body sizes would have been and see what evolutionary trajectories best fit with what we see in the modern day.”

Heat and food

The group argues that the larger size helps aquatic mammals retain heat in water that’s lower than body temperature. “When you’re very small, you lose heat back into the water so fast, there’s no way to eat enough food to keep up,” Payne said.

They also suggest that metabolism increases with size more than an animal’s ability to gather food, putting a boundary on how big aquatic mammals can grow. “Basically, animals are machines that require energy to operate. This need for energy places hard limits on what animals can do and how big they can be,” said McClain, who was a co-author on the study.

“The range of viable sizes for mammals in the ocean is actually smaller than the range of viable sizes on land,” Payne said. “To demonstrate that statistically and provide a theory behind it is something new.”

If otters are the exception at the small end, baleen whales prove the exception at the larger size. These whales expend much less energy on feeding than their toothed counterparts because they filter all their food, which makes them more efficient and allows them to grow larger than toothed whales.

“The sperm whale seems to be the largest you can get without a new adaptation,” Gearty said. “The only way to get as big as a baleen whale is to completely change how you’re eating.”

The researchers began working on the study in 2014 and they are currently assessing how well similar approaches can be used to explain body size distributions in other animal groups, especially those that have both terrestrial and aquatic species.

“The hope is there’s simpler explanations that can apply to other species, including terrestrial animals,” Payne said. “It opens up some possibility that body size can be explained by basic principles of physics and chemistry.”

Payne is also a member of Stanford Bio-X and an affiliate of the Stanford Woods Institute for the Environment.

Reference:
William Gearty, Craig R. McClain and Jonathan L. Payne. Energetic tradeoffs control the size distribution of aquatic mammals. PNAS, 2018 DOI: 10.1073/pnas.1712629115

Note: The above post is reprinted from materials provided by Stanford’s School of Earth, Energy & Environmental Sciences.

Landslide modeling after Kaikoura Quake provides data to first responders

March 26, 2018

The Stanton Landslide (center middle distance) is over 800 meters across and has left an obvious scar in the hillside above the deposit. The narrow gorge the landslide formed in limited the distance the landslide could travel but caused it to block the river that used to run here, forming the new landslide dammed lake on the left foreground. Credit: Tom Robinson

Hours after the 2016 Kaikoura earthquake hit New Zealand, researchers were able to share information with first responders about where significant landsliding might have occurred to block roads and rivers, according to a new report in the Bulletin of the Seismological Society of America.

The modeling approach used to predict earthquake-related landslides was in the middle of being tested in New Zealand when the Kaikoura quake offered a serendipitous opportunity to test its capabilities, said Tom Robinson of Durham University in the United Kingdom.

Robinson and his colleagues were able to model landslide locations and runouts (the maximum distance landslide debris travels) within 24 hours of the event and produced a second, refined model 72 hours after the event. The modeling predicted that landsliding would be widespread and could impact major roads and numerous rivers. While the approach performed well at predicting road blockages, it overpredicted the occurrence of landslides in general, which limits the model’s use in determining the exact location of all landslides.

However, this near-real time analysis allowed members of the New Zealand Civil Defence and other responders to plan reconnaissance flights over the affected regions to determine where the landslides might cause further damage.

“For me, that’s the really exciting thing about this research, that we’re actually able to translate hazard knowledge into ‘here is where the impacts could be’ and ‘here are where losses could be as a result of that,'” said Robinson.

“Landslides used to get forgotten a lot in earthquakes, but that is changing now,” he said, after recent studies have confirmed that significant damage to infrastructure such as roads often results from subsequent landsliding, and not the ground shaking that occurs during an earthquake.

In mountainous regions such as in Nepal or China, up to 25% or more of earthquake fatalities can come from landsliding, Robinson noted.

A landslide inventory completed after the magnitude 7.8 Kaikoura event counted more than 10,000 landslides, blocking roads, rivers and railways, and damaging agricultural areas, according to another BSSA study led by Chris Massey of GNS Science in New Zealand.

Robinson said the Kaikoura earthquake did comparatively little damage to buildings in New Zealand, a country with strong earthquake building codes, “yet the landslides on the roads, particularly State Highway 1, which was the main road that was affected, have been catastrophic.”

When he visited the region in November 2017, a year after the earthquake, only one lane of State Highway 1 had been opened and the road remained closed overnight and during strong rain, including a cyclone that washed new debris into the roadway. The estimate for restoring the highway to full capacity is close to NZ$1 billion, Robinson said.

Landslides are “extremely complicated to predict” and are most often studied after the fact, he noted. To remedy this, he and his colleagues have developed modeling approaches that draw from recent global data collected on landslide hazards, “to see if we can learn something from multiple events and use that to predict where landslides might happen in future events elsewhere.”

The researchers combined these data in their model with information on landslide reach angles, a measurement that helps determine the maximum runout. Their model is one of the first to attempt to predict where landslides might block roads and dam up rivers after an earthquake in near real-time.

Information on both of these impacts, but especially landslide dams, is important for first responders, “Landslide dams often happen in remote, difficult terrain, and are often spotted only by chance,” said Robinson. “These dams can overtop and cause outburst flooding very quickly, and can be very dangerous to downstream communities.”

The New Zealand model was designed to predict the likelihood of landslides occurring in 25 x 25 meter cells across the affected area. To verify the model, an inventory of landslide points collected after the earthquake was used. The model’s overprediction tendency might be an artifact of how these landslides are represented by points, Robinson said, since a large landslide might in reality encompass hundreds or thousands of cells.

Fixing the overprediction problem might also require knowing more about the factors that drive landsliding, he said. “There are also so many different factors that contribute to landsliding, and even if we know relatively well what those factors are, it still seems to be somewhat random whether a slope will fail or not.

“For instance, we know shaking and slope angle drive the majority of landsliding, but in that part of New Zealand, you have high slope angles everywhere, and everywhere got shaken strongly, but not every slope fell down, so there are other intricacies at work there,” he added.

Modeling after the Kaikoura earthquake had to be done manually, but automating the program could significantly reduce the time needed to make landslide predictions after an earthquake, Robinson said.

He and his colleagues say more high resolution global data on landslides, including 3D satellite imaging, could help refine the landsliding model and allow it to be used around the world. But storing and manipulating these data would require more computer capacity, Robinson noted. “At the moment this is just done on a simple desktop like somebody might have at home.”

“In the immediate hours after an earthquake, it’s not possible for us to get satellite imagery to map every single landslide,” he said. “This is where we think modeling could potentially fill a gap, in the days after an earthquake when responders need information.”

Reference:
“Near real-time modelling of landslide impacts to inform rapid response: an example from the 2016 Kaikoura, New Zealand,earthquake,” Bulletin of the Seismological Society of America (2018). DOI: 10.1785/0120170234

Note: The above post is reprinted from materials provided by Seismological Society of America.

Argonne’s powerful X-rays key to confirming water source deep below Earth’s surface

March 26, 2018

Using Argonne's Advanced Photon Source, researchers identified a form of water known as Ice-VII, which was trapped within diamonds that crystallized deep in the Earth's mantle. — Using Argonne’s Advanced Photon Source, researchers identified a form of water known as Ice-VII, which was trapped within diamonds that crystallized deep in the Earth’s mantle. Credit: University of Chicago.

A study published in Science last week relies on extremely bright X-ray beams from the U.S. Department of Energy’s (DOE) Advanced Photon Source (APS) at Argonne National Laboratory to confirm the presence of naturally occurring water at least 410 kilometers below the Earth’s surface. This exciting discovery could change our understanding of how water circulates deep in the Earth’s mantle and how heat escapes from the lower regions of our planet.

Through use of the APS, a DOE Office of Science User Facility, the researchers identified a form of water known as Ice-VII, which was trapped within diamonds that crystallized deep in the Earth’s mantle. This is the first time Ice-VII has been discovered in a natural sample, making the compound a new mineral accepted by the International Mineralogical Association.

“[T]hanks to the amazing technical capabilities of the APS, this team of researchers was able to pinpoint and study the exact area on the diamonds that trapped the water.” — Stephen Streiffer, Argonne Associate Laboratory Director for Photon Sciences and Director of the APS

This study is just the latest in a long line of research projects at the APS that have shed light on the composition and makeup of the deep Earth, regions that humans cannot explore directly. Instead, scientists used high-powered X-ray beams to analyze inclusions in diamonds, which were formed in the deep Earth, so as to come to conclusions about what happened in those regions.

In other geological studies at the APS, researchers have used high-pressure chambers and lasers to put materials under extreme pressure and temperatures for study, literally recreating the conditions deep below the Earth’s surface to understand what happens there.

“In this study, thanks to the amazing technical capabilities of the APS, this team of researchers was able to pinpoint and study the exact area on the diamonds that trapped the water,” said Stephen Streiffer, Argonne Associate Laboratory Director for Photon Sciences and Director of the APS. “That area was just a few microns wide. To put that in context, a human hair is about 75 microns wide.

“This research, enabled by partners from the University of Chicago and the University of Nevada, Las Vegas, among other institutions, is just the latest example of how the APS is a vital tool for researchers across scientific disciplines,” he said.

In this case, researchers analyzed rough, uncut diamonds mined from regions in China and Africa. Using an optical microscope, mineralogists first identified inclusions, or impurities, which must have formed when the diamond crystallized. Most diamonds have inclusions caused by a sample of other elements or compounds that were trapped as the carbon fused into a diamond.

“We are interested in those inclusions because they tell us about the chemical composition and conditions in the deep Earth when the diamond was formed,” said Antonio Lanzirotti, a University of Chicago Research Associate Professor and a co-author on the study.

After many millions of years, diamonds are pushed up from the Earth’s mantle to the surface, where many are mined for jewelry and industrial purposes.

To positively identify the composition of the inclusions, mineralogists needed a stronger instrument. That’s where University of Chicago’s GeoSoilEnviroCARS’s (GSECARS) beamlines at the APS came in. GSECARS operates a suite of instruments at the APS dedicated to frontier research in the Earth sciences.

Oliver Tschauner, the lead author on the study and a mineralogist at University of Nevada in Las Vegas, worked with the GSECARS group to probe more than a dozen diamonds that he had identified with this inclusion.

Because of the pressure required for diamonds to form, the scientists know that these specimens formed between 410 and 660 kilometers below the Earth’s surface.

Thanks to the very high brightness of the APS X-rays, which are a billion times more intense than conventional X-ray sources, scientists can determine the molecular or atomic makeup the specimens that are only micrometers across.

When the focused beam of X-rays hits the molecules of the specimen, they scatter. Pictures or images taken of this scattering pattern are then analyzed, as each compound or molecule shows a unique pattern.

What the team identified in this study was surprising: water, in the form of ice.

The composition of the water is the same as the water that we drink and use every day, but in a cubic crystalline form, the result of the extremely high pressure of the diamond.

This form of water, Ice-VII, was created in the lab decades ago, but this study was the first to confirm that it also forms naturally.

“This wasn’t easy to find,” said Vitali Prakapenka, a University of Chicago Research Professor and a co-author of the study, who said that the team used high-resolution diffraction techniques to get the right scans, or images, of the Ice-VII. “People have been searching for this kind of inclusion for a long time.”

The researchers said the significance of the study is profound because it shows that flowing water is present much deeper below the Earth’s surface than originally thought. Going forward, the results raise a number of important questions about how water is recycled in the Earth and how heat is circulated. Tschauner has said the discovery can help scientists create new, more accurate models of what’s going on inside the Earth, specifically how and where heat is generated under the Earth’s crust. This may help scientists better understand one of the driving mechanisms for plate tectonics.

For now, the GSECARS team is wondering whether the mineral Ice-VII will be renamed, now that it is officially a mineral. This is not the first mineral to be identified thanks to research done at the APS beamlines managed by GSECARS: Bridgmanite, the Earth’s most abundant mineral and a high-density form of magnesium iron silicate, was researched extensively at the APS before it was named. Tschauner was a lead author on that study, too.

Reference:
Ice-VII inclusions in diamonds: Evidence for aqueous fluid in Earth’s deep mantle. DOI: 10.1126/science.aao3030

Note: The above post is reprinted from materials provided by DOE/Argonne National Laboratory.

Dinosaur frills and horns did not evolve for species recognition

March 24, 2018

Head of Nasutoceratops. — Restoration of the head of Nasutoceratops. Credit: Andrey Atuchin

The elaborate frills and horns of a group of dinosaurs including Triceratops and Styracosaurus did not evolve to help species recognise each other, according to researchers at Queen Mary University of London.

It has been suggested that different species that live in the same location may evolve features in order to distinguish one another to help avoid problems such as hybridisation, where two individuals of different species produce infertile or unfit offspring.

To test this hypothesis the researchers examined patterns of diversity in the ornamentation of 46 species of ceratopsians, the horned dinosaurs, but found no difference between species that lived together and those that lived separately.

A previous research paper from Queen Mary found that the frill in one ceratopsian species, Protoceratops, may have evolved under sexual selection. These new findings appear to add evidence to this across the entire group.

The researchers also found evidence that ornamental traits seemed to evolve at a much faster rate than other traits. As these structures are costly to grow and maintain, this finding similarly points to a strong selective pressure on these traits.

The study was published in Proceedings of the Royal Society B.

Andrew Knapp, PhD candidate from the School of Biological and Chemical Sciences and lead author of the study, said: “This resolves a long-standing and hitherto untested hypothesis concerning the origin and function of ornamental traits in ceratopsian dinosaurs. Many general discussions of ceratopsian ornaments in museum signage and popular literature often include examples of what they might have been for, but these tend to be rather speculative.

“We have shown that species recognition, one of the commonest explanations, is unlikely to be responsible for the diversity or origin of ornamentation in this group.”

The researchers believe the implications extend beyond the scope of ceratopsians and have consequences for the study of evolutionary theory over vast stretches of time.

The fossil record offers an opportunity to see evolution in action over much longer time periods than can be achieved with living organisms, but it is difficult to assign explanations to unusual features such as ceratopsian ornaments with the limited information that fossils provide.

The researchers have now largely ruled out one explanation, species recognition, and provided some evidence for another, sexual selection.

Mr Knapp said: “If sexual selection is indeed the driver of ornament evolution in ceratopsians, as we are increasingly confident it is, demonstrating it through different lines of evidence can provide a crucial window into tracing its effects over potentially huge timescales.”

He added: “Modern computer models have suggested that sexual selection can promote rapid speciation, adaptation, and extinction. In our world of increasing pressure on the natural world, these predictions may have important consequences for conservation and the fate of living things everywhere.”

To test these predictions the researchers hope to look at changes in the fossil record and gather further evidence to first identify sexual selection in a fossil group.

The study was conducted in collaboration with the Raymond M. Alf Museum of Paleontology in California and Natural History Museum of Utah. It was funded by a Natural Environment Research Council (NERC) doctoral training partnerships (DTP) grant through the London DTP programme.

Reference:
Andrew Knapp, Robert J. Knell, Andrew A. Farke, Mark A. Loewen, David W. E. Hone. Patterns of divergence in the morphology of ceratopsian dinosaurs: sympatry is not a driver of ornament evolution. Proceedings of the Royal Society B: Biological Sciences, 2018; 285 (1875): 20180312 DOI: 10.1098/rspb.2018.0312

Note: The above post is reprinted from materials provided by Queen Mary University of London.

Genetic analysis uncovers the evolutionary origin of vertebrate limbs

March 24, 2018

Top: A medaka fish with normal dorsal and paired pectoral/pelvic fins. Bottom: When the ZRS and sZRS enhancers are knocked out, the fins do not develop normally. Credit: Neil Shubin, José Luis Gómez-Skarmeta

As you picture the first fish to crawl out of primordial waters onto land, it’s easy to imagine how its paired fins eventually evolved into the arms and legs of modern-day vertebrates, including humans. But a new study by researchers from the University of Chicago and the Andalusian Center for Development Biology in Spain shows how these creatures used an even more primitive genetic blueprint to develop their proto-limbs: the single dorsal, or back, fin common to all jawed fish.

The study, published this week in Nature Genetics, demonstrates that fish, mice and likely all modern-day vertebrates share genetic elements first used to develop the unpaired dorsal fin in ancient fish. They later copied these elements to produce paired appendages, like pelvic and pectoral fins, arms and legs.

“The unpaired dorsal fin is the first one you see in the fossil record,” said Neil Shubin, PhD, the Robert R. Bensley Distinguished Service Professor of Anatomy at UChicago and co-author of the new study. “Here we show that the genetic mechanisms that pattern all the fins and other paired appendages originally arose there and were redeployed to others.”

Shubin and his colleagues from Spain, led by José Luis Gómez-Skarmeta, conducted genetic analysis in mice and several kinds of fish to track the expression of Sonic hedgehog (Shh), a gene widely used in a variety of basic biological functions, but especially important in the formation of limbs.

In mice, a genetic enhancer or on/off switch called ZRS controls the expression of Shh limbs. If you knock out ZRS in a mouse, its limbs won’t develop properly. The researchers used CRISPR/Cas9 gene editing tools to knock out ZRS in the medaka, a small, popular aquarium fish also known as a Japanese rice fish. They expected that deleting ZRS in the medaka would affect its paired fins, but instead the fish didn’t grow its unpaired dorsal fin. The paired pelvic and pectoral fins developed normally.

That led the team to look for other genetic enhancers that might be involved, and they found a related “shadow enhancer” nearby called sZRS that seems to work in conjunction with the main ZRS switch. When they knocked out both ZRS and sZRS in the medaka, both its dorsal fin and paired fins were lost. That means it’s likely that ZRS was first used help develop dorsal fins, then later copied and reused as sZRS when paired fins first appeared about 475 million years ago.

“It’s very ancient, and the sequence and function are conserved across all vertebrates,” Shubin said. “It turns out the primitive role for the ZRS was involved with the dorsal fin. It’s only later that its activity in the paired fins required this other shadow enhancer.”

Shubin said understanding the activity of these enhancers helps identify the traces of evolutionary ancestors present in all vertebrates, from Tiktaalik roseae, the 375-million-year-old transitional “fishapod” species he discovered in 2004, to modern-day humans.

“A number of human maladies are based on mistakes in the ZRS that can lead extra or missing fingers, or changes in the shape of hands,” he said. “Humans probably have this shadow enhancer too, so if we want to study the dynamics of how this affects limb patterning, what we see in these fish models is a great place to start.”

Reference:
José Luis Gómez-Skarmeta et al. A conserved Shh cis-regulatory module highlights a common developmental origin of unpaired and paired fins. Nature Genetics, 2018 DOI: 10.1038/s41588-018-0080-5

Note: The above post is reprinted from materials provided by University of Chicago Medical Center.

Paleontologists put the bite on an ancient reptile from New England

March 24, 2018

Scientists have identified a new species of reptile from prehistoric Connecticut and, boy, does it have a mouth on it.

Named Colobops noviportensis, the creature lived 200 million years ago and had exceptionally large jaw muscles — setting it apart from other reptiles at the time. Even compared to the wide diversity of reptile species today, Colobops noviportensis had quite the bite.

“Colobops would have been a diminutive but plucky little beast, part of a little-known menagerie of small animals that lived among the first dinosaurs,” said Bhart-Anjan Bhullar, assistant professor and assistant curator in geology and geophysics at Yale, and senior author of a new paper about the discovery in the journal Nature Communications.

“Its tiny frame hid some big secrets,” Bhullar said. “Despite its lizard-like aspect, it is in fact an early branch-off of the lineage leading to dinosaurs and birds. Also, its little jaws could bite harder than anything else its size. Perhaps that big bite allowed it to feed on tough, armored prey impervious to weaker mouths.”

The lead author of the paper is Adam Pritchard, a former member of Bhullar’s lab who is now at the Smithsonian Institution.

Additional Yale authors of the paper are Jacques Gauthier, professor of geology and geophysics and curator of vertebrate paleontology and vertebrate zoology at the Peabody Museum; and Michael Hanson, a graduate student in geology and geophysics.

“This project was a great example of the process of science,” Pritchard said. “The skull was initially discovered in the mid-1960s. In the 1990s, the skull was subject to initial study in which it was identified as a cousin of a modern lizard-like reptile called a tuatara. Our study ups the ante again, using advanced CT scanning and 3D modeling to reveal all kinds of new features of the skull. The features are very distinctive, allowing us to establish a new species.”

The specimen is a quarter-sized skull discovered in Meriden, Conn., during roadwork in 1965. It has been part of the collections of the Yale Peabody Museum of Natural History for decades. The specimen’s new species name derives from Novus Portus, a Latinized version of New Haven — a reference to the New Haven Arkose geological formation.

The Yale team took a new look at the specimen. The researchers did a 3D reconstruction of the skull and discovered that it showed specialization in the jaw that was unprecedented in any other known small tetrapod, juvenile or adult.

“Comparisons with modern reptile dissections showed that it had incredibly well-developed jaw muscles for its size, suggesting an exceptional bite, even compared to the diversity of modern reptiles,” Pritchard said. “It’s a great illustration of the critical importance of fossils big and small for understanding the diversity of organisms.”

The researchers said the discovery means modern vertebrates originated in a world that was already populated by small and large-bodied physical extremes, in terms of how animals physically adapted to their environment.

The National Science Foundation and the Yale Peabody Museum of Natural History supported the research.

Reference:
Adam C. Pritchard, Jacques A. Gauthier, Michael Hanson, Gabriel S. Bever & Bhart-Anjan S. Bhullar. A tiny Triassic saurian from Connecticut and the early evolution of the diapsid feeding apparatus. Nature Communications, 2018 DOI: 10.1038/s41467-018-03508-1

Note: The above post is reprinted from materials provided by Yale University. Original written by Jim Shelton.

The curse of zombie fossils

March 24, 2018

Undead T. rex. — Zombie fossil? Artist’s impression of an undead T. rex. The missing parts are the result of degradation of the body after death. Credit: Herschel Hoffmeyer

New research has revealed how the history of life can be distorted by the ways animals decompose and lose body parts as they decay — and the ways in which decayed bodies ultimately become fossilised.

In a new study published in the journal Palaeontology, a group of palaeontologists from the UK and Ireland, led by the University of Leicester, has followed a macabre, and nasally-challenging road to knowledge — watching carefully as animal carcasses decompose in order to better understand the process.

Like on-screen zombies in popular TV programmes such as The Walking Dead that gradually deteriorate through time, fossils preserve only incomplete remains of the living body.

A key part of palaeontological research involves reconstructing long-extinct creatures to understand what they were like when they were alive. This knowledge allows us to answer fundamental questions — how did they move and interact with their environment? How did they feed and reproduce? Which of today’s organisms are they most like and most closely related to?

Understanding how much of a fossil is missing, and what has been changed by decay and fossilisation, helps to create a more accurate picture of ancient animals and ecosystems. This is particularly important for things lacking hard skeletons and shells — including crucial fossil evidence of early animal life on Earth.

“As soon as an organism dies, it starts to decay, and this process of decomposition inevitably involves changes in how features or body parts look: they may collapse, alter their shape or position; all too soon they liquefy and are eaten by bacteria until nothing remains,” says Professor Sarah Gabbott from the University of Leicester’s School of Geography, Geology and the Environment.

Professor Mark Purnell, lead author of the study adds: “The more a body deteriorates over time, the more body-parts are missing — rather like modern representations of zombies in Game of Thrones and The Walking Dead.

“One consequence of this decay is that palaeontologists have to work with incomplete fossils. Some of the features that are present don’t look anything like they did when the animal was alive, and many features are missing completely. The trick is to be able to recognise partially-decomposed features, and where body parts have rotted away completely.”

The approach used in the UK-Irish collaboration involves ‘laboratory decay experiments’: keeping careful records of every body part as it decays away.

The results of rotting a whole range of dead animals, from hagfish and lampreys (primitive eel-like creatures) to insects and various worms, show that carefully designed experiments provide unique insights into the processes of decomposition and fossilisation.

In the new paper they highlight the importance of understanding how a fossil is formed before trying to reconstruct it — how the processes of decay that lead to loss of body parts interact with the processes that cause them to become preserved and fossilised.

Dr Maria McNamara, collaborator in the study, adds: “If we understand this we are better able to avoid producing incomplete restorations of animals with crucial parts missing or decayed, and to recognize and be aware of the gaps in our knowledge,.”

The research is supported by the Natural Environment Research Council.

Reference:
Mark A. Purnell, Philip J. C. Donoghue, Sarah E. Gabbott, Maria E. McNamara, Duncan J. E. Murdock, Robert S. Sansom. Experimental analysis of soft-tissue fossilization: opening the black box. Palaeontology, 2018; DOI: 10.1111/pala.12360

Note: The above post is reprinted from materials provided by University of Leicester.

Two-billion-year-old salt rock reveals rise of oxygen in ancient atmosphere

March 24, 2018

A sample of 2-billion-year-old salt (pink-white recrystallized halite) with embedded fragments of calcium sulfate from a geological drill core in Russian Karelia. Credit: Photo by Aivo Lepland, Geological Survey of Norway; courtesy of Science/AAAS

A 2-billion-year-old chunk of sea salt provides new evidence for the transformation of Earth’s atmosphere into an oxygenated environment capable of supporting life as we know it.

The study by an international team of institutions including Princeton University found that the rise in oxygen that occurred about 2.3 billion years ago, known as the Great Oxidation Event, was much more substantial than previously indicated.

“Instead of a trickle, it was more like a firehose,” said Clara Blättler, a postdoctoral research fellow in the Department of Geosciences at Princeton and first author on the study, which was published online by the journal Science on Thursday, March 22. “It was a major change in the production of oxygen.”

The evidence for the profound upswing in oxygen comes from crystalized salt rocks extracted from a 1.2-mile-deep hole in the region of Karelia in northwest Russia. These salt crystals were left behind when ancient seawater evaporated, and they give geologists unprecedented clues to the composition of the oceans and atmosphere on Earth more than 2 billion years ago.

The key indication of the increase in oxygen production came from finding that the mineral deposits contained a surprisingly large amount of a component of seawater known as sulfate, which was created when sulfur reacted with oxygen.

“This is the strongest ever evidence that the ancient seawater from which those minerals precipitated had high sulfate concentrations reaching at least 30 percent of present-day oceanic sulfate as our estimations indicate,” said Aivo Lepland, a researcher at the Geological Survey of Norway, a geology specialist at Tallinn University of Technology, and senior author on the study. “This is much higher than previously thought and will require considerable rethinking of the magnitude of oxygenation of Earth’s 2-billion year old atmosphere-ocean system.”

Oxygen makes up about 20 percent of air and is essential for life as we know it. According to geological evidence, oxygen began to show up in the Earth’s atmosphere between 2.4 and 2.3 billion years ago.

Until the new study, however, geologists were uncertain whether this buildup in oxygen — caused by the growth of cyanobacteria capable of photosynthesis, which involves taking in carbon dioxide and giving off oxygen — was a slow event that took millions of years or a more rapid event.

“It has been hard to test these ideas because we didn’t have evidence from that era to tell us about the composition of the atmosphere,” Blättler said.

The recently discovered crystals provide that evidence. The salt crystals collected in Russia are over a billion years older than any previously discovered salt deposits. The deposits contain halite, which is called rock salt and is chemically identical to table salt or sodium chloride, as well as other salts of calcium, magnesium and potassium.

Normally these minerals dissolve easily and would be washed away over time, but in this case they were exceptionally well preserved deep within the Earth. Geologists from the Geological Survey of Norway in collaboration with the Karelian Research Center in Petrozavodsk, Russia, recovered the salts from a drilling site called the Onega Parametric Hole (OPH) on the western shores of Lake Onega.

The unique qualities of the sample make them very valuable in piecing together the history of what happened after the Great Oxidation Event, said John Higgins, assistant professor of geosciences at Princeton, who provided interpretation of the geochemical analysis along with other co-authors.

“This is a pretty special class of geologic deposits,” Higgins said. “There has been a lot of debate as to whether the Great Oxidation Event, which is tied to increase and decrease in various chemical signals, represents a big change in oxygen production, or just a threshold that was crossed. The bottom line is that this paper provides evidence that the oxygenation of the Earth across this time period involved a lot of oxygen production.”

The research will spur the development of new models to explain what happened after the Great Oxidation Event to cause the accumulation of oxygen in the atmosphere, Blättler said. “There may have been important changes in feedback cycles on land or in the oceans, or a large increase in oxygen production by microbes, but either way it was much more dramatic than we had an understanding of before.”

Reference:
C. L. Blättler, M. W. Claire, A. R. Prave, K. Kirsimäe, J.A. Higgins, P. V. Medvedev, A. E. Romashkin, D. V. Rychanchik, A. L. Zerkle, K. Paiste, T. Kreitsmann, I. L. Millar, J. A. Hayles, H. Bao, A. V. Turchyn, M. R. Warke, A. Lepland. Two-billion-year-old evaporites capture Earth’s great oxidation. Science, 2018; eaar2687 DOI: 10.1126/science.aar2687

Note: The above post is reprinted from materials provided by Princeton University.

Seismologists introduce new measure of earthquake ruptures

March 24, 2018

A map summarizing the new REEF measure of seismic energy for events around the Pacific Ring of Fire shows the regional patterns indicating earthquake rupture character is affected by persistent features that differ from region to region. Credit: Ye et al., Science Advances, 2018

A team of seismologists has developed a new measurement of seismic energy release that can be applied to large earthquakes. Called the Radiated Energy Enhancement Factor (REEF), it provides a measure of earthquake rupture complexity that better captures variations in the amount and duration of slip along the fault for events that may have similar magnitudes.

Magnitude is a measure of the relative size of an earthquake. There are several different magnitude scales (including the original Richter scale), with the “moment magnitude” now the most widely used measure because it is uniformly applicable to all sizes of earthquakes. The seismic energy released in an earthquake can also be measured directly from recorded ground shaking, providing a distinct measure of the earthquake process. Earthquakes of a given magnitude can have very different radiated seismic energy.

Researchers at UC Santa Cruz and California Institute of Technology (Caltech) devised REEF in an effort to understand variations in the rupture characteristics of the largest and most destructive earthquakes, such as the 2004 Sumatra earthquake (magnitude 9.2) and 2011 Tohoku earthquake in Japan (magnitude 9.1). They introduced the new measurement in a paper published March 21 in Science Advances. First author Lingling Ye, a former UC Santa Cruz graduate student and Caltech postdoctoral researcher, is now at the Sun Yat-sen University in China. Her coauthors are Hiroo Kanamori at Caltech and Thorne Lay at UC Santa Cruz.

REEF is measured by the ratio of the earthquake’s actual measured radiated energy (in seismic waves recorded around the world) to the minimum possible energy that an event of equal seismic moment and rupture duration would produce. If the rupture is jerky and irregular, it radiates more seismic energy, especially at high frequencies, and this indicates frictional conditions and dynamic processes on the fault plane during rupture, Lay explained.

The researchers made systematic measurements of REEF for 119 recent major earthquakes of magnitudes 7.0 to 9.2. They found clear regional patterns, with some subduction zones having higher REEF ruptures on average than other zones.

“This indicates, for the first time, that energy release is influenced by regional properties of each fault zone,” said Lay, a professor of Earth and planetary sciences at UCSC.

The precise cause of some regions radiating higher energy in an event of given size is still under investigation, but may be linked to regional differences in the roughness of the faults, in the fluid distributions on the faults, or in the sediments trapped in the fault zone, he said.

Further research using REEF could help seismologists achieve better understanding of earthquake mechanics and earthquake hazards around the world.

This research was supported by the National Science Foundation of China, Chinese Academy of Sciences, and U.S. National Science Foundation.

Note: The above post is reprinted from materials provided by University of California – Santa Cruz. Original written by Tim Stephens.

Radar images show large swath of Texas oil patch is heaving and sinking at alarming rates

March 24, 2018

A new study by an SMU geophysical team found alarming rates of ground movement at various locations across a 4000-square-mile area of four Texas counties. Credit: Zhong Lu and Jin-Woo Kim, SMU

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Two giant sinkholes near Wink, Texas, may just be the tip of the iceberg, according to a new study that found alarming rates of new ground movement extending far beyond the infamous sinkholes.

That’s the finding of a geophysical team from Southern Methodist University, Dallas that previously reported the rapid rate at which the sinkholes are expanding and new ones forming.

Now the team has discovered that various locations in large portions of four Texas counties are also sinking and uplifting.

Radar satellite images show significant movement of the ground across a 4000-square-mile area — in one place as much as 40 inches over the past two-and-a-half years, say the geophysicists.

“The ground movement we’re seeing is not normal. The ground doesn’t typically do this without some cause,” said geophysicist Zhong Lu, a professor in the Roy M. Huffington Department of Earth Sciences at SMU and a global expert in satellite radar imagery analysis.

“These hazards represent a danger to residents, roads, railroads, levees, dams, and oil and gas pipelines, as well as potential pollution of ground water,” Lu said. “Proactive, continuous detailed monitoring from space is critical to secure the safety of people and property.”

The scientists made the discovery with analysis of medium-resolution (15 feet to 65 feet) radar imagery taken between November 2014 and April 2017. The images cover portions of four oil-patch counties where there’s heavy production of hydrocarbons from the oil-rich West Texas Permian Basin.

The imagery, coupled with oil-well production data from the Texas Railroad Commission, suggests the area’s unstable ground is associated with decades of oil activity and its effect on rocks below the surface of the earth.

The SMU researchers caution that ground movement may extend beyond what radar observed in the four-county area. The entire region is highly vulnerable to human activity due to its geology — water-soluble salt and limestone formations, and shale formations.

“Our analysis looked at just this 4000-square-mile area,” said study co-author and research scientist Jin-Woo Kim, a research scientist in the SMU Department of Earth Sciences.

“We’re fairly certain that when we look further, and we are, that we’ll find there’s ground movement even beyond that,” Kim said. “This region of Texas has been punctured like a pin cushion with oil wells and injection wells since the 1940s and our findings associate that activity with ground movement.”

Lu, Shuler-Foscue Chair at SMU, and Kim reported their findings in the Nature publication Scientific Reports, in the article “Association between localized geohazards in West Texas and human activities, recognized by Sentinel-1A/B satellite radar imagery.”

The researchers analyzed satellite radar images that were made public by the European Space Agency, and supplemented that with oil activity data from the Texas Railroad Commission.

The study is among the first of its kind to identify small-scale deformation signals over a vast region by drawing from big data sets spanning a number of years and then adding supplementary information.

The research is supported by the NASA Earth Surface and Interior Program, and the Shuler-Foscue Endowment at SMU.

Imagery captures changes that might otherwise go undetected

The SMU geophysicists focused their analysis on small, localized, rapidly developing hazardous ground movements in portions of Winkler, Ward, Reeves and Pecos counties, an area nearly the size of Connecticut. The study area includes the towns of Pecos, Monahans, Fort Stockton, Imperial, Wink and Kermit.

The images from the European Space Agency are the result of satellite radar interferometry from recently launched open-source orbiting satellites that make radar images freely available to the public.

With interferometric synthetic aperture radar, or InSAR for short, the satellites allow scientists to detect changes that aren’t visible to the naked eye and that might otherwise go undetected.

The satellite technology can capture ground deformation with an accuracy of sub-inches or better, at a spatial resolution of a few yards or better over thousands of miles, say the researchers.

Ground movement associated with oil activity

The SMU researchers found a significant relationship between ground movement and oil activities that include pressurized fluid injection into the region’s geologically unstable rock formations.

Fluid injection includes waste saltwater injection into nearby wells, and carbon dioxide flooding of depleting reservoirs to stimulate oil recovery.

Injected fluids increase the pore pressure in the rocks, and the release of the stress is followed by ground uplift. The researchers found that ground movement coincided with nearby sequences of wastewater injection rates and volume and CO2 injection in nearby wells.

Also related to the ground’s sinking and upheaval are dissolving salt formations due to freshwater leaking into abandoned underground oil facilities, as well as the extraction of oil.

Sinking and uplift detected from Wink to Fort Stockton

As might be expected, the most significant subsidence is about a half-mile east of the huge Wink No. 2 sinkhole, where there are two subsidence bowls, one of which has sunk more than 15.5 inches a year. The rapid sinking is most likely caused by water leaking through abandoned wells into the Salado formation and dissolving salt layers, threatening possible ground collapse.

At two wastewater injection wells 9.3 miles west of Wink and Kermit, the radar detected upheaval of about 2.1 inches that coincided with increases in injection volume. The injection wells extend about 4,921 feet to 5,577 feet deep into a sandstone formation.

In the vicinity of 11 CO2 injection wells nearly seven miles southwest of Monahans, the radar analysis detected surface uplift of more than 1 inch. The wells are about 2,460 feet to 2,657 feet deep. As with wastewater injection, CO2 injection increased pore pressure in the rocks, so when stress was relieved it was followed by uplift of about 1 inch at the surface.

The researchers also looked at an area 4.3 miles southwest of Imperial, where significant subsidence from fresh water flowing through cracked well casings, corroded steel pipes and unplugged abandoned wells has been widely reported.

Water there has leaked into the easily dissolved Salado formation, created voids, and caused the ground to sink and water to rise from the subsurface, including creating Boehmer Lake, which didn’t exist before 2003.

Radar analysis by the SMU team detected rapid subsidence ranging from three-fourths of an inch to nearly 4 inches around active wells, abandoned wells and orphaned wells.

“Movements around the roads and oil facilities to the southwest of Imperial, Texas, should be thoroughly monitored to mitigate potential catastrophes,” the researchers write in the study.

About 5.5 miles south of Pecos, their radar analysis detected more than 1 inch of subsidence near new wells drilled via hydraulic fracturing and in production since early 2015. There have also been six small earthquakes recorded there in recent years, suggesting the deformation of the ground generated accumulated stress and caused existing faults to slip.

“We have seen a surge of seismic activity around Pecos in the last five to six years. Before 2012, earthquakes had not been recorded there. At the same time, our results clearly indicate that ground deformation near Pecos is occurring,” Kim said. “Although earthquakes and surface subsidence could be coincidence, we cannot exclude the possibility that these earthquakes were induced by hydrocarbon production activities.”

Scientists: Boost the network of seismic stations to better detect activity

Kim stated the need for improved earthquake location and detection threshold through an expanded network of seismic stations, along with continuous surface monitoring with the demonstrated radar remote sensing methods.

“This is necessary to learn the cause of recent increased seismic activity,” Kim said. “Our efforts to continuously monitor West Texas with this advanced satellite technique can help sustain safe, ongoing oil production.”

Near real-time monitoring of ground deformation possible in a few years

The satellite radar datasets allowed the SMU geophysicists to detect both two-dimension east-west deformation of the ground, as well as vertical deformation.

Lu, a leading scientist in InSAR applications, is a member of the Science Team for the dedicated U.S. and Indian NASA-ISRO (called NISAR) InSAR mission, set for launch in 2021 to study hazards and global environmental change.

InSAR accesses a series of images captured by a read-out radar instrument mounted on the orbiting satellite Sentinel-1A/B. The satellites orbit 435 miles above the Earth’s surface. Sentinel-1A was launched in 2014 and Sentinel-1B in 2016 as part of the European Union’s Copernicus program.

The Sentinel-1A/B constellation bounces a radar signal off the earth, then records the signal as it bounces back, delivering measurements. The measurements allow geophysicists to determine the distance from the satellite to the ground, revealing how features on the Earth’s surface change over time.

“Near real-time monitoring of ground deformation at high spatial and temporal resolutions is possible in a few years, using multiple satellites such as Sentinel-1A/B, NISAR and others,” said Lu. “This will revolutionize our capability to characterize human-induced and natural hazards, and reduce their damage to humanity, infrastructure and the energy industry.”

Reference:
Jin-Woo Kim, Zhong Lu. Association between localized geohazards in West Texas and human activities, recognized by Sentinel-1A/B satellite radar imagery. Scientific Reports, 2018; 8 (1) DOI: 10.1038/s41598-018-23143-6

Note: The above post is reprinted from materials provided by Southern Methodist University.

Diamonds from the deep: Study suggests water may exist in Earth’s lower mantle

March 16, 2018

The molecular structure of ice-VII (upper right) is shown with an artistic rendering of the Earth and a cutaway view of the inner Earth (right). Crystallized water, in the form of ice-VII, was found in diamond samples studied at Berkeley Lab. Its presence suggests liquid water may exist at extreme depths. Credit: Wikimedia Commons

Water on Earth runs deep – very deep. The oceans have been measured to a maximum depth of 7 miles, though water is known to exist well below the oceans. Just how deep this hidden water reaches, and how much of it exists, are the subjects of ongoing research.

Now a new study suggests that water may be more common than expected at extreme depths approaching 400 miles and possibly beyond – within Earth’s lower mantle. The study, which appeared March 8 in the journal Science, explored microscopic pockets of a trapped form of crystallized water molecules in a sampling of diamonds from around the world.

Diamond samples from locations in Africa and China were studied through a variety of techniques, including a method using infrared light at the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab). Researchers used Berkeley Lab’s Advanced Light Source (ALS), and Argonne National Laboratory’s Advanced Photon Source, which are research centers known as synchrotron facilities.

The tiny traces of crystallized water, trapped in spaces called inclusions that measure just a few microns (millionths of a meter) in length, contain the molecular signature of ice VII. This crytallized water likely formed from liquid water existing at very high pressures, according to the study.

The structure and chemical studies helped the scientists to determine the pressures and temperatures at which the diamonds formed. This allowed the scientists to estimate the depths of their formation.

Oliver Tschauner, the study’s lead author and a professor of research in the Department of Geoscience at the University of Nevada, Las Vegas, said it was surprising that so many of the studied diamonds from a random sampling seemed to originate from deep inside the Earth, within and even beyond the so-called transition zone sandwiched between Earth’s upper and lower mantles.

While only about 60 diamonds had previously been confirmed to originate at depths greater than about 190 miles, the latest study added several more to this tally.

“It seems many diamonds come from greater depths,” Tschauner said. “In the past, people had focused more on larger inclusions,” tens of times the size of the ones that were the focus of the latest study. “Some of these small inclusions may have been overlooked before,” he added.

Researchers concluded that some of the inclusions likely were formed from fluid existing at depths of 250 miles to 340 miles beneath Earth’s surface. Others may have formed at depths ranging from 380 miles to 500 miles – possibly within Earth’s “shallow” lower mantle.

“It’s not just a curiosity to have a diamond residing deep in Earth’s mantle – this is direct evidence for aqueous fluid in the deep Earth,” Tschauner said.

The pressures that formed these deeper diamonds are estimated at approximately 24 to 25 gigapascals, which is about 224 times more pressure than exists at the bottom the ocean’s deepest point in its Mariana Trench.

The composition of the fluid that was trapped in the inclusions appears to be complex, with traces of carbonates, oxides, and salt, Tschauner said.

The research team enlisted infrared spectroscopy at the ALS’s Beamline 1.4, which helped them to observe the chemistry of the tiny inclusions.

Hans Bechtel, a research scientist in the Scientific Support Group at the ALS, explained that the infrared technique measures vibrational signatures that detail chemistry at the microscopic level. “With synchrotron light, we can focus down to 2 to 10 microns in the infrared,” he said, “and scan across each sample to create a ‘hyperspectral image’ that reveals the detailed chemical composition.”

It’s not yet possible to estimate how much watery fluid exists in Earth’s transition zone and how it’s distributed, Tschauner said, but more diamond studies should help with the estimates.

Such studies can also help scientists learn about how much water “recycling” goes on in the mantle, and the process by which ocean water reaches into the mantle, for example.

Tschauner said he’s already exploring ways to better prepare diamond samples for future studies – perhaps even using methods enlisted by jewelers – to better understand their microscopic chemistry.

This new thrust of research provides a unique opportunity to “see” inside the inner Earth, Tschauner noted. “It probably will open new avenues in studies.”

The ALS and Advanced Photon Source are DOE Office of Science User Facilities.

Researchers from the University of Chicago, California Institute of Technology, China University of Geosciences, University of Hawaii at Manoa, and Royal Ontario Museum also participated in the study. The work was supported by the U.S. Department of Energy Office of Basic Energy Sciences and the National Science Foundation.

Reference:
Ice-VII inclusions in diamonds: Evidence for aqueous fluid in Earth’s deep mantle. DOI: 10.1126/science.aao3030

Note: The above post is reprinted from materials provided by DOE/Lawrence Berkeley National Laboratory.

The secrets of garnet reveal source of water to fuel powerful volcanoes and earthquakes

March 15, 2018

Among geologists who study powerful earthquakes and volcanoes, there is a mystery: as one of Earth’s tectonic plates slides beneath another in a subduction zone, water is squeezed from certain minerals, lubricating earthquakes and fueling volcanoes in hot spots like the Pacific Ocean “Ring of Fire.” But equations that predict where the forces of subduction wring water from stone consistently point to locations far from the site of actual cataclysms.

By applying a new spectroscopy technique to garnet containing fragments of quartz, metamorphic petrologist Frank Spear of Rensselaer Polytechnic Institute thinks he’s solved the puzzle. His early research shows that the equations are incomplete, lacking the significant variable of “overstepping,” the additional energy needed to initiate a process, in this case, the decomposition of water-bearing minerals.

“The real culprit in powerful volcanoes and earthquakes is water, but scientists have been unable to determine where that water comes from,” said Spear, a professor and head of the Rensselaer Department of Earth and Environmental Sciences. “Conventional thermodynamic equations predict that water is released at too shallow a depth to occur at the known locations of volcanoes and earthquakes. But when you factor in the overstepping we’ve discovered, the locations coincide. The idea of overstepping is an enormous paradigm shift.”

His research is supported by a three-year $419,247 grant from the National Science Foundation.

As one tectonic plate is pushed beneath another in a subduction zone, sediments and minerals are carried deep into the Earth, with pressure and temperature mounting with increasing depth. Early in the process liquid water is squeezed from the pore spaces between rocks, but many minerals – such as micas, serpentines, and chlorites – contain water as part of their mineral structure. Chlorite, for example, contains about 10 percent water by weight. When water-bearing minerals finally succumb to increased temperature and pressure, they release water.

The water acts as a lubricant in the fault zone created between two plates, reducing the strain on the fault and allowing the plates to slide past one another, producing an earthquake. Subduction zones produce some of the world’s biggest and most destructive earthquakes; the largest magnitude earthquake yet recorded – a magnitude 9.5 earthquake in 1960 near Valdivia, Chile – occurred in a subduction zone. The water also acts as a flux on surrounding rock, depressing the melting temperature of rock, which melts into magma that rises to the surface and erupts as a volcano.

At the point at which the water is released, it creates clues Spear tracked back to its origin. New minerals form in the metamorphosing crust, including garnet, which is produced by the breakdown of water-bearing chlorite. The garnet forms under pressure, and sometimes, as it does so, it traps fragments of surrounding minerals in its grip, fragments that retain a record of the pressure under which the garnet formed. Spear found such garnets, which formed around tiny fragments of quartz, on an island in the Greek Cyclades.

In his lab, Spear and his graduate students used Raman spectroscopy – commonly used in chemistry to identify molecular composition of a sample – to examine the quartz embedded in the garnet. In Raman spectroscopy, laser light is shined onto a sample, and the energy of the photons is shifted up or down based on the interactions between the light and the sample. The difference between the frequency of the outgoing and returning light provides a definitive structure signature.

Quartz at ambient pressure produces a well-known signature. But the peak of the signature from the quartz in the Cyclades samples was shifted to a higher value, indicating the pressure on the grain. Because the Raman signal shift of quartz has been carefully calibrated, Spear was able to use it to determine the pressure, and therefore the depth and temperature, at which the garnet crystallized around the quartz.

“What we discovered when we did this is that the garnet forms not at the shallow depth where the thermodynamic calculations predicted, but much deeper down, near the origin of volcanoes and earthquakes,” said Spear.

The finding also indicates that the garnet doesn’t crystalize at equilibrium, as is the basis of thermodynamic calculations predicting that process. That, said Spear, “was a total surprise.” While initiation of most processes requires activation energy – or overstepping – to some extent, researchers always assumed that the activation energy to initiate nucleation of garnet would be trivial. But the results suggest significant overstepping of 50 to 70 degrees Celsius.

The initial research, published in a series of papers beginning in 2014, was based on three samples from a single site on Sifnos. The new funding will support a broader investigation using 10 to 20 samples taken from five separate locations, to determine whether the findings were “a quirk, or a universal truth.” Spear is also working on developing calculations – and a new “maximum driving force method” – that will incorporate observed overstepping to yield more accurate predictions.

Spear’s research fulfills The New Polytechnic, an emerging paradigm for higher education which recognizes that global challenges and opportunities are so great they cannot be adequately addressed by even the most talented person working alone. Rensselaer serves as a crossroads for collaboration—working with partners across disciplines, sectors, and geographic regions—to address complex global challenges, using the most advanced tools and technologies, many of which are developed at Rensselaer. Research at Rensselaer addresses some of the world’s most pressing technological challenges—from energy security and sustainable development to biotechnology and human health. The New Polytechnic is transformative in the global impact of research, in its innovative pedagogy, and in the lives of students at Rensselaer.

Reference:
Adrian E. Castro et al. Reaction overstepping and re-evaluation of peak P‒T conditions of the blueschist unit Sifnos, Greece: implications for the Cyclades subduction zone, International Geology Review (2016). DOI: 10.1080/00206814.2016.1200499

Note: The above post is reprinted from materials provided by Rensselaer Polytechnic Institute.

Scientists capture sounds of volcanic thunder

March 15, 2018

This satellite image shows Bogoslof volcano erupting on May 28, 2017. The eruption began about 18 minutes prior to this image and the cloud rose to an altitude greater than 12 kilometers (40,000 feet) above sea level. Credit: Dave Schneider / Alaska Volcano Observatory & U.S. Geological Survey.

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Researchers report in a new study that they’ve documented rumblings of volcanic thunder for the first time, a feat considered nearly impossible by many volcanologists.

Microphones set out to detect volcanic eruptions in Alaska’s Aleutian Islands recorded sounds of Bogoslof volcano erupting over eight months from December 2016 to August 2017. Researchers analyzing the recordings identified several cracking sounds from eruptions on March 8 and June 10 as volcanic thunder, a phenomenon the study authors said has never before been captured in audio recordings.

Observers have described hearing volcanic thunder in the past, but scientists have been unable to disentangle the booms of thunder caused by volcanic lightning from the cacophony of bellows and blasts that accompany an explosive eruption. In the new study, researchers used microphones on a nearby island and maps of volcanic lightning strokes to identify the sounds of thunder.

“It’s something that people who’ve been at eruptions have certainly seen and heard before, but this is the first time we’ve definitively caught it and identified it in scientific data,” said Matt Haney, a seismologist at the Alaska Volcano Observatory in Anchorage and lead author of the new study accepted for publication in Geophysical Research Letters, a journal of the American Geophysical Union.

Analyzing volcanic thunder offers scientists a new way of detecting volcanic lightning and potentially a way to estimate the size of an ash plume, according to Jeff Johnson, a geophysicist at Boise State University who was not connected to the new study.

Haney and his team found the intensity of the thunder matched the intensity of the lightning, meaning researchers might be able to use thunder as a proxy for volcanic lightning, Johnson said. The intensity of lightning in a volcanic plume can tell scientists how big the plume is and how hazardous it might be.

“Understanding where lightning is occurring in the plume tells us about how much ash has been erupted, and that’s something that’s notoriously difficult to measure,” Johnson said. “So if you’re locating thunder over a long area, you could potentially say something about how extensive the plume is.”

Monitoring impending eruptions

Volcanic eruptions are inherently noisy – explosions of smoke, ash and magma shake the ground and create loud bangs and rumbles that reverberate for miles. Lightning is common in volcanic plumes because particles of ash and ice scrape and collide with each other and become electrified. Researchers assumed volcanic lightning is followed by thunder, as it is during thunderstorms, but they had not yet been able to tease out thunderclaps from the noises of the eruption itself, and many scientists considered it impossible, according to Haney.

In the new study, scientists detected thunder at Bogoslof volcano in Alaska’s Aleutian Islands, a chain of more than 50 volcanic islands in the northern Pacific Ocean.

Researchers constantly monitor the islands from afar for signs of impending eruptions. They use seismic sensors to pick up ground movement before or during an eruption, arrays of microphones to detect sounds of ash exploding skyward and a global network of lightning sensors to detect lightning strokes within an ash plume. Thunderstorms are rare in the Aleutian Islands, so when sensors detect lightning, it most likely means there’s an ongoing eruption, Haney said.

Bogoslof started erupting in December 2016 and erupted more than 60 times through August 2017. Many of the eruptions produced towering clouds of ash more than six kilometers (20,000 feet) high that disrupted air travel throughout the region.

Isolating thunderclaps

Bogoslof’s eruptions on March 8 and June 10 created ideal conditions for observing volcanic thunder, Haney said. Both eruptions generated immense ash plumes that persisted for several hours after the eruptions ceased. Without the din of an eruption in the background, researchers had a better chance of hearing cracks of thunder caused by lightning in the plume.

Worldwide lightning sensors detected lightning strokes in the ash plumes for several minutes after each eruption ended. In the new study, Haney and his colleagues compared the timing and location of the lightning strokes to sounds recorded by a microphone array on a nearby island.

They found the timing and volume of the sounds the microphones picked up matched the lightning data in a way only thunder could.

On March 8, the microphones recorded at least six distinct bursts of sound that occurred three minutes after lightning activity in the plume peaked. The timing of the bursts means they were almost certainly thunderclaps caused by the lightning: The microphones were 60 kilometers (40 miles) away from the volcano, so it would have taken sound three minutes to reach the microphones. That the thunder was picked up so far away also means it was quite loud, Haney said.

On June 10, the microphones picked up bursts of sound coming from a slightly different direction than sounds from the eruption. The location of the bursts corresponded to areas of peak lightning activity, according to the study.

“If people had been observing the eruption in person, they would have heard this thunder,” Haney said. “I expect that going forward, other researchers are going to be excited and motivated to look in their datasets to see if they can pick up the thunder signal.”

Reference:
Volcanic thunder from explosive eruptions at Bogoslof volcano, Alaska. Geophysical Research Letters. DOI: 10.1002/2017GL076911

Note: The above post is reprinted from materials provided by American Geophysical Union.

Scientists find seismic imaging is blind to water

March 15, 2018

seismic waves are essentially blind to a very common substance found throughout the Earth's interior: water. — Researchers at MIT and the Australian National University have found that seismic waves are essentially blind to a very common substance found throughout the Earth’s interior: water. Credit: Christine Daniloff/MIT

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When an earthquake strikes, nearby seismometers pick up its vibrations in the form of seismic waves. In addition to revealing the epicenter of a quake, seismic waves can give scientists a way to map the interior structures of the Earth, much like a CT scan images the body.

By measuring the velocity at which seismic waves travel at various depths, scientists can determine the types of rocks and other materials that lie beneath the Earth’s surface. The accuracy of such seismic maps depends on scientists’ understanding of how various materials affect seismic waves’ speeds.

Now researchers at MIT and the Australian National University have found that seismic waves are essentially blind to a very common substance found throughout the Earth’s interior: water.

Their findings, published today in the journal Nature, go against a general assumption that seismic imaging can pick up signs of water deep within the Earth’s upper mantle. In fact, the team found that even trace amounts of water have no effect on the speed at which seismic waves travel.

The results may help scientists reinterpret seismic maps of the Earth’s interior. For instance, in places such as midocean ridges, magma from deep within the Earth erupts through massive cracks in the seafloor, spreading away from the ridge and eventually solidifying as new oceanic crust.

The process of melting at tens of kilometers below the surface removes tiny amounts of water that are found in rocks at greater depth. Scientists have thought that seismic images showed this “wet-dry” transition, corresponding to the transition from rigid tectonic plates to deformable mantle beneath. However, the team’s findings suggest that seismic imaging may be picking up signs of not water, but rather, melt – tiny pockets of molten rock.

“If we see very strong variations [in seismic velocities], it’s more likely that they’re due to melt,” says Ulrich Faul, a research scientist in MIT’s Department of Earth, Atmospheric, and Planetary Sciences. “Water, based on these experiments, is no longer a major player in that sense. This will shift how we interpret images of the interior of the Earth.”

Faul’s co-authors are lead author Christopher Cline, along with Emmanuel David, Andrew Berry, and Ian Jackson, of the Australian National University.

A seismic twist

Faul, Cline, and their colleagues originally set out to determine exactly how water affects seismic wave speeds. They assumed, as most researchers have, that seismic imaging can “see” water, in the form of hydroxyl groups within individual mineral grains in rocks, and as molecular-scale pockets of water trapped between these grains. Water, even in tiny amounts, has been known to weaken rocks deep in the Earth’s interior.

“It was known that water has a strong effect in very small quantities on the properties of rocks,” Faul says. “From there, the inference was that water also affects seismic wave speeds substantially.”

To measure the extent to which water affects seismic wave speeds, the team produced different samples of olivine – a mineral that constitutes the majority of Earth’s upper mantle and determines its properties. They trapped various amounts of water within each sample, and then placed the samples one at a time in a machine engineered to slowly twist a rock, similar to twisting a rubber band. The experiments were done in a furnace at high pressures and temperatures, in order to simulate conditions deep within the Earth.

“We twist the sample at one end and measure the magnitude and time delay of the resulting strain at the other end,” Faul says. “This simulates propagation of seismic waves through the Earth. The magnitude of this strain is similar to the width of a thin human hair – not very easy to measure at a pressure of 2,000 times atmospheric pressure and a temperature that approaches the melting temperature of steel.”

The team expected to find a correlation between the amount of water in a given sample and the speed at which seismic waves would propagate through that sample. When the initial samples did not show the anticipated behavior, the researchers modified the composition and measured again, but they kept getting the same negative result. Eventually it became inescapable that the original hypothesis was incorrect.

“From our [twisting] measurements, the rocks behaved as if they were dry, even though we could clearly analyze the water in there,” Faul says. “At that point, we knew water makes no difference.”

A rock, encased

Another unexpected outcome of the experiments was that seismic wave velocity appeared to depend on a rock’s oxidation state. All rocks on Earth contain certain amounts of iron, at various states of oxidation, just as metallic iron on a car can rust when exposed to a certain amount of oxygen. The researchers found, almost unintentionally, that the oxidation of iron in olivine affects the way seismic waves travel through the rock.

Cline and Faul came to this conclusion after having to reconfigure their experimental setup. To carry out their experiments, the team typically encases each rock sample in a cylinder made from nickel and iron. However, in measuring each sample’s water content in this cylinder, they found that hydrogen atoms in water tended to escape out of the rock, through the metal casing. To contain hydrogen, they switched their casing to one made from platinum.

To their surprise they found that the type of metal surrounding the samples affected their seismic properties. Separate experiments showed that what in fact changed was the amount of Fe3+ in olivine. Normally the oxidation state of iron in olivine is 2+. As it turns out, the presence of Fe3+ produces imperfections which affect seismic wave speeds.

Faul says that the group’s findings suggest that seismic waves may be used to map levels of oxidation, such as at subduction zones – regions in the Earth where oceanic plates sink down into the mantle. Based on their results, however, seismic imaging cannot be used to image the distribution of water in the Earth’s interior. What some scientists interpreted as water may in fact be melt – an insight that may change our understanding of how the Earth shifts its tectonic plates over time.

“An underlying question is what lubricates tectonic plates on Earth,” Faul says. “Our work points toward the importance of small amounts of melt at the base of tectonic plates, rather than a wet mantle beneath dry plates. Overall these results may help to illuminate volatile cycling between the interior and the surface of the Earth.”

Reference:
Redox-influenced seismic properties of upper-mantle olivine, Nature (2018). DOI:10.1038/nature25764

Note: The above post is reprinted from materials provided by Massachusetts Institute of Technology.

Are palaeontologists naming too many species?

March 15, 2018

Ichthyosaur skeleton Niedersächsisches Landesmuseum Lower Saxony State Museum Germany

A comprehensive new study looking at variations in Ichthyosaurus, a common British Jurassic ichthyosaur (sea-going reptile) also known as ‘Sea Dragons’, has provided important information into recognizing new fossil species.

Professor Judy Massare (SUNY College at Brockport, NY, USA) and Dean Lomax (The University of Manchester) have studied hundreds of specimens of Ichthyosaurus. After their latest research project the pair urge caution in naming new fossil species on the basis of just a few fragmentary or isolated remains.

For their research Prof Massare and Lomax focused on one particular part of the Ichthyosaurus skeleton, the hindfin (or back paddle). The purpose was to evaluate the different forms among the six-known species of Ichthyosaurus. They examined 99 specimens which could provide useful information.

Early in their research, they found different types of hindfin that initially appeared to represent different species. However, the more specimens they examined the more ‘variation’ they uncovered, such as differences in the size and number of bones. They determined that a single hindfin alone could not be used to distinguish among species of Ichthyosaurus, but that a particular variation was more common in certain species.

Lomax explains: “As we have such a large, complete sample size, which is relatively unique among such fossil vertebrates, our study can help illustrate the limitations that palaeontologists face when dealing with few or even just one specimen.”

Their findings show that with only a few specimens, features can be found that differ substantially from one specimen to the next and thus appear as if there are several species. Whereas, in reality, with a much larger sample size the gaps in the ‘unique’ variations are filled in, showing that differences are simply the result of individual variation and a lack of the full picture.

Prof Massare said: “We described a few hindfins, which might have been called a new species if they were found in isolation. Instead, we had enough specimens to determine that it was just an extreme variation of a common form.”

Palaeontologists fall into one of two camps when it comes to naming species, ‘lumpers’ and ‘splitters’. The former ‘lump’ groups of similar specimens together, whereas the latter opt to split-up specimens and distinguish new species. However, in this new study, if the team opted to split-up the specimens based on the variation found, it would suggest a huge number of species.

“If we considered the variation as unique, it would mean we would be naming about 30 new species. This would be similar to what was done in the 19th Century when any new fossil find, from a new location or horizon, was named as a new species if it differed slightly from previously known specimens.

“As lots of new fossil species are named every year, in some cases, such as with fragmentary or limited remains, the decision to name a new species should be considered very carefully.” Added Lomax.

References:

Judy A. Massare, Dean R. Lomax. Hindfins of Ichthyosaurus: effects of large sample size on ‘distinct’ morphological characters. Geological Magazine, 2018; 1 DOI: 10.1017/S0016756818000146
Dean R. Lomax, Mark Evans, Simon Carpenter. An ichthyosaur from the UK Triassic-Jurassic boundary: A second specimen of the leptonectid ichthyosaur Wahlisaurus massarae Lomax 2016. Geological Journal, 2018; DOI: 10.1002/gj.3155

Note: The above post is reprinted from materials provided by University of Manchester.

Scientists discover evidence of early human innovation, pushing back evolutionary timeline

March 15, 2018

The first evidence of human life in the Olorgesailie Basin comes from about 1.2 million years ago. For hundreds of the thousands of years, people living there made and used large stone-cutting tools called handaxes (left). According to three new studies published in Science, early humans in East Africa had–by about 320,000 years ago–begun using color pigments and manufacturing more sophisticated tools (right) than those of the Early Stone Age handaxes, tens of thousands of years earlier than previous evidence has shown in eastern Africa. The sophisticated tools (right) were carefully crafted and more specialized than the large, all-purpose handaxes (left). Many were points designed to be attached to a shaft and potentially used as projectile weapons, while others were shaped as scrapers or awls. The National Museums of Kenya loaned the artifacts pictured above to conduct the analyses published in Science. Credit: Human Origins Program, Smithsonian

Anthropologists at the Smithsonian’s National Museum of Natural History and an international team of collaborators have discovered that early humans in East Africa had — by about 320,000 years ago — begun trading with distant groups, using color pigments and manufacturing more sophisticated tools than those of the Early Stone Age. These newly discovered activities approximately date to the oldest known fossil record of Homo sapiens and occur tens of thousands of years earlier than previous evidence has shown in eastern Africa. These behaviors, which are characteristic of humans who lived during the Middle Stone Age, replaced technologies and ways of life that had been in place for hundreds of thousands of years.

Evidence for these milestones in humans’ evolutionary past comes from the Olorgesailie Basin in southern Kenya, which holds an archeological record of early human life spanning more than a million years. The new discoveries, reported in three studies published March 15 in the journal Science, indicate that these behaviors emerged during a period of tremendous environmental variability in the region. As earthquakes remodeled the landscape and climate fluctuated between wet and dry conditions, technological innovation, social exchange networks and early symbolic communication would have helped early humans survive and obtain the resources they needed despite unpredictable conditions, the scientists say.

“This change to a very sophisticated set of behaviors that involved greater mental abilities and more complex social lives may have been the leading edge that distinguished our lineage from other early humans,” said Rick Potts, director of the National Museum of Natural History’s Human Origins Program.

Potts has been leading the Human Origin Program’s research in Olorgesailie for more than 30 years in collaboration with the National Museums of Kenya. He is the lead author on one of the three Science publications that describe the adaptive challenges that early humans faced during this phase of evolution. Alison Brooks, a professor of anthropology at George Washington University’s Center for the Advanced Study of Human Paleobiology and an associate of the museum’s Human Origins Program, is lead author on the paper that focuses on the evidence of early resource exchange and use of coloring materials in the Olorgesailie Basin. A third paper, by Alan Deino at the Berkeley Geochronology Center and colleagues, details the chronology of the Middle Stone Age discoveries.

The first evidence of human life in the Olorgesailie Basin comes from about 1.2 million years ago. For hundreds of the thousands of years, people living there made and used large stone-cutting tools called handaxes. Beginning in 2002, Potts, Brooks and their team discovered a variety of smaller, more carefully shaped tools in the Olorgesailie Basin. Isotopic dating by Deino and collaborators revealed that the tools were surprisingly old — made between 320,000 and 305,000 years ago. These tools were carefully crafted and more specialized than the large, all-purpose handaxes. Many were points designed to be attached to a shaft and potentially used as projectile weapons, while others were shaped as scrapers or awls.

While the handaxes of the earlier era were manufactured using local stones, the Smithsonian team found small stone points made of non-local obsidian at their Middle Stone Age sites. The team also found larger, unshaped pieces of the sharp-edged volcanic stone at Olorgesailie, which has no obsidian source of its own. The diverse chemical composition of the artifacts matches that of a wide range of obsidian sources in multiple directions 15 to 55 miles away, suggesting exchange networks were in place to move the valuable stone across the ancient landscape.

The team also discovered black and red rocks — manganese and ocher — at the sites, along with evidence that the rocks had been processed for use as coloring material. “We don’t know what the coloring was used on, but coloring is often taken by archeologists as the root of complex symbolic communication,” Potts said. “Just as color is used today in clothing or flags to express identity, these pigments may have helped people communicate membership in alliances and maintain ties with distant groups.”

Hoping to understand what might have driven such fundamental changes in human behavior, the research team integrated data from a variety of sources to assess and reconstruct the ancient environment in which the users of these artifacts lived. Their findings suggest that the period when these behaviors emerged was one of changing landscapes and climate, in which the availability of resources would have been unreliable.

Geological, geochemical, paleobotanical and faunal evidence indicates that an extended period of climate instability affected the region beginning around 360,000 years ago, at the same time earthquakes were continually altering the landscape. Although some researchers have proposed that early humans evolved gradually in response to an arid environment, Potts says his team’s findings support an alternative idea. Environmental fluctuations would have presented significant challenges to inhabitants of the Olorgesailie Basin, prompting changes in technology and social structures that improved the likelihood of securing resources during times of scarcity.

The research teams for the three studies published in Science include collaborators from the following institutions: the Smithsonian Institution, the National Museums of Kenya, George Washington University, the Berkeley Geochronology Center, the National Science Foundation, the University of Illinois at Urbana-Champaign, the University of Missouri, the University of Bordeaux (Centre National de la Recherche Scientifique), the University of Utah, Harvard University, Santa Monica College, the University of Michigan, the University of Connecticut, Emory University, the University of Bergen, Hong Kong Baptist University and the University of Saskatchewan.

Funding for this research was provided by the Smithsonian, the National Science Foundation and George Washington University.

Reference:
Richard Potts, Anna K. Behrensmeyer, J. Tyler Faith, Christian A. Tryon, Alison S. Brooks, John E. Yellen, Alan L. Deino, Rahab Kinyanjui, Jennifer B. Clark, Catherine Haradon, Naomi E. Levin, Hanneke J. M. Meijer, Elizabeth G. Veatch, R. Bernhart Owen, Robin W. Renaut. Environmental dynamics during the onset of the Middle Stone Age in eastern Africa. Science, 2018 DOI: 10.1126/science.aao2200

Note: The above post is reprinted from materials provided by Smithsonian.

60-year-old paleontological mystery of a ‘phantom’ dicynodont

March 14, 2018

Skeleton of the dicynodont Placerias — This is a skeleton of the dicynodont Placerias, a close relative of the newly-discovered Pentasaurus, with dicynodont trackways (Pentasauropus). Credit: Christian Kammerer

A new study has re-discovered fossil collections from a 19th century hermit that validate ‘phantom’ fossil footprints collected in the 1950s showing dicynodonts coexisting with dinosaurs.

Before the dinosaurs, around 260 million years ago, a group of early mammal relatives called dicynodonts were the most abundant vertebrate land animals. These bizarre plant-eaters with tusks and turtle-like beaks were thought to have gone extinct by the Late Triassic Period, 210 million years ago, when dinosaurs first started to proliferate. However, in the 1950s, suspiciously dicynodont-like footprints were found alongside dinosaur prints in southern Africa, suggesting the presence of a late-surviving phantom dicynodont unknown in the skeletal record. These “phantom” prints were so out-of-place that they were disregarded as evidence for dicynodont survival by paleontologists. A new study has re-discovered fossil collections from a 19th century hermit that validate these “phantom” prints and show that dicynodonts coexisted with early plant-eating dinosaurs. While this research enhances our knowledge of ancient ecosystems, it also emphasizes the often-overlooked importance of trace fossils, like footprints, and the work of amateur scientists.

“Although we tend to think of paleontological discoveries coming from new field work, many of our most important conclusions come from specimens already in museums,” says Dr. Christian Kammerer, Research Curator of Paleontology at the North Carolina Museum of Natural Sciences and author of the new study.

The re-discovered fossils that solved this mystery were originally collected in South Africa in the 1870s by Alfred “Gogga” Brown. Brown was an amateur paleontologist and hermit who spent years trying, with little success, to interest European researchers in his discoveries. Brown had shipped these specimens to the Natural History Museum in Vienna in 1876, where they were deposited in the museum’s collection but never described.

“I knew the Brown collections in Vienna were largely unstudied, but there was general agreement that his Late Triassic collections were made up only of dinosaur fossils. To my great surprise, I immediately noticed clear dicynodont jaw and arm bones among these supposed ‘dinosaur’ fossils,” says Kammerer. “As I went through this collection I found more and more bones matching a dicynodont instead of a dinosaur, representing parts of the skull, limbs, and spinal column.” This was exciting — despite over a century of extensive collection, no skeletal evidence of a dicynodont had ever been recognized in the Late Triassic of South Africa.

Before this point, the only evidence of dicynodonts in the southern African Late Triassic was from questionable footprints: a short-toed, five-fingered track named Pentasauropus incredibilis (meaning the “incredible five-toed lizard foot”). In recognition of the importance of these tracks for suggesting the existence of Late Triassic dicynodonts and the contributions of “Gogga” Brown in collecting the actual fossil bones, the re-discovered and newly described dicynodont has been named Pentasaurus goggai (“Gogga’s five-[toed] lizard”).

“The case of Pentasaurus illustrates the importance of various underappreciated sources of data in understanding prehistory,” says Kammerer. “You have the contributions of amateur researchers like ‘Gogga’ Brown, who was largely ignored in his 19th century heyday, the evidence from footprints, which some paleontologists disbelieved because they conflicted with the skeletal evidence, and of course the importance of well-curated museum collections that provide scientists today an opportunity to study specimens collected 140 years ago.”

Reference:
Christian F. Kammerer. The first skeletal evidence of a dicynodont from the lower Elliot Formation of South Africa. Palaeontologia Africana, 2018

Note: The above post is reprinted from materials provided by North Carolina Museum of Natural Sciences.

Scientists helping to improve understanding of plate tectonics

March 14, 2018

Volcanic Eruption — Plate tectonics is responsible for diverse geological phenomena including continental drift, mountain building and the occurrence of volcanoes and earthquakes. Image credit: Walter Lim, Flickr

Scientists at The Australian National University (ANU) are helping to improve understanding of how rocks in Earth’s hot, deep interior enable the motions of tectonic plates, which regulate the water cycle that is critical for a habitable planet.

Research team leader Professor Ian Jackson said tectonic plates were continuously created at mid-ocean ridges and destroyed when they sink back into the Earth’s mantle.

“Plate tectonics is responsible for diverse geological phenomena including continental drift, mountain building and the occurrence of volcanoes and earthquakes,” said Professor Jackson from the ANU Research School of Earth Sciences.

The stirring of the Earth’s interior, which is responsible for the plate motions at the surface, has resulted in the Earth’s gradual cooling over its 4.5 billion-year life.

He said defects allowed the normally strong and hard minerals of the Earth’s deep interior to change their shape and flow like viscous fluid on geological timescales.

“We have found that flaws in the regular atomic packing in the dominant upper-mantle mineral, called olivine, that become more prevalent under oxidising conditions, substantially reduce the speeds of seismic waves,” Professor Jackson said.

Seismic waves, caused by earthquakes, are used to image the Earth’s deep interior in a manner similar to medical CAT scanning.

“Our new findings challenge a long-held theory that defects involving water absorption in these normally dry rocks could control both their viscosity and seismic properties,” Professor Jackson said.

ANU Research School of Earth Sciences (RSES) PhD scholar Chris Cline is the lead author of the study undertaken in collaboration with RSES colleagues and Professor Ulrich Faul at the Massachusetts Institute of Technology in the United States.

The team used specialised equipment in a laboratory at ANU to make synthetic specimens similar to upper mantle rocks and measured their rigidity, which controls seismic wave speeds, under conditions simulating those of the Earth’s mantle.

Professor Jackson said the research was particularly relevant to environments where old, cold, and oxidised tectonic plates sink into the Earth’s hot interior.

“We have the potential to help map the extent of oxidised regions of the Earth’s mantle that play such an important role in the chemical evolution of Earth,” he said.

Reference:
C. J. Cline II, U. H. Faul, E. C. David, A. J. Berry & I. Jackson. Redox-influenced seismic properties of upper-mantle olivine. Nature, 2018 DOI: 10.1038/nature25764

Note: The above post is reprinted from materials provided by Australian National University.

Underwater volcano behavior captured by timely scientific expedition

March 14, 2018

Underwater bathymetric view with gas venting captured in April 2017. Credit: Imperial College London

Researchers got a rare opportunity to study an underwater volcano in the Caribbean when it erupted while they were surveying the area.

The research, published today in the journal Geochemistry, Geophysics, Geosystems, provides new insight into the little-studied world of underwater volcanoes. It investigated a volcano named Kick-’em-Jenny (KeJ), which is thought to be named after the turbulent waters nearby.

The team from Imperial College London, Southampton and Liverpool universities, in collaboration with The University of the West Indies Seismic Research Centre (SRC), were collecting ocean-bottom seismometers aboard the NERC research ship R.R.S. James Cook as part of a larger experiment when they were alerted to the volcano erupting.

Direct observation of submarine eruptions are very rare, but having the ship nearby allowed them to get to the volcano in time to record the immediate aftermath of the eruption.

Using ship-based imaging technology, the team was able to survey the volcano, observing gas coming from the central cone. The data was then combined with previous surveys going back more than 30 years to reveal the long-term pattern of activity.

Kick-’em-Jenny is one of the Caribbean’s most active volcanoes. It sits eight kilometres off the northern coast of the island of Grenada, and was first discovered in 1939 when a 300-metre column of ash and dust was spotted rising from the ocean.

However, volcanic activity at KeJ is usually detected by accompanying seismic activity picked up on land-based seismometers. These recordings show that the volcano is active on a decadal timescale.

Lead author PhD student Robert Allen, from the Department of Earth Science & Engineering at Imperial, said: “There are surveys of the Kick-’em-Jenny area going back 30 years, but our survey in April 2017 is unique in that it immediately followed an eruption. This gave us unprecedented data on what this volcanic activity actually looks like, rather than relying on interpreting seismic signals.”

The team found that the volcano has frequent cycles of lava ‘dome’ growth followed by collapse through landslides. Similar cycles have been recently witnessed on the nearby volcanic island of Montserrat.

Co-author Dr Jenny Collier, from the Department of Earth Science & Engineering at Imperial, said: “Kick-’em-Jenny is a very active volcano but because it is submarine is less well studied than other volcanoes in the Caribbean. Our research shows that whilst it has quite regular cycles, it is on a relatively small scale, which will help inform future monitoring strategies.”

SRC Director Professor Richard Robertson said: “This study has confirmed very useful recent insights on the activity and evolution of Kick-’em-Jenny volcano. For us, the agency with responsibility for monitoring this volcano, the results of this collaborative research project enable us to better quantify our existing model of this volcano and help in developing strategies for managing future eruptions.”

Any volcano on land which was as lively as KeJ would be constantly monitored by satellites and an array of local instruments looking for the slightest change in behaviour that could precede a major volcanic eruption.

Under the ocean this job is much more difficult, as the electromagnetic energy emitted by satellites cannot penetrate the sea surface and instruments are much more difficult to set up on the volcano itself. Scientists therefore know comparatively little about the growth and long-term behaviour of a fully submerged volcanic cone like KeJ.

The most famous submarine volcanoes are those that lead to the formation of new islands, such as the eruption of Surtsey in Iceland in the 1960s. However, rather than a growing cone, the surveys show significant mass loss from KeJ due to frequent landslides in recent decades.

Comparison with recent studies elsewhere has shown that similar, frequent, small volume landslides may be a fundamental mechanism in the long-term evolution of active submarine volcanoes.

Reference:
R. W. Allen, C. Berry, T. J. Henstock, J. S. Collier, F. J-Y. Dondin, A. Rietbrock, J. L. Latchman, R. E. A. Robertson. 30 Years in the Life of an Active Submarine Volcano: A Time-Lapse Bathymetry Study of the Kick-‘em-Jenny Volcano, Lesser Antilles. Geochemistry, Geophysics, Geosystems, 2018; DOI: 10.1002/2017GC007270

Note: The above post is reprinted from materials provided by Imperial College London. Original written by Hayley Dunning.

The early bird got to fly: Archaeopteryx was an active flyer

March 13, 2018

The Munich specimen of the transitional bird Archaeopteryx. It preserves a partial skull (top left), shoulder girdle and both wings slightly raised up (most left to center left), the ribcage (center), and the pelvic girdle and both legs in a 'cycling' posture (right); all connected by the vertebral column from the neck (top left, under the skull) to the tip of the tail (most right). Imprints of its wing feathers are visible radiating from below the shoulder and vague imprints of the tail plumage can be recognized extending from the tip of the tail. — The Munich specimen of the transitional bird Archaeopteryx. It preserves a partial skull (top left), shoulder girdle and both wings slightly raised up (most left to center left), the ribcage (center), and the pelvic girdle and both legs in a ‘cycling’ posture (right); all connected by the vertebral column from the neck (top left, under the skull) to the tip of the tail (most right). Imprints of its wing feathers are visible radiating from below the shoulder and vague imprints of the tail plumage can be recognized extending from the tip of the tail. Credit: ESRF/Pascal Goetgheluck

The question of whether the Late Jurassic dino-bird Archaeopteryx was an elaborately feathered ground dweller, a glider, or an active flyer has fascinated palaeontologists for decades. Valuable new information obtained with state-of-the-art synchrotron microtomography at the ESRF, the European Synchrotron (Grenoble, France), allowed an international team of scientists to answer this question in Nature Communications. The wing bones of Archaeopteryx were shaped for incidental active flight, but not for the advanced style of flying mastered by today’s birds.

Was Archaeopteryx capable of flying, and if so, how? Although it is common knowledge that modern-day birds descended from extinct dinosaurs, many questions on their early evolution and the development of avian flight remain unanswered. Traditional research methods have thus far been unable to answer the question whether Archaeopteryx flew or not. Using synchrotron microtomography at the ESRF’s beamline ID19 to probe inside Archaeopteryx fossils, an international team of scientists from the ESRF, Palacký University, Czech Republic, CNRS and Sorbonne University, France, Uppsala University, Sweden, and Bürgermeister-Müller-Museum Solnhofen, Germany, shed new light on this earliest of birds.

Reconstructing extinct behaviour poses substantial challenges for palaeontologists, especially when it comes to enigmatic animals such as the famous Archaeopteryx from the Late Jurassic sediments of southeastern Germany that is considered the oldest potentially free-flying dinosaur. This well-preserved fossil taxon shows a mosaic anatomy that illustrates the close family relations between extinct raptorial dinosaurs and living dinosaurs: the birds. Most modern bird skeletons are highly specialised for powered flight, yet many of their characteristic adaptations in particularly the shoulder are absent in the Bavarian fossils of Archaeopteryx. Although its feathered wings resemble those of modern birds flying overhead every day, the primitive shoulder structure is incompatible with the modern avian wing beat cycle.

“The cross-sectional architecture of limb bones is strongly influenced by evolutionary adaptation towards optimal strength at minimal mass, and functional adaptation to the forces experienced during life,” explains Prof. Jorge Cubo of the Sorbonne University in Paris. “By statistically comparing the bones of living animals that engage in observable habits with those of cryptic fossils, it is possible to bring new information into an old discussion,” says senior author Dr. Sophie Sanchez from Uppsala University, Sweden

Archaeopteryx skeletons are preserved in and on limestone slabs that reveal only part of their morphology. Since these fossils are among the most valuable in the world, invasive probing to reveal obscured or internal structures is therefore highly discouraged. “Fortunately, today it is no longer necessary to damage precious fossils,” states Dr. Paul Tafforeau, beamline scientist at the ESRF. “The exceptional sensitivity of X-ray imaging techniques for investigating large specimens that is available at the ESRF offers harmless microscopic insight into fossil bones and allows virtual 3D reconstructions of extraordinary quality. Exciting upgrades are underway, including a substantial improvement of the properties of our synchrotron source and a brand new beamline designated for tomography. These developments promise to give even better results on much larger specimens in the future.”

Scanning data unexpectedly revealed that the wing bones of Archaeopteryx, contrary to its shoulder girdle, shared important adaptations with those of modern flying birds. “We focused on the middle part of the arm bones because we knew those sections contain clear flight-related signals in birds,” says Dr. Emmanuel de Margerie, CNRS, France. “We immediately noticed that the bone walls of Archaeopteryx were much thinner than those of earthbound dinosaurs but looked a lot like conventional bird bones,” continues lead author Dennis Voeten of the ESRF. “Data analysis furthermore demonstrated that the bones of Archaeopteryx plot closest to those of birds like pheasants that occasionally use active flight to cross barriers or dodge predators, but not to those of gliding and soaring forms such as many birds of prey and some seabirds that are optimised for enduring flight.”

“We know that the region around Solnhofen in southeastern Germany was a tropical archipelago, and such an environment appears highly suitable for island hopping or escape flight,” remarks Dr. Martin Röper, Archaeopteryx curator and co-author of the report. “Archaeopteryx shared the Jurassic skies with primitive pterosaurs that would ultimately evolve into the gigantic pterosaurs of the Cretaceous. We found similar differences in wing bone geometry between primitive and advanced pterosaurs as those between actively flying and soaring birds,” adds Vincent Beyrand of the ESRF.

Since Archaeopteryx represents the oldest known flying member of the avialan lineage that also includes modern birds, these findings not only illustrate aspects of the lifestyle of Archaeopteryx but also provide insight into the early evolution of dinosaurian flight. “Indeed, we now know that Archaeopteryx was already actively flying around 150 million years ago, which implies that active dinosaurian flight had evolved even earlier!” says Prof. Stanislav Bureš of Palacký University in Olomouc. “However, because Archaeopteryx lacked the pectoral adaptations to fly like modern birds, the way it achieved powered flight must also have been different. We will need to return to the fossils to answer the question on exactly how this Bavarian icon of evolution used its wings,” concludes Voeten.

It is now clear that Archaeopteryx is a representative of the first wave of dinosaurian flight strategies that eventually went extinct, leaving only the modern avian flight stroke directly observable today.

Reference:
Dennis F. A. E. Voeten, Jorge Cubo, Emmanuel de Margerie, Martin Röper, Vincent Beyrand, Stanislav Bureš, Paul Tafforeau, Sophie Sanchez. Wing bone geometry reveals active flight in Archaeopteryx. Nature Communications, 2018; 9 (1) DOI: 10.1038/s41467-018-03296-8

Note: The above post is reprinted from materials provided by European Synchrotron Radiation Facility.

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