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Researchers help map and scout for hydrothermal vents in Gulf of California

This hydrothermal chimney was one of several discovered by MBARI scientists in the southern Pescadero Basin.
This hydrothermal chimney was one of several discovered by MBARI scientists in the southern Pescadero Basin. Credit: MBARI

Almost 4,000 meters below the sea surface, in the southern Pescadero Basin, jagged ivory towers rise from the seafloor and emit hot shimmering fluid. They are the deepest known hydrothermal vents in the Gulf of California.

These deep-sea chimneys were discovered by MBARI scientists in 2015. The researchers call them the Auka vents. What’s intriguing is that these vents spew chemicals and host animals that are very different from those seen at Alarcón Rise, which is just 100 miles away.

On October 31, 2018, an interdisciplinary team of researchers embarked on a 21-day expedition on board the research vessel Falkor, operated by the Schmidt Ocean Institute. They will zoom in further on the Auka vents’ geology, chemistry, and biology, while continuing to look for more hydrothermal vents in the basin.

For David Caress, an MBARI geophysicist, returning to the Pescadero Basin will be especially exciting. “It will be fun to explore a place that I was involved in discovering,” he said. On this expedition, he will lead the seabed mapping team.

The Falkor carries a multibeam sonar that can make 50-meter resolution maps of the seafloor near the Auka vents. But this resolution isn’t good enough to reveal smaller features like hydrothermal chimneys.

To create more detailed maps, the same sonar technology will be deployed on an underwater robot designed by MBARI engineers and scientists, which will fly 50 meters (164 feet) above the seabed. Travelling at three knots, this autonomous underwater vehicle (AUV) can map an area about 250 meters (820 feet) wide and show features as small as a meter across. MBARI scientists made the 2015 discovery using the very same AUV.

During this expedition, geologists will use the AUV to search for new vent fields elsewhere in the Pescadero Basin, particularly the unexplored waters of Northern Pescadero Basin.

While the AUV explores surrounding areas, a sophisticated sensor package, also designed by an MBARI team, will be used to make much finer, one-centimeter resolution maps of the Auka vents. Loaded onto a remote underwater vehicle (ROV SuBastian), this package combines acoustic and optical technologies—sonar, lidar, and high-resolution stereo cameras.

These three instruments work in tandem. Multibeam sonars work where lidars won’t, for example in muddy waters. And small soft animals on the seafloor, especially sea cucumbers and sponges can be mapped with lidar but not sonar, because sound waves don’t reflect off their bodies. The camera photos, on the other hand, allow scientists to identify and size the animals.

Although this powerful ocean imaging system wasn’t used during the 2015 surveys, Caress said that his team has been testing and tweaking the system for quite a few years off the California coast, and is excited to see the new maps that will be generated.

But doing the research 3,800 meters (12,500 feet) below the surface comes with its own challenges. “We are going really deep, on a ship we have never been on, using an ROV we have never used, and the likelihood of everything working at the first go is really small. It’s often hard, but things work out eventually,” said Caress.

The expedition consists of two legs. During the first leg, researchers will carry out centimeter-scale mapping of the Auka vents using the ROV, while also making meter-scale maps of unexplored areas using the AUV, to find new chimneys. If new vents are found, geologists on board will use the ROV to collect sediment and geology samples. They also plan to collect samples of the hot fluids coming from the vents.

During the second leg, the focus will be on understanding the diversity, distribution, and metabolism of creatures living at and around the vent sites. Guided by the maps and photomosaics produced on the first leg, the biological team will explore the peculiar assemblages of tubeworms, polychaetes and chemosynthetic microbes residing there. The aim will be to compare the animals and microbes at different vent sites and link these to the chemical environments of the sites.

Such comprehensive research has the potential to advance our knowledge of the deep sea. And, with hydrothermal vents increasingly becoming a target of deep-sea mining, such interdisciplinary research may help identify areas that are unique and need protection.

Note: The above post is reprinted from materials provided by Monterey Bay Aquarium Research Institute.

Where water goes after fracking is tied to earthquake risk

This is an aerial view of hydraulic fracturing operations across the Jonah field, a large natural gas field in Wyoming.
This is an aerial view of hydraulic fracturing operations across the Jonah field, a large natural gas field in Wyoming. Credit: EcoFlight

In addition to producing oil and gas, the energy industry produces a lot of water, about 10 barrels of water per barrel of oil on average. New research led by The University of Texas at Austin has found that where the produced water is stored underground influences the risk of induced earthquakes.

Beyond supporting the link between water disposal and induced seismicity, the research also describes factors that can help reduce earthquake risk.

“If we want to manage seismicity, we really need to understand the controls,” said lead author Bridget Scanlon, a senior research scientist at UT’s Bureau of Economic Geology.

The research was published Oct. 31 in the journal Seismological Research Letters. Co-authors include Matthew Weingarten, assistant professor at San Diego State University; Kyle Murray, adjunct professor at the University of Oklahoma; and Robert Reedy, research scientist associate at the Bureau of Economic Geology. The bureau is a research unit at the UT Jackson School of Geosciences.

The researchers found that the increased pressure that is caused by storing produced water inside geologic formations raises the risk of induced seismicity. The risk increases with the volume of water injected, both at the well and regional scale, as well as the rate of injection.

Researchers specifically looked at water stored near tight oil plays, including the Bakken, Eagle Ford and Permian shale plays, and Oklahoma overall, which has high levels of induced seismicity in concentrated areas. Researchers found marked differences in the degree of seismic activity associated with underground water storage.

For example, the study found that in Oklahoma 56 percent of wells used to dispose of produced water are potentially associated with earthquakes. The next highest is the Eagle Ford Shale of South Texas, where 20 percent are potentially associated with earthquakes.

The study reported that the different levels of induced seismic activity relate to, among other reasons, how the water is managed and where it is stored underground. In Oklahoma, the tendency to store water in deep geologic formations — which are often connected to faults that can trigger earthquakes when stressed — has increased the risk of induced seismicity. In the other areas, water is stored at shallower depths, which limits exposure to potentially risky faults.

In conventional energy production, water is usually injected back into the reservoir that produced the oil and gas, which stabilizes pressure within the reservoir. However, water produced during hydraulic fracturing–the method used to access energy in tight oil plays– cannot be returned because the rock pores are too small for the water to be injected back into the rock. That water is usually injected into nearby geologic formations, which can increase pressure on the surrounding rock.

The findings are consistent with directives issued by the Oklahoma Corporation Commission (OCC) in 2015 to mitigate seismicity, which included reducing injection rates and regional injection volumes by 40 percent in deep wells. This study confirmed the changes resulted in a 70 percent reduction in the number of earthquakes over a 3.0 magnitude in 2017 compared with the peak year of 2015.

“Everything they (the OCC) did is supported by what we have in this article,” said Murray. “The decisions they made, the directives that they put out, are supported by statistical associations we found.”

The reduction in earthquakes in Oklahoma shows that subsurface management practices can influence seismic risk. However, Scanlon said the changes could come with trade-offs. For example, shallow disposal may help lower the risk of earthquakes, but the shallower storage depths could increase the risk of the produced water contaminating overlying aquifers.

“There’s no free lunch,” Scanlon said. “You keep iterating and doing things, but you must keep watching to see what’s happening.”

Reference:
Managing Basin‐Scale Fluid Budgets to Reduce Injection‐Induced Seismicity from the Recent U.S. Shale Oil Revolution. DOI: 10.1785/0220180223

Note: The above post is reprinted from materials provided by University of Texas at Austin.

Dinosaurs put all colored birds’ eggs in one basket, evolutionarily speaking

An assortment of paleognath and neognath bird eggs and a fossil theropod egg (on the right).
An assortment of paleognath and neognath bird eggs and a fossil theropod egg (on the right). Credit: Jasmina Wiemann/Yale University

A new study says the colors found in modern birds’ eggs did not evolve independently, as previously thought, but evolved instead from dinosaurs.

According to researchers at Yale, the American Museum of Natural History, and the University of Bonn, birds inherited their egg color from non-avian dinosaur ancestors that laid eggs in fully or partially open nests. The researchers’ findings appear Oct. 31 in the online edition of the journal Nature.

“This completely changes our understanding of how egg colors evolved,” said the study’s lead author, Yale paleontologist Jasmina Wiemann. “For two centuries, ornithologists assumed that egg color appeared in modern birds’ eggs multiple times, independently.”

The egg colors of birds reflect characteristic preferences in nesting environments and brooding behaviors. Modern birds use only two pigments, red and blue, to create all of the various egg colors, spots, and speckles.

Wiemann and her colleagues analyzed 18 fossil dinosaur eggshell samples from around the world, using non-destructive laser microspectroscopy to test for the presence of the two eggshell pigments. They found them in eggshells belonging to Eumaniraptoran dinosaurs, which include small, carnivorous dinosaurs such as Velociraptor.

“We infer that egg color co-evolved with open nesting habits in dinosaurs,” Wiemann said. “Once dinosaurs started to build open nests, exposure of the eggs to visually hunting predators and even nesting parasites favored the evolution of camouflaging egg colors, and individually recognizable patterns of spots and speckles.”

Co-author Mark Norell, the Macaulay Curator of Paleontology at the American Museum of Natural History, noted that “Colored eggs have been considered a unique bird characteristic for over a century. Like feathers and wishbones, we now know that egg color evolved in their dinosaur predecessors long before birds appeared.”

Reference:
Dinosaur egg colour had a single evolutionary origin, Nature (2018). DOI: 10.1038/s41586-018-0646-5

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

Researchers discover earliest recorded lead exposure in 250,000-year-old Neanderthal teeth

A 250,000-year-old Neanderthal tooth yields an unprecedented record of the seasons of birth, nursing, illness, and lead exposures over the first three years of this child’s life.
A 250,000-year-old Neanderthal tooth yields an unprecedented record of the seasons of birth, nursing, illness, and lead exposures over the first three years of this child’s life. Credit: Tanya Smith & Daniel Green

Using evidence found in teeth from two Neanderthals from southeastern France, researchers from the Department of Environmental Medicine and Public Health at the Icahn School of Medicine at Mount Sinai report the earliest evidence of lead exposure in an extinct human-like species from 250,000 years ago.

This study is the first to report lead exposure in Neanderthal and is the first to use teeth to reconstruct climate during and timing of key developmental events including weaning and nursing duration— key determinants of population growth.

Results of the study will be published online in Science Advances on October 31st.

The international research team of biological anthropologists, archaeologists, earth scientists, and environmental exposure experts measured barium, lead and oxygen in the teeth for evidence of nursing, weaning, chemical exposure, and climate variations across the growth rings in the teeth. Elemental analysis of the teeth revealed short-term exposure to lead during cooler seasons, possibly from ingestion of contaminated food or water, or inhalation from fires containing lead.

During fetal and childhood development, a new tooth layer is formed every day. As each of these ‘growth rings’ forms, some of the many chemicals circulating in the body are captured in each layer, which provides a chronological record of exposure. The research team used lasers to sample these layers and reconstruct the past exposures along incremental markings, similar to using growth rings on a tree to determine the tree’s growth history.

This evidence allowed the team to relate the individuals’ development to ancient seasons, revealing that one Neanderthal was born in the spring, and that both Neanderthal children were more likely to be sick during colder periods. The findings are consistent with mammals’ pattern of bearing offspring during periods of increased food availability. The nursing duration of 2.5 years in one individual is similar to the average age of weaning in preindustrial human populations. The researchers note they can’t make broad generalizations about Neanderthals due to the small study size, but that their research methods offer a new approach to answering questions about long extinct species.

“Traditionally, people thought lead exposure occurred in populations only after industrialization, but these results show it happened prehistorically, before lead had been widely released into the environment,” said one of the study’s lead authors, Christine Austin, Ph.D., Assistant Professor in the Department of Environmental Medicine and Public Health at the Icahn School of Medicine at Mount Sinai. “Our team plans to analyze more teeth from our ancestors and investigate how lead exposures may have affected their health and how that may relate to how our bodies respond to lead today.”

“Dietary patterns in our early life have far reaching consequences for our health, and by understanding how breastfeeding evolved we can help guide the current population on what is good breastfeeding practice,” said Manish Arora Ph.D., BDS, MPH, Professor and Vice Chairman Department of Environmental Medicine and Public Health at the Icahn School of Medicine. “Our research team is working on applying these techniques in contemporary populations to study how breastfeeding alters health trajectories including those of neurodevelopment, cardiac health and other high priority health outcomes.”

“This study reports a major breakthrough in the reconstruction of ancient climates, a significant factor in human evolution, as temperature and precipitation cycles influenced the landscapes and food resources our ancestors relied on,” said the study’s lead author Tanya Smith, Ph.D., Associate Professor at Griffith University.

Reference:
T.M. Smith el al., “Wintertime stress, nursing, and lead exposure in Neanderthal children,” Science Advances (2018). DOI: 10.1126/sciadv.aau9483 

Note: The above post is reprinted from materials provided by The Mount Sinai Hospital.

Naturally occurring ‘batteries’ fueled organic carbon synthesis on Mars

Mars
This is a mosaic image of Mars created from over 100 images taken by Viking Orbiters in the 1970s. Credit: NASA

Mars’ organic carbon may have originated from a series of electrochemical reactions between briny liquids and volcanic minerals, according to new analyses of three Martian meteorites from a team led by Carnegie’s Andrew Steele published in Science Advances.

The group’s analysis of a trio of Martian meteorites that fell to Earth–Tissint, Nakhla, and NWA 1950–showed that they contain an inventory of organic carbon that is remarkably consistent with the organic carbon compounds detected by the Mars Science Laboratory’s rover missions.

In 2012, Steele led a team that determined the organic carbon found in 10 Martian meteorites did indeed come from the Red Planet and was not due to contamination from Earth, but also that the organic carbon did not have a biological origin. This new work takes his research to the next step–trying to understand how Mars’ organic carbon was synthesized, if not by biology.

Organic molecules contain carbon and hydrogen, and sometimes include oxygen, nitrogen, sulfur, and other elements. Organic compounds are commonly associated with life, although they can be created by non-biological processes as well, which are referred to as abiotic organic chemistry.

“Revealing the processes by which organic carbon compounds form on Mars has been a matter of tremendous interest for understanding its potential for habitability,” Steele said.

He and his co-authors took a deep dive into the minerology of these three Martian meteorites. Using advanced microscopy and spectroscopy, they were able to determine that the meteorites’ organic compounds were likely created by electrochemical corrosion of minerals in Martian rocks by a surrounding salty liquid brine.

“The discovery that natural systems can essentially form a small corrosion-powered battery that drives electrochemical reactions between minerals and surrounding liquid has major implications for the astrobiology field,” Steele explained.

A similar process could occur anywhere that igneous rocks are surrounded by brines, including the subsurface oceans of Jupiter’s moon Europa, Saturn’s moon Enceladus, and even some environments here on Earth, particularly early in this planets’ history.

The team included Carnegie’s Pamela Conrad and Jianhua Wang; Liane Benning, Richard Wirth, and Anja Schreiber of the German Research Centre for Geosciences; Sandra Siljeström of the RISE Research Institutes of Sweden; Marc Fries and Francis McCubbin of the NASA Johnson Space Center; Karyn Rogers of Rensselaer Polytechnic Institute; Jen Eigenbrode of NASA’s Goddard Space Flight Center; A. Needham of USRA–Science and Technology Institute; David Kilcoyne of Lawrence Berkeley National Laboratory; and Juan Diego Rodriguez Blanco of University of Leeds.

The paper is dedicated to the memory of Erik Hauri, a Carnegie scientist and co-author on the paper who died in September.

Note: The above post is reprinted from materials provided by Carnegie Institution for Science.

Location of wastewater disposal drives induced seismicity at US oil sites

Rig "An oil platform"
Representative Image: An oil platform

The depth of the rock layer that serves as the disposal site for wastewater produced during unconventional oil extraction plays a significant role in whether that disposal triggers earthquakes in the U.S., according to a new study that takes a broad look at the issue.

The research published in Seismological Research Letters reviewed data on wastewater disposal for oil sites in Oklahoma, eastern Montana, western North Dakota, Texas and New Mexico.

Seismicity levels are higher in Oklahoma compared to the other states in part because wastewater is injected deeper into the ground in Oklahoma, nearer to the underlying basement rock, according to study author Bridget Scanlon of the University of Texas at Austin and her colleagues.

The cumulative volume of wastewater injected into the earth in Oklahoma is also higher than in the other oil-producing areas, and can also be linked to increased rates of seismicity in the state, the researchers concluded.

The findings differ from an earlier study based on data in the mid-continent, which did not find a significant correlation between total disposed wastewater volume, or between depth of injection, and increased seismicity. The new study contains an additional 3.5 years’ worth of data on injection volume and seismicity in Oklahoma, however, and also uses a new map of basement rock depth, said Scanlon.

Unconventional U.S. oil production, which extracts oil from shales and tight rocks using hydraulic fracturing and horizontal wells, has been linked to an increase in human-induced earthquakes across the mid-continent of the United States for nearly a decade. The main driver of this increase in seismicity is the injection of wastewater produced by extraction, which increases pore pressure within rocks and can affect stress along faults in the rock layers selected for disposal.

The “tightness” of the oil-producing rock layers at these sites means that wastewater can’t be injected back into the same layers, so companies have instead found “looser,” more permeable rock layers in which to drill disposal wells.

The study by Scanlon and colleagues examined wastewater injection rates, cumulative regional injection volumes and injection proximity to basement rock for tight oil plays in Oklahoma, the Bakken play (Montana and North Dakota), the Eagle Ford play (Texas) and the Permian play (Texas and New Mexico).

Many of the wastewater disposal wells in Oklahoma are drilled into a rock layer called the Arbuckle Formation, which lies adjacent to the basement and is much deeper than the rock layers used for disposal in the Bakken, Eagle Ford and Permian plays.

Wells drilled into the Arbuckle drain water into the formation without the need for pressure at the wellhead, and the rock zone is highly permeable, which makes it an appealing disposal site, said Kyle Murray, a co-author on the study from the Oklahoma Geological Survey. The Arbuckle also has extraction wells only “in a few small areas, so disposal does not diminish producing wells.”

The ease of using the Arbuckle as a disposal site might be one reason why oil producers have chosen deeper disposal sites in Oklahoma compared to the other regions, “but drilling shallower wells and disposing in shallower zones in other plays may be related to economics. Deeper wells are much more expensive and not always successful,” he added.

Murray said oil field operators in these other regions may also know about the studies linking the increase in seismicity in Oklahoma to injection proximity to basement rock, causing them to avoid deep disposal at their sites.

The researchers noted that their findings are consistent with the reduced seismicity documented in Oklahoma after directives by the Oklahoma Corporation Commission in 2014 and 2016 to reduce injection rates and regional injection volumes, as well as to plug disposal wells drilled into the basement. These directives have led to a 70 percent reduction in the number of magnitude 3.0 or larger earthquakes in the state in 2017, relative to 2015.

There are tradeoffs between injecting wastewater into shallow versus deep rock layers, the researchers note. Shallower wells, which often cost two to three times less than deeper wells and would appear to trigger lower levels of seismicity, could contaminate aquifers with saltwater or interfere with oil production wells.

Scanlon and colleagues say one way to reduce the amount of overall wastewater injection might be to repurpose the wastewater for hydraulic fracturing. “The value of reusing produced water for hydraulic fracturing is similar to re-injecting produced water for water flooding in conventional oil reservoirs, to maintain pressure,” Scanlon said. “Reusing produced water for hydraulic fracturing would reduce water sourcing issues and water depletion related to that, and would also reduce wastewater disposal and related potential seismicity.”

This strategy might work best in places where the wastewater produced is roughly similar to the amounts needed for hydraulic fracturing, however. In Oklahoma, for instance, hydraulic fracturing operations would use up only 10 percent of the amount of produced wastewater.

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

Micro-earthquakes preceding a 4.2 earthquake near Istanbul as early warning signs?

Illustration of the North Anatolian fault zone
Illustration of the North Anatolian fault zone (CCBY 3.0: Bohnhoff et.al., Scientific Drilling, 5, 1-10, 2017, doi:10.5194/sd-5-1-2017).

One of the high-risk geological structures lies near Istanbul, a megacity of 15 million people. The North Anatolian fault, separating the Eurasian and Anatolian tectonic plates, is a 1.200 kilometer-long fault zone running between eastern Turkey and the northern Aegean Sea. Since the beginning of the 20th century its seismic activity has caused more than 20.000 deaths. A large (Mw > 7) earthquake is overdue in the Marmara section of the fault, just south of Istanbul.

In a new study, led by Peter Malin and Marco Bohnhoff of the GFZ German Research Center for Geosciences, the authors report on the observation of foreshocks that, if analyzed accordingly and in real-time, may possibly increase the early-warning time before a large earthquake from just a few seconds up to several hours. However, the authors caution: „The results are so far based on only one – yet encouraging – field example for an ,earthquake preparation sequence’ typically known from repeated rock-deformation laboratory experiments under controlled conditions”, says Marco Bohnhoff.

The study from Peter Malin and Marco Bohnhoff, together with colleagues from the AFAD Disaster and Emergency Management Presidency in Turkey, uses waveform data from the recently implemented GONAF borehole seismic network. GONAF operates at low-magnitude detection. It allowed identifying a series of micro-earthquakes prior to an earthquake of magnitude 4.2 which occurred in June 2016 south of Istanbul and which was the largest event in the region in several years.

In the latest issue of Scientific Reports, seismic data from the GONAF network, set up by GFZ in collaboration with AFAD along the Marmara Sea near Istanbul, is processed and analyzed with novel processing techniques. The high resolution borehole seismic array allowed for the detection of tens of seismic events prior to the mainshock. These small events would have been below the detection threshold of most seismic networks worldwide. By means of the new processing technique, clustering and similarity of the seismic signals was shown to substantially increase in the hours prior to the Mw 4.2 earthquake. If this so-called emergent failure process would be a persistent feature of seismicity there, implementing real-time processing of the novel technique could extend the warning time for future earthquakes in the Istanbul region and lead to a major improvement in the early-warning system for the densely populated area of the Turkish megacity.

“Our study shows a substantial increase in self-similarity of the micro-quakes during the hours before the mainshock,” says Professor Bohnhoff of the GFZ; “while the current early-warning system in place in Istanbul relies on the arrival times of seismic waves emitted from the hypocentre to the city and is therefore restricted to a couple of seconds at maximum”. While similar precursory activity has been detected for recent large earthquakes in Japan (2011 Mw9 Tohoku-Oki) and Chile (2014 Mw8.1 Iquique), this is at present by no means a ubiquitous observation and needs further testing before its implementation.

Reference:
Malin, E.P., Bohnhoff, M., Blümle, F., Dresen, G., Martínez-Garzón, P., Nurlu, M., Ceken, U., Kadirioglu, F.T., Kartal, R.F., Kilic, T., Yanik, K., 2018. Microearthquakes preceding a M4.2 Earthquake Offshore Istanbul. Nature Scientific Reports. DOI: 10.1038/s41598-018-34563-9

Note: The above post is reprinted from materials provided by GFZ GeoForschungsZentrum Potsdam, Helmholtz Centre.

Paleontologists discovered six new species in the East African Rift

Ammonite Fossil
Ammonite Fossil

Sometimes hidden clues beneath our feet can reveal intriguing stories about the impacts of environmental change.

Six new species of invertebrates were discovered during a paleontological exploration of rift deposits in southwestern Tanzania by Ohio University professor, Nancy Stevens and her research team. After analyzing invertebrate fossils that were alive 24 to 26 million years ago in the Rukwa Rift Basin, OHIO paleontologists published the first documentation of a rapid diversification of freshwater gastropod species at a time of pivotal environment change in this specific area. Their article, “Morphological diversification of ampullariid gastropods (Nsungwe Formation, Late Oligocene, Rukwa Rift Basin, Tanzania) is coincident with onset of East African rifting,” was published in Papers in Palaeontology.

“From the very start of this project, I was extremely intrigued because we were working on rare fossils from a geologically interesting location,” said Y. Ranjeev Epa, M.S. ’17, an Ohio University geology master’s student who studied and identified the fossils for his thesis. “These fossils had a lot of interesting stories to tell us and I am very happy that we were able to expand the existing knowledge on the evolutionary history, ecology and biogeography of this family.”

The new species evolved in what is now known as the East African Rift about 25 million years ago, as the Horn of Africa began splitting away from the mainland due to movements of the earth’s plates. This interval in time is called the late Oligocene, a key period of transition between ancient and more modern ecosystems. The research team emphasized how the discovery of these new species can help us understand how organisms respond to environmental change.

“The timing of this evolutionary burst is coincident with the onset of the timing of the East African Rift,” said Dr. Alycia Stigall, Professor of Geological Sciences, a researcher on the team. “The new rift produced novel environments, and the gastropods very rapidly evolved to exploit new niches.”

The fossils examined in the study were collected by Stevens and her research group, which has been conducting paleobiological and geological research in the Rukwa Rift Basin in Tanzania for nearly two decades. Their research has produced the most precise age for the onset of rifting in the western branch of the East African Rift System, as well as the earliest evidence of the split between Old World monkeys and apes. Until now, the evolutionary history of invertebrate faunas in this area have barely been studied.

Previously, the Rukwa Rift Basin team has reported on the discovery of other new species to science, including dinosaurs and bizarre mammal-like crocs from older deposits in the region. It is clear that the Rukwa Rift preserves a special window into the evolution of ecosystems on the African continent, with potentially even more discoveries to come.

Reference:
Y. Ranjeev Epa et al. Morphological diversification of ampullariid gastropods (Nsungwe Formation, Late Oligocene, Rukwa Rift Basin, Tanzania) is coincident with onset of East African rifting, Papers in Palaeontology (2018). DOI: 10.1002/spp2.1108

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

Tiny beetle trapped in amber might show how landmasses shifted

The fossil beetle, Propiestus archaicus, preserved in amber.
The fossil beetle, Propiestus archaicus, preserved in amber. Credit: Field Museum, Shuhei Yamamoto

In 2016, Shuhei Yamamoto obtained a penny-sized piece of Burmese amber from Hukawng Valley in northern Myanmar, near China’s southern border. He had a hunch that the three-millimeter insect trapped inside the amber could help ansshow why our world today looks the way it does.

After carefully cutting and polishing the amber, Yamamoto determined that the insect, smaller than the phone-end of an iPhone charger, was a new species to science. The beetle, which lived 99 million years ago, is a relative of insects alive today that live under tree bark, and it’s giving scientists hints about how Earth’s landmasses were arranged millions of years ago.

“This is a very rare find,” Yamamoto said, a Field Museum researcher and lead author of a paper in the Journal of Systematic Palaeontology describing the new species. The fossil beetle is one of the oldest known members of its family — its name, Propiestus archaicus, refers to the fact that it’s an ancient relative of the flat rove beetles in the Piestus genus today of which now dominates the South America.

While dinosaurs roamed much of Earth 99 million years ago during the Late Cretaceous era, Propiestus, with its flattened body and short legs, was busy conquering smaller turf underneath the bark of rotting trees. Its long, slender antennae were the clear giveaway to Yamamoto that Propiestus was lived in this environment — similar to today’s flat rove beetles.

“The antennae probably had a highly sensitive ability as a sensory organ,” Yamamoto said. Smaller hair-like structures attached perpendicular to the antennae would have increased its ability to feel out its surroundings. “There wouldn’t have been a lot of space available in the beetle’s habitat, so it was important to be able to detect everything,” he explains.

Propiestus is just one of the hundreds of thousands of Burmese amber inclusions — another word for the objects trapped inside the amber — that scientists have extensively researched over the last 15 years. Many small insects that lived during the Cretaceous era met their maker at the hands of tree sap that engulfed the bugs and hardened into amber. The bugs trapped inside fossilized and remained frozen for millions of years, unaffected by the passage of time. The hardened amber, covered by soil, decayed leaves, and other organic material, eventually blended in with its surroundings.

Because of this, amber in nature doesn’t look like it does in jewelry — in fact, it doesn’t look like anything special at all. The small clumps of unpolished amber look like rocks, meaning only those experienced in amber identification, mostly local miners, are able to find them.

After miners extract the amber, the clumps are either sold into the jewelry trade or to scientists like Yamamoto to study the inclusions. For Yamamoto’s piece of amber, he used sandpaper to carefully polish the amber just enough to make Propiestus clearly visible.

“It was very exciting, because the cutting process is very sensitive,” Yamamoto said. “If you cut too fast or apply too much pressure, you destroy the inclusion inside very quickly.”

Once the amber was polished, the beetle was clearly visible, enabling Yamamoto and his colleagues to study the beetle and determine its closest living relatives. Propiestus’s flat rove beetle cousins alive today are found mostly in South America, with the exception of one species in Southern Arizona. Myanmar, where Propiestus was found, is literally on the other side of the globe from these places. But it hasn’t always been that way.

Millions of years ago, Myanmar and South America were actually quite close to each other, all fused together as part of the megacontinent Gondwanaland, which formed when the earlier megacontinent Pangea broke apart. Gondwanaland itself eventually broke apart, helping to form the continents we recognize on a map today.

Scientists have a clear sense of which of today’s continents and subcontinents would have comprised Gondwanaland and which would have made up its sister continent, Laurasia. However, the detailed timing and pattern of Gondwanaland’s split into smaller continents is disputable. Searching for supporting or contrasting evidence means analyzing fossils, some as small as Propiestus, to compare their similarities to other organisms discovered across the globe that might have inhabited the same space long ago.

“Like koalas and kangaroos today, certain animals that we think lived in Gondwanaland are only found in one part of the world. Although Propiestus went extinct long ago, our finding probably shows some amazing connections between Southern Hemisphere and Myanmar,” Yamamoto said. “Our finding fits well with the hypothesis that, unlike today, Myanmar was once located in the Southern Hemisphere.”

Many inclusions in Burmese amber that have been researched in the last 15 years, including Propiestus, show signs that show traits in common with insects from Gondwanaland. By studying these tiny creatures trapped in amber, we’re finding answers to the questions surrounding Earth’s structure and the life it supported millions of years ago.

“This fossil helps us understand life in the Mesozoic era,” he said. “We need to think about everything from that time, both big and small.”

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

Incredible moment Anak Krakatau erupts, Oct 2018

Krakatoa, or Krakatau (Indonesian: Krakatau), is a volcanic island situated in the Sunda Strait between the islands of Java and Sumatra in the Indonesian province of Lampung. The name is also used for the surrounding island group comprising the remnants of a much larger island of three volcanic peaks which was obliterated in a cataclysmic 1883 eruption.

In 1927, a new island, Anak Krakatau, or “Child of Krakatoa”, emerged from the caldera formed in 1883 and is the current location of eruptive activity.

The most notable eruptions of Krakatoa culminated in a series of massive explosions over August 26–27, 1883, which were among the most violent volcanic events in recorded history.

With an estimated Volcanic Explosivity Index (VEI) of 6, the eruption was equivalent to 200 megatons of TNT (840 PJ)—about 13,000 times the nuclear yield of the Little Boy bomb (13 to 16 kt) that devastated Hiroshima, Japan, during World War II, and four times the yield of Tsar Bomba (50 Mt), the most powerful nuclear device ever detonated.

The 1883 eruption ejected approximately 25 km3 (6 cubic miles) of rock. The cataclysmic explosion was heard 3,600 km (2,200 mi) away in Alice Springs, as well as on the island of Rodrigues near Mauritius, 4,780 km (2,970 mi) to the west.

According to the official records of the Dutch East Indies colony, 165 villages and towns were destroyed near Krakatoa, and 132 were seriously damaged. At least 36,417 people died, and many more thousands were injured, mostly from the tsunamis that followed the explosion. The eruption destroyed two-thirds of the island of Krakatoa.

Eruptions in the area since 1927 have built a new island at the same location, named Anak Krakatau (which is Indonesian for “Child of Krakatoa”). Periodic eruptions have continued since, with recent eruptions in 2009, 2010, 2011, and 2012. In late 2011, this island had a radius of roughly 2 kilometres (1.2 mi), and a highest point of about 324 metres (1,063 ft) above sea level, growing 5 metres (16 ft) each year. In 2017 the height of Anak Krakatau was reported as over 400 metres above sea level.

Dechen Cave, Germany

Dechen Cave, Germany
Dechen Cave, Germany

The Dechen Cave (German: Dechenhöhle) in Iserlohn, Germany is one of the most beautiful and most visited show caves in Germany. It is located in the northern part of the Sauerland at Iserlohn (Grüne district). 360 metres of the 870-metre long cave have been laid out for visitors, beginning at the spot where, in 1868, the cave was discovered by two railway workers.

The cave is named after Oberberghauptmann Heinrich von Dechen (1800–1889), in recognition of his contribution to researching the geology of the Rhineland and Westphalia.

Due to its discovery by rail workers, the cave was first owned by the local railway company – which built the Letmathe–Fröndenberg railway – and later on by the National railway company, the last one was the Deutsche Bundesbahn. In 1983 the cave was taken over by the Mark Sauerland Touristik GmbH.

Because the cave was found and owned by the railway, a halt was built next to the visitors’ entrance. Today, the Ruhr-Sieg-Express (RE16) and Ruhr-Sieg-Bahn (RB91) services stop at the halt. Both the RE16 and the RB91 services are operated by Abellio Rail NRW. It is the only cave in Germany with its own halt.

Summery:

Location: Sauerland, Germany
Length: 870 metres
Elevation: 250 metres
Discovery: 1868
Geology: Rhenish Massif
Show cave opened: 1868
Show cave length: 360 metres

 

The formation of large meteorite craters is unraveled

66 million years ago a meteorite of a diameter 14 km wide struck the Earth with an enormous speed of 20.000 kilometers per hour drilling itself 20 km into the Earth's crust
66 million years ago a meteorite of a diameter 14 km wide struck the Earth with an enormous speed of 20.000 kilometers per hour drilling itself 20 km into the Earth’s crust (1). Due to the impact temperatures of 10.000°C emerged temporarily, melting and evaporating the meteorite and parts of the Earth’s crust. A shock wave arose molding a crater 30 km deep and 100 km wide (2). As the crater collapsed, the mass of rock behaved like a viscous mass, shooting up to form a 20 km high mountain (3). The liquid mass of the rocks of the collapsed mountain moved beyond the crater margins and solidified. This led both to the summit ring and to the flattening and widening of the crater (4). Credit: UHH/Min/Fuchs

About 66 million years ago, a meteorite hit the Earth of the Yucatan Peninsula in what is now Mexico. This event triggered a mass extinction that eradicated approximately 75 percent of all species and ended the era of dinosaurs. Like Prof. Dr. Ulrich Riller of the Institute of Geology of the University of Hamburg and co-workers report in “Nature”, the hitherto mysterious formation of the crater and its mountaneous peak ring. The peak rises in the middle of the crater above the otherwise flat crater floor. In the future, these findings can help to decipher the formation of the largest craters in our solar system.

Much has been written and discussed about the gigantic crater with a diameter of about 200 kilometers, the center of which lies near the Mexican port city of Chicxulub. How the giant crater took its form has been a mystery until today. In particular, the formation of a circular series of hills could not be explained in detail. This so-called peak ring rises in the crater several hundreds of meters above the shallow ground and can therefore be found in other large craters in our solar system.

The structural geologist Prof. Dr. Ulrich Riller and an international team of scientists have now succeeded in describing for the first time the extreme mechanical behavior of rocks in the event of a large meteorite impact. The researchers found the evidence in the Chicxulub Crater as part of Expedition 364 of the International Ocean Discovery Program (IODP) and the International Continental Scientific Drilling Program (ICDP).

Computer simulations have shown that craters this size form within a few minutes. This means that solid rock behaves like a fluid for a short time and solidifies very quickly during cratering. As the science team reports in the current issue of the journal “Nature”, their research supports the hypothesis of so-called acoustic fluidization, where rock behaves like a viscous mass through contemporary pressure changes (vibrations). The obtained drill cores display a variety of zones of broken rock, which the team considers to be evidence of transient fluidity of the rock. The team was able to transmit the results in numeric models, which simulate the exact formation of the crater and peak ring.

“The results of our research team have far-reaching consequences for understanding the formation of large impact craters in our solar system,” explains Prof. Riller.

Reference:
Rock fluidisation during peak-ring formation of large impact structures, Nature 562, 511 (2018). DOI: 10.1038/s41586-018-0607-z

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

What is a Plutonic Igneous Rock?

Igneous intrusion
Representative Image: Igneous intrusion

In geology, a pluton is a body of intrusive igneous rock (called a plutonic rock) that is crystallized from magma slowly cooling below the surface of the Earth. Plutons include batholiths, stocks, dikes, sills, laccoliths, lopoliths, and other igneous formations. In practice, “pluton” usually refers to a distinctive mass of igneous rock, typically several kilometers in dimension, without a tabular, or flat, shape like those of dikes and sills. Examples of plutons include Denali (formerly Mount McKinley) in Alaska; Cuillin in Skye, Scotland; Cardinal Peak in Washington State; Mount Kinabalu in Malaysia; and Stone Mountain in the US state of Georgia.

The most common rock types in plutons are granite, granodiorite, tonalite, monzonite, and quartz diorite. Generally light colored, coarse-grained plutons of these compositions are referred to as granitoids.

The term originated from Pluto, the classical god of the underworld. The use of the name and concept goes back to the beginnings of the science of geology in the late 18th century and the then hotly debated theories of plutonism (or vulcanism), and neptunism regarding the origin of basalt.

New species of ‘missing link’ between dinosaurs and birds identified

Dr. John Nudds with Archaeopteryx fossil specimen at the European Synchrotron in Grenoble.
Dr. John Nudds with Archaeopteryx fossil specimen at the European Synchrotron in Grenoble. Credit: Image courtesy of The University of Manchester

Known as the ‘Icon of Evolution’ and ‘the missing link’ between dinosaurs and birds, Archaeopteryx has become one of the most famous fossil discoveries in Palaeontology.

Now, as part of an international team of scientists, researchers at The University of Manchester have identified a new species of Archaeopteryx that is closer to modern birds in evolutionary terms.

Dr John Nudds, from the University’s School of Earth and Environmental Sciences, and the team have been re-examining one of the only 12 known specimens by carrying out the first ever synchrotron examination, a form of 3D X-ray analysis, of an Archaeopteryx.

Thanks to this new insight, the team says that this individual Archaeopteryx fossil, known as ‘specimen number eight’, is physically much closer to a modern bird than it is to a reptile. Therefore, it is evolutionary distinctive and different enough to be described as a new species — Archaeopteryx albersdoerferi.

The research, which is being published in journal Historical Biology, says that some of the differing skeletal characteristics of Archaeopteryx albersdoerferi include the fusion of cranial bones, different pectoral girdle (chest) and wing elements, and a reinforced configuration of carpals and metacarpals (hand) bones.

These characteristics are seen more in modern flying birds and are not found in the older Archaeopteryx lithographica species, which more resembles reptiles and dinosaurs.

Specimen number eight is the youngest of all the 12 known specimens by approximately half a million years. This age difference in comparison to the other specimens is a key factor in describing it as a new species.

Dr Nudds explains: “By digitally dissecting the fossil we found that this specimen differed from all of the others. It possessed skeletal adaptations which would have resulted in much more efficient flight. In a nutshell we have discovered what Archaeopteryx lithographica evolved into — i.e. a more advanced bird, better adapted to flying — and we have described this as a new species of Archaeopteryx.”

Archaeopteryx was first described as the ‘missing link’ between reptiles and birds in 1861 — and is now regarded as the link between dinosaurs and birds. Only 12 specimens have ever been found and all are from the late Jurassic of Bavaria, now Germany, dating back approximately 150 million years.

Lead author, Dr Martin Kundrát, from the University of Pavol Jozef Šafárik, Slovakia, said: “This is the first time that numerous bones and teeth of Archaeopteryx were viewed from all aspects including exposure of their inner structure. The use of synchrotron microtomography was the only way to study the specimen as it is heavily compressed with many fragmented bones partly or completely hidden in limestone.”

Dr Nudds added: “Whenever a missing link is discovered, this merely creates two further missing links — what came before, and what came after! What came before was discovered in 1996 with the feathered dinosaurs in China. Our new species is what came after. It confirms Archaeopteryx as the first bird, and not just one of a number of feathered theropod dinosaurs, which some authors have suggested recently. You could say that it puts Archaeopteryx back on its perch as the first bird!”

Reference:
Martin Kundrát, John Nudds, Benjamin P. Kear, Junchang Lü, Per Ahlberg. The first specimen of Archaeopteryx from the Upper Jurassic Mörnsheim Formation of Germany. Historical Biology, 2018; 31 (1): 3 DOI: 10.1080/08912963.2018.1518443

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

Tortoise evolution: How did they become so big?

Fossil tortoise
Fossil tortoise at the Central Natural Science Collections at MLU. Credit: Markus Scholz / MLU

Tortoises are a group of terrestrial turtles globally distributed in habitats ranging from deserts to forests and include species such as the Greek and the Galapagos tortoise. Some species evolved large body sizes with a shell length exceeding 1 metre whereas others are no larger than 6-8 centimetres. Despite a particular interest from naturalists ever since the times of Darwin, the evolution of gigantism in tortoises remains enigmatic.

The fact that all living giant tortoises are insular may suggest that their evolution followed the so-called island rule: a trend toward dwarfism of large animals and gigantism of small animals on islands. An example of insular dwarfism is the Florida key deer, a dwarf version of the mainland white-tailed deer; its small size may be an adaptation to the limited resources found on the islands. Insular gigantism is best exemplified by the famous dodo, an extinct flightless pigeon from Mauritius, probably evolving large body size due to release from predatory pressure. Previous studies on extant tortoises were partly inconclusive: giant size has been linked to the absence of predatory mammals in islands but it has been also proposed that tortoises were already giants when they reached the remote archipelagos. Since very few giant tortoise species survive to the present, these hypotheses are impossible to test without analysing extinct species through the help of the fossil record.

In a recent study in the journal “Cladistics,” Dr Evangelos Vlachos from the Paleontological Museum of Trelew, Argentina, and Dr Márton Rabi from the Martin Luther University Halle-Wittenberg (MLU), funded by the German VolkswagenStiftung, assembled the most comprehensive family tree of extinct and extant tortoises so far. The researchers analysed genetic data from living species together with osteological data from fossil and living tortoises.

This is the first study of such global scale to allow for investigating body size evolution in tortoises. The fossils reveal a very different picture of the past compared to the present. Giant size evolved on multiple occasions independently in mainland Asia, Africa, Europe, North and South America at different times of Earth history. However, all of these species went extinct at latest during the Pleistocene ice age.

“The fossils highlight a great number of extinct mainland giant species and suggest that the evolution of giant size was not linked to islands,” says Dr Evangelos Vlachos.

Instead, living insular giant tortoises, such as the ones from Galapagos and Seychelles, more likely represent survivors of unrelated giant species that once inhabited South America, East Africa, and/or Madagascar.

“Giant tortoises may have been better island colonizers because they can tolerate water and food shortage during an oceanic dispersal for a longer period than smaller species. Giant tortoises have been reported to survive 740 km of floating in the ocean,” says Dr Márton Rabi.

What led to the extinction of these mainland giants remains enigmatic. For the ice age species, it may have been a combination of predatory (including human) pressure and climate change. It is likewise unclear, if not the island rule, then what is driving tortoises to repeatedly evolve into giant forms?

“We expect that warmer climate and predator pressure plays a role in the evolution of giant size but the picture is complex and our sampling of the fossil record is still limited.” — Vlachos adds.

An unexpected outcome of the study was that the Mediterranean tortoises (familiar due to their popularity as pets) actually represent a dwarf lineage as their ancestors turned out to be considerably larger.

“Tortoises have been around for more than 55 million years and we are now able to better understand the evolution of this successful group. Today, however, out of the approximately 43 living species 17 are considered endangered and many more are vulnerable largely due to human-induced habitat loss; this is a disappointing fact.” — Rabi points out.

Reference:
Evangelos Vlachos, Márton Rabi. Total evidence analysis and body size evolution of extant and extinct tortoises (Testudines: Cryptodira: Pan-Testudinidae). Cladistics, 2017; DOI: 10.1111/cla.12227

Note: The above post is reprinted from materials provided by Martin-Luther-Universität Halle-Wittenberg.

‘Superlungs’ gave dinosaurs the energy to run and fight

Dinosaurs
Credit: Chinese Academy of Sciences

In the oxygen-poor air of the Mesozoic era, nothing should have been able to move very fast. But Velociraptors could run 64 kilometers per hour. Their secret weapon: superefficient, birdlike lungs, which would have pumped in a constant supply of oxygen, according to a new study. This unique adaptation may have given all dinos a leg up on their competition.

Biologists have long known that birds, which descend from one branch of extinct dinosaurs, have an unusual, sophisticated respiratory system that enables powered flight. But paleontologists have long debated whether those superlungs arose only in birds or earlier in dinosaurs.

Unlike humans and other mammals, whose lungs expand and deflate, bird lungs are rigid. Special air sacs alongside the lungs do the heavy lifting instead, pumping air through the lungs, where the oxygen diffuses into the bloodstream. The lungs are attached to the vertebrae and ribs, which form the “ceiling” of the rib cage—all of which helps keep the lungs stationary. A connector called the costovertebral joint, where the ribs and vertebrae meet, provides further support. That setup allows for a continuous stream of oxygen and requires less energy than inflating and deflating the lungs. It also allows paleontologists studying fossils to learn a lot about the lungs by examining the bones around them.

To find out when these superlungs evolved, paleobiologists Robert Brocklehurst and William Sellers of The University of Manchester in the United Kingdom, and biologist Emma Schachner of Louisiana State University in Baton Rouge turned to computer models. They compared the shapes of skeletal features like vertebrae and ribs in a range of bird and nonavian dinosaur species.

Many dinosaurs, including therapods like Velociraptor and Spinosaurus, a large carnivorous dinosaur, had similar lung architecture to birds, the team reports today in Royal Society Open Science. These dinosaurs sported a costovertebral joint and the birdlike bony “ceiling” of vertebrae and ribs that helps keep the lungs rigid.

All of this suggests dinos had the same kind of efficient respiratory organs as birds, the team concludes. These superlungs may help explain why dinosaurs were able to dominate and spread, despite the rarified air of the Mesozoic, Brocklehurst says. Back then, the air was only 10% to 15% oxygen, compared with 20% today.

The work sheds light on how birds’ extraordinary lungs evolved, says Jingmai O’Connor, a paleontologist with the Institute of Vertebrate Paleontology and Paleoanthropology at the Chinese Academy of Sciences in Beijing. “Birds are really weird compared to all other animals,” she says. “They have this highly evolved respiration system, [and] we’ve always wondered, ‘How did this evolve?'” Now, it seems likely that superlungs first developed in dinosaurs, and only later on evolved to support powered flight in birds, she says.

But O’Connor adds that just because a fossil has the bone structure for birdlike lungs doesn’t necessarily mean it actually had such lungs. Finding lung tissue, which is almost never preserved, would be the clincher. She described what may be the first preserved lungs found in a bird fossil at the Society of Vertebrate Paleontology’s annual meeting in Albuquerque, New Mexico, last week and in a paper in the Proceedings of the National Academy of Sciences yesterday. In that 120-million-year-old, dove-size bird from China, she and her team noted that although the putative lungs were sophisticated, the skeletal structure around them was primitive, suggesting bones and soft tissue may not evolve in lockstep.

Not everyone is sure O’Connor’s bird organs are really lungs, however. The structures could be a mineral artifact, speculates Corwin Sullivan, a paleontologist at the University of Alberta in Edmonton, Canada, who studies the evolution of avian respiratory systems. But even if so, he says, the specimen is “absolutely fascinating.”

Reference:

  1. Robert J. Brocklehurst et al. Vertebral morphometrics and lung structure in non-avian dinosaurs, Royal Society Open Science (2018). DOI: 10.1098/rsos.180983
  2. Xiaoli Wang et al. Archaeorhynchus preserving significant soft tissue including probable fossilized lungs, Proceedings of the National Academy of Sciences (2018). DOI: 10.1073/pnas.1805803115

Note: The above post is reprinted from materials provided by Chinese Academy of Sciences.

Dig at Italy’s Pompeii volcanic site yields 5 skeletons

The remains of skeletons that were found in the Pompeii archaeological site, Italy, Wednesday, Oct. 24, 2018. The Italian news agency ANSA says new excavations in the ancient buried city of Pompeii have yielded the undisturbed skeletons of people who had taken refuge from the eruption of Mount Vesuvius in A.D.79. The director of the Pompeii archaeological site, Massimo Osanna, told ANSA on Wednesday the skeletons, believed to be two women and three children, were still intact, having been left undisturbed despite looting at the site centuries ago.
The remains of skeletons that were found in the Pompeii archaeological site, Italy, Wednesday, Oct. 24, 2018. The Italian news agency ANSA says new excavations in the ancient buried city of Pompeii have yielded the undisturbed skeletons of people who had taken refuge from the eruption of Mount Vesuvius in A.D.79. The director of the Pompeii archaeological site, Massimo Osanna, told ANSA on Wednesday the skeletons, believed to be two women and three children, were still intact, having been left undisturbed despite looting at the site centuries ago. Credit: Ciro Fusco/ANSA via AP

Italian news agency ANSA says new excavations in the ancient buried city of Pompeii have yielded the undisturbed skeletons of people who took refuge from the eruption of Mount Vesuvius in A.D.79.

The director of the Pompeii archaeological site, Massimo Osanna, told ANSA on Wednesday the skeletons were still intact, having been left undisturbed despite looting at the site centuries ago.

Osanna called it “a shocking find, but also very important for history.”

The bones — believed to be those of two women and three children — were discovered inside a house holding a charcoal inscription that historians say dates the deadly eruption to October, two months later than previously thought.

Archaeologists think the people sought safety in a small room but were either crushed when the roof caved in or burned.

Note: The above post is reprinted from materials provided by The Associated Press. All rights reserved.

Relationship between tremors, water at the Cascadia margin

Rice University scientists studied how the density of microseismicity, or small tremors, related to the seismic structure of the Pacific Northwest in the United States. Red lines in the graphic at left correspond to cross-sections from northern Washington (top), central Oregon (middle), and northern California (bottom).
Rice University scientists studied how the density of microseismicity, or small tremors, related to the seismic structure of the Pacific Northwest in the United States. Red lines in the graphic at left correspond to cross-sections from northern Washington (top), central Oregon (middle), and northern California (bottom). The researchers determined a strong correlation exists between tremor density and underthrusting sediments (brown material in the graphics on right). Fluids that are released from the downgoing slab are concentrated in these sediments and lead to very slow seismic velocities in the region. Credit: Jonathan Delph/Rice University

The earthquakes are so small and deep that someone standing in Seattle would never feel them. In fact, until the early 2000s, nobody knew they happened at all. Now, scientists at Rice University have unearthed details about the structure of Earth where these tiny tremors occur.

Rice postdoctoral researcher and seismologist Jonathan Delph and Earth scientists Fenglin Niu and Alan Levander make a case for the incursion of fluid related to slippage deep inside the Cascadia margin off the Pacific Northwest’s coast.

Their paper, which appears in the American Geophysical Union journal Geophysical Research Letters, links fluids escaping from deep subduction to the frequent shakes that Delph said happen in relative slow motion when compared to the sudden, violent jolts occasionally felt by Southern Californians at the southern end of the west coast.

“These aren’t large, instantaneous events like a typical earthquake,” Delph said. “They’re seismically small, but there’s a lot of them and they are part of the slow-slip type of earthquake that can last for weeks instead of seconds.”

Delph’s paper is the first to show variations in the scale and extent of fluids that come from dehydrating minerals and how they relate to these low-velocity quakes. “We are finally at the point where we can address the incredible amount of research that’s been done in the Pacific Northwest and try to bring it all together,” he said. “The result is a better understanding of how the seismic velocity structure of the margin relates to other geologic and tectonic observations.”

The North American plate and Juan de Fuca plate, a small remnant of a much larger tectonic plate that used to subduct beneath North America, meet at the Cascadia subduction zone, which extends from the coast of northern California well into Canada. As the Juan de Fuca plate moves to the northeast, it sinks below the North American plate.

Delph said fluids released from minerals as they heat up at depths of 30 to 80 kilometers propagate upward along the boundary of the plates in the northern and southern portions of the margin, and get trapped in sediments that are subducting beneath the Cascadia margin.

“This underthrust sedimentary material is being stuck onto the bottom of the North American plate,” he said. “This can allow fluids to infiltrate. We don’t know why, exactly, but it correlates well with the spatial variations in tremor density we observe. We’re starting to understand the structure of the margin where these tremors are more prevalent.”

Delph’s research is based on extensive seismic records gathered over decades and housed at the National Science Foundation-backed IRIS seismic data repository, an institutional collaboration to make seismic data available to the public.

“We didn’t know these tremors existed until the early 2000s, when they were correlated with small changes in the direction of GPS stations at the surface,” he said. “They’re extremely difficult to spot. Basically, they don’t look like earthquakes. They look like periods of higher noise on seismometers.

“We needed high-accuracy GPS and seismometer measurements to see that these tremors accompany changes in GPS motion,” Delph said. “We know from GPS records that some parts of the Pacific Northwest coast change direction over a period of weeks. That correlates with high-noise ‘tremor’ signals we see in the seismometers. We call these slow-slip events because they slip for much longer than traditional earthquakes, at much slower speeds.”

He said the phenomenon isn’t present in all subduction zones. “This process is pretty constrained to what we call ‘hot subduction zones,’ where the subducting plate is relatively young and therefore warm,” Delph said. “This allows for minerals that carry water to dehydrate at shallower depths.

“In ‘colder’ subduction zones, like central Chile or the Tohoku region of Japan, we don’t see these tremors as much, and we think this is because minerals don’t release their water until they’re at greater depths,” he said. “The Cascadia subduction zone seems to behave quite differently than these colder subduction zones, which generate large earthquakes more frequently than Cascadia. This could be related in some way to these slow-slip earthquakes, which can release as much energy as a magnitude 7 earthquake over their duration. This is an ongoing area of research.”

Reference:
Jonathan R. Delph, Alan Levander, Fenglin Niu. Fluid Controls on the Heterogeneous Seismic Characteristics of the Cascadia Margin. Geophysical Research Letters, 2018; DOI: 10.1029/2018GL079518

Note: The above post is reprinted from materials provided by Rice University. Original written by Mike Williams.

Mexico’s 2017 Tehuantepec quake suggests a new worry

Last September’s magnitude 8.2 Tehuantepec earthquake happened deep, rupturing both mantle and crust, on the landward side of major subduction zone in the Pacific Ocean off Mexico’s far south coast.

Initially, it was believed the earthquake was related to a seismic gap, occurring where the Cocos ocean plate is being overridden by a continental plate, in an area that had not had a quake of such magnitude since 1787. Subduction zone megaquakes generally occur near the top of where plates converge.

The epicenter, however, was 46 kilometers (28 miles) deep in the Cocos plate, well under the overriding plate and where existing earthquake modeling had said it shouldn’t happen, a 13-member research team reported Oct. 1 in the journal Nature Geoscience after an analysis of data from multiple sources.

“We don’t yet have an explanation on how this was possible,” said the study’s lead author Diego Melgar, an earth scientist at the University of Oregon. “We can only say that it contradicts the models that we have so far and indicates that we have to do more work to understand it.”

Earthquakes do occur in such locations, where a descending plate’s own weight creates strong forces that stretch the slab as it dives down toward the mantle, but have been seen only under older and cooler subduction zones. The 1933 Sanriku, Japan, earthquake was one. It generated a 94-foot tsunami that killed 1,522 people and destroyed more than 7,000 homes.

The Mexican quake, ruptured the descending slab and generated a 6-foot tsunami, which likely was limited in size by the angle of the overriding continental plate so close to shore, Melgar said.

“This subducting plate is still very young and warm, geologically speaking,” he said. “It really shouldn’t be breaking.”

Subduction zone ages and their temperatures relate to their distance from mid-ocean ridges, where plates are made in temperatures of 1,400 degrees Celsius (2,552 degrees Fahrenheit), Melgar said. The 25-million-year-old Cocos subduction zone is 600 miles from the mid-ocean ridge where it began. Japan’s subduction zone is much further from the ridge and 130-million-years old.

Temperatures cool as plates move outward. Tension-related earthquakes, the researchers noted, have been restricted to older plates with temperatures that are cooler than 650 degrees Celsius (1,202 degrees Fahrenheit).

Melgar’s team theorizes that seawater infiltration into the fabric of the stressed and diving Cocos plate has possibly accelerated the cooling, making it susceptible to tension earthquakes previously seen only in older and colder locations. It’s also possible, the researchers noted, that the 8.0 magnitude 1933 Oaxaca earthquake, previously thought to be in a traditional subduction zone event, was instead similar to the one that struck last year.

If such water-driven cooling is possible, it could suggest other areas, especially Guatemala southward in Central America, and the U.S. West Coast are susceptible to tension-zone earthquakes, Melgar said.

The Cascadia subduction zone, from northern California to British Columbia, is 15 million years old and warmer than the similar geology along the Mexican-Central America coastlines, but could still be at risk.

Building codes and hazard maps should reflect the potential danger, he added.

“Our knowledge of these places where large earthquakes happen is still imperfect,” Melgar said. “We can still be surprised. We need to think more carefully when we make hazard and warning maps. We still need to do a lot of work to be able to provide people with very accurate information about what they can expect in terms of shaking and in terms of tsunami hazard.”

Reference:
Diego Melgar, Angel Ruiz-Angulo, Emmanuel Soliman Garcia, Marina Manea, Vlad. C. Manea, Xiaohua Xu, M. Teresa Ramirez-Herrera, Jorge Zavala-Hidalgo, Jianghui Geng, Nestor Corona, Xyoli Pérez-Campos, Enrique Cabral-Cano, Leonardo Ramirez-Guzmán. Deep embrittlement and complete rupture of the lithosphere during the Mw 8.2 Tehuantepec earthquake. Nature Geoscience, 2018; DOI: 10.1038/s41561-018-0229-y

Note: The above post is reprinted from materials provided by University of Oregon. Original written by Jim Barlow.

Crater from asteroid that killed the dinosaurs reveals how broken rocks can flow like liquid

A mile-long sediment core drilled by the International Ocean Discovery Program helped researchers uncover how the Chicxulub crater formed.
A mile-long sediment core drilled by the International Ocean Discovery Program helped researchers uncover how the Chicxulub crater formed. Credit: International Ocean Discovery Program

Sixty-six million years ago, an asteroid the size of a small city smashed into Earth. This impact, the one that would lead to the end of the dinosaurs, left a scar several miles underground and more than 115 miles wide.

Chicxulub, which lies underneath the Yucatán Peninsula of Mexico, is the best-preserved large impact crater on Earth, although it’s buried underneath a half mile of rocks. It’s also the only crater on the planet with a mountainous ring of smashed rocks inside its outer rim, called a peak ring. How these features form has long been debated, but a new study in Nature shows they’re a product of extremely strong vibrations that let rock flow like liquid for a crucial few minutes after the impact.

When an asteroid crashes into Earth, it leaves a bowl-shaped pit, just like you’d expect. But it doesn’t just leave a dent. If the asteroid is big enough, the resulting crater can be more than 20 miles deep, at which point it becomes unstable and collapses.

“For a while, the broken rock behaves as a fluid,” said Jay Melosh, a professor of earth, atmospheric and planetary sciences at Purdue University. “There have been a lot of theories proposed about what mechanism allows this fluidization to happen, and now we know it’s really strong vibrations shaking the rock constantly enough to allow it to flow.”

This mechanism, known as “acoustic fluidization,” is the process that allows the ring of mountains in the crater’s center to rise within minutes of the asteroid’s strike. (This idea was first proposed by Melosh in 1979). Craters are essentially the same on all the terrestrial planets (Earth, Mercury, Venus, Mars and our moon), but they’re hard to study in space for obvious reasons: We can’t look at them with the same detail we can on Earth.

The Chicxulub crater isn’t easily accessible by traditional standards either; it’s been buried throughout the last 66 million years. So the International Ocean Discovery Program (a group within the International Continental Scientific Drilling Program), did the only thing they could — they dug. The team drilled a core roughly six inches in diameter and a mile into Earth, collecting rock that was shattered and partly melted by the impact that wiped out the dinosaurs.

In examining fracture zones and patterns in the core, the international research team found an evolution in the vibration sequence that would allow debris to flow.

“These findings help us understand how impact craters collapse and how large masses of rock behave in a fluid-like manner in other circumstances, such as landslides and earthquakes,” Melosh said. “Towns have been wiped out by enormous landslides, where people thought they were safe but then discovered that rock will flow like liquid when some disturbance sets a big enough mass in motion.”

The extinction of the dinosaurs itself was probably not directly affected by the crater’s internal collapse — other, external effects of the impact did them in, Melosh said. Regardless, it’s important to understand the consequences of a large asteroid strike on Earth. Because cratering is the same on all the terrestrial planets, these findings also validate the mechanics of impacts everywhere in the solar system.

Reference:
Ulrich Riller, Michael H. Poelchau, Auriol S. P. Rae, Felix M. Schulte, Gareth S. Collins, H. Jay Melosh, Richard A. F. Grieve, Joanna V. Morgan, Sean P. S. Gulick, Johanna Lofi, Abdoulaye Diaw, Naoma McCall, David A. Kring. Rock fluidization during peak-ring formation of large impact structures. Nature, 2018; 562 (7728): 511 DOI: 10.1038/s41586-018-0607-z

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

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