Fossils turn out to be a rich source of information

February 10, 2016

Fossils turn out to-GeologyPage — This is a detailed mold of the beetle’s fragile legs and outer structure, thereby preserving them. Internal organs, for instance the genitalia, have also been preserved in a mineral way. Credit: Copyright Achim Schwermann/Thomas van de Kamp

For more than 70 years, fossilized arthropods from Quercy, France, were almost completely neglected because they appeared to be poorly preserved. With the help of the Synchrotron Radiation Facility ANKA at the Karlsruhe Institute of Technology (KIT), an international and interdisciplinary team of researchers with substantial participation from the University of Bonn has now been able to X-ray the 30-million-year-old beetle fossils. The internal structures are shown in such detail that the scientists were able to create an extensive description and an evolutionary analysis of the beetles. The results of this study have now been published in the professional journal eLIFE.

The beetles, just a few millimeters long, come from a collection of fossilized arthropods — mainly insects — that was collected in Quercy, France more than 100 years ago. “The last time they were studied in detail was in 1944. Until now, people were mainly interested in the vertebrates from this fossil site,” says paleontologist Dr. Achim Schwermann from the Steinmann Institute at the University of Bonn. One reason the insects had been so neglected until now is that the samples outwardly seemed poorly preserved.

With the help of modern imaging methods, however, their internal structures could now be unlocked. The researchers analyzed the fossils in the Synchrotron Radiation Facility ANKA at the Karlsruhe Institute of Technology (KIT), using X-ray computed tomography. That allowed them to create a three-dimensional image of the insides of the opaque fossils. “The actual measurement process only took a few seconds,” explains engineer Tomy dos Santos Rolo from the KIT in Karlsruhe. “During that time, the object is rotated in the path of the X-ray and imaged from various directions. After the measurement, we can digitally reconstruct the three-dimensional object.”

Reconstruction allows for a modern description

This digital reconstruction of one beetle-specimen quickly showed that it was a male animal. “The genitals have been preserved, for the most part,” says biologist Dr. Heiko Schmied from the University of Bonn. “That gives us an opportunity to describe the beetle as a representative sample according to modern standards.” Beetle species in particular are often classified based on the shape of their genitalia. An evolutionary analysis allowed the researchers to re-evaluate how the fossilized beetle species fit into the family of hister beetles (Histeridae), a family that still exists today. “I have never seen the inside of a hister beetle in such detail before,” remarks Dr. Michael Caterino from Clemson University, South Carolina. In addition to the well-preserved genitalia, this specimen also shows mouth parts and the throat, the gastrointestinal tract and the complex respiratory system.

“A diamond in the rough”

The scientists discovered that the outwardly unpromising beetle fossils had internal organs that were amazingly well preserved. The precise detail in the fossilized beetles goes well beyond what is normally seen in fossilized arthropods. “The unusually well-preserved soft tissue shows that the beetles must have become petrified within a very short amount of time, probably hours or days,” explains Dr. Schwermann.

One beetle specimen that is partly embedded in the rock shows the outer structure of the carapace. The attached rock thus conveys what the beetle’s outer shell originally looked like. “Surprisingly, the beetle that looks the least well preserved from the outside has the best level of preservation inside,” says biologist Dr. Thomas van de Kamp from the KIT in Karlsruhe. The attached rock protected even its fragile extremities from being destroyed by external environmental influences.

Unexpected potential in old collections

While the fossilized arthropods from Quercy in France were considered less interesting during their initial study in the 1940s, this old collection turns out to be a rich source of information. “That makes us, as researchers, look at the old collections in museums and universities in a new way,” says Dr. Schwermann. The research team now plans to study other similarly preserved fossils. The fact that the Quercy beetles had been largely ignored for 70 years highlights the unrecognized potential of old collections.

Reference:
Achim H Schwermann, Tomy dos Santos Rolo, Michael S Caterino, Günter Bechly, Heiko Schmied, Tilo Baumbach, Thomas van de Kamp. Preservation of three-dimensional anatomy in phosphatized fossil arthropods enriches evolutionary inference. eLife, 2016; 5 DOI: 10.7554/eLife.12129

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

Clams help date duration of ancient methane seeps in the Arctic

February 10, 2016

Clams help date duration-GeologyPage — The two clam species that dominated the fossil community in the High Arctic: (a) Phreangena s.l. and (b) Isorroprondon sp. Credit: William L. Locke

Clams, mussels, scallops and oysters sound like delicious items on a restaurant menu. But bivalves such as these are much more than that: They function as a delicate record of changing environments and climate.

They live for a long time in one place, all the while accumulating information about their environment in their shells.

Precise timing of a climate gas release

17,707 to 16,680 years ago, around the end of the last Ice Age, clams were alive and kicking on the seabed of the Arctic Ocean above 79° North. That is a pretty accurate time frame that proves persistent methane release from the Arctic Ocean floor for approximately a thousand years.

CAGE scientists discovered the colonies while X-raying two sediment cores from the ocean floor offshore Svalbard, collected at 1200-meter water depth. The discovery was published in Geochemistry, Geophysics and Geosystems.

“We have not discovered these chemosynthetic-based communities in any of the other cores found this far North, and as far as I know they have never been observed in the high Arctic at all.” says principal author, professor William Ambrose, visiting scholar at CAGE.

Don´t need sunlight to thrive

The clams did not exist in a food chain based on photosynthesis. The sunlight does not penetrate this deep into the ocean. Instead, they derived a large portion of their sustenance from a community of bacteria that convert carbon in the ocean into sugars and other byproducts with the help of methane seeping from the ocean floor.

“Our calculations show that 43 percent of their nutrition came from methane. The rest comes from different sources, among others photosynthetic material falling through the water. But at this depth that is not a lot. The methane is key to this species living there.” says Ambrose

Hot and cold release

Methane seeps out from the ocean floor in two environments: hydrothermal vents, huge plumes of hot smoke that appear close to areas of volcanic activity; or from less dramatic cold seeps that are more elusive. Both environments, however, are characterized as deep-sea biological oases that support an abundance of chemosynthetic-based communities.

“Bivalves of this species on the modern seabed as well as in the sediment are a good indicator of methane release.” says Ambrose

Clams act as natural observatories

The release measured in this study was recorded in Vestnesa Ridge. This is an area known as a gas hydrate province with at least a million years of methane release. Gas hydrates are a solid, ice-like form of methane stored under the ocean floor. They release methane gas when they melt.

Several spots in Vestnesa are very active today, even releasing huge columns of gas up to 800 meters tall. Others are inactive. How the release gets activated has been established previously by CAGE research. But the duration of the release event is not easily understood.

“Bivalves act like natural observatories. These clams have average life span up to 30 years. Some species can even be hundreds of years old.”

Think of the clamshells as vinyl records, recording methane release through decades in the groves of their shells, without missing a beat. A shell bed of 30 cm, such as one found in the sediment core from Vestnesa Ridge, represents a formidable record collection, which can be played back by measuring isotopes and elements in the shells

“By dating when the clams lived, and the isotopic values in their shells, we were able to calculate that methane had to persistently leak out of its natural reservoir at this particular site for a thousand years for this clam collection to form.”

Takes advantage of CAGE expertise

The precise, and robust dating of such an event in our planet’s distant history is not a straightforward process, and does not depend on clams alone. A lot of elements must be in place to achieve this degree of precision: microfossils must be dated, carbonate crusts also, and tectonic movements must be understood.

“This study really takes advantage of the close proximity of all the different expertise that is available at CAGE and is a good example of interdisciplinary work. ” concludes Ambrose.

Reference:
William G. Ambrose et al. Bivalve shell horizons in seafloor pockmarks of the last glacial-interglacial transition: a thousand years of methane emissions in the Arctic Ocean, Geochemistry, Geophysics, Geosystems (2015). DOI: 10.1002/2015GC005980

Note: The above post is reprinted from materials provided by Centre forArctic Gas Hydrate, Environment and Climate.

Fossil record disappears at different rates

February 10, 2016

Fossil record disappears-GeologyPage — These are the remains of a mammoth that was killed by humans near LaPrele Creek in Converse County, Wyo., about 13,000 years ago. New University of Wyoming research shows wide variation in the rates at which the bones of ancient animals in the Americas have been lost. Credit: Danny Walker and Wyoming State Archaeologist’s Office Photo

Statistical analysis by University of Wyoming researchers shows wide variation in the rates at which the bones of ancient animals in the Americas have been lost.

Considerably more of the fossil record of creatures such as mammoths, mastodons, camels, horses and ground sloths has been lost in what is now the continental United States and South America than in Alaska and areas near the Bering Strait. That variation complicates efforts to reconstruct the population sizes of those species across North and South America, conclude Professor Todd Surovell and graduate student Spencer Pelton in UW’s Department of Anthropology.

“While bone preservation in Arctic regions is aided by cold temperatures and the presence of permafrost, considerably more bone has been lost over time in regions farther south — in fact, at a faster rate than the sediments in which they were deposited have eroded,” Surovell says. “That means researchers must adjust for those differences as they estimate the numbers of these animals, many of which are now extinct, across the Americas.”

The research appears today in Biology Letters, a Royal Society journal that publishes short, highly innovative, cutting-edge research articles and opinion pieces accessible to scientists from across the biological sciences.

Surovell, whose past research has linked human hunting to the extinction of large mammals in the Americas, conducted the latest study by compiling radiocarbon dates of bones from animals of the Pleistocene era, which ended just under 12,000 years ago. He and Pelton also looked at the rates at which sedimentary deposits were lost over time.

While cautioning against applying their conclusions to the fossil record before or after the Pleistocene, the researchers suggest further research into the differences in the rates at which animal bones are lost from region to region.

Reference:
Todd A. Surovell, Spencer R. Pelton, Spatio-temporal variation in the preservation of ancient faunal remains. DOI: 10.1098/rsbl.2015.0823

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

Unrest and eruptions

February 10, 2016

Seismic, deformation, and gas activity (unrest) typically precedes volcanic eruptions. Tracking the changes of this activity with monitoring data makes it increasingly possible to successfully forecast eruptions from stratovolcanoes. However, this is not the case for monogenetic volcanoes (usually the result of a single magmatic pulse). Eruptions from these volcanoes tend to be small but are particularly difficult to anticipate since they occur at unexpected locations, and there is very limited instrumental monitoring data.

Many monogenetic volcanic fields occur in high-density, populated areas and tourist destinations (e.g. Canary Islands, Auckland City, Mexico City, Izu-Tobu volcanic field), and thus even a small eruption can have a major economic and societal impact. Helena Albert and colleagues have compiled historical accounts of felt seismicity and combined this information with petrological studies to propose a new conceptual model.

Albert and colleagues show that seismic crises occur about a year, two to three months, and a few weeks before eruption, and that these correspond to magmatic intrusions and mixing at mid-crustal depths, followed by magma transport to the surface. They propose a general model for these eruptions in which early dike intrusions in the crust do not erupt (e.g., stalled intrusions) and make small plumbing systems, but they probably are key in creating a thermal and rheological pathway for later dikes to be able to reach the surface.

These observations provide a conceptual framework for better anticipating monogenetic eruptions in similar settings and magmatic fluxes and should lead to improved strategies for mitigation of their associated hazards and risks.

Reference:
Years to weeks of seismic unrest and magmatic intrusions precede monogenetic eruptions
Helena Albert et al., Central Geophysical Observatory, Spanish Geographic Institute (IGN), 28014, Madrid, Spain. DOI: 10.1130/G37239.1

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

The Nullarbor Plain’s ancient forests revealed

February 10, 2016

The Nullarbor Plain-GeologyPage — Scientists examined fossilised pollen inside stalagmites to shed new light on the Nullarbor’s climate history

Rather than the treeless, limestone expanse we know today, the Plain was flush with gum and eucalyptus trees, banksias and other flowering plants now confined to Australia’s east coast.

Scientists at the University of Melbourne used new techniques to date fossilised pollen and reveal the Plain’s ‘big wet’ — a dramatic transformation in climate that occurred around five million years ago.

The finding sheds new light on the environmental history of the Nullarbor, a former seabed that was lifted above the sea 14 million years ago.

“The Nullarbor region had a relatively dry climate until five million years ago, but then the vegetation suddenly changed,” said palaeoclimate scientist Dr Kale Sniderman.

“In just 100,000 years, it became a forest of gums and banksias, which suggests a rainfall of two or up to four times higher than today.”

The Nullarbor Plain — an area covering 200,000 km2 bordering the Great Australian Bight between South and Western Australia — is today a treeless saltbush shrubland and the largest exposure of limestone in the world.

It receives an average of 250 mm of rain each year, but before five million years ago the rainfall was approximately 480mm, Dr Sniderman said.

During the ‘big wet’ between five and 3.5 million years ago precipitation rose to an estimated 1220mm.

Investigating the climate history of Australia’s desert regions is traditionally difficult for scientists, given the scarcity of fossils and the difficulty in accurately dating them.

This research successfully employed new methods of dating and analysis, by focusing on the dating of Nullarbor speleothems (stalagmites, stalactites and flowstones).

Until now, it has been impossible to date speleothems more than about 500,000 years old.

Paper co-author Professor Jon Woodhead, also from the University’s School of Earth Sciences, has spent the past decade perfecting methods of dating these old samples, and can now date speleothems of any age.

Dr Sniderman was then able to dissolve Professor Woodhead’s dated samples to examine ancient pollen trapped within them.

“Most didn’t contain any pollen, which isn’t surprising since many speleothems grew in caves that had no openings to the surface,” Dr Sniderman said.

“But some did contain fossil pollen, which revealed the nature of the vegetation growing at those times.

“Through that we’ve been able to develop a new understanding of the history of the Nullarbor’s climate.”

Prof Woodhead said the research showed there was much more to the Nullarbor than its iconic landform.

“It is also home to a scientific treasure trove of palaeoclimate information that has potential global significance,” he said.

The research has been published in the latest edition of the journal, Proceedings of National Academy of Sciences.

Reference:
J. M. Kale Sniderman, Jon D. Woodhead, John Hellstrom, Gregory J. Jordan, Russell N. Drysdale, Jonathan J. Tyler, and Nicholas Porch. Pliocene reversal of late Neogene aridification. PNAS, 2016 DOI: 10.1073/pnas.1520188113

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

Mysterious Menominee crack is unusual geological pop-up feature

February 10, 2016

Mysterious Menominee-GeologyPage — A photo taken in 2010 of the Menominee Crack, a ‘pop-up’ geological feature. Credit: Wayne Pennington/ Michigan Technological University

Seismologists studying a massive crack in the ground that appeared north of Menominee, Michigan in 2010 now think they know what the unusual feature might be. But as they explain in their study published this week in the journal Seismological Research Letters, there are still some mysteries to clear up about the strange geological occurrence in the rural Michigan woods.

A team of scientists led by Wayne Pennington of Michigan Technological University says that the crack, which lies along the crest of a two-meter-high ridge that appeared at the same time, is probably a “pop-up” feature. Pop-ups occur in places where shallowly-buried rock layers spring upward after having been weighed down by rock or ice. Pop-ups–sometimes called “A-tents” for their shape–may develop in places where the earth rebounds upward after an overlying glacier shrinks away, or when rock overburden is removed in a quarry.

However, the last glaciers retreated from Menominee 11,000 years ago–and there isn’t any quarrying in the area.

“One of our reasons for publishing this was that in our search of the literature we could find no other mention of modern pop-ups that didn’t occur at something like the base of a quarry, where people had removed massive amounts of rock earlier,” Pennington explained. “As far as we can tell, this is a one-of-a-kind event.”

Residents near Menominee heard a loud noise and shaking in the early morning of October 4, 2010, and soon discovered the crack when they went into the nearby woods to clean up the debris left from removing a big double-trunked white pine tree a few days earlier. The crack split the ground for 110 meters, and was as deep as 1.7 meters in some places. Tree trunks tilted at precarious angles on either side of the fracture.

Pennington went to visit the site on his way back home from a scientific conference, he recalled. He paced off some measurements in his dress shoes and collected some GPS data with his phone. “I was completely blown away by it, because it wasn’t what I was expecting when I saw it,” he recalled. “It wasn’t like anything I had seen before.”

Although the crack was the most dramatic feature, Pennington was intrigued by the new ridge underneath it. “I kept trying to think of ways that there could have been an uplift from a thrusting earthquake or something, but anything like that requires such a huge amount of displacement in order to produce that amount of crustal shortening, that nothing made sense.”

He shared the photos and data with his colleagues, until Stanford University geophysicist Norm Sleep pointed out that the feature formed from a shallow-buried layer of limestone, and looked like a pop-up. “This made perfect sense to us,” Pennington said, “except for what caused it. And that then became the puzzle.”

The researchers needed to get a better look at the rock underneath the ridge to confirm that it was a pop-up, so they turned to a technique called seismic refraction. The technique measures the speed of seismic waves as they travel within layers of the earth, as determined at different distances from the seismic source. In this case, the seismologists used a sledgehammer to strike a large metal ball lying on the ground, and captured the resulting seismic waves.

In broken rock, the waves travel faster as they move parallel to cracks in the rock, and slower when they move perpendicular to the cracks and have to travel across the fractures. The scientists found a pattern of refraction speeds that seemed to be consistent with the intense bending and then fracturing of the brittle limestone of a pop-up feature.

But what caused the pop-up to…pop-up? Without the usual suspects in play, Pennington and his colleagues had to do a little detective work. The limestone in the area may have been stressed almost to the point of cracking when the last glaciers retreated, they say. The recent removal of the double-trunked pine, which may have weighed as much as 2000 kilograms–over two tons–could have been the final straw, allowing the rock to bend upward when that weight was removed.

“There’s a 60% chance that this explanation we provide is the right one,” Pennington noted. “But since we haven’t seen this kind of thing elsewhere, and the tree is such a small effect, we wonder if there might be something else.”

The seismologists studied aerial photos of the region to see how soil has been removed in the past 50 years from road work and a re-design of the area’s drainage system. These changes might have channeled more rainwater below the surface, potentially weakening the rock as it froze and thawed, the scientists suggest.

Pennington said “no one should be losing sleep” over the strange feature, which technically counted as the first natural earthquake in Michigan’s Upper Peninsula–measuring less than magnitude 1.

“It may be a one-of-a kind phenomenon,” he said. “But if it happens again, we’ll be all over it, trying to figure it out.”

Reference:
Pennington et al. Menominee Crack: Bedrock Pop-Up Event near Menominee, Michigan. Seismological Research Letters, 2016 DOI: 10.1785/0220150161

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

Fossil discovery: Extraordinary ‘big-mouthed’ fish from Cretaceous Period

February 9, 2016

Fossil discovery-GeologyPage — An international team of scientists have discovered two new plankton-eating fossil fish species, of the genus called Rhinconichthys, which lived 92 million years ago in the oceans of the Cretaceous Period. Credit: Image by Robert Nicholls

An international team of scientists have discovered two new plankton-eating fossil fish species of the genus called Rhinconichthys (Rink-O-nik-thees) from the oceans of the Cretaceous Period, about 92 million years ago, when dinosaurs roamed the planet.

One of the authors of the study, Kenshu Shimada, a paleobiologist at DePaul University, said Rhinconichthys are exceptionally rare, known previously by only one species from England. But a new skull from North America, discovered in Colorado along with the re-examination of another skull from Japan have tripled the number of species in the genus with a greatly expanded geographical range. According to Shimada, who played a key role in the study, these species have been named R. purgatoirensis and R. uyenoi, respectively.

“I was in a team that named Rhinconichthys in 2010, which was based on a single species from England, but we had no idea back then that the genus was so diverse and so globally distributed,” said Shimada.

The new study, “Highly specialized suspension-feeding bony fish Rhinconichthys (Actinopterygii: Pachycormiformes) from the mid-Cretaceous of the United States, England and Japan,” will appear in the forthcoming issue of the international scientific journal Cretaceous Research.

The research team includes scientists from government, museum, private sector and university careers. They include Bruce A. Schumacher from the United Sates Forest Service who discovered the new specimen. It also includes researchers, Jeff Liston from the National Museum of Scotland and Anthony Maltese from the Rocky Mountain Dinosaur Resource Center.

Rhinconichthys belongs to an extinct bony fish group called pachycormids, which contains the largest bony fish ever to have lived. The new study specifically focuses on highly elusive forms of this fish group that ate plankton.

Rhinconichthys was estimated to be more than 6.5 feet and fed on plankton. It had a highly unusual specialization for bony fish. According to Shimada, one pair of bones called hyomandibulae formed a massive oar-shaped lever to protrude and swing the jaws open extra wide, like a parachute, in order to receive more plankton-rich water into its mouth, similar to the way many sharks open their mouth.

A planktivorous diet, also called suspension-feeding, is known among some specialized aquatic vertebrates today, including the Blue Whale, Manta Ray and Whale Shark. The name Rhinconichthys means a fish like the Whale Shark, Rhincodon. Suspension-feeding in the dinosaur era is a new emerging area of research.

“Based on our new study, we now have three different species of Rhinconichthys from three separate regions of the globe, each represented by a single skull,” Shimada noted. “This tells just how little we still know about the biodiversity of organisms through Earth’s history. It’s really mindboggling.”

Reference:
Bruce A. Schumacher, Kenshu Shimada, Jeff Liston, Anthony Maltese. Highly specialized suspension-feeding bony fish Rhinconichthys (Actinopterygii: Pachycormiformes) from the mid-Cretaceous of the United States, England, and Japan. Cretaceous Research, 2016; 61: 71 DOI: 10.1016/j.cretres.2015.12.017

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

Researchers find that earthquakes on thrust faults can spread 10 times farther to a second nearby thrust fault than previously thought

February 9, 2016

Researchers find that earthquakes-GeologyPage — These are interferogram images of the earthquakes in Pakistan. Credit: UC Riverside

A team of researchers, including one from the University of California, Riverside, has discovered that earthquake ruptures can jump much further than previously thought, a finding that could have severe implications on the Los Angeles area and other regions in the world.

The scientists found that an earthquake that initiates on one thrust fault can spread 10 times farther than previously thought to a second nearby thrust fault, vastly expanding the possible range of “earthquake doublets,” or double earthquakes.

That could mean in areas such as Los Angeles, where there are multiple thrust faults close to each other, an earthquake from one thrust fault could spread to another fault, creating twice as much devastation.

One potential bad scenario involves a single earthquake spreading between the Puente Hills thrust fault, which runs under downtown Los Angeles, and the Sierra Madre thrust fault, located close to Pasadena, said Gareth Funning, an associate professor of earth sciences at UC Riverside, and a co-author of a paper published online today (Feb. 8, 2016) about the research in the journal Nature Geoscience.

Other susceptible areas where there are multiple thrust faults are in close proximity include the Ventura, Calif. area, the Middle East, particularly Tehran, Iran, and the front of the Himalayas, in countries such as Afghanistan, Pakistan, India and Nepal.

The researchers studied a 1997 earthquake in Pakistan, originally reported as a magnitude 7.1 event, showing that it was in fact composed of two ‘subevents’ — a magnitude 7.0 earthquake, that was followed 19 seconds later by a magnitude 6.8 event, located 50 kilometers (30 miles) to the southeast.

Funning considers the two earthquakes as subevents of one ‘mainshock,’ as opposed to the second earthquake being an aftershock, because they happened so close together in time and were so similar in size. There were many aftershocks in the following minutes and hours, but most of them were much smaller.

The scientists used satellite radar images, precise earthquake locations, modeling and back projection of seismic radiation to prove the seismic waves from the first subevent caused the second to initiate, effectively ‘jumping’ the 50 kilometer distance between the two. Scientists previously thought an earthquake could only leap up to five kilometers.

The finding has implications for seismic hazard forecasts developed by the United States Geological Survey. The current forecast model does not include the possibility of a similar double earthquake on the thrust faults in the Los Angeles area.

“This is another thing to worry about,” Funning said. “The probability of this happening in Los Angeles is probably pretty low, but it doesn’t mean it can’t happen.”

Funning started work on the paper about 12 years ago as a graduate student at the University of Oxford. He was the first to find the satellite data for the earthquakes in Pakistan, which occurred in a largely unpopulated area, and notice they occurred close together in space and time.

After dropping the work for several years, he, along with lead author Ed Nissen of the Colorado School of Mines, picked it up about three to four years ago, in part because of the possible implications for the Los Angeles area, which has a similar plate boundary, with similar faults, similar distances apart as the region in Pakistan where the 1997 earthquake doublet occurred.

Thrust faults happen when one layer of rock is pushed up over another, often older, layer of rock by compressional forces. Thrust faults came to the attention of Californians after the 1994 Northridge earthquake, about 20 miles northwest of Los Angeles, which occurred on a thrust fault.

Thrust faults are not as well understood by scientists as strike-slip faults, such as the San Andreas, in part because they are not as visible in the landscape, and do not preserve evidence for past earthquakes as well.

Video

Reference:
E. Nissen, J. R. Elliott, R. A. Sloan, T. J. Craig, G. J. Funning, A. Hutko, B. E. Parsons, T. J. Wright. Limitations of rupture forecasting exposed by instantaneously triggered earthquake doublet. Nature Geoscience, 2016; DOI: 10.1038/ngeo2653

Note: The above post is reprinted from materials provided by University of California – Riverside.

Researchers find new cause of strong earthquakes

February 9, 2016

Researchers find new-GeologyPage — Penn State researcher Christelle Wauthier led a study to investigate ties between two natural disasters occurring eight months apart in the Democratic Republic of Congo in 2002: an eruption of the Nyiragongo volcano (pictured), and a magnitude 6.2 earthquake. Credit: Christelle Wauthier / Penn State

A geologic event known as diking can cause strong earthquakes — with a magnitude between 6 and 7, according to an international research team.

Diking can occur all over the world but most often occurs in areas where the Earth’s tectonic plates are moving apart, such as Iceland, Hawaii and parts of Africa in the East African Rift System. As plates spread apart, magma from beneath the Earth’s surface rises into the space, forming vertical magma intrusions, known as dikes. The dike pushes on the surrounding rocks, creating strain.

“Diking is a known phenomenon, but it has not been observed by geophysical techniques often,” said Christelle Wauthier, assistant professor of geosciences, Penn State who led the study. “We know it’s linked with rift opening and it has implications on plate tectonics. Here, we see that it also could pose hazards to nearby communities.”

The team investigated ties between two natural disasters from 2002 in the Democratic Republic of the Congo, East African Rift System. On Jan. 17, the Nyiragongo volcano erupted, killing more than 100 people and leaving more than 100,000 people homeless. Eight months later a magnitude 6.2 earthquake struck the town of Kalehe, which is 12 miles from the Nyiragongo volcano. Several people died during the Oct. 24 earthquake, and Kalehe was inundated with water from nearby Lake Kivu.

“The Kalehe earthquake was the largest recorded in the Lake Kivu area, and we wanted to find out whether it was coincidence that, eight months before the earthquake, Nyiragongo erupted,” said Wauthier.

The researchers used a remote sensing technique, Interferometric Synthetic Aperture Radar, to measure changes to the Earth’s surface before and after both natural disasters.

“This technique produces ground surface deformation maps. Then, you can invert those deformation maps to find a source that could explain the observed deformation. For the deformation observed in January 2002, we found that the most likely explanation, or best-fitting model, was a 12-mile diking intrusion in between Nyiragongo and Kalehe,” said Wauthier.

The researchers used the same technique for the October 2002 magnitude 6.2 earthquake, analyzing seismicity in addition to ground-deformation changes. They found that there was a fault on the border of the East African Rift System that slipped, triggering the earthquake.

“We were able to identify the type of fault that slipped, and we also had the best-fitting model for the dike intrusion,” said Wauthier. “Knowing both of those, we performed a Coulomb stress-change analysis and found that the January 2002 dike could have induced the October 2002 earthquake.”

Coulomb stress-change analysis is a modeling technique that calculates the stress changes induced by a deformation source at potential receiver faults throughout a region. If the Coulomb stress changes are positive, it means that the source is bringing the receiver fault closer to failure — closer to slipping and generating an earthquake. This type of analysis is regularly applied to assess whether an earthquake in one region could trigger a secondary earthquake nearby.

The researchers hypothesized that the dike opening pushed outward against the adjacent rocks. These rocks became strained and passed stress to rocks adjacent to them, accumulating stress on rocks on a fault in the Kalehe area. The dike brought this fault closer to failure and, eight months later, a small stress perturbation could have triggered the start of the magnitude 6.2 earthquake.

“We’ve known that every time magma flows through the Earth’s crust, you create stress and generate seismicity,” said Wauthier. “But these are normally very low magnitude earthquakes. This study suggests that a diking event has the potential to lead to a large earthquake,” said Wauthier.

The researchers report their findings in the current issue of Geochemistry, Geophysics, Geosystems.

Collaborators include Benoit Smets, European Center for Geodynamics and Seismology, Vrije Universiteit Brussel and Royal Museum for Central Africa; and Derek Keir, University of Southampton.

The National Research Fund of Luxembourg, the Belgian Science Policy Office and the U.K. Natural Environment Research Council supported this research.

Reference:
C. Wauthier, B. Smets, D. Keir. Diking-induced moderate-magnitude earthquakes on a youthful rift border fault: The 2002 Nyiragongo-Kalehe sequence, D.R. Congo. Geochemistry, Geophysics, Geosystems, 2015; 16 (12): 4280 DOI: 10.1002/2015GC006110

Note: The above post is reprinted from materials provided by Penn State. The original item was written by Liam Jackson.

Petroleum reservoir simulation using super element method

February 6, 2016

Petroleum reservoir simulation-GeologyPage

The study conducted by researches of Kazan Federal University describes the theoretical framework and results of using a rapid three-dimensional super element model of oil field development.

Simulation of oil field development is traditionally performed using full-scale filtration models (Roxar Tempest More, S?hlumberger Eclipse, etc.) on ?omputational grids with a cell size of approximately several tens of meters horizontally and tens of centimeters vertically. Such models require specification of an excessive number of parameters, and in case of large fields, they contain millions of cells. This complicates their adaptation and makes it virtually impossible to use them for multivariant prediction calculations. To overcome these problems when optimizing the system of oil field development helps a super element modeling method.

Testing of the model on the real oil fields and comparison between the results from numerical simulation and the corresponding results obtained using the traditional models on small grids confirm the wide opportunities and prospects of the super element model for rapid calculations.

The model makes it possible to speed up the calculation of two-phase filtration in an oil reservoir by hundreds of times due to the use of large computational cells – super elements, the number of which corresponds to the number of wells in the field.

The super element model is able to describe arbitrarily oriented wellbores, hydraulic fractures, tectonic faults and geological bodies. In each individual case, this requires using auxiliary fine grids and solving the corresponding mathematical problems.

Accuracy of the numerical solution is ensured by a formulation of the problem in terms of the smooth mean fields of pressure and saturation with a selective refinement of the solution in the vicinity of the wells on independent detailed nested grids.

The model is implemented by an actual software system for maintenance and monitoring of oil field development, which helped build the super element models for the development of a number of fields in Kazakhstan and Russia.

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

Central Appalachia flatter due to mountaintop mining

February 6, 2016

Central Appalachia-GeologyPage — Years of blowing away mountain ridges in search of coal and depositing the excess rock in nearby valleys have dramatically flattened the landscape in parts of Central Appalachia. These maps show the elevation of West Virginia’s Mud River watershed before and after mountaintop mining became widespread. To see the impact on other West Virginia watersheds. Credi: Matthew Ross, Duke University.

Forty years of mountaintop coal mining have made parts of Central Appalachia 60 percent flatter than they were before excavation, says new research by Duke University.

The study, which compares pre- and post-mining topographic data in southern West Virginia, is the first to examine the regional impact of mountaintop mines on landscape topography and how the changes might influence water quality.

“There hasn’t been a large-scale assessment of just the simple full topographic impact of mountaintop mining, which occupies more than 10 percent of the land in the region we studied,” said Matthew Ross, an ecology PhD student and lead author on the study.

“[We found] the impact is deep and extensive,” Ross said. “It is locally large and more wide-ranging than other forms of mining.” The study is published online in the journal Environmental Science and Technology.

In mountaintop mining, bedrock is blasted away to uncover coal seams below the surface. Excess rock is deposited in nearby valleys, creating what are called valley fills.

By comparing digitized topographic maps from West Virginia before mountaintop mining became extensive with elevation data collected by aircraft in 2010, the researchers found that the mines and valley fills could range anywhere from 10 to 200 meters deep. Across the region, the average slope of the land dropped by more than 10 degrees post-mining.

As part of the study, Ross collaborated with Duke University’s Data+ program to develop a web-based app that allows users to toggle between pre- and post-mining topographic maps in each watershed of the study. The app dramatically visualizes how the landscapes have been flattened by the transfer of rock from mountain peaks to mountain valleys.

“We tend to measure the impact of human activity based on the area it affects on a map, but mountaintop mining is penetrating much more deeply into the earth than other land use in the region like forestry, agriculture or urbanization,” said Emily Bernhardt, a professor of biology at Duke and co-author on the study. “The depth of these impacts is changing the way the geology, water, and vegetation interact in fundamental ways that are likely to persist far longer than other forms of land use.”

Of particular interest to the team is how the conversion from solid bedrock to porous valley fills changes the way water moves through the area, and whether this increases the likelihood that water will pick up alkaline mine pollutants.

“You go from having shallow soil that is between half a meter and two meters deep, to something that is like a soil that is a hundred meters deep. The way the water moves through those two different landscapes is really different,” Ross said. “There are valley fills that are the size of an Olympic swimming pool and then there are valley fills that are 10,000 Olympic swimming pools, so there is a huge range in the capacity they have to hold water.”

Ross says the data from this study indicates a correlation between the total volume of displaced rock and the concentration of certain pollutants, like selenium, downstream.

“We have data that the water quality impacts can last at least 30 years, but the geomorphology impacts might last thousands of years,” said Ross. “Once you have these flat plateaus, it sets up a whole new erosion machine and a whole new way that the landscape will be shaped into the future.”

Bernhardt said the findings should also inform planning in the region. “Even if we stopped mountaintop mining tomorrow, what kind of landscape is going to be left behind, and what are the constraints on what the landscape can be used for?”

Years of blowing away mountain ridges in search of coal and depositing the excess rock in nearby valleys have dramatically flattened the landscape in parts of Central Appalachia. This animation shows an elevation map of West Virginia’s Mud River watershed before and after mountaintop mining became widespread. Credit: Matthew Ross, Duke University.

Reference:
“Deep Impact: Effects of Mountaintop Mining on Surface Topography, Bedrock Structure, and Downstream Waters,” Matthew R. V. Ross, Brian L. McGlynn, Emily S. Bernhardt. Environmental Science and Technology, January 22, 2016. DOI: 10.1021/acs.est.5b04532

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

The Earth Shook, but It Wasn’t an Earthquake

February 6, 2016

The Earth Shook-GeologyPage — A seismic station near Hammonton, N.J., picked up eight sonic booms on Jan. 28, starting around 1:20pm. Top (red) line shows low-frequency sound, below human hearing range. Second (black) line shows coinciding bursts of air pressure. Bottom three lines show ground shaking at different frequencies. The infrasound and seismic signals might have lasted about 10 seconds each, producing 6-8 seconds of shaking felt by people. Graphic courtesy of Won-Young Kim, Lamont Cooperative Seismic Network

Last Thursday, thousands of people from southern New Jersey to Long Island and coastal Connecticut felt the earth tremble. Between 1:20 pm and 2:40 pm, dishes, desks and buildings shook for up to 20 seconds—in some locations, several times. With everyone thinking earthquake, Twitter and Facebook lit up; news reporters scrambled; calls poured into police, the U.S. Geological Survey, and Columbia University’s Lamont-Doherty Earth Observatory, which maintains the region’s network of 50-some seismographic stations.

The U.S. Northeast sees dozens of quakes each year, most too small to feel. One of the biggest, a 2011 magnitude 5.8 tremor in Virginia, cracked scattered buildings including the Washington Monument—but even that was minor compared to historic quakes in California and elsewhere. The most recent was on Jan. 16, 2016, near Martinsburg, West Virginia, felt some 28 miles from its epicenter, but harmless. Given the breadth of reports, Thursday’s event initially looked big.

But seismometers registered no obvious ground movement. Won-Young Kim, head of the seismic network, quickly concluded that the source was not nature, but man. “In this region, when a lot of people report shaking, and there’s no comparable signal in the ground, you suspect a sonic boom,” he said. Specifically, a military jet breaking the sound barrier. The USGS quickly concurred, saying it had registered at least nine sonic booms. A little after 4 p.m., the U.S. Navy fessed up: Two fighter jets, a stealth F-35C and an F-18, had been conducting what it described as “routine” supersonic test flights off the coast. The media and emergency responders signed off on the story, and went back to whatever else they were doing.

Sonic booms are shock waves created as an aircraft surpasses the speed of sound, about 767 miles per hour. Supersonic military aircraft fly almost daily over the ocean, but booms rarely reach land, because shock waves generally travel downward in a narrow path. However, waves may spread much farther in certain cold-weather conditions. One explanation: When earth’s surface is cold, a layer of warmer air may build around the altitude that jets fly, and this layer deflects waves far to the side. Prevailing winter winds could also help push shock waves toward land. The waves deliver sound, and a burst of air pressure. People may hear a rumble or crack, but often the frequencies are in the very low-frequency infrasound range, below the perception of the human ear. In any case, if the waves are strong enough, they can cause earthquake-like shaking on the surface.

The East Coast boom issue dates to at least the winter of 1977-78, when similar shock waves hit many communities. The military denied responsibility, so rumors and speculations abounded: secret weapons tests; operations of spacecraft or submarines; giant methane bubbles erupting from the seafloor. Lamont seismologists hypothesized that small earthquakes were emanating from areas lacking adequate instrumentation; or oil companies might be igniting explosives offshore to explore for petroleum reserves. David Simpson, then Lamont’s head of seismology, set out an array of portable seismometers near Cape May, N.J., where many complaints came from, but got little useful information. “This was a big mystery that lasted for months,” said Lamont seismologist emeritus John Armbruster. “It shows the frustrations of dealing with a culture of military secrecy.”

Members of Congress, alarmed about the repeated episodes, demanded an investigation from then president Jimmy Carter, and Carter turned it over to the Office of Naval Research. Carter’s science advisor was a Lamont alumnus: the influential seismologist and oceanographer Frank Press. Press might have had something to do with the eventual resolution. In any case, after months of research, the government finally issued a report admitting that its own jets were to blame.

That has not stopped people from being scared by the booms; earthquake alarms linked to them are still a regular event (though the extent of the more recent ones may be due as much to the ubiquity and instantaneous nature of social media as to the weather or the actual number of flights). From Maryland to New Jersey, a series of booms sparked concern along the coast in October 2012, and again in February 2014. Two days before the most recent event, residents of Charleston, S.C., were also frightened by tremors. At least in these events, the military has been quick to step up and take responsibility.

Because the shock waves travel through the air, not the ground, conventional seismic instruments don’t generally pick them up—that is, unless they strike hard enough to cause buildings or ground to shake. Even then, the motion might not be picked up unless there happens to be an instrument close by, because compared to a real earthquake, the effects are relatively weak and local.

That said, the latest booms were relatively powerful. Kim says he measured eight. A conventional seismometer near the southern New Jersey town of Hammonton registered a series of ground vibrations. The Lamont lab is still analyzing data, but other seismometers in New Jersey and Long Island may also have picked up ground motion.

A new set of seismic stations installed since 2013 also have air-pressure sensors, and detectors for infrasound, which can clearly detect sonic booms (along with hopefully less common events such as nuclear bomb tests or large meteors streaking through the air). At Hammonton and at least five other stations in New Jersey and Connecticut, infrasound detectors picked up acoustic waves. An air-pressure sensor at Hammonton also jumped at the same time. “Some things, we don’t hear, but they still have energy,” said Kim.

Note: The above post is reprinted from materials provided by Earth Institute, Columbia University. The original article was written by Kevin Krajick.

Ancient wildebeest-like animal shared ‘bizarre’ feature with dinosaur

February 5, 2016

Ancient wildebeest-GeologyPage — An artist’s interpretation of Rusingoryx atopocranion on the Late Pleistocene plains of what is now Rusinga Island, Lake Victoria. Scientists have found many links between Rusingoryx and hadrosaur dinosaurs — particularly the large, hollow dome that makes a crest on top of the animal’s skull. Credit: Todd S. Marshall

By poring over the fossilized skulls of ancient wildebeest-like animals (Rusingoryx atopocranion) unearthed on Kenya’s Rusinga Island, researchers have discovered that the little-known hoofed mammals had a very unusual, trumpet-like nasal passage similar only to the nasal crests of lambeosaurine hadrosaur dinosaurs. The findings reported in the Cell Press journal Current Biology on February 4 offer “a spectacular example” of convergent evolution between two very distantly related taxa and across tens of millions of years, the researchers say.

“The nasal dome is a completely new structure for mammals– it doesn’t look like anything you could see in an animal that’s alive today,” says Haley O’Brien of Ohio University, Athens. “The closest example would be hadrosaur dinosaurs with half-circle shaped crests that enclose the nasal passages themselves.”

This evolutionary convergence may be explained by similarities in the way Rusingoryx and hadrosaurs lived. In fact, hadrosaurs are sometimes referred to as the “cows of the Cretaceous.”

For Tyler Faith of the University of Queensland, one of the study’s corresponding authors, it all started in 2009. He and his colleagues were working on a field program in the Lake Victoria region when other scientists directed them to a site they called Bovid Hill. The hill had been so named because of an abundance of fossil Bovidae, the group including antelopes and buffaloes, eroding from its surface.

“After several years of collecting fossils from Bovid Hill, it became very clear that most of the fossils belonged to the poorly known species Rusingoryx atopocranion, described from the same site in 1983, and that we may be dealing with an entire herd that was somehow wiped out and buried at the site,” Faith says.

The researchers also uncovered stone tools and butchered bone, raising the possibility that early modern humans had something to do with the peculiar concentration of Rusingoryx skeletons. In 2011, study co-author Kirsten Jenkins of the University of Minnesota took charge of excavations, hoping to find more complete fossils and to establish why so many skeletons had ended up in that spot. Along the way, she found several intact skulls.

“I was astonished to see that [the skulls] looked unlike any antelope that I had ever seen–the only thing more surprising would have been fossil zebras with horns growing from their heads!” Faith says. “The anatomy was clearly remarkable.”

Faith and O’Brien later decided to explore the anatomy further in six skulls representing Rusingoryx juveniles and adults. The similarity to hadrosaurs was immediately clear to the researchers when they opened CT scan files revealing the inner structures of those bones.

“We were expecting the inside of the dome to have something closer to normal mammalian anatomy, but once we took a look at the CT scans, we were pretty shocked,” O’Brien says.

At first, the researchers thought the hollow nasal dome might have had something to do with thermoregulation. Now, based on their anatomical investigations together with acoustical modeling, they think the trumpet-like nasal tube may have allowed Rusingoryx to deepen its normal vocal calls. In fact, their calculations suggest that the animals might have been able to call at levels very close to infrasound, such that other animals may not have been able to hear individuals in the herd calling back and forth to each other.

Both Rusingoryx and hadrosaur dinosaurs are thought to have been highly social, O’Brien explains. They might have communicated with each other across fairly large distances.

“Vocalizations can alert predators, and moving their calls into a new frequency could have made communication safer,” she says. “On top of this, we know that [both] Rusingoryx and hadrosaurs were consummate herbivores, each having their own highly specialized teeth. Their respective, remarkable dental specializations may have initiated changes in the lower jaw and cheek bones that ultimately led to the type of modification we see in the derived, crest-bearing forms.”

The researchers say they will continue to explore the developmental shifts required to produce the animals’ bizarre morphology. They’d also like to understand what ultimately led the once-thriving Rusingoryx to disappear.

Reference:
Current Biology, O’Brien et al.: “Unexpected Convergent Evolution of Nasal Domes between Pleistocene Bovids and Cretaceous Hadrosaur Dinosaurs” DOI: 10.1016/j.cub.2015.12.050

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

Can slow creep along thrust faults help forecast megaquakes?

February 5, 2016

Can slow creep along thrust-GeologyPage — Diagram showing the edge of the continental plate on which the island of Japan sits (green). At the Japan Trench (right edge), the Pacific Plate (orange) pushes under the wedge-shaped Japanese plate, driving west and downward in quiet slips at a rate of about 8 cm/year. Some places (locked areas) get stuck, however, with small locked areas generating repeated small quakes and larger locked areas generating larger quakes. The new study found that an increase in the frequency of these small off-shore earthquakes presaged larger quakes, including the 2011 Tohoku-oki quake. Credit: Image courtesy of University of California, Berkeley

In Japan and areas like the Pacific Northwest where megathrust earthquakes are common, scientists may be able to better forecast large quakes based on periodic increases and decreases in the rate of slow, quiet slipping along the fault.

This hope comes from a new study by Japanese and UC Berkeley seismologists, looking at the more than 1,000-kilimeter-long fault off northeast Japan where the devastating 2011 Tohoku-oki earthquake originated, generating a tsunami that killed thousands. There, the Pacific Plate is trundling under the Japan plate, not only causing megaquakes like the magnitude 9 in 2011, but giving rise to a chain of Japanese volcanoes.

The scientists studied 28 years of earthquake measurements, looking at quakes of magnitude 2.5 or greater between 1984 and 2011. They discovered 1,515 locations off the coast of Japan where small repeating earthquakes happen — 6,126 quakes in all.

According to co-author Robert Nadeau, a UC Berkeley seismologist and a fellow with the Berkeley Institute for Data Science (BIDS), an analysis of these quakes found that larger, more destructive earthquakes — those of magnitude 5 or greater — occurred much more frequently when the periodic slow-slip was fastest. This included the great Tohoku-oki earthquake, which also devastated a nuclear power plant and led to widespread radioactive contamination.

“The persistence of the periodic pattern over time may help us refine earthquake probabilities in the future by taking into account the times of expected slow-slip pulses,” he said. “Right now, seismologists gives forecasts on a 30-year time frame and assume nothing is changing on a shorter time scale. Our study points out that things are changing, and in a periodic way. So it may be possible for scientists to give shorter time ranges of greater and lower probability for larger events to happen.”

The research was led by Naoki Uchida, a seismologist at Tohoku University, and included UC Berkeley seismologist Roland Burgmann, professor of earth and planetary science. They published their findings in the Jan. 29 issue of Science.

Slip, Nadeau said, is the relative motion between two sides of a fault, sometimes but not always resulting in ground shaking. So-called slow-slip or creep is what scientists call “fault slip,” which happens quietly, without generating shaking, not even microquakes or faint tremors.

Regions of a fault that slip quietly are considered to be weak or un-coupled. But within these un-coupled regions of rock underground there are variously-sized patches of fault that are much stronger, or coupled. These patches resist the quiet slip happening around them, only slipping when the pushing and pulling from the surrounding quiet slip stresses them to their breaking point and they “snap” in an earthquake.

“There is a relationship, which we showed here in California, between the time between ‘snaps’ on the small, strong patches where earthquakes happen and how much slip took place on the quiet fault surrounding them,” Nadeau said. “Using this relationship for thousands of repeating earthquakes in Japan, we were able to map out the evolution of slow-slip on the megathrust. Then, by studying the pattern of this evolution, we discovered the periodic nature of the megathrust slow-slip and its relationship to larger earthquakes.”

Nadeau and the late UC Berkeley seismologist Thomas McEvilly showed 12 years ago that periodic slow slip occurred all along the San Andreas Fault, from Parkfield to Loma Prieta, Calif. In 2009 the group also observed deeper, transient and periodic slow-slip on the San Andreas — this time associated with faint shaking called tremor — and that it was linked with two larger quakes occurring in 2003 and 2004 at San Simeon and Parkfield, Calif. respectively.

“The phenomenon we found in Japan may not be limited to megathrust zones,” he said. “Our 2004 study, more limited in scope than this one, showed a similar periodic slip process and an association between larger quakes — those of magnitude 3.5 or greater — and repeating earthquakes along the 170 km stretch of San Andreas Fault that we studied.”

Reference:
N. Uchida, T. Iinuma, R. M. Nadeau, R. Burgmann, R. Hino. Periodic slow slip triggers megathrust zone earthquakes in northeastern Japan. Science, 2016; 351 (6272): 488 DOI: 10.1126/science.aad3108

Note: The above post is reprinted from materials provided by University of California, Berkeley. The original item was written by Robert Sanders.

Modern microbial ecosystems provide window to early life on Earth

February 5, 2016

Modern microbial ecosystems-GeologyPage — Elongate nested stromatolites, previously unknown in Hamelin Pool. Credit: Pamela Reid, Ph.D., UM Rosenstiel School of Marine and Atmospheric Science

New research from a University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science-led science team provides new insight into one of the world’s most diverse and extensive ecosystems of living microbes. The study offers a new perspective on the growth and structure of rare, microbial reefs, called stromatolites, which are a window into the emergence and evolution of life on Earth.

The international research team spent three years collecting data to map one of the few living stromatolite communities in the world, located in Shark Bay in Western Australia. The map of stromatolites produced by the scientists from an area in Shark Bay, called Hamelin Pool, revealed eight distinct “stromatolite provinces,” each characterized by distinct morphological structures, many of which were previously unknown. The results altered previous growth models for Shark Bay stromatolites and documented the importance of mineral precipitation in the formation of the stromatolite framework, a feature shared with Precambrian stromatolites that date back three billion years.

Stromatolites are buildups of limestone, similar to coral reefs, but formed by microbial mats. The activities of the microorganisms, particularly cyanobacteria, result in accretion of grains and precipitation of cements. Fossilized remains of stromatolites hold ancient records of early life for 75 percent of Earth’s history. Stromatolite-forming microbes generated the oxygen in the atmosphere that allowed the evolution of higher organisms, including humans.

“The stromatolites in Shark Bay are a spectacular living laboratory that should be the best studied microbial system in the world,” said UM Rosenstiel School Professor of Marine Geosciences Pamela Reid, a co-author of the study.

Despite their abundance on early Earth, stromatolites are rare in the modern world and are not well understood. Modern stomatolites, such as those in Shark Bay in Western Australia, develop in extreme, high saline environments where animal grazing and competition with organisms such as corals and seaweeds are scarce.

“The time to study Shark Bay stromatolites is now as they are vulnerable to rising sea levels in the coming decades” said lead author Erica Suosaari, UM Rosenstiel School alumna and current research fellow. “Continued monitoring and detailed studies of the Shark Bay World Heritage site will be critical for management and conservation of this unique landscape, and will advance our understanding of early Earth.”

The new findings on morphological diversity, microbial communities, and mineral precipitation in living stromatolites in Shark Bay indicate the importance of this system as a window into early Earth, providing a basis for reconstructing ancient environments and understanding how microbial communities interacted with these environments.

Reference:
E. P. Suosaari, R. P. Reid, P. E. Playford, J. S. Foster, J. F. Stolz, G. Casaburi, P. D. Hagan, V. Chirayath, I. G. Macintyre, N. J. Planavsky, G. P. Eberli. New multi-scale perspectives on the stromatolites of Shark Bay, Western Australia. Scientific Reports, 2016; 6: 20557 DOI: 10.1038/srep20557

Note: The above post is reprinted from materials provided by University of Miami Rosenstiel School of Marine & Atmospheric Science.

Long-term global warming not driven naturally

February 5, 2016

Long-term global warming-GeologyPage — The Earth’s thin atmosphere as viewed from space. A new study from NASA and Duke finds natural cycles alone aren’t sufficient to explain warming trends observed over the last century. Credit: NASA

By examining how Earth cools itself back down after a period of natural warming, a study by scientists at Duke University and NASA’s Jet Propulsion Laboratory confirms that global temperature does not rise or fall chaotically in the long run. Unless pushed by outside forces, temperature should remain stable.

The new evidence may finally help put the chill on skeptics’ belief that long-term global warming occurs in an unpredictable manner, independently of external drivers such as human impacts.

“This underscores that large, sustained changes in global temperature like those observed over the last century require drivers such as increased greenhouse gas concentrations,” said lead author Patrick Brown, a PhD student at Duke’s Nicholas School of the Environment. Natural climate cycles alone are insufficient to explain such changes, he said.

Brown and his colleagues published their peer-reviewed research Feb. 1 in the Journal of Climate.

Using global climate models and NASA satellite observations of Earth’s energy budget from the last 15 years, the study finds that a warming Earth is able to restore its temperature equilibrium through complex and seemingly paradoxical changes in the atmosphere and the way radiative heat is transported.

Scientists have long attributed this stabilization to a phenomenon known as the Planck Response, a large increase in infrared energy that Earth emits as it warms. Acting as a safety valve of sorts, this response creates a negative radiative feedback that allows more of the accumulating heat to be released into space through the top of the atmosphere.

The new Duke-NASA research, however, shows it’s not as simple as that.

“Our analysis confirmed that the Planck Response plays a dominant role in restoring global temperature stability, but to our surprise we found that it tends to be overwhelmed locally by heat-trapping positive energy feedbacks related to changes in clouds, water vapor, and snow and ice,” Brown said. “This initially suggested that the climate system might be able to create large, sustained changes in temperature all by itself.”

A more detailed investigation of the satellite observations and climate models helped the researchers finally reconcile what was happening globally versus locally.

“While global temperature tends to be stable due to the Planck Response, there are other important, previously less appreciated, mechanisms at work too,” said Wenhong Li, assistant professor of climate at Duke. These other mechanisms include a net release of energy over regions that are cooler during a natural, unforced warming event. And there can be a transport of energy from the tropical Pacific to continental and polar regions where the Planck Response overwhelms positive, heat-trapping local effects.

“This emphasizes the importance of large-scale energy transport and atmospheric circulation changes in restoring Earth’s global temperature equilibrium after a natural, unforced warming event,” Li said.

Reference:
Patrick T. Brown, Wenhong Li, Jonathan H. Jiang, Hui Su. Unforced Surface Air Temperature Variability and Its Contrasting Relationship with the Atmospheric TOA Energy Flux at Local and Global Spatial Scales. Journal of Climate, February 2016 DOI: 10.1175/JCLI-D-15-0384

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

Discovery of ‘Jurassic butterflies’

February 4, 2016

IU paleobotanist David Dilcher is a co-author on a study out today in the Proceedings of the Royal Society: B that identifies a Jurassic age insect whose behavior and appearance closely mimic a butterfly — but whose emergence on Earth predates the butterfly by about 40 million years.

Dilcher — who made international headlines last year for his role in discovering the mythical “first flower” — said these proverbial “first butterflies” survived in a similar manner as their modern sister insects by visiting plants with “flower-like” reproductive organs producing nectar and pollen.

The butterfly-like insects, which went on to evolve into a different form of insect from the modern butterfly, is an extinct “lacewing” of the genus kalligrammatid called Oregramma illecebrosa. Another genus of this insect — of the order Neuroptera — survives into our modern era, and are commonly known as fishflies, owlflies or snakeflies.

The discovery of the insect was made possible by the examination of well-preserved fossils recently recovered from ancient lake deposits in northeastern China and eastern Kazakhstan. The study was led by Conrad Labandeira, a curator at the Smithsonian Institution’s National Museum of Natural History, and Dong Ren of Capital Normal University in Beijing, China, where the fossils are housed.

“Poor preservation of lacewing fossils had always stymied attempts to conduct a detailed morphological and ecological examination of the kalligrammatid,” Dilcher said. “Upon examining these new fossils, however, we’ve unraveled a surprisingly wide array of physical and ecological similarities between the fossil species and modern butterflies, which shared a common ancestor 320 million years ago. ”

The species are an example of convergent evolution, Dilcher explains, where two distantly related animals develop similar characteristics independently.

As a paleobotanist, Dilcher contributed to the study by describing these ecological similarities, including the insect’s relationship to a type of fossilized plant found in the same region of China as the insect fossils. An extinct order of seed plants called bennettitales, these plants first appeared about 250 million years ago during the Triassic period, surviving for nearly 200 million years until the end of the late Cretaceous period.

Based on their examination, which drew in part upon microscopically small clues such as the fossilized remains of food and pollen trapped in the mouthparts of the insects, Dilcher and colleagues concluded kalligrammatid fed upon bennettitales using a long tongue to probe nectar deep within the plant. The insects also possessed hairy legs that allowed for carrying pollen from the male flower-like reproductive organs of one plant to the flower-like female reproductive organs of another.

Eventually, this system of pollination by long-tongued lacewings traveling between plants with exposed reproductive parts — called gymnosperms — gave way to more familiar system of insect pollinators and modern flowers, or angiosperms, in which the reproductive parts of the plants are contained with a protective seed.

However, another evolutionary innovation found in the ancient lacewing fossils’ wings remained remarkably unchanged over the course of millennia: so-called “eye spots.”

This unique pattern on the wings, arising over 200 million years ago, is nearly identical to markings on the modern owl butterfly. To this day, owl butterflies use these circular marks as a defense mechanism against predators, which mistake the spots as the eyes of a larger, more threatening animal.

Evolution is a great innovator, Dilcher said. But at the same time: “if it worked once, why not try it again.”

This work was supported in part by the National Basic Research Program of China, National Science Foundation of China, National Institutes of Health and Swedish National Space Board.

Reference:
Conrad C. Labandeira, Qiang Yang, Jorge A. Santiago-Blay, Carol L. Hotton, Antónia Monteiro, Yong-Jie Wang, Yulia Goreva, ChungKun Shih, Sandra Siljeström, Tim R. Rose, David L. Dilcher, Dong Ren. The evolutionary convergence of mid-Mesozoic lacewings and Cenozoic butterflies. Proceedings of the Royal Society B: Biological Sciences, 2016; 283 (1824): 20152893 DOI: 10.1098/rspb.2015.2893

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

Research may explain mysterious deep earthquakes in subduction zones

February 4, 2016

Research may explain mysterious-GeologyPage — The mineral lawsonite undergoes brittle failure at high temperature and pressure, as evidenced by the cracks seen in the sample above. That brittleness could trigger earthquakes in subduction zones where lawsonite is present. Credit: Hirth Lab / Brown University

Geologists from Brown University may have finally explained what triggers certain earthquakes that occur deep beneath the Earth’s surface in subduction zones, regions where one tectonic plate slides beneath another.

Subduction zones are some of the most seismically active areas on earth. Earthquakes in these spots that occur close to the surface can be devastating, like the one that struck Japan in 2011 triggering the Fukushima nuclear disaster. But quakes also occur commonly in the subducting crust as it pushes deep below the surface — at depths between 70 and 300 kilometers. These quakes, known as intermediate depth earthquakes, tend to be less damaging, but can still rattle buildings.

Intermediate depth quakes have long been something of a mystery to geologists.

“They’re enigmatic because the pressures are so high at that depth that the normal process of frictional sliding associated with earthquakes is inhibited,” said Greg Hirth, professor of earth, environmental, and planetary sciences at Brown. “The forces required to get things to slip just aren’t there.”

But through a series of lab experiments, Hirth and postdoctoral researcher Keishi Okazaki have shown that as water escapes from a mineral called lawsonite at high temperatures and pressures, the mineral becomes prone to the kind of brittle failure required to trigger an earthquake.

“Keishi’s experiments were basically the first tests at conditions appropriate for where these earthquakes actually happen in the earth,” Hirth said. “They’re really the first to show strong evidence for this dehydration embrittlement.”

The work will be published on February 4, 2016 in the journal Nature.

The experiments were done in what’s known as a Grigg’s apparatus. Okazaki placed samples of lawsonite in a cylinder and heated it up through the range of temperatures where water becomes unstable in lawsonite at high pressures. A piston then increased the pressure until the mineral began to deform. A tiny seismometer fixed to the apparatus detected sudden cracking in the lawsonite, a signal consistent with brittle failure.

Okazaki performed similar experiments using a different mineral, antigorite, which had been previously implicated as contributing to intermediate depth seismicity. In contrast to lawsonite, the antigorite failed more gradually — squishing rather than cracking — suggesting that antigorite does not play a role in these quakes.

“That’s one of the cool things about this,” Hirth said. “For 50 years everyone has assumed this is a process related to antigorite, despite the fact that there wasn’t much evidence for it. Now we have good experimental evidence of this dehydration process involving lawsonite.”

If lawsonite is indeed responsible for intermediate depth earthquakes, it would explain why such quakes are common in some subduction zones and not others. The formation of lawsonite requires high pressures and low temperatures. It is found in so-called “cold” subduction zones in which the suducting crust is older and therefore cooler in temperature. One such cold zone is found in northwest Japan. But conditions in “hot” subduction zones, like the Cascadia subduction zone off the coast of Washington state, aren’t conducive to the formation of lawsonite.

“In hot subduction zones, we have very few earthquakes in the subducting crust because we have no lawsonite,” Okazaki said. “But in cold subduction zones, we have lawsonite and we get these earthquakes.”

Ultimately, Hirth says research like this might help scientists to better understand why earthquakes happen at different places under different conditions.

“Trying to put into the context of all earthquakes how these processes are working might be important not just for understanding these strange types of earthquakes, but all earthquakes,” he said. “We don’t really understand a lot of the earthquake cycle. Predictability is the ultimate goal, but we’re still at the stage of thinking about what’s the recipe for different kinds of earthquakes. This appears to be one of those recipes.”

Reference:
Keishi Okazaki, Greg Hirth. Dehydration of lawsonite could directly trigger earthquakes in subducting oceanic crust. Nature, 2016; 530 (7588): 81 DOI: 10.1038/nature16501

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

Examining how terrestrial life’s building blocks may have first formed

February 4, 2016

Examining how terrestrial life's -GeologyPage

How did life begin? This is one of the most fundamental questions scientists puzzle over. To address it, they have to look not just back to the primordial Earth, but out into space. Now, scientists propose in the Journal of the American Chemical Society a new set of cosmic chemical reactions that could have contributed to the formation of life on our planet.

In the earliest minutes of the universe’s formation, from the energy of the big bang, hydrogen and helium formed. All of the other elements developed later in the hot interiors of new stars through the nucleochemical transformation of hydrogen into carbon, nitrogen, oxygen and others. A few million years later, supernova explosions in these stars flung elements into the surrounding space, forming water and hydrocarbons — compounds containing carbon and hydrogen such as methane and methanol. How more complex hydrocarbons evolved, including those that would eventually lead to life on Earth, remains an open question. Some astrophysicists propose that they all came from methane, which is composed of one carbon atom and four hydrogen atoms. But George Olah, Surya Prakash and colleagues have a different idea.

The researchers found that methanol, an abundant derivative of methane and better known on Earth as “wood alcohol,” is more reactive than methane itself. Through experiments and calculations, they demonstrated that methanol can give rise to varied hydrocarbons, their derivatives and products, including their ions (carbocations and carbanions), which have been observed in outer space. The scientists believe that when these hydrocarbons and other products were transported to Earth by asteroids or comets, they continued to evolve in the planet’s unique “goldilocks” conditions — liquid water, a breathable atmosphere and moderate temperatures — ultimately leading to life as we know it.

Reference:
George A. Olah, Thomas Mathew, G. K. Surya Prakash, Golam Rasul. Chemical Aspects of Astrophysically Observed Extraterrestrial Methanol, Hydrocarbon Derivatives, and Ions. Journal of the American Chemical Society, 2016; DOI: 10.1021/jacs.6b00343

Note: The above post is reprinted from materials provided by American Chemical Society.

Significant changes in rhino bone health over 50 million years

February 4, 2016

Significant changes in rhino-GeologyPage — Examples of each pathology category and the 1-4 rating system are given along with a short description. Credit: Stilson et al.

While rhino species evolved and increased in size over 50 million years, their bones may have strained to support their massive and active bodies, according to a study published February 3, 2016 in the open-access journal PLOS ONE by Kelsey Stilson from the University of Chicago and colleagues from the University of Oregon.

The signs of bone health issues, like bone degeneration, inflammation, and infection have been observed in the bones of many extinct North American and living African and Asian rhino species. Scientists are interested in exploring the relationship between animal size, bone health, and bone function in an evolutionary context. The authors of this study evaluated seven physical indicators of bone health, rhino mass, and bone structure in six extinct and one living rhinoceros species from 50 million years ago to the present. For context, non-avian dinosaurs went extinct around 65 million years ago.

The authors found the incidence of osteopathology increased from 28% to 65-80% as new species evolved. The only living species in this study, the black rhino, displayed 50% fewer osteopathologies than the more derived extinct taxa. The researchers also found that with increasing body mass, indicators of disease in the bones also significantly increased. The authors suggest these results may reflect a part of the complex system of adaptations in rhinos over millions of years, where increased mass, running, and/or increased life span are selected for, to the detriment of long-term bone health. The authors say this work has important implications for the future health of hoofed animals and possibly even humans.

Reference:
Kelsey T. Stilson, Samantha S. B. Hopkins, Edward Byrd Davis. Osteopathology in Rhinocerotidae from 50 Million Years to the Present. PLOS ONE, 2016; 11 (2): e0146221 DOI: 10.1371/journal.pone.0146221

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

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Examining how terrestrial life’s building blocks may have first formed

Significant changes in rhino bone health over 50 million years

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