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Geologists discover ancient buried canyon in South Tibet

This photo shows the Yarlung Tsangpo Valley close to the Tsangpo Gorge, where it is rather narrow and underlain by only about 250 meters of sediments. The mountains in the upper left corner belong to the Namche Barwa massif. Previously, scientists had suspected that the debris deposited by a glacier in the foreground was responsible for the formation of the steep Tsangpo Gorge — the new discoveries falsify this hypothesis. Credit: Ping Wang

A team of researchers from Caltech and the China Earthquake Administration has discovered an ancient, deep canyon buried along the Yarlung Tsangpo River in south Tibet, north of the eastern end of the Himalayas. The geologists say that the ancient canyon–thousands of feet deep in places–effectively rules out a popular model used to explain how the massive and picturesque gorges of the Himalayas became so steep, so fast.

“I was extremely surprised when my colleagues, Jing Liu-Zeng and Dirk Scherler, showed me the evidence for this canyon in southern Tibet,” says Jean-Philippe Avouac, the Earle C. Anthony Professor of Geology at Caltech. “When I first saw the data, I said, ‘Wow!’ It was amazing to see that the river once cut quite deeply into the Tibetan Plateau because it does not today. That was a big discovery, in my opinion.”

Geologists like Avouac and his colleagues, who are interested in tectonics–the study of the earth’s surface and the way it changes–can use tools such as GPS and seismology to study crustal deformation that is taking place today. But if they are interested in studying changes that occurred millions of years ago, such tools are not useful because the activity has already happened. In those cases, rivers become a main source of information because they leave behind geomorphic signatures that geologists can interrogate to learn about the way those rivers once interacted with the land–helping them to pin down when the land changed and by how much, for example.

“In tectonics, we are always trying to use rivers to say something about uplift,” Avouac says. “In this case, we used a paleocanyon that was carved by a river. It’s a nice example where by recovering the geometry of the bottom of the canyon, we were able to say how much the range has moved up and when it started moving.”

The team reports its findings in the current issue of Science.

Last year, civil engineers from the China Earthquake Administration collected cores by drilling into the valley floor at five locations along the Yarlung Tsangpo River. Shortly after, former Caltech graduate student Jing Liu-Zeng, who now works for that administration, returned to Caltech as a visiting associate and shared the core data with Avouac and Dirk Scherler, then a postdoc in Avouac’s group. Scherler had previously worked in the far western Himalayas, where the Indus River has cut deeply into the Tibetan Plateau, and immediately recognized that the new data suggested the presence of a paleocanyon.

Liu-Zeng and Scherler analyzed the core data and found that at several locations there were sedimentary conglomerates, rounded gravel and larger rocks cemented together, that are associated with flowing rivers, until a depth of 800 meters or so, at which point the record clearly indicated bedrock. This suggested that the river once carved deeply into the plateau.

To establish when the river switched from incising bedrock to depositing sediments, they measured two isotopes, beryllium-10 and aluminum-26, in the lowest sediment layer. The isotopes are produced when rocks and sediment are exposed to cosmic rays at the surface and decay at different rates once buried, and so allowed the geologists to determine that the paleocanyon started to fill with sediment about 2.5 million years ago.

The researchers’ reconstruction of the former valley floor showed that the slope of the river once increased gradually from the Gangetic Plain to the Tibetan Plateau, with no sudden changes, or knickpoints. Today, the river, like most others in the area, has a steep knickpoint where it meets the Himalayas, at a place known as the Namche Barwa massif. There, the uplift of the mountains is extremely rapid (on the order of 1 centimeter per year, whereas in other areas 5 millimeters per year is more typical) and the river drops by 2 kilometers in elevation as it flows through the famous Tsangpo Gorge, known by some as the Yarlung Tsangpo Grand Canyon because it is so deep and long.

Combining the depth and age of the paleocanyon with the geometry of the valley, the geologists surmised that the river existed in this location prior to about 3 million years ago, but at that time, it was not affected by the Himalayas. However, as the Indian and Eurasian plates continued to collide and the mountain range pushed northward, it began impinging on the river. Suddenly, about 2.5 million years ago, a rapidly uplifting section of the mountain range got in the river’s way, damming it, and the canyon subsequently filled with sediment.

“This is the time when the Namche Barwa massif started to rise, and the gorge developed,” says Scherler, one of two lead authors on the paper and now at the GFZ German Research Center for Geosciences in Potsdam, Germany.

That picture of the river and the Tibetan Plateau, which involves the river incising deeply into the plateau millions of years ago, differs quite a bit from the typically accepted geologic vision. Typically, geologists believe that when rivers start to incise into a plateau, they eat at the edges, slowly making their way into the plateau over time. However, the rivers flowing across the Himalayas all have strong knickpoints and have not incised much at all into the Tibetan Plateau. Therefore, the thought has been that the rapid uplift of the Himalayas has pushed the rivers back, effectively pinning them, so that they have not been able to make their way into the plateau. But that explanation does not work with the newly discovered paleocanyon.

The team’s new hypothesis also rules out a model that has been around for about 15 years, called tectonic aneurysm, which suggests that the rapid uplift seen at the Namche Barwa massif was triggered by intense river incision. In tectonic aneurysm, a river cuts down through the earth’s crust so fast that it causes the crust to heat up, making a nearby mountain range weaker and facilitating uplift.

The model is popular among geologists, and indeed Avouac himself published a modeling paper in 1996 that showed the viability of the mechanism. “But now we have discovered that the river was able to cut into the plateau way before the uplift happened,” Avouac says, “and this shows that the tectonic aneurysm model was actually not at work here. The rapid uplift is not a response to river incision.”

Reference:
P. Wang, D. Scherler, J. Liu-Zeng, J. Mey, J.-P. Avouac, Y. Zhang, D. Shi. Tectonic control of Yarlung Tsangpo Gorge revealed by a buried canyon in Southern Tibet. Science, 2014; 346 (6212): 978 DOI: 10.1126/science.1259041

Note : The above story is based on materials provided by California Institute of Technology.

Deep-earth carbon offers clues on origin of life on Earth

A composite image of the Western hemisphere of the Earth. Credit: NASA

New findings by a Johns Hopkins University-led team reveal long unknown details about carbon deep beneath the Earth’s surface and suggest ways this subterranean carbon might have influenced the history of life on the planet.

The team also developed a new, related theory about how diamonds form in the Earth’s mantle.

For decades scientists have had little understanding of how carbon behaved deep below the Earth’s surface even as they learned more and more about the element’s vital role at the planet’s crust. Using a model created by Johns Hopkins geochemist Dimitri Sverjensky, he, Vincenzo Stagno of the Carnegie Institution of Washington and Fang Huang, a Johns Hopkins graduate student, have become the first to calculate how much carbon and what types exist in fluids at 100 miles below the Earth’s surface at temperatures up to 2,100 degrees F.

In an article published this week in the journal Nature Geoscience, Sverjensky and his team demonstrate that in addition to the carbon dioxide and methane already documented deep in subduction zones, there exists a rich variety of organic carbon species that could spark the formation of diamonds and perhaps even become food for microbial life.

“It is a very exciting possibility that these deep fluids might transport building blocks for life into the shallow Earth,” said Sverjensky, a professor in the Department of Earth and Planetary Sciences. “This may be a key to the origin of life itself.”

Sverjensky’s theoretical model, called the Deep Earth Water model, allowed the team to determine the chemical makeup of fluids in the Earth’s mantle, expelled from descending tectonic plates. Some of the fluids, those in equilibrium with mantle peridotite minerals, contained the expected carbon dioxide and methane. But others, those in equilibrium with diamonds and eclogitic minerals, contained dissolved organic carbon species including a vinegar-like acetic acid.

These high concentrations of dissolved carbon species, previously unknown at great depth in the Earth, suggest they are helping to ferry large amounts of carbon from the subduction zone into the overlying mantle wedge where they are likely to alter the mantle and affect the cycling of elements back into the Earth’s atmosphere.

The team also suggested that these mantle fluids with dissolved organic carbon species could be creating diamonds in a previously unknown way. Scientists have long believed diamond formation resulted through chemical reactions starting with either carbon dioxide or methane. The organic species offer a range of different starting materials, and an entirely new take on the creation of the gemstones.

Note : The above story is based on materials provided by Johns Hopkins University

Burrowing dinosaurs to be featured in new exhibit

burrowingdin-1
An artist’s illustration portrays an Oryctodromeus head. Credit: Lee Hall

A unique burrowing dinosaur that cared for its young in dens will be featured in a new exhibit opening Saturday, Nov. 22, at Montana State University’s Museum of the Rockies.

Discovered in southwest Montana and eastern Idaho, the adult Oryctodromeus would have been the size of a golden retriever but its long tail made it about seven feet long, said MSU paleontologist David Varricchio, whose findings and those of his graduate students inspired the “Burrowing Dinosaurs” exhibit.

“It’s really bizarre. I never would have thought of a burrowing dinosaur,” said Pat Leiggi, administrative director of paleontology and director of exhibits at the museum. “What’s cool about it is that it is the first occurrence of a burrowing or denning dinosaur. It’s new. It’s unique.”

Former MSU grad student Yoshihiro Katsura found the first remains 10 years ago while prospecting on public land about 15 miles from Lima, Mont. The fact that an adult and two juvenile Oryctodromeus were jumbled together in a burrow was significant, Varricchio said in a 2007 paper published by the British scientific journal, Proceedings of the Royal Society B.

“The presence of an adult and two juveniles within a denning chamber represents some of the best evidence for dinosaur parental care,” Varricchio wrote. “The burrow likely protected the adult and young Oryctodromeus from predators and harsh environmental conditions.”

The Oryctodromeus lived 95 million years ago. That’s 20 to 30 million years before the more familiar dinosaurs of prehistoric Montana, Varricchio said. The Hell Creek Formation of eastern Montana, for example, holds 65-million-year-old Tyrannosaurus rex skeletons. The Two Medicine Formation near Choteau yielded 75-million-year-old dinosaur eggs and babies.

An artist’s illustration of the dinosaur burrow found in southwest Montana. Credit: Lee Hall

The Oryctodromeus that Varricchio and MSU doctoral student L.J. Krumenacker now study came from the Blackleaf Formation of southwest Montana and the Wayan Formation of eastern Idaho.

The “Burrowing Dinosaurs” exhibit will show a cross section of the dinosaur’s burrow with two juveniles and an adult inside of it, Leiggi said. It will also contain a small rodent in a separate area of the burrow. At the top entrance of the burrow will be an adult Lull-mounted Oryctodromeus. A Lull mount is a model that shows a skeleton on one half and a flesh-covered version on the other. On the lower right-hand side of the burrow will be a partially reconstructed oviraptor egg clutch and a cast of the two oviraptor eggs that were discovered nearby.

The new exhibit will sit in the museum’s Hall of Giants where a Titanosaur and two Deinonychus dinosaurs were displayed, Leiggi said. Those fossils will be sent in January to a sister institution, the Fukui Prefectural Dinosaur Museum in Katsuyama, Japan.

“The Siebel Dinosaur Complex was designed to change as we learn new things about dinosaurs,”Leiggi said. “This is a great example of that, what we are trying to accomplish.”

Krumenacker, who has been working more than a decade at the Idaho field site, said that field work is much easier for him than helping create an exhibit. He is excited about the opportunity, however.

“I have never gotten to help with something like this,” Krumenacker said. “It’s nice to see the dinosaur you are working on put together.”

The public will see an accurate picture of the Oryctodromeus, because – between the sites in Montana and Idaho—the researchers found almost every part of the burrowing dinosaur, Krumenacker said. All that’s missing are its fingertips and pieces of its head.

Varricchio said he, too, is looking forward to sharing the burrowing dinosaurs in a Museum of the Rockies exhibit. Although he now works out of Traphagen Hall and Gaines Hall on the MSU campus, he spent a lot of time at the museum as a graduate student and later as collection manager.

Note : The above story is based on materials provided by Montana State University

Laser from plane discovers Roman goldmines in Spain

These are ancient goldmines in the Eria river valley, with channels and reservoirs for exploitation. The model generated with LiDAR data (left) allows these structures to be located on aerial photos (right). Credit: J. Fernández Lozano et al.
These are ancient goldmines in the Eria river valley, with channels and reservoirs for exploitation. The model generated with LiDAR data (left) allows these structures to be located on aerial photos (right). Credit: J. Fernández Lozano et al.

“The volume of earth exploited is much greater than previously thought and the works performed are impressive, having achieved actual river captures, which makes this valley extremely important in the context of Roman mining in the north-east of the Iberian Peninsula,” as Javier Fernández Lozano, geologist at the University of Salamanca and co-author of this study published in the ‘Journal of Archaeological Science’, tells SINC.

The specialists consider that the systems for the transport and storage of water were copied from those already existing in North Africa, where the Egyptians had been employing them for centuries. Some details of the methodology used appear in texts such as those of the Pliny the Elder, the Roman procurator in charge of overseeing mining in Hispania.

“We have established that the labour that went into extracting the resource until its exhaustion was so intensive that after removing the gold from surface sediments, operations continued until reaching the rocks with the auriferous quartz veins underneath,” explains Fernández Lozano.

The researcher stresses that the real discoverer was the LiDAR technology: “Unlike traditional aerial photography, this airborne laser detection system allows the visualisation of archaeological remains under vegetation cover or intensely ploughed areas”.

From aircraft or drones

LiDAR comprises a laser sensor which scans the ground from an aircraft or drone with geographical references provided by GPS ground stations. The data obtained is represented by point clouds, which are processed with a piece of software to construct a cartographic model where the forms are identified, such as old reservoirs or channels.

This technology was developed by NASA in the sixties to analyse the retreating sea ice in the Arctic and composition of the oceans. Since then their use has been extended to topography, cadastral mapping, geology and archaeology. According to the authors, the study of Roman mining in the Eria valley is the first piece of ‘geo-archaeology’ performed with LiDAR in Spain.

“Our intention is to continue working with this technique to learn more about mineral mining in the Roman Empire and clear up any mysteries such as why Rome abandoned such a precious resource as gold from one day to the next,” concludes the researcher.

Reference:
Javier Fernández-Lozano, Gabriel Gutiérrez-Alonso, Miguel Fernández-Morán. “Using airborne LiDAR sensing technology and aerial orthoimages to unravel roman water supply systems and gold works in NW Spain (Eria valley, León)”. Journal of Archaeological Science, 12 Nov 2014 (online).

Note : The above story is based on materials provided by Spanish Foundation for Science and Technology (FECYT)

‘Fountain of youth’ underlies Antarctic mountains

Images of the ice-covered Gamburtsev Mountains revealed water-filled valleys, as seen by the cluster of vertical lines in this image. Credit: Creyts
Images of the ice-covered Gamburtsev Mountains revealed water-filled valleys, as seen by the cluster of vertical lines in this image. Credit: Creyts

Time ravages mountains, as it does people. Sharp features soften, and bodies grow shorter and rounder. But under the right conditions, some mountains refuse to age. In a new study, scientists explain why the ice-covered Gamburtsev Mountains in the middle of Antarctica looks as young as they do.

The Gamburtsevs were discovered in the 1950s, but remained unexplored until scientists flew ice-penetrating instruments over the mountains 60 years later. As this ancient hidden landscape came into focus, scientists were stunned to see the saw-toothed and towering crags of much younger mountains. Though the Gamburtsevs are contemporaries of the largely worn-down Appalachians, they looked more like the Rockies, which are nearly 200 million years younger.

More surprising still, the scientists discovered a vast network of lakes and rivers at the mountains’ base. Though water usually speeds erosion, here it seems to have kept erosion at bay. The reason, researchers now say, has to do with the thick ice that has entombed the Gamburtsevs since Antarctica went into a deep freeze 35 million years ago.

“The ice sheet acts like an anti-aging cream,” said the study’s lead author, Timothy Creyts, a geophysicist at Columbia University’s Lamont-Doherty Earth Observatory. “It triggers a series of thermodynamic processes that have almost perfectly preserved the Gamburtsevs since ice began spreading across the continent.”

Scientists hypothesize that cold temperatures and high pressures push the water uphill, in the same direction as overlying ice flows. This causes ridgelines to refreeze, thus warding off erosion. Credit: Creyts

The study, which appears in the latest issue of the journal Geophysical Research Letters, explains how the blanket of ice covering the Gamburtsevs has preserved its rugged ridgelines.

Snow falling at the surface of the ice sheet draws colder temperatures down, closer to protruding peaks in a process called divergent cooling. At the same time, heat radiating from bedrock beneath the ice sheet melts ice in the deep valleys to form rivers and lakes. As rivers course along the base of the ice sheet, high pressures from the overlying ice sheet push water up valleys in reverse. This uphill flow refreezes as it meets colder temperature from above. Thus, ridgelines are cryogenically preserved.

The oldest rocks in the Gamburtsevs formed more than a billion years ago, in the collision of several continents. Though these prototype mountains eroded away, a lingering crustal root became reactivated when the supercontinent Gondwana ripped apart, starting about 200 millionyears ago. Tectonic forces pushed the land up again to form the modern Gamburtsevs, which range across an area the size of the Alps. Erosion again chewed away at the mountains until earth entered a cooling phase 35 million years ago. Expanding outward from the Gamburtsevs, a growing layer of ice joined several other nucleation points to cover the entire continent in ice.

The researchers say that the mechanism that stalled aging of the Gamburtsevs at higher elevations may explain why some ridgelines in the Torngat Mountains on Canada’s Labrador Peninsula and the Scandinavian Mountains running through Norway, Sweden and Finland appear strikingly untouched. Massive ice sheets covered both landscapes during the last ice age, which peaked about 20,000 years ago, but many high-altitude features bear little trace of this event.

“The authors identify a mechanism whereby larger parts of mountains ranges in glaciated regions–not just Antarctica — could be spared from erosion,” said Stewart Jamieson, a glaciologist at Durham University who was not involved in the study. “This is important because these uplands are nucleation centers for ice sheets. If they were to gradually erode during glacial cycles, they would become less effective as nucleation points during later ice ages.”

Ice sheet behavior, then, may influence climate change in ways that scientists and computer models have yet to appreciate. As study coauthor Fausto Ferraccioli, head of the British Antarctic Survey’s airborne geophysics group, put it: “If these mountains in interior East Antarctica had been more significantly eroded then the ice sheet itself may have had a different history.”

Other authors: Hugh Carr and Tom Jordan of the British Antarctic Survey; Robin Bell, Michael Wolovick and Nicholas Frearson of Lamont-Doherty; Kathryn Rose of University of Bristol; Detlef Damaske of Germany’s Federal Institute for Geosciences and Natural Resources; David Braaten of Kansas University; and Carol Finn of the U.S. Geological Survey.

Reference:
Timothy T. Creyts, Fausto Ferraccioli, Robin E. Bell, Michael Wolovick, Hugh Corr, Kathryn C. Rose, Nicholas Frearson, Detlef Damaske, Tom Jordan, David Braaten, Carol Finn. Freezing of ridges and water networks preserves the Gamburtsev Subglacial Mountains for millions of years. Geophysical Research Letters, 2014; DOI: 10.1002/2014GL061491

Note : The above story is based on materials provided by The Earth Institute at Columbia University.

New technology may speed up, build awareness of landslide risks

Aerial view, Oso landslide, Snohomish County, March 27, 2014 Photo by Jonathan Godt, Courtesy U.S. Geological Survey
Aerial view, Oso landslide, Snohomish County, March 27, 2014 Photo by Jonathan Godt, Courtesy U.S. Geological Survey

CORVALLIS, Ore. – Engineers have created a new way to use lidar technology to identify and classify landslides on a landscape scale, which may revolutionize the understanding of landslides in the U.S. and reveal them to be far more common and hazardous than often understood.

The new, non-subjective technology, created by researchers at Oregon State University and George Mason University, can analyze and classify the landslide risk in an area of 50 or more square miles in about 30 minutes – a task that previously might have taken an expert several weeks to months. It can also identify risks common to a broad area rather than just an individual site.

And with such speed and precision, it reveals that some landslide-prone areas of the Pacific Northwest are literally covered by landslides from one time or another in history. The system is based on new ways to use light detecting and ranging, or lidar technology, that can seemingly strip away vegetation and other obstructions to show land features in their bare form.

“With lidar we can see areas that are 50-80 percent covered by landslide deposits,” said Michael Olsen, an expert in geomatics and the Eric HI and Janice Hoffman Faculty Scholar in the OSU College of Engineering. “It may turn out that there are 10-100 times more landslides in some places than we knew of before.

“We’ve always known landslides were a problem in the Pacific Northwest,” Olsen said. “Many people are just now beginning to realize how big the problem is.”

An outline of the new technology was recently published in Computers and Geosciences, a professional journal.

Oregon and Washington, especially in the Coast Range and Cascade Range, are already areas commonly known to have landslides, and as a result Oregon’s Department of Geology and Mineral Industries has become a national leader in mapping of them, Olsen said. But previous approaches are slow, and the new technology, called a Contour Connection Method, could radically speed up widespread mapping, and build both professional and public awareness of the issue.

Despite the prevalence and frequency of landslides, they are not generally covered by most homeowner insurance policies; coverage can be purchased separately, but most people don’t. And with increasing population growth, more and more people are moving into more remote locations, or building in scenic areas near the hills around cities where landslide risk might be high.

“A lot of people don’t think in geologic terms, so if they see a hill that’s been there for a long time, they assume there’s no risk,” said Ben Leshchinsky, a geotechnical engineer in the OSU College of Forestry. “And many times they don’t want to pay extra to have an expert assess landslide risks or do something that might interfere with their land development plans.”

Lidar is already a powerful tool, but the new system developed at OSU offers an automated way to improve the use of it, and could usher in a new era of landslide awareness, experts say. Information could be more routinely factored into road, bridge, land use, zoning, building and other decisions.

With this technology, a computer automatically looks for land features, such as suddenly steeper areas of soil, that might be evidence of a past landslide. It then searches the terrain for other features, such as a “toe” of soils at the base of the landslide. And in minutes it can make unbiased, science-based classifications of past landslides that consistently use the same criteria.

The technology was applied to the region surrounding the landslide of March, 2014, that killed 43 people near the small town of Oso, Washington. In about nine minutes it was able to analyze more than 2,200 acres and many prehistoric landslide features that are readily apparent in lidar images, in this region known for slope instability.

Eventually, adaptations of the technology might even allow for real-time monitoring of soil movement, the researchers said.

Note : The above story is based on materials provided by Oregon State University.The original article was written by Michael Olsen.

Geologists shed light on formation of Alaska Range

Denali (Mount McKinley). Credit: SU Arts and Sciences

Geologists in the College of Arts and Sciences have recently figured out what has caused the Alaska Range to form the way it has and why the range boasts such an enigmatic topographic signature. The narrow mountain range is home to some of the world’s most dramatic topography, including 20,320-foot Denali (Mount McKinley), North America’s highest mountain.

Professor Paul Fitzgerald and a team of students and fellow scientists have been studying the Alaska Range along the Denali fault. They think they know why the fault is located where it is and what accounts for the alternating asymmetrical, mountain-scale topography along the fault.

Their findings were the subject of a recent paper in the journal Tectonics.

In 2002, the Denali fault, which cuts across south-central Alaska, was the site of a magnitude-7.9 earthquake and was felt as far away as Texas and Louisiana. It was the largest earthquake of its kind in more than 150 years.

“Following the earthquake, researchers flocked to the area to examine the effects,” says Fitzgerald, who serves as professor of Earth Sciences and an associate dean for the college. “They were fascinated by how the frozen ground behaved; the many landslides [the earthquake] caused; how bridges responded; and how the Trans-Alaska oil pipeline survived, as it was engineered to do so.”

Geologists were also surprised by how the earthquake began on a previously unknown thrust-fault; then propagated eastward, along the Denali fault, and finally jumped onto another fault, hundreds of kilometers away.

“From our perspective, the earthquake has motivated analyses of why the highest mountains in the central Alaska Range occur south of the Denali fault and the highest mountains in the eastern Alaska Range occur north of the fault — something that has puzzled us for years,” Fitzgerald adds. “It’s been an enigma staring us in the face.”

He attributes the Alaska Range’s alternating topographic signatures to a myriad of factors: contrasting lithospheric strength between large terranes (i.e., distinctly different rock units); the location of the curved Denali fault; the transfer of strain inland from southern Alaska’s active plate margin; and the shape of the controlling former continental margin against weaker suture-zone rocks.

It’s no secret that Alaska is one of the most geologically active areas on the planet. For instance, scientists know that the North American Plate is currently overriding the Pacific Plate at the latter’s southern coast, while the Yakutat microplate is colliding with North America.

As a result of plate tectonics, Alaska is an amalgamation of terranes that have collided with the North American craton and have accreted to become part of North America. Cratons are pieces of continents that have been largely stable for hundreds of millions of years.

Terranes often originate as volcanic islands (like those of Hawaii) and, after colliding with one another or a continent, are separated by large discrete faults. When terranes collide and accrete, they form a suture, also known as a collision zone, which is made up of weak, crushed rock. During deformation, suture-zone rocks usually deform first, especially if they are adjacent to a strong rock body.

“Technically, the Denali fault is what we’d call an ‘intercontinental right-lateral strike-slip fault system,'” says Fitzgerald, adding that a strike-slip fault occurs when rocks move horizontally past one another, usually on a vertical fault. “This motion includes a component of slip along the fault and a component of normal motion against the fault that creates mountains. Hence, the shape of the fault determines which of the two components is predominant and where mountains form.”

In Alaska, the shape of the accreted terranes generally controls the location of the Denali fault and the mountains that form along it, especially at the bends in the trace of the fault.

Fitzgerald: “Mount McKinley and the central Alaska Range lie within the concave curve of the Denali fault. There, higher topography and greater exhumation [uplift of rock] occur south of the Denali fault, exactly where you’d expect a mountain range to form, given the regional tectonics. In the eastern Alaska Range, higher topography and greater exhumation are found north of the fault, on its convex side-not an expected pattern at all and very puzzling.”

Using mapped surface geology, geophysical data, and thermochronology (i.e., time-temperature history of the rocks), Fitzgerald and colleagues have determined that much of Alaska’s uplift and deformation began some 25 million years ago, when the Yakutat microplate first started colliding with North America. The bold, glacier-clad peaks comprising the Alaska Range actually derive from within the aforementioned “weak suture-zone rocks” between the terranes.

While mountains are high and give the impression of strength, they are built largely from previously fractured rock units. Rock movement along the Denali fault drives the uplift of the mountains, which form at bends in the fault, where previously fractured suture-zone rocks are pinned against the stronger former North American continental margin.

“The patterns of deformation help us understand regional tectonics and the formation of the Alaska Range, which is fascinating to geologists and non-geologists alike,” says Fitzgerald. “Being able to determine patterns or how to reveal them, while others see chaos, is often the key to finding the answer to complex problems. … To us scientists, the real significance of this work is that it helps us understand the evolution of our planet, how faults and mountain belts form, and why earthquakes happen. It also provides a number of hypotheses about Alaskan tectonics and rock deformation that we can test, using the Alaska Range as our laboratory.”

In addition to Fitzgerald, the paper was co-authored by Sarah Roeske, a research scientist at the University of California, Davis; Jeff Benowitz, a research scientist at the Geophysical Institute at the University of Alaska Fairbanks; Steven Riccio and Stephanie Perry, graduate students in Earth Sciences at Syracuse; and Phillip Armstrong, professor and chair of geological sciences at California State University, Fullerton.

Reference:
Steven J. Riccio, Paul G. Fitzgerald, Jeff A. Benowitz, Sarah M. Roeske. The role of thrust faulting in the formation of the eastern Alaska Range: Thermochronological constraints from the Susitna Glacier Thrust Fault region of the intracontinental strike-slip Denali Fault system. Tectonics, 2014; DOI: 10.1002/2014TC003646

Note : The above story is based on materials provided by Syracuse University. The original article was written by Rob Enslin.

Prehistoric landslide discovery rivals largest known on surface of Earth

A catastrophic landslide, one of the largest known on the surface of the Earth, took place within minutes in southwestern Utah more than 21 million years ago. Credit: Image courtesy of Kent State University

A catastrophic landslide, one of the largest known on the surface of the Earth, took place within minutes in southwestern Utah more than 21 million years ago, reports a Kent State University geologist in a paper published in the November issue of the journal Geology.

The Markagunt gravity slide, the size of three Ohio counties, is one of the two largest known continental landslides (larger slides exist on the ocean floors). David Hacker, Ph.D., associate professor of geology at Kent State University at Trumbull, and two colleagues discovered and mapped the scope of the Markagunt slide over the past two summers.

His colleagues and co-authors are Robert F. Biek of the Utah Geological Survey and Peter D. Rowley of Geologic Mapping Inc. of New Harmony, Utah.

Geologists had known about smaller portions of the Markagunt slide before the recent mapping showed its enormous extent. Hiking through the wilderness areas of the Dixie National Forest and Bureau of Land Management land, Hacker identified features showing that the Markagunt landslide was much bigger than previously known.

The landslide took place in an area between what is now Bryce Canyon National Park and the town of Beaver, Utah. It covered about 1,300 square miles, an area as big as Ohio’s Cuyahoga, Portage and Summit counties combined.

Its rival in size, the “Heart Mountain slide,” which took place around 50 million years ago in northwest Wyoming, was discovered in the 1940s and is a classic feature in geology textbooks.

The Markagunt could prove to be much larger than the Heart Mountain slide, once it is mapped in greater detail.

“Large-scale catastrophic collapses of volcanic fields such as these are rare but represent the largest known landslides on the surface of the Earth,” the authors wrote. The length of the landslide — over 55 miles — also shows that it was as fast moving as it was massive, Hacker said.

Evidence showing that the slide was catastrophic — occurring within minutes — included the presence of pseudotachylytes, rocks that were melted into glass by the immense friction. Any animals living in its path would have been quickly overrun. Evidence of the slide is not readily apparent to visitors today. “Looking at it, you wouldn’t even recognize it as a landslide,” Hacker said.

But internal features of the slide, exposed in outcrops, yielded evidence such as jigsaw puzzle rock fractures and shear zones, along with the pseudotachylytes.

Hacker, who studies catastrophic geological events, said the slide originated when a volcanic field consisting of many strato-volcanoes, a type similar to Mount St. Helens in the Cascade Mountains, which erupted in 1980, collapsed and produced the massive landslide.

The collapse may have been caused by the vertical inflation of deeper magma chambers that fed the volcanoes. Hacker has spent many summers in Utah mapping geologic features of the Pine Valley Mountains south of the Markagunt where he has found evidence of similar, but smaller slides from magma intrusions called laccoliths.

What is learned about the mega-landslide could help geologists better understand these extreme types of events. The Markagunt and the Heart Mountain slides document for the first time how large portions of ancient volcanic fields have collapsed, Hacker said, representing “a new class of hazards in volcanic fields.”

While the Markagunt landslide was a rare event, it shows the magnitude of what could happen in modern volcanic fields like the Cascades.

“We study events from the geologic past to better understand what could happen in the future,” he said. The next steps in the research, conducted with his co-authors on the Geology paper, will be to continue mapping the slide, collect samples from the base for structural analysis and date the pseudotachylytes.

Hacker, who earned his Ph.D. in geology at Kent State, joined the faculty in 2000 after working for an environmental consulting company. He is co-author of the book Earth’s Natural Hazards: Understanding Natural Disasters and Catastrophes, published in 2010.

Reference:
D. B. Hacker, R. F. Biek, P. D. Rowley. Catastrophic emplacement of the gigantic Markagunt gravity slide, southwest Utah (USA): Implications for hazards associated with sector collapse of volcanic fields. Geology, 2014; 42 (11): 943 DOI: 10.1130/G35896.1

Note : The above story is based on materials provided by Kent State University.

Fossils suggest ancestor of horses and rhinos

An artist’s depiction ofCambaytherium thewissi. Credit: Elaine Kasmer

Fossils suggest ancestor of horses and rhinos originated on the Asian subcontinent while it was still an islandWorking at the edge of a coal mine in India, a team of Johns Hopkins researchers and colleagues have filled in a major gap in science’s understanding of the evolution of a group of animals that includes horses and rhinos. That group likely originated on the subcontinent when it was still an island headed swiftly for collision with Asia, the researchers report Nov. 20 in the online journal Nature Communications.

Modern horses, rhinos and tapirs belong to a biological group, or order, called Perissodactyla. Also known as “odd-toed ungulates,” animals in the order have, as their name implies, an uneven number of toes on their hind feet and a distinctive digestive system. Though paleontologists had found remains of Perissodactyla from as far back as the beginnings of the Eocene epoch, about 56 million years ago, their earlier evolution remained a mystery, says Ken Rose, Ph.D., a professor of functional anatomy and evolution at the Johns Hopkins University School of Medicine.

Rose and his research team have for years been excavating mammal fossils in the Bighorn Basin of Wyoming, but in 2001 he and Indian colleagues began exploring Eocene sediments in Western India because it had been proposed that perissodactyls and some other mammal groups might have originated there. In an open-pit coal mine northeast of Mumbai, they uncovered a rich vein of ancient bones. Rose says he and his collaborators obtained funding from the National Geographic Society to send a research team to the mine site at Gujarat in the far Western part of India for two weeks at a time once every year or two over the last decade.

The mine yielded what Rose says was a treasure trove of teeth and bones for the researchers to comb through back in their home laboratories. Of these, more than 200 fossils turned out to belong to an animal dubbed Cambaytherium thewissi, about which little had been known. The researchers dated the fossils to about 54.5 million years old, making them slightly younger than the oldest known Perissodactyla remains, but, Rose says, it provides a window into what a common ancestor of all Perissodactyla would have looked like. “Many of Cambaytherium’s features, like the teeth, the number of sacral vertebrae, and the bones of the hands and feet, are intermediate between Perissodactyla and more primitive animals,” Rose says. “This is the closest thing we’ve found to a common ancestor of the Perissodactyla order.”

Cambaytherium and other finds from the Gujarat coal mine also provide tantalizing clues about India’s separation from Madagascar, lonely migration, and eventual collision with the continent of Asia as the Earth’s plates shifted, Rose says. In 1990, two researchers, David Krause and Mary Maas of Stony Brook University, published a paper suggesting that several groups of mammals that appear at the beginning of the Eocene, including primates and odd- and even-toed ungulates, might have evolved in India while it was isolated. Cambaytherium is the first concrete evidence to support that idea, Rose says. But, he adds, “It’s not a simple story.”

“Around Cambaytherium’s time, we think India was an island, but it also had primates and a rodent similar to those living in Europe at the time,” he says. “One possible explanation is that India passed close by the Arabian Peninsula or the Horn of Africa, and there was a land bridge that allowed the animals to migrate. But Cambaytherium is unique and suggests that India was indeed isolated for a while.”

Rose said his team was “very fortunate that we discovered the site and that the mining company allowed us to work there,” although he added, “it was frustrating to knowing that countless fossils were being chewed up by heavy mining equipment.” When coal extraction was finished, the miners covered the site, he says. His team has now found other mines in the area to continue digging.

Note : The above story is based on materials provided by Johns Hopkins University School of Medicine

Ancient New Zealand ‘dawn whale’ identified

University of Otago researchers have described a new genus of ancient baleen whales that they have named Tohoraata (a Māori term which can be translated as Dawn Whale). The genus belongs to the toothless filter-feeding family Eomysticetidae, and it is the first time members of this family have been identified in the Southern Hemisphere. They named the younger of the two fossil whales, which may be a descendent of the elder, as Tohoraata raekohao (pictured). Raekohao means ‘holes in the forehead’. Researcher Robert Boessenecker says this whale lived between 26-25 million years ago and vaguely resembles a minke whale but was more slender and serpent-like. Its skull, which contains a number of holes near its eye sockets for arteries, was probably about two metres in length and the whole animal would have been eight metres long. Credit: Copyright Robert Boessenecker

University of Otago palaeontologists are rewriting the history of New Zealand’s ancient whales by describing a previously unknown genus of fossil baleen whales and two species within it.

Otago Department of Geology PhD student Robert Boessenecker and his supervisor Professor Ewan Fordyce have named the new genus Tohoraata, which translates as ‘Dawn Whale’ in Māori.

The two whales, which lived between 27-25 million years ago, were preserved in a rock formation near Duntroon in North Otago. At that time the continent of Zealandia was largely or completely under water and the whales were deposited on a continental shelf that was perhaps between 50 to 100 metres deep.

The new genus that the fossils represent belongs to the toothless filter-feeding family Eomysticetidae, and it is the first time members of this family have been identified in the Southern Hemisphere.

They named the younger of the two fossil whales, which may be a descendent of the elder, as Tohoraata raekohao. Raekohao means ‘holes in the forehead’.

Mr Boessenecker says this whale lived between 26-25 million years ago and vaguely resembles a minke whale but was more slender and serpent-like. Its skull, which contains a number of holes near its eye sockets for arteries, was probably about two metres in length and the whole animal would have been eight metres long.

“This new species differs from modern baleen whales in having a smaller braincase and a skull that is generally much more primitive, with substantially larger attachments for jaw muscles. The lower jaw retains a very large cavity indicating that its hearing capabilities were similar to archaic whales.”

The researchers also determined that the older fossil whale from the site, which was collected in 1949 and named in 1956, had been misidentified as belonging to the genus Mauicetus, a more advanced type of whale called a “cetothere.” They have now changed its name from Mauicetus waitakiensis to Tohoraata waitakiensis.

Mr Boessenecker says this particular fossil had been poorly understood for more than 50 years and only with this study was it proven not to be from its originally attributed genus. The two whales have now become the first eomysticetids to be reported outside of South Carolina, USA, and Japan.

“Researchers contend with confusing or surprising fossils in museum collections all the time. Often, the best way to solve these mysteries is to go out and dig up another one, which is what Professor Fordyce and his colleagues did in 1993 when they collected the partial skull of Tohoraata raekohao.”

Eomysticetids occupy an important position in the evolutionary tree of cetaceans: they are the earliest toothless baleen-bearing cetaceans, and in many characteristics are intermediate between toothed baleen whales and modern baleen whales, he says.

“They are the first baleen whales to have been completely toothless, and are therefore the earliest known cetaceans to have wholly relied upon filter feeding.”

Reference:
Robert W. Boessenecker, R. Ewan Fordyce. A new Eomysticetid (Mammalia: Cetacea) from the Late Oligocene of New Zealand and a re-evaluation of ‘Mauicetus’waitakiensis. Papers in Palaeontology, 2014; DOI: 10.1002/spp2.1005

Note : The above story is based on materials provided by University of Otago.

Small volcanic eruptions could be slowing global warming

The Sarychev Peak Volcano, on Matua Island, erupted on June 12, 2009. New research shows that eruptions of this size may contribute more to the recent lull in global temperature increases than previously thought. Credit: NASA

Small volcanic eruptions might eject more of an atmosphere-cooling gas into Earth’s upper atmosphere than previously thought, potentially contributing to the recent slowdown in global warming, according to a new study.

Scientists have long known that volcanoes can cool the atmosphere, mainly by means of sulfur dioxide gas that eruptions expel. Droplets of sulfuric acid that form when the gas combines with oxygen in the upper atmosphere can remain for many months, reflecting sunlight away from Earth and lowering temperatures. However, previous research had suggested that relatively minor eruptions—those in the lower half of a scale used to rate volcano “explosivity”—do not contribute much to this cooling phenomenon.

Now, new ground-, air- and satellite measurements show that small volcanic eruptions that occurred between 2000 and 2013 have deflected almost double the amount of solar radiation previously estimated. By knocking incoming solar energy back out into space, sulfuric acid particles from these recent eruptions could be responsible for decreasing global temperatures by 0.05 to 0.12 degrees Celsius (0.09 to 0.22 degrees Fahrenheit) since 2000, according to the new study accepted to Geophysical Research Letters, a journal of the American Geophysical Union.

These new data could help to explain why increases in global temperatures have slowed over the past 15 years, a period dubbed the ‘global warming hiatus,’ according to the study’s authors.

The warmest year on record is 1998. After that, the steep climb in global temperatures observed over the 20th century appeared to level off. Scientists previously suggested that weak solar activity or heat uptake by the oceans could be responsible for this lull in temperature increases, but only recently have they thought minor volcanic eruptions might be a factor.

Climate projections typically don’t include the effect of volcanic eruptions, as these events are nearly impossible to predict, according to Alan Robock, a climatologist at Rutgers University in New Brunswick, N.J., who was not involved in the study. Only large eruptions on the scale of the cataclysmic 1991 Mount Pinatubo eruption in the Philippines, which ejected an estimated 20 million metric tons (44 billion pounds) of sulfur, were thought to impact global climate. But according to David Ridley, an atmospheric scientist at the Massachusetts Institute of Technology in Cambridge and lead author of the new study, classic climate models weren’t adding up.

“The prediction of global temperature from the [latest] models indicated continuing strong warming post-2000, when in reality the rate of warming has slowed,” said Ridley. That meant to him that a piece of the puzzle was missing, and he found it at the intersection of two atmospheric layers, the stratosphere and the troposphere— the lowest layer of the atmosphere, where all weather takes place. Those layers meet between 10 and 15 kilometers (six to nine miles) above the Earth.

Traditionally, scientists have used satellites to measure sulfuric acid droplets and other fine, suspended particles, or aerosols, that erupting volcanoes spew into the stratosphere. But ordinary water-vapor clouds in the troposphere can foil data collection below 15 km, Ridley said. “The satellite data does a great job of monitoring the particles above 15 km, which is fine in the tropics. However, towards the poles we are missing more and more of the particles residing in the lower stratosphere that can reach down to 10 km.”

To get around this, the new study combined observations from ground-, air- and space-based instruments to better observe aerosols in the lower portion of the stratosphere.

Four lidar systems measured laser light bouncing off aerosols to estimate the particles’ stratospheric concentrations, while a balloon-borne particle counter and satellite datasets provided cross-checks on the lidar measurements. A global network of ground-based sun-photometers, called AERONET, also detected aerosols by measuring the intensity of sunlight reaching the instruments. Together, these observing systems provided a more complete picture of the total amount of aerosols in the stratosphere, according to the study authors.

Including these new observations in a simple climate model, the researchers found that volcanic eruptions reduced the incoming solar power by -0.19 ± 0.09 watts of sunlight per square meter of the Earth’s surface during the ‘global warming hiatus’, enough to lower global surface temperatures by 0.05 to 0.12 degrees Celsius (0.09 to 0.22 degrees Fahrenheit). By contrast, other studies have shown that the 1991 Mount Pinatubo eruption warded off about three to five watts per square meter at its peak, but tapered off to background levels in the years following the eruption. The shading from Pinatubo corresponded to a global temperature drop of 0.5 degrees Celsius (0.9 degrees Fahrenheit).

Robock said the new research provides evidence that there may be more aerosols in the atmosphere than previously thought. “This is part of the story about what has been driving climate change for the past 15 years,” he said. “It’s the best analysis we’ve had of the effects of a lot of small volcanic eruptions on climate.”

Ridley said he hopes the new data will make their way into climate models and help explain some of the inconsistencies that climate scientists have noted between the models and what is being observed.

Robock cautioned, however, that the ground-based AERONET instruments that the researchers used were developed to measure aerosols in the troposphere, not the stratosphere. To build the best climate models, he said, a more robust monitoring system for stratospheric aerosols will need to be developed.

Reference:
“Total volcanic stratospheric aerosol optical depths and implications for global climate change” onlinelibrary.wiley.com/doi/10… 014GL061541/abstract

Note : The above story is based on materials provided by American Geophysical Union

Fossils cast doubt on climate-change projections on habitats

Maps show predicted locations vs. fossil record of shrew and flying squirrels Credit: University of Oregon

Leave it to long-dead short-tailed shrew and flying squirrels to outfox climate-modelers trying to predict future habitats.

Evidence from the fossil record shows that gluttonous insect-eating shrew didn’t live where a species distribution technique drawn by biologists put it 20,000 years ago to survive the reach of glaciers, says University of Oregon geologist Edward B. Davis. The shrew is not alone.

According to a new study by Davis and colleagues, fossil records of five ancient mammalian species that survived North America’s last glacial period point to weaknesses in the use of ecological niche models and hindcasting to predict future animal and plant habitats. As a result, Davis says, the modeling needs to be fine-tuned for complexities that might be harvested from fossils.

Ecological niches use modern habitat distributions and climate; hindcasting adds predictive power by adding major past climate shifts into the models. That modeling combination — as seen in a 2007 study led by Eric Waltari, then of the American Museum of Natural History in New York — had the short-tailed shrew surviving the last ice age in mostly Texas and the Deep South. Conclusions drawn in other studies, Davis noted in the new study, also are biased toward southern locations for ice-age surviving mammals of the Pleistocene Epoch.

Edward Davis, professor of geological sciences at the University of Oregon Credit: University of Oregon

Short-tailed shrew, according to fossil records, did not live in the predicted ranges. Instead they lived across north central and northeast United States, closer to the glaciers and where they are widely found today.

“It’s almost as though it is living in all of the places that the model says it shouldn’t be living in and not in any of the places that the model says it should be living in,” said Davis, who also is manager of the paleontological collection at the UO Museum of Natural and Cultural History. “This suggests to me that whatever the model is keying on is not actually important to the shrew.”

Nor to the American marten, two species of flying squirrels and the Gapper’s red-backed vole, all of which lived mostly outside of predicted ranges, according to the fossil record. Northern and southern flying squirrels, the Davis study found, shared a compressed geographic region. It may be, Davis said, that some species tolerate competition under harsh conditions but separate when abundant resources are available.

Davis noted that an important but under-cited 2010 paper on rodents by Robert Guralnick of the University of Colorado and Peter B. Pearman of the Swiss Federal Research Institute also showed problems with hindcast projections. Those for lowland rodents in the last ice age did not hold up, but those for a higher elevation species did.

“Our findings say that we need to pay more attention to the potential problems we have with some of our modern methods, and the way that we can improve our understanding of how species interact with the environment,” said Davis, who added that his study was inspired by Waltari’s. “The way to improve our forecasting is to include data from the fossil record. It can give us more information about the environments that species have lived in and could live in.”

The findings appear in the November issue of the journal Ecography. In a special section of the journal, the Davis paper is packaged with four papers on research initially presented in a symposium on conservation paleobiogeography in 2013 at a biennial meeting of the International Biography Society. The Davis paper is co-authored by Jenny L. McGuire, now at Georgia Tech University, and former UO doctoral student John D. Orcutt, who is now at Cornell College in Iowa.

Davis and McGuire co-hosted the symposium, edited the special issue and penned an editorial that accompanies the five papers. Conservation paleobiogeography, Davis said, “is the idea that we can help people understand questions that arise from conservation needs using data from the fossil record.” Doing so, he said, may explain how species shift their ecological roles, or evolve, to survive amid abrupt changes in their habitats.

“Our paper raises questions about some of the work on projecting future ranges of mammals, and we suggest some directions forward,” Davis said. “We have concerns about the precision of the modeling techniques now being used. We don’t have any concerns about climate change happening and that it going to cause geographic range shifts for mammals and plants. The thing I want to do, as a scientist, is to have the best models possible so as we’re making informed decisions as a society.”

Reference:
Edward Byrd Davis, Jenny L. McGuire, John D. Orcutt. Ecological niche models of mammalian glacial refugia show consistent bias. Ecography, 2014; DOI: 10.1111/ecog.01294

Note : The above story is based on materials provided by University of Oregon.

Jurassic climate of large swath of western U.S. was more complex than previously known

The first detailed chemical analysis of ancient soil from the Morrison Formation — a massive source of significant dinosaur discoveries for more than 100 years — reveals there was an unexpected abrupt change from arid to wet environments during the Jurassic. Credit: Image courtesy of Southern Methodist University

First detailed chemical analysis of ancient soil from the Morrison Formation — a massive source of significant dinosaur discoveries for more than 100 years — reveals there was an unexpected abrupt change from arid to wet environments during the Jurassic.

The climate 150 million years ago of a large swath of the western United States was more complex than previously known, according to new research from Southern Methodist University, Dallas.

It’s been held that the climate during the Jurassic was fairly dry in New Mexico, then gradually transitioned to a wetter climate northward to Montana.

But based on new evidence, the theory of a gradual transition from a dry climate to a wetter one during the Jurassic doesn’t tell the whole story, says SMU paleontologist Timothy S. Myers, lead author on the study.

Geochemical analysis of ancient soils, called paleosols, revealed an unexpected and mysterious abrupt transition from dry to wet even though some of the samples came from two nearby locales, Myers said.

Myers discovered the abrupt transition through geochemical analysis of more than 40 ancient soil samples.

He collected the samples from the Morrison Formation, a vast rock unit that has been a major source of significant dinosaur discoveries for more than 100 years.

The Morrison extends from New Mexico to Montana, sprawling across 13 states and Canada, formed from sediments deposited during the Jurassic.

Myers’ study is the first in the Morrison to significantly draw on quantitative data — the geochemistry of the rocks.

The abrupt transition, Myers says, isn’t readily explained.

“I don’t have a good explanation,” he said. “Normally when you see these dramatic differences in climate in areas that are close to one another it’s the result of a stark variation in topography. But in this case, there weren’t any big topographic features like a mountain range that divided these two localities in the Jurassic.”

Surprisingly, paleosols from the sample areas did not reveal marked differences until they were analyzed using geochemical weathering indices.

“It’s sobering to think that by just looking at the paleosols superficially at these localities, they don’t appear incredibly different. We see the same types of ancient soils in both places,” Myers said. “So these are some fairly major climate differences that aren’t reflected in the basic ancient soil types. Yet this is what a lot of scientists, myself included, depend on for a first pass idea of paleoclimate in an area — certain types of soils form in drier environments, others in wetter, others in cooler, that sort of thing.”

That didn’t hold true for the current study.

With the geochemical analysis, Myers estimated the mean average precipitation during the Jurassic for northern Montana was approximately 45 inches, 20 inches for northern Wyoming and 30 inches for New Mexico.

“This changes how we view the distribution of the types of environments in the Morrison,” Myers said. “Too many times we talk about the Morrison as though it was this monolithic unit sprinkled with patchy, but similar, variations. But it’s incredibly large. It spans almost 10 degrees of latitude. So it’s going to encompass a lot of different environments. Regions with broadly similar climates can have internal differences, even over short distances. That’s the take-home.”

Myers is a postdoctoral scholar in SMU’s Shuler Museum of Paleontology in the Roy M. Huffington Department of Earth Sciences, Dedman College.

He reported his findings, “Multiproxy approach reveals evidence of highly variable paleoprecipitation in the Upper Jurassic Morrison Formation (western United States),” in The Geological Society of America Bulletin.

Co-authors of the study were Neil J. Tabor, SMU earth sciences professor and an expert in ancient soil, and Nicholas Rosenau, a stable isotope geochemist, Dolan Integration Group.

The popular artistic representations we see today of dinosaurs in a landscape setting are based on bits of evidence from plant and animal fossils found in various places, Tabor said. While that’s based on the best information to date, it’s probably inaccurate, he said. Myers’ findings provide new insights to many studies that have been done prior to his. This will drive paleontologists and geologists to seek out more quantitative data about the ancient environment.

“The geology of the Morrison has been studied exhaustively from an observational standpoint for 100 years,” Tabor said. “I have no doubt there will be many more fossil discoveries in the Morrison, even though over the past century we’ve gained a pretty clear understanding of the plants and animals at that time. But now we can ask deeper questions about the landscape and how organisms in the ancient world interacted with their environment.”

Surprising results: Northern locale more arid than southern locale

The Morrison Formation has produced some of our most familiar dinosaurs, as well as new species never seen before. Discoveries began in the late 1800s and ultimately precipitated the Bone Wars — the fossil equivalent of California’s Gold Rush.

After Myers studied dinosaur fossils from the Morrison, he became curious about the climate. Embarking on the geochemical analysis, Myers, like scientists before him, hypothesized the climate would be similar to modern zonal circulation patterns, which are driven by the distribution of the continents. Under that hypothesis, New Mexico would be relatively arid, and Wyoming and Montana both would be wetter at the time dinosaurs roamed the landscape.

Myers analyzed 22 paleosol samples from northern New Mexico, 15 from northern Wyoming and seven from southern Montana. The samples from Montana were younger than those from New Mexico, but roughly contemporary with the samples from Wyoming.

“We found that, indeed, New Mexico was relatively arid,” Myers said. “But the surprising part was that the Wyoming locality was more arid and had less rainfall than New Mexico, even though it was at a higher latitude, and above the mid-latitude arid belt. And the Montana locality, which is not far from the Wyoming locality, had the highest rainfall of all three. And there’s a very abrupt transition between the two.”

During the Jurassic, the Morrison was between 30 degrees north and 45 degrees north, which is about five degrees south of where it sits now. Its sediments were deposited from 155 to 148 million years ago. Some areas show evidence of a marine environment, but most were continental. The mean average precipitation determined for the Jurassic doesn’t match our modern distribution, Myers said.

Study underscores that understanding climate requires multiple approaches

Previously scientists speculated on the climate based on qualitative measures, such as types of soils or rocks, or types of sedimentary structures, and inferred climate from that.

“I tried to find quantitative information, but no one had done it,” Myers said. “There are entire volumes about Morrison paleoclimate, but not a single paper with quantitative estimates. Given the volume of important fossils that have come out of the Morrison, and how significant this formation is, it just struck me as important that it be done.”

Myers classified the fossil soils according to the Mack paleosol classification, and established the elemental composition of each one to determine how much weathering the paleosols had undergone.

“There are some elements, such as aluminum, that are not easily weathered out of soils,” Myers said. “There are others that are easily flushed out. We looked at the ratio of the elements, such as aluminum versus elements easily weathered. From that, we used the ratios to determine how weathered or not the soil was.”

These findings suggest that scientists must use different approaches to quantify paleoclimate, he said.

“It’s not enough to just look at soil types and draw conclusions about the paleoclimate,” Myers said. “It’s not even enough to look at rainfall in this quantitative fashion. There are numerous factors to consider.”

Funding for the study was provided by SMU Dedman College’s Roy M. Huffington Department of Earth Sciences, SMU’s Institute for the Study of Earth and Man, The Jurassic Foundation, Western Interior Paleontological Society, The Paleontological Society and The Geological Society of America.

Reference:
T. S. Myers, N. J. Tabor, N. A. Rosenau. Multiproxy approach reveals evidence of highly variable paleoprecipitation in the Upper Jurassic Morrison Formation (western United States). Geological Society of America Bulletin, 2014; 126 (7-8): 1105 DOI: 10.1130/B30941.1

The above story is based on materials provided by Southern Methodist University. The original article was written by Margaret Allen.

The price Hawaiians are prepared to pay for living near volcanoes

No one was hurt. Credit: EPA

The destruction caused by the lava of Kilauea are grabbing the attention of the international media. Last week, footage showed this eruption claiming its first house in Pahoa and people began to question whether to try to halt the flow of lava and how you might go about it.

But the daughter of the family’s home that was destroyed was remarkably sanguine about losing the family home:

If you’re going to live on a volcano, it’s about her (the Hawaiian Goddess Pele), not us … if she wants her land back, then get out of the way. I like to call it ‘paradise tax’.

The volcano is part of their culture. Pele is such a dominant force in Hawaiian’s lives they tend to accept the possibility that it might erupt. For a lot of Hawaiians, their respect for the volcano god appears to override their fear of eruptions.

For instance, the now-displaced family is building another home on older, solidified lava. Hawaii is entirely volcanic due to being situated on a hot spot resulting in a continual output of volcanic material. As far as I am aware, the family did not have insurance. This shows their ability to bounce back and recover from a hazardous event.

Not everyone responds in the same way. Some people are scared, some panic or remain anxious. And yet Hawaiian people have dealt with Kilauea’s almost continuous eruption for more than 50 years now. Over the course of many generations, they are actively learning about the volcano and the risks it poses.

Hawaii hasn’t lost many lives to the lava of Kilauea – mainly because the lava flows are slow (due to a combination of its properties and the land it flows over) – slow enough, at least, for people to respond in time and adjust to the situation (for example evacuating like the Pahoa family did a month before their home was destroyed) but also because of the combined efforts of the public, the civil defence and government authorities.

To date, Kilauea has destroyed more than 200 properties, many roads and claimed the lives of four people in modern times. Historically, the largest number killed by a Mount Kilauea explosion was in 1790, ranging from 80-400 people, a number still being debated.

Someone’s got your back

The civil defence teams, with the combined efforts of volcanologists and all those involved in keeping the people safe, have experience in how to deal with and adapt to the ever-evolving situation. A recent update shows a collective calm and professionalism, presenting the information in a way that Hawaiians can comprehend.

The risk of property being destroyed is neither exaggerated nor underestimated. The authorities explain the risk by presenting as much information as available – and Hawaiians tend to trust that the authorities are being realistic. This feeds into how people learn and assess the risk to themselves and their properties.

Business as usual

At present there appears to be little chance of halting the advancing lava flow. The properties of the lava and external influences, such as the steepness of the terrain, mean that the point at which the lava flow might stop naturally is not yet apparent.

What has been shown in news bulletins are the more runny lava flows that volcanologists call “pāhoehoe” (the “hoe” meaning “to paddle” in Hawaiian) but this is not representative of the reality of the eruption which is producing more viscous, slower moving lava (or “aʻā” as it is known locally). As in Italy and Iceland there have been attempts to stop lava flows in Hawaii but with mixed results. For instance, according to a report in NPR,a US$2m engineering project successfully diverted lava flows near Mount Etna in 1983. But a similar attempt in Hawaii in 1955 and 1960, however, failed because of lack of proper understanding of the situation.

Given the effectiveness of the volcanic hazard management system in place in Hawaii, I have no doubt that such attempts will be made if they are reasonable, through the combined efforts of volcanologists, engineers, the civil defence and a guaranteed investment for the project.

But in case the Hawaiian authorities don’t succeed in halting or diverting the eruption and the flow of lava, we mustn’t underestimate the power of Hawaiian culture and belief to deal with such volcanoes. Living in such parts of the world, disaster resilience is not an urgency but a way of life.

Note : The above story is based on materials provided by The Conversation
This story is published courtesy of The Conversation (under Creative Commons-Attribution/No derivatives).

High earthquake danger in Tianjin, China

Earthquakes greater than or equal to M6 from A.D. 1000 to the present in the North China Basin against a background of microseismicities between 2009 and 2013. Credit: An Yin et al. and Geology

With a population of 11 million and located about 100 km from Beijing (22 million people) and Tangshan (7 million people), Tianjin lies on top of the Tangshan-Hejian-Cixian fault that has been the site of 15 devastating earthquakes in the past 1,000 years. An example of the disastrous events is the 1976 magnitude 7.6 Tangshan Earthquake, which killed a quarter million people.

To assess future seismic hazards along the fault, scientists from the University of California at Los Angeles (UCLA) and the Chinese Earthquake Administration (CEA) have reconstructed, for the first time, a spatial pattern of major earthquakes along the fault. Their reconstruction is based on (1) detailed analysis of the available instrumental records in the past few decades; (2) historical records in the past ~4,000 years; and (3) pre-historical records tracing back nearly 11,000 years.

A surprising finding from this work is the existence of a 160-km seismic gap centered at Tianjin, which has not been ruptured by any major earthquake for more than 8,400 years. As the average earthquake cycle is about 8,700 years, the authors suggest that the 160-km Tianjin fault segment, capable of generating a devastating earthquake similar to the 1976 Tangshan earthquake, may be the next to rupture.

Reference:
A possible seismic gap and high earthquake hazard in the North China Basin, An Yin et al., Structural Geology Group, China University of Geosciences (Beijing), Beijing 100083, China and Dept. of Earth, Planetary, and Space Sciences, University of California-Los Angeles, Los Angeles, California 90095-1567, USA. Published online ahead of print on 14 Nov. 2014; http://dx.doi.org/10.1130/G35986.1

Note : The above story is based on materials provided by Geological Society of America

Neanderthals cleared of driving mammoths over cliff in mass slaughter

Woolly mammoth (Mammuthus primigenius). Photograph: Andrew Nelmerm/Getty Images/Dorling Kindersley

Heaps of mammoth and woolly rhino bones found piled up at the foot of a cliff were thought to be the grim results of Neanderthals driving the beasts over the edge.

The piles of bones are a major feature at La Cotte de St Brelade on Jersey, one of the most spectacular Neanderthal sites in Europe. But the claim that they mark the remains of mass slaughter has been all but ruled out by a fresh investigation.

Researchers have found that the plateau that ends at the cliff edge was so rocky and uneven that mammoths and other weighty beasts would never have ventured up there. Even if the creatures had clambered so high, the Neanderthals would have had to chase them down a steep dip and back up the other side long before the animals reached the cliff edge and plunged to their doom.

“I can’t imagine a way in which Neanderthals would have been able to force mammoths down this slope and then up again before they even got to the edge of the headland,” said Beccy Scott, an archaeologist at the British Museum. “And they’re unlikely to have got up there in the first place.”

Hundreds of thousands of stone tools and bone fragments have been uncovered at the Jersey site where Neanderthals lived on and off for around 200,000 years. The site was apparently abandoned from time to time when the climate cooled, forcing the Neanderthals back to warmer territory.

Scott and her colleagues drew on a survey of the seabed that stretches away from the cliff to reconstruct the landscape when the Neanderthals lived there. The land, now submerged under higher sea levels, was cut with granite ravines, gullies and dead-end valleys – a terrain perfect for stalking and ambushing prey.

“The site would have been an ideal vantage point for Neanderthal hunters. They could have looked out over the open plain and watched mammoths, woolly rhinos and horses moving around. They could see what was going on, and move out and ambush their prey,” said Scott. Details of the study are published in the journal Antiquity.

The researchers have an alternative explanation for the bone heaps. Neanderthals living there may have brought the bones there after hunts, or from scavenged carcasses, and used them for food, heating and even building shelters. Older sediments at the site are rich with burnt bone and charcoal, suggesting the bones were used as fuel. The heaps of bones were preserved when Neanderthals last abandoned the site, and a fine dust of silt blew over and preserved the remains.

Archaeologists have investigated the site at La Cotte de St Brelade since the mid-19th century. More artefacts have been unearthed here than at all the other Neanderthal sites in the British Isles put together.

The exposed coastal site, one of the last resting places of the Neanderthals, was battered by fierce storms in February, raising fears that ancient remains at the site had been destroyed.

Note : The above story is based on materials provided by theguardian.com. The original article was written by Ian Sample”science correspondent”.

Subtle shifts in the Earth could forecast earthquakes, tsunamis

University of South Florida graduate student Denis Voytenko prepares a GPS unit for a high-precision geodetic measurement. Credit: Jacob Richardson

Earthquakes and tsunamis can be giant disasters no one sees coming, but now an international team of scientists led by a University of South Florida professor have found that subtle shifts in the earth’s offshore plates can be a harbinger of the size of the disaster.

In a new paper published today in the Proceedings of the National Academy of Sciences, USF geologist Tim Dixon and the team report that a geological phenomenon called “slow slip events” identified just 15 years ago is a useful tool in identifying the precursors to major earthquakes and the resulting tsunamis. The scientists used high precision GPS to measure the slight shifts on a fault line in Costa Rica, and say better monitoring of these small events can lead to better understanding of maximum earthquake size and tsunami risk.

“Giant earthquakes and tsunamis in the last decade — Sumatra in 2004 and Japan in 2011 — are a reminder that our ability to forecast these destructive events is painfully weak,” Dixon said.

Dixon was involved in the development of high precision GPS for geophysical applications, and has been making GPS measurements in Costa Rica since 1988, in collaboration with scientists at Observatorio Vulcanológico y Sismológico de Costa Rica, the University of California-Santa Cruz, and Georgia Tech. The project is funded by the National Science Foundation.

Slow slip events have some similarities to earthquakes (caused by motion on faults) but release their energy slowly, over weeks or months, and cannot be felt or even recorded by conventional seismographs, Dixon said. Their discovery in 2001 by Canadian scientist Herb Dragert at the Pacific Geoscience Center had to await the development of high precision GPS, which is capable of measuring subtle movements of the Earth.

The scientists studied the Sept. 5, 2012 earthquake on the Costa Rica subduction plate boundary, as well as motions of the Earth in the previous decade. High precision GPS recorded numerous slow slip events in the decade leading up to the 2012 earthquake. The scientists made their measurements from a peninsula overlying the shallow portion of a megathrust fault in northwest Costa Rica.

The 7.6-magnitude quake was one of the strongest earthquakes ever to hit the Central American nation and unleased more than 1,600 aftershocks. Marino Protti, one of the authors of the paper and a resident of Costa Rica, has spent more than two decades warning local populations of the likelihood of a major earthquake in their area and recommending enhanced building codes.

A tsunami warning was issued after the quake, but only a small tsunami occurred. The group’s finding shed some light on why: slow slip events in the offshore region in the decade leading up to the earthquake may have released much of the stress and strain that would normally occur on the offshore fault.

While the group’s findings suggest that slow slip events have limited value in knowing exactly when an earthquake and tsunami will strike, they suggest that these events provide critical hazard assessment information by delineating rupture area and the magnitude and tsunami potential of future earthquakes.

The scientists recommend monitoring slow slip events in order to provide accurate forecasts of earthquake magnitude and tsunami potential.

Reference:
Timothy H. Dixon, Yan Jiang, Rocco Malservisi, Robert McCaffrey, Nicholas Voss, Marino Protti, and Victor Gonzalez. Earthquake and tsunami forecasts: Relation of slow slip events to subsequent earthquake rupture. PNAS, 2014 DOI: 10.1073/pnas.1412299111

Note : The above story is based on materials provided by University of South Florida (USF Health).

Mid West site turns up diverse flora and fauna fossils

“Relatively little is known, particularly in Australia, about the early Triassic faunas and floras,” Dr Haig says.Image: Sam Heck

Preliminary sampling at a Mid West shale outcrop has turned up one of the most diverse collections of early Triassic fossils ever recorded.

The fossils include the remains of plants and animals that lived in part of a shallow estuarine basin extending deep into the supercontinent Gondwanaland’s interior, about 250 million years ago.

Most of coastal WA, and Australia’s western continental shelf, comprise a fragment of this basin, as does part of present-day Antarctica.

Present-day India was immediately adjacent and it later opened up in a rift that formed the Indian Ocean.

UWA Honorary Research Fellow micro-palaeontologist David Haig says besides microorganisms his team found insects, crustaceans and macroplant remains never before recorded from this time and place.

“The early Triassic [250−200 million years ago] is particularly interesting because it’s the time immediately after the end-of-Permian mass extinction,” he says.

“Relatively little is known, particularly in Australia, about the early Triassic faunas and floras.

“Although it’s a numerically small assemblage it has really given us an insight into the diversity of things just after this end-of-Permian extinction.”

Dr Haig says the series of shallow inland seas at the time provided conditions in many ways similar to estuaries today.

Ancient inland seas comparable to modern estuaries
These condition include variable salinity and variable temperature with periodic inflows of freshwater, which brought in terrestrial fossils.

“Because these seas were highly variable in terms of salinity the biota that lived in these seas would have withstood probably large changes in salinity and temperature,” he says.

“The main importance of the study is to bring to light what is a seemingly very diverse biota.”

He says he made the find with stratigrapher Dr Arthur Mory and mineralogist Dr Jenny Bevan while scoping out a site for a student field trip and he immediately recognised some very interesting fossils.

“We brought slabs of rock back to UWA and carefully cleft them to get bedding surfaces,” Dr Haig says.

“The fossils are very tiny so they have to be examined under a stereo microscope, and when we did this we found a whole variety of things.

“When I found something of interest I numbered the specimens and I took photographs of the specimens.”

They then contacted specialists to send the photographs to for identification.

Dr Haig stressed that they cannot yet determine diversity within individual plant and animal groups.

They are yet to enlist the aid of specialist taxonomists, and also need to collect more samples at the site.

Note : The above story is based on materials provided by Science Network WA

Turbulence in molten core helps amplify Earth’s magnetic field

Image of the ‘Derviche Tourneur Sodium’ experiment. The outer stainless steel sphere (in the center of the image) contains a smaller inner sphere (or core) made of copper. 40 liters of liquid sodium are enclosed between the two spheres. The ratio of the radii of the two spheres is identical to that between the Earth’s inner core and the core-mantle boundary. By analogy, the sodium therefore represents the liquid outer core. Credit: © CNRS Photothèque – PERRIN Emmanuel

Researchers at the Institut des Sciences de la Terre (CNRS/Université Joseph Fourier Grenoble 1/IRD/Université de Savoie/IFSTTAR) have shown that turbulence, random motion that takes place in the molten metal in Earth’s core, makes a contribution to our planet’s magnetic field. To obtain this result, they modeled Earth’s outer core using liquid sodium enclosed between two rotating concentric metal spheres, a set-up they dubbed the Derviche Tourneur Sodium (DTS) experiment.1

Their findings have just been published in the journal Physical Review Letters.

Like many planets and most stars, Earth produces its own magnetic field by dynamo action, i.e. because of the motion of an electrically conducting fluid-in this case, a mixture of molten iron and nickel. This ocean of liquid metal, the outer core, surrounds the inner core, which is made of solid metal. It is set in motion by the convection caused by the cooling of the core. The resulting flow is particularly complex: in addition to movement of fluid over long distances, which is well understood and generates a magnetic field, there are also turbulent fluctuations, involving erratic, random motion over short distances. Although turbulence also exists in the atmosphere and the oceans, the turbulence in Earth’s core is different, since it is under the combined influence of Earth’s rotation and of a strong magnetic field. It is not currently possible to reproduce this distinctive turbulence either by laboratory experiments or by computer simulations.2 Until now, it was therefore impossible for geophysicists to determine its role with regard to the magnetic field.

In order to better understand the interactions between turbulence and the magnetic field, researchers at the Institut des Sciences de la Terre, in Grenoble, used the Derviche Tourneur Sodium experiment, begun in 2005. In this miniature model of Earth’s core, 40 litres of liquid sodium (an electrically conducting fluid) is enclosed in the space between two concentric spheres. What makes this model unique is that a magnet in the center of the inner sphere provides a strong magnetic field, while the rotation of this core drives the flow of the conducting liquid very effectively. Under these conditions, the liquid sodium is subjected to a strong magnetic field and to fast rotation, as would be expected in Earth’s core, and undergoes both large-scale motion and random fluctuations.

Sensors placed around the outer sphere and inside the sodium were used to map the magnetic field, while ultrasound beams measured the rate of flow of the fluid using the Doppler effect. The data enabled the researchers to show that turbulent motion increases the fluid’s ability to conduct electricity and therefore amplifies the magnetic field, rather than reducing it as earlier experiments had appeared to show. This phenomenon, observed for the first time in the laboratory, was confirmed by numerical simulations.

The findings also apply to planets with a magnetic field and to stars. The discovery of this new component of the magnetic field may explain why in the case of Venus, Earth’s ‘twin’ planet, the liquid metal core does not produce a magnetic field. Closer to home, a better understanding of these turbulent fluctuations could help us to understand magnetic field reversals.

(1) Refers to the members of the Sufi order, the whirling dervishes (‘derviches tourneurs’ in French), who perform a whirling dance.

(2) A complete numerical simulation of the motions taking place in the outer core would make it necessary to cover a wide range of scales with a very small time step, which is out of reach with current capabilities.

Reference:
Simon Cabanes, Nathanaël Schaeffer, Henri-Claude Nataf. Turbulence Reduces Magnetic Diffusivity in a Liquid Sodium Experiment. Physical Review Letters, 2014; 113 (18) DOI: 10.1103/PhysRevLett.113.184501

Note : The above story is based on materials provided by CNRS.

Lava Flows From Kilauea Volcano

Scientists warn that if the lava flow from Kilauea continues on its path, it could reach a small patch of homes on Hawaii’s Big Island in about a week. (September 5)

Video Source : Associated Press

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