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Evidence indicates Yucatan Peninsula likely hit by tsunami 1,500 years ago

“The force required to rip this reef material from the seafloor and deposit it that far above the shoreline had to have been tremendous,” said CU-Boulder scientist Larry Benson. “We think the tsunami wave height was at least 15 feet and potentially much higher than that.” Credit: Illustration by Samantha Davies, University of Colorado

The eastern coastline of Mexico’s Yucatan Peninsula, a mecca for tourists, may have been walloped by a tsunami between 1,500 and 900 years ago, says a new study involving Mexico’s Centro Ecological Akumal (CEA) and the University of Colorado Boulder.

There are several lines of evidence for an ancient tsunami, foremost a large, wedge-shaped berm about 15 feet above sea level paved with washing machine-sized stones, said the researchers. Set back in places more than a quarter of a mile from shore, the berm stretches for at least 30 miles, alternating between rocky headlands and crescent beaches as it tracks the outline of the Caribbean coast near the plush resorts of Playa del Carmen and Cancun.

Radiocarbon dates of peat beneath the extensive berm indicate a tsunami, which may have consisted of two or even three giant waves, likely slammed the coastline sometime after A.D. 450. In addition, ruins of Post-Classic Mayan structures built between A.D. 900 and 1200 were found atop parts of the berm, indicating the tsunami occurred prior to that time.

“I was quite shocked when I first walked these headlands and saw this large berm paved with boulders running long distances in both directions,” said CEA scientist Charles Shaw. “My initial thought was that a huge wave came through here in the past, and it must have packed quite a punch.”

A paper on the subject by Shaw and Larry Benson, an adjunct curator of anthropology at the University of Colorado Museum of Natural History, was published online this week in the Journal of Coastal Research.

The boulders that cover the face and top of the berm are composed of coral and fine-grained limestone, said Benson. “The force required to rip this reef material from the seafloor and deposit it that far above the shoreline had to have been tremendous,” he said. “We think the tsunami wave height was at least 15 feet and potentially much higher than that.”

In addition, the researchers have found “outlier berms,” spanning some 125 miles along the Yucatan coastline that suggest the tsunami impacted a very large region. “I think there is a chance this tsunami affected the entire Yucatan coast,” said Benson.

The berm is composed of two layers of coarse sand as well as both small and large boulders. The beaches between the headland areas contain mostly sandy carbonate material with small boulders that likely were eroded from nearby bays during the event, said Shaw.

It is not clear what might have caused the tsunami, which can be triggered by a variety of events ranging from earthquakes and underwater landslides to volcanic eruptions and oceanic meteor strikes. While scientists have found evidence a “super-typhoon” deposited rocky berms on the Australian coastline, the sediments in those berms occur in well-sorted bands, while the Yucatan berm is composed of coarse, unlayered sands suggesting different processes were involved in sediment deposition.

“If hurricanes can build these types of berms, why is there only a single berm off the Yucatan coast given the numerous hurricanes that have made landfall there over the past century?” said Shaw. “That is a big part of our argument for a tsunami wave. We think we have the pieces of evidence we need for this event to have occurred.”

Benson and Shaw suggest the tsunami could be more accurately dated by coring mangrove swamp sediments found along the coast in order to locate the carbonate sand deposited by the massive wave, then radiocarbon dating the peaty material above and below the sand.

One implication of the Yucatan tsunami is the potential destruction another one could cause. While the geologic evidence indicates tsunamis in the region are rare — only 37 recorded in the Caribbean basin since 1492 — the Yucatan coastline, which was only lightly populated by Mayans 1,500 years ago, is now home to a number of lavish resort communities and villages inhabited by some 1.4 million people.

“If such an event occurs in the future, it would wreak havoc along the built-up coastline, probably with a great loss of life,” said Benson. But it’s far more likely that powerful hurricanes like the Class 5 Hurricane Gilbert that made landfall on the Yucatan Peninsula in 1988, killing 433 people in the Caribbean and the Gulf of Mexico and causing more than $7 billion in damage, will slam the coastline, said the researchers.

Reference:
Charles E. Shaw and Larry Benson. Possible Tsunami Deposits on the Caribbean Coast of the Yucatán Peninsula. Journal of Coastal Research, 2014; DOI: 10.2112/JCOASTRES-D-14-00084.1

Note: The above story is based on materials provided by University of Colorado at Boulder.

Genetics reveals where emperor penguins survived the last ice age

A group of emperor penguins is resting and preening next to a tide crack in the ice near the Gould Bay colony. Credit: Dr Tom Hart

A study of how climate change has affected emperor penguins over the last 30,000 years found that only three populations may have survived during the last ice age, and that the Ross Sea in Antarctica was likely the refuge for one of these populations

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The Ross Sea is likely to have been a shelter for emperor penguins for thousands of years during the last ice age, when much of the rest of Antarctica was uninhabitable due to the amount of ice.

The findings, published today in the journal Global Change Biology, suggest that while current climate conditions may be optimal for emperor penguins, conditions in the past were too extreme for large populations to survive.

A team of researchers, led by scientists from the universities of Southampton, Oxford, Tasmania and the Australian Antarctic Division, and supported in Antarctica by Adventure Network International, examined the genetic diversity of modern and ancient emperor penguin populations in Antarctica to estimate how they had been changing over time.

The iconic species is famed for its adaptations to its icy world, breeding on sea ice during the Antarctic winter when temperatures regularly drop below -30 °C. However, the team discovered that conditions were probably too harsh for emperor penguins during the last ice age and that the population was roughly seven times smaller than today and split up into three refugial populations.

Gemma Clucas, a PhD student from Ocean and Earth Science at the University of Southampton and one of the lead authors of the paper, explained: “Due to there being about twice as much sea ice during the last ice age, the penguins were unable to breed in more than a few locations around Antarctica. The distances from the open ocean, where the penguins feed, to the stable sea ice, where they breed, was probably too far. The three populations that did manage to survive may have done so by breeding near to polynyas — areas of ocean that are kept free of sea ice by wind and currents.”

One of these polynyas that supported a population of emperor penguins throughout the last ice age was probably in the Ross Sea. The researchers found that emperor penguins that breed in the Ross Sea are genetically distinct from other emperor penguins around Antarctica.

Jane Younger, a PhD student from the Australian Institute for Marine and Antarctic Sciences and the other lead author of the paper, said: “Our research suggests that the populations became isolated during the last ice age, pointing to the fact that the Ross Sea could have been an important refuge for emperor penguins and possibly other species too.”

Climate change may affect the Ross Sea last out of all regions of Antarctica. Due to changes in wind patterns associated with climate change, the Ross Sea has in fact experienced increases rather than decreases in the extent of winter sea ice over the last few decades, although this pattern is predicted to reverse by the end of the century.

Dr Tom Hart from the University of Oxford and one of the organisers of this study added: “It is interesting that the Ross Sea emerges as a distinct population and a refuge for the species. It adds to the argument that the Ross Sea might need special protection.”

Reference:
Jane L. Younger, Gemma V. Clucas, Gerald Kooyman, Barbara Wienecke, Alex D. Rogers, Philip N. Trathan, Tom Hart, Karen J. Miller. Too much of a good thing: sea ice extent may have forced emperor penguins into refugia during the last glacial maximum. Global Change Biology, 2015; DOI: 10.1111/gcb.12882

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

Discovery of 2.8-million-year-old jaw sheds light on early humans

This is a close up view of the mandible just steps from where it was sighted by Chalachew Seyoum, ASU graduate student, who is from Ethiopia. Credit: Brian Villmoare

A fossil lower jaw found in the Ledi-Geraru research area, Afar Regional State, Ethiopia, pushes back evidence for the human genus — Homo — to 2.8 million years ago, according to a pair of reports published March 4 in the online version of the journal Science. The jaw predates the previously known fossils of the Homo lineage by approximately 400,000 years. It was discovered in 2013 by an international team led by Arizona State University scientists Kaye E. Reed, Christopher J. Campisano and J Ramón Arrowsmith, and Brian A. Villmoare of the University of Nevada, Las Vegas.

For decades, scientists have been searching for African fossils documenting the earliest phases of the Homo lineage, but specimens recovered from the critical time interval between 3 and 2.5 million years ago have been frustratingly few and often poorly preserved. As a result, there has been little agreement on the time of origin of the lineage that ultimately gave rise to modern humans. At 2.8 million years, the new Ledi-Geraru fossil provides clues to changes in the jaw and teeth in Homo only 200,000 years after the last known occurrence of Australopithecus afarensis (“Lucy”) from the nearby Ethiopian site of Hadar.

Found by team member and ASU graduate student Chalachew Seyoum, the Ledi-Geraru fossil preserves the left side of the lower jaw, or mandible, along with five teeth. The fossil analysis, led by Villmoare and William H. Kimbel, director of ASU’s Institute of Human Origins, revealed advanced features, for example, slim molars, symmetrical premolars and an evenly proportioned jaw, that distinguish early species on the Homo lineage, such as Homo habilis at 2 million years ago, from the more apelike early Australopithecus. But the primitive, sloping chin links the Ledi-Geraru jaw to a Lucy-like ancestor.

“In spite of a lot of searching, fossils on the Homo lineage older than 2 million years ago are very rare,” says Villmoare. “To have a glimpse of the very earliest phase of our lineage’s evolution is particularly exciting.”

In a report in the journal Nature, Fred Spoor and colleagues present a new reconstruction of the deformed mandible belonging to the 1.8 million-year-old iconic type-specimen of Homo habilis (“Handy Man”) from Olduvai Gorge, Tanzania. The reconstruction presents an unexpectedly primitive portrait of the H. habilis jaw and makes a good link back to the Ledi fossil.

“The Ledi jaw helps narrow the evolutionary gap between Australopithecus and early Homo,” says Kimbel. “It’s an excellent case of a transitional fossil in a critical time period in human evolution.”

Global climate change that led to increased African aridity after about 2.8 million years ago is often hypothesized to have stimulated species appearances and extinctions, including the origin of Homo. In the companion paper on the geological and environmental contexts of the Ledi-Geraru jaw, Erin N. DiMaggio, of Pennsylvania State University, and colleagues found the fossil mammal assemblage contemporary with this jaw to be dominated by species that lived in more open habitats–grasslands and low shrubs–than those common at older Australopithecus-bearing sites, such as Hadar, where Lucy’s species is found.

“We can see the 2.8 million year aridity signal in the Ledi-Geraru faunal community,” says research team co-leader Kaye Reed, “but it’s still too soon to say that this means climate change is responsible for the origin of Homo. We need a larger sample of hominin fossils, and that’s why we continue to come to the Ledi-Geraru area to search.”

The research team, which began conducting field work at Ledi-Geraru in 2002, includes:

  • Erin N. DiMaggio (Pennsylvania State University), Christopher J. Campisano (ASU Institute of Human Origins and School of Human Evolution and Social Change), J. Ramón Arrowsmith (ASU School of Earth and Space Exploration), Guillaume Dupont-Nivet (CNRS Géosciences Rennes), and Alan L. Deino (Berkeley Geochronology Center), who conducted the geological research
  • Faysal Bibi (Museum für Naturkunde, Leibniz Institute for Evolution and Biodiversity Science), Margaret E. Lewis (Stockton University), John Rowan (ASU Institute of Human Origins and School of Human Evolution and Social Change), Antoine Souron (Human Evolution Research Center, University of California, Berkeley), and Lars Werdelin (Swedish Museum of Natural History), who identified the fossil mammals
  • Kaye E. Reed (ASU Institute of Human Origins and School of Human Evolution and Social Change), who reconstructed the past habitats based on the faunal communities
  • David R. Braun (George Washington University), who conducted archaeological research
  • Brian A. Villmoare (University of Nevada Las Vegas), William H. Kimbel (ASU Institute of Human Origins and School of Human Evolution and Social Change), and Chalachew Seyoum (ASU Institute of Human Origins and School of Human Evolution and Social Change, and Authority for Research and Conservation of Cultural Heritage, Addis Ababa), who analyzed the hominin fossil

Reference:
Brian Villmoare, William H. Kimbel, Chalachew Seyoum, Christopher J. Campisano, Erin Dimaggio, John Rowan, David R. Braun, J. Ramon Arrowsmith, Kaye E. Reed. Early Homo at 2.8 Ma from Ledi-Geraru, Afar, Ethiopia. Science, 2015 DOI: 10.1126/science.aaa1343

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

New data provided by seabed sediments on the climate within the Mediterranean basin over the course of the last 20,000 years

Schematic map of the Mediterranean, showing its different basins and its main wind and fluvial patterns. Credit: Image courtesy of University of Granada

An international team of scientists which included three University of Granada and the Andalusian Institute of Earth Sciences researchers (a joint UGR-CISC centre) have found new data on the weather in the Mediterranean basin over the course of the past 20,000 years thanks to the chemical composition of sediments deposited in its seabed.

This work has been published in the journal Quaternary Science Reviews. Its authors include Francisca Martínez Ruiz y David Gallego Torres (Andalusia Institute of Earth Sciences, CSIC-UGR), both of them members of the RNM179 research group, as well as Miguel Ortega Huertas (from the Mineralogy and Petrology Department). The other co-authors are Miriam Kastner (Scripps Institution of Oceanography, UCSD, La Jolla, USA), Marta Rodrigo Gámiz (NIOZ Royal Netherlands Institute for Sea Research, Texel, The Netherlands) and Vanesa Nieto Moreno (Biodiversität und Klima Forschungszentrum, Frankfurt am Main, Germany).

Francisca Martínez Ruiz is the principal author. This researcher at the Andalusian Institute of Earth Sciences explains that “the study of the chemical composition of seabed sediments is particularly interesting because, beyond mere instrumental data, only indirect markers can provide information about what the climate was like in the past”

This high-resolution study of seabed sediments allows for a description of the climate in the past which will contribute to our knowledge of current climate change, and also to speculate with different climate change scenarios for the future. For purposes such as these “The Mediterranean is” according to Francisca Martínez, “an exceptional natural lab for paleoenvironmental research, since its nature as a semi-enclosed basin makes it particularly sensitive to, and turns it into an amplifier of, the effects of global change.”

Last Glacial Maximum

The interval of time surveyed by this scientific publication is of particular interest due to the significant climate changes that have taken place since the Last Glacial Maximum (LGM), such as the last Heinrich event (periods during which waves of icebergs dropped from glaciers and crossed the North Atlantic), the Bolling-Allerod transition, the Younger Dryas (a phase of climate cooling towards the end of the Pleistocene) and Holocene climate oscillations.

Scientists have evaluated the usefulness of the different geochemical and mineralogical markers for climatic variability, and have concluded that those which provide the most reliable and accurate sort of information are the following: Ti/Al relations (i.e. titanium and aluminium) and Zr/Al (zirconium and aluminium) for the interpretation of variations in wind patterns, and therefore for the reconstruction of arid and wet cycles; relations MG/Al (magnesium and aluminium), K(Al (potassium and aluminium) and Rb/Al (rubidium and aluminium) as markers for the variation in fluvial patterns, and the conditions for oxygenation reconstructed thanks to the relations between trace metals (U, Mo, V, Co, Ni, Cr, i.e. uranium, molybdenum, vanadium, cobalt, nickel and chromium)

The study of biological productivity has turned out to be of particular interest. It was reconstructed from the barium (Ba) content in sediments derived from biogenic baryte.

“Given that much climate change is cyclical,” prof. Martínez points out, “predicting the evolution of future climate and its control mechanisms, both natural and anthropogenic, requires a proper understanding of past climate systems, and of the response of its different components (atmosphere, biosphere, lithosphere, hydrosphere, cryosphere) at a scale larger than that of instrumental record.”

Reference:
F. Martinez-Ruiz, M. Kastner, D. Gallego-Torres, M. Rodrigo-Gámiz, V. Nieto-Moreno, M. Ortega-Huertas. Paleoclimate and paleoceanography over the past 20,000 yr in the Mediterranean Sea Basins as indicated by sediment elemental proxies. Quaternary Science Reviews, 2015; 107: 25 DOI: 10.1016/j.quascirev.2014.09.018

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

3-D imaging reveals hidden forces behind clogs, jams, avalanches, earthquakes

Physicists are using this computerized 3-D rendering of beads in a box to serve as a model for soil, sand or snow. Colored lines show the network of forces as the virtual particles are pushed together. Thick red lines connect the particles that are experiencing the brunt of the force. By studying the forces inside granular materials as they’re pressed, pushed or squeezed, the researchers hope to better understand phenomena like the jamming of grain hoppers or the early warning signs of earthquakes and avalanches. Credit: Nicolas Brodu.

Pick up a handful of sand, and it flows through your fingers like a liquid. But when you walk on the beach, the sand supports your weight like a solid. What happens to the forces between the jumbled sand grains when you step on them to keep you from sinking?
An international team of researchers collaborating at Duke University have developed a new way to measure the forces inside materials such as sand, soil or snow under pressure.

Described in the March 5 issue of Nature Communications, the technique uses lasers coupled with force sensors, digital cameras and advanced computer algorithms to peer inside and measure the forces between neighboring particles in 3-D.

The new approach will allow researchers to better understand phenomena like the jamming of grain hoppers or the early warning signs of earthquakes and avalanches, said study co-author Nicolas Brodu, now at the French institute Inria.

Whether footprints in sand, or the force of gravity on a mountain slope, physicists have long sought to understand what happens inside granular materials as they’re pressed, pushed or squeezed.

For centuries this simple question has been surprisingly difficult to answer. But more recently, thanks to advances in 3-D imaging techniques and the number-crunching power of computers, researchers are starting to get a better picture of what happens when granular materials like soil or snow are pushed together.

Brodu, along with physicists Robert Behringer of Duke University and Joshua Dijksman of Wageningen University in the Netherlands, describe how they use simple tools to measure the network of forces at it spreads from one particle to the next.

The researchers use a solution of hundreds of translucent hydrogel beads in a Plexiglass box to simulate materials like soil, sand or snow.

A piston repeatedly pushes down on the beads in the box while a sheet of laser light scans the box, and a camera takes a series of cross-sectional images of the illuminated sections.

Like MRI scans used in medicine, the technique works by converting these cross-sectional “slices” into a 3-D image.

Custom-built imaging software stacks the hundreds of thousands of 2-D images together to reconstruct the surface of each individual particle in three dimensions, over time. By measuring the tiny deformations in the particles as they are squeezed together, the researchers are able to calculate the forces between them.

The new approach will help researchers better understand a range of natural and manmade hazards, such as why farmworkers stepping into grain bins sometimes experience a quicksand effect and are suddenly sucked under.

“This gives us hope of understanding what happens in disasters like a landslide, when packed soil and rocks on a mountain become loose and slide down,” Brodu said. “First it acts like a solid, and then for reasons physicists don’t completely understand, all of a sudden it destabilizes and starts to flow like a liquid. This transition from solid to liquid can only be understood if you know what’s going on inside the soil.”

The team has already used results from their technique to create a new model for the way particulate matter behaves, which is concurrently published in the journal Physical Review E.

Video:

Physicists are using this computerized 3-D rendering of beads in a box to serve as a model for soil, sand or snow. Colored lines show the network of forces as the virtual particles are pushed together. Thick red lines connect the particles that are experiencing the brunt of the force. By studying the forces inside granular materials as they’re pressed, pushed or squeezed, the researchers hope to better understand phenomena like the jamming of grain hoppers or the early warning signs of earthquakes and avalanches.
Credit: Video courtesy of Nicolas Brodu.

Reference:
“Spanning the Scales of Granular Materials through Microscopic Force Imaging,” Brodu, N., J. A. Dijksman and R. P. Behringer. Nature Communications, March 2015. DOI: 10.1038/ncomms7361

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

Earliest known fossil of the genus Homo dates to 2.8 to 2.75 million years ago

A caravan moves across the Lee Adoyta region in the Ledi-Geraru project area near the early Homo site. The hills behind the camels expose sediments that are younger than 2.67 million year old, providing a minimum age for the LD 350-1 mandible. Credit: Erin DiMaggio, Penn State

The earliest known record of the genus Homo — the human genus — represented by a lower jaw with teeth, recently found in the Afar region of Ethiopia, dates to between 2.8 and 2.75 million years ago, according to an international team of geoscientists and anthropologists. They also dated other fossils to between 2.84 and 2.58 million years ago, which helped reconstruct the environment in which the individual lived.
“The record of hominin evolution between 3 and 2.5 million years ago is poorly documented in surface outcrops, particularly in Afar, Ethiopia,” said Erin N. DiMaggio, research associate in the department of geosciences, Penn State.

Hominins are the group of primates that include Homo sapiens — humans — and their ancestors. The term is used for the branch of the human evolutionary line that exists after the split from chimpanzees.

Directly dating fossils this old is impossible, so geologists use a variety of methods to date the layers of rock in which the fossils are found. The researchers dated the recently discovered Ledi-Geraru fossil mandible, known by its catalog number LD 350-1, by dating various layers of volcanic ash or tuff using argon40 argon39 dating, a method that measures the different isotopes of argon and determines the age of the eruption that created the sample. They present their results in today’s (Mar. 4) online issue of Science Express.

“We are confident in the age of LD 350-1,” said DiMaggio, lead author on the paper. “We used multiple dating methods including radiometric analysis of volcanic ash layers, and all show that the hominin fossil is 2.8 to 2.75 million years old.”

The area of Ethiopia where LD 350-1 was found is part of the East African Rift System, an area that undergoes tectonic extension, which enabled the 2.8 million-year-old rocks to be deposited and then exposed through erosion, according to DiMaggio. In most areas in Afar, Ethiopia, rocks dating to 3 to 2.5 million years ago are incomplete or have eroded away, so dating those layers and the fossils they held is impossible. In the Ledi-Geraru area, these layers of rocks are exposed because the area is broken by faults that occurred after the sedimentary rocks were deposited.

By dating volcanic ash layers below the fossils and then above the fossils, geologists can determine the youngest and oldest dates when the animal that became the fossil could have lived.

Other fossils found in this area include those of prehistoric antelope, water dependent grazers, prehistoric elephants, a type of hippopotamus and crocodiles and fish. These fossils fall within the 2.84 to 2.54 million years ago time range. Kaye E. Reed, University Professor, Institute of Human Origins, Arizona State University, analyzed the fossil assemblage to try to learn about the ecological community in which the LD 350-1 early Homo lived.

The fossils suggest that the area was a more open habitat of mixed grasslands and shrub lands with a gallery forest — trees lining rivers or wetlands. The landscape was probably similar to African locations like the Serengeti Plains or the Kalahari. Some researchers suggest that global climate change intensifying roughly 2.8 million years ago resulted in African climate variability and aridity and this spurred evolutionary changes in many mammal lines.

“We can see the 2.8 million-year-old aridity signal in the Ledi-Geraru faunal community,” said Reed. “But it’s still too soon to say that this means climate change is responsible for the origin of Homo. We need a larger sample of hominin fossils and that’s why we continue to come to the Ledi-Geraru area to search.”

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

Volcano Villarrica erupts in southern Chile

Volcano Villarrica in southern Chile erupted in the early hours of Tuesday “Mar-3-2015”, sending ash and lava high into the sky, and forcing the evacuation of nearby communities.

A New Level of Earthquake Understanding

The notorious San Andreas Fault runs virtually the entire length of California. Credit: Courtesy of US Geological Survey

U.S. Department of Energy (DOE)’s Lawrence Berkeley National Laboratory (Berkeley Lab) is reporting the successful study of stress fields along the San Andreas fault at the microscopic scale, the scale at which earthquake-triggering stresses originate.
Working with a powerful microfocused X-ray beam at Berkeley Lab’s Advanced Light Source (ALS), a DOE Office of Science User Facility, researchers applied Laue X-ray microdiffraction, a technique commonly used to map stresses in electronic chips and other microscopic materials, to study a rock sample extracted from the San Andreas Fault Observatory at Depth (SAFOD). The results could one day lead to a better understanding of earthquake events.

“Stresses released during an earthquake are related to the strength of rocks and thus in turn to the rupture mechanism,” says Martin Kunz, a beamline scientist with the ALS’s Experimental Systems Group. “We found that the distribution of stresses in our sample were very heterogeneous at the micron scale and much higher than what has been reported with macroscopic approximations. This suggests there are different processes at work at the microscopic and macroscopic scales.”

Kunz is one of the co-authors of a paper describing this research in the journal Geology. The paper is titled “Residual stress preserved in quartz from the San Andreas Fault Observatory at Depth.” Co-authors are Kai Chen, Nobumichi Tamura and Hans-Rudolf Wenk.

Most earthquakes occur when stress that builds up in rocks along active faults, such as the San Andreas, is suddenly released, sending out seismic waves that make the ground shake. The pent- up stress results from the friction caused by tectonic forces that push two plates of rock against one another.

“In an effort to better understand earthquake mechanisms, several deep drilling projects have been undertaken to retrieve material from seismically active zones of major faults such as SAFOD,” says co-author Wenk, a geology professor with the University of California (UC) Berkeley’s Department of Earth and Planetary Science and the leading scientist of this study. “These drill-core samples can be studied in the laboratory for direct information about physical and chemical processes that occur at depth within a seismically active zone. The data can then be compared with information about seismicity to advance our understanding of the mechanisms of brittle failure in the Earth’s crust from microscopic to macroscopic scales.”

Kunz, Wenk and their colleagues measured remnant or “fossilized” stress fields in fractured quartz crystals from a sample taken out of a borehole in the San Andreas Fault near Parkfield, California at a depth of 2.7 kilometers. The measurements were made using X-ray Laue microdiffraction, a technique that can determine elastic deformation with a high degree of accuracy. Since minerals get deformed by the tectonic forces that act on them during earthquakes, measuring elastic deformation reveals how much stress acted on the minerals during the quake.

“Laue microdiffraction has been around for quite some time and has been exploited by the materials science community to quantify elastic and plastic deformation in metals and ceramics, but has been so far only scarcely applied to geological samples,” says co-author Tamura, a staff scientist with the ALS’s Experimental Systems Group who spearheads the Laue diffraction program at the ALS.

Using ALS beamline 12.3.2, researchers carried out an X-ray microdiffraction study on quartz grains from the San Andreas Fault Observatory at Depth and found a heterogeneous distribution of stress.

The measurements were obtained at ALS beamline 12.3.2, a hard (high-energy) X-ray diffraction beamline specialized for Laue X-ray microdiffraction.

“ALS Beamline 12.3.2 is one of just a few synchrotron-based X-ray beamlines in the world that can be used to measure residual stresses using Laue micro diffraction,” Tamura says.

In their analysis, the Berkeley researchers found that while some of the areas within individual quartz fragments showed no elastic deformation, others were subjected to stresses in excess of 200 million pascals (about 30,000 psi). This is much higher than the tens of millions of pascals of stress reported in previous indirect strength measurements of SAFOD rocks.

“Although there are a variety of possible origins of the measured stresses, we think these measured stresses are records of seismic events shocking the rock,” says co-author Chen of China’s Xi’an Jiantong University. It is the only mechanism consistent with the geological setting and microscopic observations of the rock.”

The authors believe their Laue X-ray microdiffraction technique has great potential for measuring the magnitude and orientation of residual stresses in rocks, and that with this technique quartz can serve as “paleo-piezometer” for a variety of geological settings and different rock types.

“Understanding the stress fields under which different types of rock fail will help us better understand what triggers earthquakes,” says Kunz. “Our study could mark the beginning of a whole new era of quantifying the forces that shape the Earth.”

Reference:
K. Chen, M. Kunz, N. Tamura, H.-R. Wenk. Residual stress preserved in quartz from the San Andreas Fault Observatory at Depth. Geology, 2015; 43 (3): 219 DOI: 10.1130/G36443.1

Note: The above story is based on materials provided by DOE/Lawrence Berkeley National Laboratory.

Methane oxidation fuelled by algal oxygen production

Round diatoms (Di) in close proximity to methane-oxidizing bacteria (fluorescent green). Combination of fluorescence microscopy and X-ray spectroscopic mapping of silica. (Source: Eawag / MPI-Bremen)

Methane emissions are strongly reduced in lakes with anoxic bottom waters. But here — contrary to what has previously been assumed — methane removal is not due to archaea or anaerobic bacteria. A new study on Lake Cadagno in Canton Ticino shows that the microorganisms responsible are aerobic proteobacteria. The oxygen they require is produced in situ by photosynthetic algae.

In contrast to oceans, freshwater lakes — and tropical reservoirs — are significant sources of methane emissions. Methane, a greenhouse gas, arises from the degradation of organic material settling on the bottom. Although lakes occupy a much smaller proportion of Earth’s surface than oceans, they account for a much larger proportion of methane emissions. Well-mixed lakes, in turn, are the main contributors, while emissions from seasonally or permanently stratified lakes with anoxic bottom waters are greatly reduced. It has been assumed to date that the methane-removing processes occurring in such lakes are the same as those in marine systems. But a new study carried out on Lake Cadagno (Canton Ticino) by researchers from Eawag and the Max Planck Institute for Marine Microbiology (Bremen, Germany) shows that this is not the case.

Typical profiles of oxygen and methane concentrations in Lake Cadagno. Methane consumption occurs in a relatively thin water layer at a depth of 10–13 metres. (Data: Eawag / MPI-Bremen)

The scientists demonstrated that methane is almost completely consumed in the anoxic waters of Lake Cadagno, but they did not detect any known anaerobic methane-oxidizing bacteria — or archaea, which are responsible for marine methane oxidation. Instead, water samples collected from a depth of around 12 metres were found to contain abundant aerobic proteobacteria — up to 240,000 cells per millilitre.

“We wondered, of course, how these aerobic bacteria can survive in anoxic waters,” says first author Jana Milucka of the Max Planck Institute for Marine Microbiology. To answer this question, the behaviour of the bacteria was investigated in laboratory experiments: methane oxidation was found to be stimulated only when oxygen was added to the samples incubated in vitro, or when they were exposed to light. The scientists concluded that the oxygen required by the bacteria is produced by photosynthesis in neighbouring diatoms. Analysis by fluorescence microscopy showed that methane-oxidizing bacteria belonging to the family Methylococcaceae occur in close proximity to diatoms and can thus utilize the oxygen they generate .

Thanks to the combined activity of bacteria and diatoms, methane is thus consumed in the lake rather than being released into the atmosphere. This type of methane removal has not previously been described in freshwater systems. Project leader Carsten Schubert of Eawag comments: “For lakes with anoxic layers, and also for certain marine zones, it looks as if the textbooks will have to be rewritten.” Aerobic methane-oxidizing bacteria may play a significant role wherever sufficient light penetrates to anoxic water layers; according to Schubert, this is the case in most Swiss lakes. Similar observations have already been made in Lake Rotsee near Lucerne, in studies not yet published. Research will now focus on deeper lakes, where initial investigations suggest that different processes occur.

Reference:
Jana Milucka, Mathias Kirf, Lu Lu, Andreas Krupke, Phyllis Lam, Sten Littmann, Marcel MM Kuypers, Carsten J Schubert. Methane oxidation coupled to oxygenic photosynthesis in anoxic waters. The ISME Journal, 2015; DOI: 10.1038/ismej.2015.12

Note: The above story is based on materials provided by EAWAG: Swiss Federal Institute of Aquatic Science and Technology.

Banded ironstone formation theory challenges current thinking

Banded Iron Formation at Fortescue Falls, Karijini National Park. Credit: Graeme Churchard

A UWA geologist has proposed a hypothesis which threatens to overturn conventional notions of the way Banded Ironstone Formations (BIF) first evolved.

BIF is a sedimentary rock with stripes of iron and silica which is well known to geologists and rock collectors.
While it is generally accepted that BIF formed when dissolved iron oxidised and settled to the bottoms of early seas, geologist Desmond Lascelles says this would have been impossible as iron is only soluble in acid.

“Ferrous iron is not soluble in sea water,” he says.

“It only occurs as colloidal ferric iron or ferrous iron in sea water which precipitates out, but you can’t end up with sufficient iron in solution to form a banded iron formation.”

As none of these compounds are water soluble, Dr Lascelles says the ocean cannot form a large reservoir of iron.

He says silica, which forms the lighter bands in BIF, is similarly insoluble.

While it initially mixes with water it precipitates out as it ages so large quantities never occur in solution.

Instead, he says, the iron and silica compounds came from hydrothermal vents on the ocean floor known as “black smokers”.

Build-up happens around vents

The “smoke” is the precipitated iron oxides and iron silicates that end up as a mound around the vent.

Dr Lascelles says water currents redistribute these mounds and the particles settle elsewhere as layers of mud that harden to become banded ironstone.

Known BIF deposits are at least 1.8 billion years old, which is 600 million years after the “great oxidation event” when green plants first oxygenated the atmosphere and ocean.

Younger BIF has not been found, supporting the conventional notion that newly-oxygenated seas quickly lost their reservoir of dissolved iron, which literally rusted forming most of the world’s BIF within a relatively short period.

However, Dr Lascelles says the apparent increase in the amount of BIF in the Paleoproterozoic era (2,500 to 1,600 million years ago) had nothing to do with oxygen in the atmosphere.

Instead he attributes it to the introduction of plate tectonics and the movement of continents, after stable continents first formed.

Dr Lascelles says younger BIF forms on the ocean floor but the tectonic plates supporting it are then subducted under the continents.

According to his model, banded ironstone has been forming throughout history and new deposits may still be occurring, under suitable conditions, from hydrothermal vents deep beneath the ocean.

Reference:
Lascelles, D: Plate tectonics caused the demise of banded iron formations in Applied Earth Science DOI 10.1179/1743275814Y.0000000043

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

Pre-1950 structures suffered the most damage from August 2014 Napa quake

This image shows locations of the mainshock (red dot), aftershocks, surface ruptures (red lines), and locations of permanent (unfilled triangles) and temporary (filled triangles) seismic stations. Credit: Seismological Research Letters

SAN FRANCISCO–An analysis of buildings tagged red and yellow by structural engineers after the August 2014 earthquake in Napa links pre-1950 buildings and the underlying sedimentary basin to the greatest shaking damage, according to one of six reports on the Napa quake published in the March/April issue of Seismological Research Letters (SRL).
“This data should spur people to retrofit older homes,” said John Boatwright, a geophysicist with the U.S. Geological Survey (USGS) in Menlo Park and the lead author of a study that analyzed buildings tagged by the City of Napa.

The South Napa earthquake was the largest earthquake to strike the greater San Francisco Bay Area since the magnitude 6.9 Loma Prieta earthquake in 1989, damaging residential and commercial buildings from Brown’s Valley through historic downtown Napa.

“The larger faults, like the San Andreas and Hayward faults, get the public’s attention, but lesser known faults, like the West Napa fault, can cause extensive damage. Unreinforced brick masonry and stone buildings have been shown to be especially vulnerable to earthquakes,” said Erol Kalkan, a research structural engineer at USGS and guest editor of the SRL special issue, which features six technical reports that cover different aspects of the magnitude 6.0 South Napa earthquake on August 24, 2014.

This image shows red and yellow tags plotted on the street grid and topography of Napa. Credit: Seismological Research Letters

The South Napa earthquake occurred on the West Napa Fault system, a recognized but poorly studied fault lying between the longer Rodgers Creek and Green Valley faults, and caused strong ground motions, as detailed in the paper by Tom Brocher et al. The mapped surface rupture was unusually large for a moderate quake, extending nearly eight miles from Cuttings Wharf in the south to just west of Alston Park in the north.

An extensive sedimentary basin underlies much of Napa Valley, including the City of Napa. The basin, which may be as much as 2 km deep beneath the city, appears to have amplified the ground motion. A close look at the damaged buildings within the city revealed a clear pattern.

“Usually I look to certain factors that influence ground motion at a specific site – proximity to the fault rupture, directivity of the rupture process and the geology underneath the site,” said Boatwright. “The source distance and the direction of rupture did not strongly condition the shaking damage in Napa.”

Boatwright et al., analyzed data provided by structural engineers who inspected and tagged damaged buildings after the earthquake. The 165 red tags (prohibited access) and 1,707 yellow tags (restricted access) stretched across the city but were primarily concentrated within the residential section that lies between State Route 29 and the Napa River, including the historic downtown area.

When comparing the distribution of red and yellow-tagged buildings to the underlying sedimentary basin, to the pre-1950 development of Napa and to the recent alluvial geology of Napa Valley, the most severe damage correlates to the age of the buildings–pre-1950 construction–and their location within the basin. Less damaged areas to the east and west of central Napa lie outside of the sedimentary basin, and the moderately damaged neighborhoods to the north lie inside the basin but are of more recent construction.

Although the city’s buildings suffered extensive damage, there were few reports of ground failure, such as liquefaction and landslides. Brocher et al. suggest the timing of the earthquake near the end of the dry season, the three-year long drought and resulting low water table inhibited the liquefaction of the top layers of sandy deposits, sparing the area greater damage.

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

Lightning plus volcanic ash make glass

This is a secondary electron image showing a glass spherule formed in high-voltage flashover experiments to examine the effect of ash contamination on electrical insulators. Photo by Kimberly Genareau. Credit: Kimberly Genareau, Genareau et al., Geology, Geological Society of America.

In their open-access paper for Geology, Kimberly Genareau and colleagues propose, for the first time, a mechanism for the generation of glass spherules in geologic deposits through the occurrence of volcanic lightning. The existence of fulgurites — glassy products formed in rocks and sediments struck by cloud-to-ground lightning — provide direct evidence that geologic materials can be melted via natural lightning occurrence.

Lightning-induced volcanic spherules (LIVS) form in the atmosphere from the physical transformation of volcanic ash particles into spheres of glass due to the high heat generated by lightning discharge. Examples of these textures were discovered in deposits from two volcanic eruptions where lightning was extensively documented: The 23 March 2009 eruption of Mount Redoubt, Alaska, USA, and the April-May 2010 eruption of Eyjafjallajökull, Iceland.

In some cases, the individual spherules are smooth, while in other instances the surfaces are interrupted by holes or cracks that appear to result from outward expansion of the spherule interior. Analogue laboratory experiments, examining the flashover mechanism across high voltage insulators contaminated by volcanic ash, confirm that glass spherules can be formed from the high heat generated by electrical discharge.

Reference:
Lightning-induced volcanic spherules
Kimberly Genareau et al., University of Alabama, Tuscaloosa, Alabama, USA. Published online ahead of print on 27 Feb. 2015; http://dx.doi.org/10.1130/G36255.1. This article is OPEN ACCESS online.

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

Volcanoes: How they’re formed and why they erupt. Videographic

Villarrica volcano in southern Chile began erupting early Tuesday forcing the evacuation of some 3,000 people in nearby villages, the government said. VIDEOGRAPHIC

Video Provided by: AFP news agency

Core work: Iron vapor gives clues to formation of Earth and moon

The Z machine is in Albuquerque, N.M., and is part of the Pulsed Power Program, which started at Sandia National Laboratories in the 1960s. Pulsed power concentrates electrical energy and turns it into short pulses of enormous power, which are then used to generate X-rays and gamma rays. Credit: Randy Montoya

Recreating the violent conditions of Earth’s formation, scientists are learning more about how iron vaporizes and how this iron rain affected the formation of Earth and Moon. The study is published March 2 in Nature Geoscience.
“We care about when iron vaporizes because it is critical to learning how Earth’s core grew,” said co-author Sarah Stewart, UC Davis professor of Earth and Planetary Sciences.

Shock and release

Scientists from Lawrence Livermore National Laboratory, Sandia National Laboratory, Harvard University and UC Davis used one of the world’s most powerful radiation sources, the Sandia National Laboratories Z-machine, to recreate conditions that led to Earth’s formation. They subjected iron samples to high shock pressures in the machine, slamming aluminum plates into iron samples at extremely high speeds. They developed a new shock-wave technique to determine the critical impact conditions needed to vaporize the iron.

The researchers found that the shock pressure required to vaporize iron is much lower than expected, which means more iron was vaporized during Earth’s formation than previously thought.

Iron rain

Lead author Richard Kraus, formerly a graduate student under Stewart at Harvard, is now a research scientist at Lawrence Livermore National Laboratory. He said the results may shift how planetary scientists think about the processes and timing of Earth’s core formation.

“Rather than the iron in the colliding objects sinking down directly to the Earth’s growing core, the iron is vaporized and spread over the surface within a vapor plume,” said Kraus. “This means that the iron can mix much more easily with Earth’s mantle.”

After cooling, the vapor would have condensed into an iron rain that mixed into Earth’s still-molten mantle.

To the moon

This process may also explain why the Moon, which is thought to have formed by this time, lacks iron-rich material despite being exposed to similarly violent collisions. The authors suggest the Moon’s reduced gravity could have prevented it from retaining most of the vaporized iron.

Reference:
Richard G. Kraus, Seth Root, Raymond W. Lemke, Sarah T. Stewart, Stein B. Jacobsen, Thomas R. Mattsson. Impact vaporization of planetesimal cores in the late stages of planet formation. Nature Geoscience, 2015; DOI: 10.1038/ngeo2369

Note: The above story is based on materials provided by University of California – Davis. The original article was written by Kat Kerlin.

What’s beneath Hawaii’s most active volcano?

Aerial view of Kilauea volcano. Credit: Flickr user exfordy

Step away from the villages and idyllic beaches of Hawaii, and you may think you’ve been transported to the moon. Walking along the lava flows of the Kilauea volcano, the landscape changes from a lush tropical paradise to one that’s bleak and desolate, the ground gray and rippled with hardened lava.

That’s how Christelle Wauthier, assistant professor in the Department of Geosciences and the Institute for CyberScience at Penn State, describes it, anyway.

Wauthier has been studying Kilauea volcano for several years and is getting ready to start a new project at Penn State—one using a radar imaging technique that researchers call interferometric synthetic aperture radar (InSAR) to try to peer below its surface and learn more about why the volcano is so volatile.

Kilauea is the most active of the five volcanoes that make up the island of Hawaii. It’s been erupting continuously since 1983, so far spewing 3.5 cubic kilometers of lava onto the surrounding landscape. The lava usually flows southward, but last year an eruption started creeping east toward the nearby village of Pahoa.

The flow was inconsistent—advancing anywhere from 10 yards to one-quarter mile a day—but it was enough to cause evacuations and lots of anxiety for the residents of the small village.

Wauthier says the volcano’s recent brush with the island’s inhabitants reinforced the importance of studying not just what’s happening on the surface of the volcano, but also what’s going on below.

“The volcano has been erupting for 31 years, so obviously there’s a lot of magma coming from below,” said Wauthier. “There’s lots of magma moving up and out, so one of the questions we’re asking is where are all these magma sources and how do they relate to each other?”

One of the keys to answering this question is found in the deformations happening on the surface of Kilauea. While a deformation is simply a change on the volcano’s exterior, what it implies goes much deeper—there has to be something below the surface causing the change. And without X-ray glasses to diagnose what’s happening, Wauthier uses InSAR to try to piece together what might be going on.

“InSAR is a remote-sensing technique that combines radar data taken from satellites to create images that show subtle movements in the ground’s surface,” said Wauthier. “In this case, the movements we’re studying are deformations on Kilauea.”

To begin the process, Wauthier gathers satellite data from archived databases. She looks for information about changes in elevation from before and after a “natural hazard event”—an eruption or earthquake, for example. Wauthier then uses this data to create two images: one from before the natural hazard event and one from after. This shows how the event changed the ground’s surface.

The two pictures can then be combined to create a single, much more comprehensive InSAR image called an interferogram, which uses color to represent movement.

Wauthier says that while InSAR images can certainly be created from two images, she also uses a time-series approach called Multi-Temporal (MT)-InSAR when enough radar images are available. This technique uses multiple images instead of two.

“This approach is much more accurate, but it also requires much more data and computing power,” Wauthier said. “The powerful computer clusters and IT facilities available through the Institute for CyberScience here at Penn State are tremendously helpful by providing the necessary computing power and efficiency.”

After Wauthier creates the InSAR images, she can begin to use them to predict what might be happening underneath Kilauea. She uses an approach called inverse modeling to estimate what caused the deformation.

“Basically, we use what’s happening on the surface of the volcano to find a ‘best fit model’ for what’s happening underground,” said Wauthier. “For example, if we know the ground rose here but sank over there, we’ll come up with a best guess for the type of magma process—like a magma reservoir or intrusion—that’s below.”

But magma processes aren’t the only things that could be affecting Kilauea’s volatility. The southern flank of the volcano is moving away from the island, and Wauthier says this could also be influencing the volcano’s magma plumbing system and activity.

Wauthier says that although the flank is slipping seaward at an average speed of 6 to 10 centimeters a year, earthquakes in the past have caused more drastic movement and have even generated tsunamis.

Remote-sensing technologies like InSAR are important because they allow researchers like Wauthier to do important research without physically being on location. (Although when you’re studying the Hawaiian landscape, you might want to be.)

Wauthier says she would like to return to Hawaii one day, but in the meantime, she hopes the project will help uncover information that could help the people of Hawaii as well as other scientists at the U.S. Geological Society Hawaiian Volcano Observatory. Having a better understanding of Kilauea would help researchers better grasp the behavior of other ocean islands volcanoes.

“Ideally, we’d like to get a much better picture of the underground magma systems and how they interact with the flank slip,” she said. “The flank instabilities can cause earthquakes and tsunamis, so we’d like to be able to understand and forecast those better. Hopefully, the more we know about these natural hazards, the more we can help people anticipate and mitigate their risks.”

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

How were fossil tracks made by Early Triassic swimming reptiles so well preserved?

Tracy J. Thomson stands next to a block with numerous swim tracks in Capitol Reef National Park, Utah. Credit: Tracy Thomson.

A type of vertebrate trace fossil gaining recognition in the field of paleontology is that made by various tetrapods (four-footed land-living vertebrates) as they traveled through water under buoyant or semibuoyant conditions.
Called fossil “swim tracks,” they occur in high numbers in deposits from the Early Triassic, the Triassic being a geologic period (250 to 200 million years ago) that lies between the Permian and Jurassic. Major extinction events mark the start and end of the Triassic.

While it is known that tetrapods made the tracks, what is less clear is just why the tracks are so abundant and well preserved.

Paleontologists at the University of California, Riverside have now determined that a unique combination of factors in Early Triassic delta systems resulted in the production and unusually widespread preservation of the swim tracks: delayed ecologic recovery, depositional environments, and tetrapod swimming behavior.

“Given their great abundance in Lower Triassic strata, swim tracks have the potential to provide a wealth of information regarding environmental exploitation by reptiles during this critical time in their evolution following the end-Permian mass extinction,” said Mary L. Droser, a professor of paleontology in the Department of Earth Sciences, who led the research. “They also provide important data for our interpretation of Early Triassic sedimentological and stratigraphic processes. The Early Triassic period follows the largest mass extinction event in Earth’s history. The fossil record shows that a prolonged period of delayed ecologic recovery persisted throughout the Early Triassic.”

She explained that the fossil swim tracks are important and unique records of the aquatic behaviors and locomotion mechanics of tetrapods, and reveal a hidden biodiversity. They also constitute an excellent natural laboratory for investigating the paleoenvironmental and paleoecological conditions associated with their production and preservation.

Droser and Tracy J. Thomson, her former graduate student, surveyed the temporal distribution of the swim tracks seen in fossils in Utah, and report online this month, ahead of print, in the journal Geology that it is not the tetrapod swimming behavior alone, but the prevalence of unbioturbated substrates resulting from the unique combination of ecological and environmental conditions during the Early Triassic that led to the abundant production and preservation of swim tracks.

They identify three interacting factors that composed a “Goldilocks” effect in promoting the production and preservation of Lower Triassic swim tracks. These factors were (1) ecological, i.e., delayed ecologic recovery resulting in the lack of well-mixed sediment, (2) paleoenvironmental, i.e., depositional environments that promoted the production of firmground substrates, and (3) behavioral, i.e., the presence of tetrapods capable of aquatic locomotion such as swimming or bottom walking.

“During the Early Triassic, sediment mixing by animals living within the substrate was minimal,” said Thomson, the first author of the research paper who is now pursuing a doctoral degree at UC Davis. “This strongly contributed to the widespread production of firm-ground substrates that are ideal for recording and preserving trace fossils like swim tracks.”

Thomson explained that the end-Permian mass extinction event resulted in ecologic restructuring of both the marine and terrestrial realms. Bioturbation was suppressed, resulting in no extensively mixed sediment layer, thereby allowing fine-grained, low-water-content firmgrounds to develop near the sediment-water interface.

“Early Triassic deltas and their paleoenvironments were favorable habitats for functionally amphibious reptiles,” Droser said. “There were few animals living in the sediment mixing it up after the extinction, and so the muds became firm and cohesive providing ideal conditions for preservation. Periodic flooding supplied coarser grained material, enhancing swim track preservation.”

Reference:
T. J. Thomson, M. L. Droser. Swimming reptiles make their mark in the Early Triassic: Delayed ecologic recovery increased the preservation potential of vertebrate swim tracks. Geology, 2015; 43 (3): 215 DOI: 10.1130/G36332.1

Note: The above story is based on materials provided by University of California – Riverside.

Map outlines western Oregon landslide risks from a subduction zone earthquake

New landslide maps have been developed that will help the Oregon Department of Transportation determine which coastal roads and bridges in Oregon are most likely to be usable following a major subduction zone earthquake that is expected in the future of the Pacific Northwest.

The maps were created by Oregon State University and the Oregon Department of Geology and Mineral Industries, or DOGAMI, as part of a research project for ODOT. They outline the landslide risks following a large earthquake on the Cascadia Subduction Zone.

The mapping is part of ongoing ODOT efforts to preserve the critical transportation routes that will facilitate response and recovery.

“Landslides are a natural part of both the Oregon Coast Range and Cascade Range, but it’s expected there will be a significant number of them that are seismically induced from a major earthquake,” said Michael Olsen, an assistant professor in the OSU School of Civil and Construction Engineering. “A massive earthquake can put extraordinary additional strain on unstable slopes that already are prone to landslides.”

Landslides are already a serious geologic hazard for western Oregon. But during an earthquake, lateral ground forces can be as high as half the force of gravity.

The Coast Range is of special concern, officials say, because it will be the closest part of the state to the actual subduction zone earthquake, and will experience the greatest shaking and ground movement. The research identified some of the most vulnerable landslide areas in Oregon as parts of the Coast Range between Tillamook and Astoria, and from Cape Blanco south to the California border – in each case, from the coast to about 30 miles inland.

“Major landslides have been identified by DOGAMI throughout western Oregon using high-resolution lidar mapping,” Olsen said. “Some experts believe that a number of these landslides date back to the last subduction zone earthquake in Oregon, in 1700. Coast Range slopes that are filled with weak layers of sedimentary rock are particularly vulnerable, and many areas are already on the verge of failure.”

According to the new map, the highway corridors to the coast that will face comparatively less risk from landslides will be Oregon Highway 36 from near Eugene to Florence; Oregon Highway 38 from near Cottage Grove to Reedsport; Oregon Highway 18 from Salem to Lincoln City; and large portions of U.S. Highway 30 from Portland to Astoria. However, landslides or other damages could occur on any road to the coast or in the Cascade Range due to the anticipated high levels of ground shaking.

The new research, along with other considerations, will help ODOT and other officials determine which areas merit the most investment in coming years as part of long-term planning for the expected earthquake. Given the high potential for damage and minimal resources available for mitigation, experts may choose to focus their efforts on highway corridors that are expected to receive less damage from the earthquake, Olsen said.

The research reflected in the new map considered such factors as slope, direction of ground movement, soil type, vegetation, distance to rivers, roads and fault locations, peak ground acceleration, peak ground velocity, annual precipitation averages, and other factors.

ODOT, Oregon State and DOGAMI have been state leaders in research on risks posed by the Cascadia Subduction Zone, earthquake and tsunami impacts, and initiatives to help the state prepare for a future disaster that scientists say is a certainty.

Officials said it’s important to consider not just the damage to structures that can occur as a result of an earthquake, but also landslide and transportation issues.

“ODOT recognizes the potential not only for casualties due to landslides during and after an earthquake, but also for the likelihood of isolating whole segments of the state’s population,” one ODOT official said. “Thousands of people in the coastal communities would be stranded and cut off from rescue, relief and recovery that would arrive by surface transport.”

ODOT recently completed a seismic vulnerability assessment and selected lifeline corridor routes to prioritize following an earthquake.  ODOT also maintains an unstable slopes program, evaluating the frequency of rockfalls and landslides affecting highway corridors.

DOGAMI recently released another open file report as part of the Oregon Resilience Plan, which evaluated multiple potential hazards resulting from a Cascadia subduction zone earthquake, including landslides, liquefaction, and tsunamis.

Some recent efforts at OSU have also focused on understanding the different concerns raised by a subduction zone earthquake compared to the type of strike-slip faults more common in California, on which many seismic plans are based. Subduction earthquakes tend to be larger, affect a wider area and last longer.

Reference:
DOGAMI Open-File Report O-15-01, “Landslide Susceptibility Analysis of Lifeline Routes in the Oregon Coast Range,” by Rubini Mahalingam; Michael J. Olsen; Mahyar Sharifi-Mood; and Daniel T. Gillins, Oregon State University School of Civil and Construction Engineering.

ODOT Research Report SPR-740, “Impacts of Potential Seismic Landslides on Lifeline Corridors,” by Michael J. Olsen; Scott A. Ashford; Rubini Mahalingam; Mahyar Sharifi-Mood; Matt O’Banion and Daniel T. Gillins, Oregon State University School of Civil and Construction Engineering. Download the report:  http://1.usa.gov/18352DF

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

NASA Image of Colima Eruption

Colima Volcano, one of Mexico’s most active, is at it again. The Operational Land Imager (OLI) on Landsat 8 captured this natural-color view of an ash plume from Colima on February 8, 2015.

Prior to this image on February 5, ash was reported to have reached an altitude of 7.9 kilometers (26,000 feet). The occurrence of lava-block avalanches decreased by late February, but residents were still warned to remain at least 5 kilometers away from the volcano.

Video of the eruption that includes footage of the eruption from February 4-9, 2015, can be viewed
here.

Download large image (3 MB, JPEG, 2000×2000)

References and Related Reading
Global Volcanism Program, Smithsonian Institution (2015) Colima. Accessed February 23, 2015.
The Telegraph (2015, February 12) Watch: Moment Colima volcano erupts in Mexico. Accessed February 23, 2015.

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

Crocodiles rocked pre-Amazonian Peru

This model is a life reconstruction of the head of Gnatusuchus pebasensis, a 13-million-year-old, short-faced crocodile with globular teeth that was thought to use its snout to “shovel” mud bottoms, digging for clams and other mollusks. Model by Kevin Montalbán-Rivera. Credit: Copyright Aldo Benites-Palomino

Thirteen million years ago, as many as seven different species of crocodiles hunted in the swampy waters of what is now northeastern Peru, new research shows. This hyperdiverse assemblage, revealed through more than a decade of work in Amazon bone beds, contains the largest number of crocodile species co-existing in one place at any time in Earth’s history, likely due to an abundant food source that forms only a small part of modern crocodile diets: mollusks like clams and snails. The work, published today in the journal Proceedings of the Royal Society B, helps fill in gaps in understanding the history of the Amazon’s remarkably rich biodiversity.

“The modern Amazon River basin contains the world’s richest biota, but the origins of this extraordinary diversity are really poorly understood,” said John Flynn, Frick Curator of Fossil Mammals at the American Museum of Natural History and an author on the paper. “Because it’s a vast rain forest today, our exposure to rocks–and therefore, also to the fossils those rocks may preserve–is extremely limited. So anytime you get a special window like these fossilized “mega-wetland” deposits, with so many new and peculiar species, it can provide novel insights into ancient ecosystems. And what we’ve found isn’t necessarily what you would expect.”

Before the Amazon basin had its river, which formed about 10.5 million years ago, it contained a massive wetland system, filled with lakes, embayments, swamps, and rivers that drained northward toward the Caribbean, instead of today’s pattern of eastward river flow to the Atlantic Ocean. Knowing the kind of life that existed at that time is crucial to understanding the history and origins of modern Amazonian biodiversity. But although invertebrates like mollusks and crustaceans are abundant in Amazonian fossil deposits, evidence of vertebrates other than fish have been very rare.

Since 2002, Flynn has been co-leading prospecting and excavating expeditions with colleagues at fossil outcrops of the Pebas Formation in northeastern Peru. These outcrops have preserved life from the Miocene, including the seven species of crocodiles discussed in Proceedings B. Three of the species are entirely new to science, the strangest of which is Gnatusuchus pebasensis, a short-faced caiman with globular teeth that is thought to have used its snout to “shovel” mud bottoms, digging for clams and other mollusks. The new work suggests that the rise of Gnatusuchus and other “durophagous,” or shell-crunching, crocodiles is correlated with a peak in mollusk diversity and numbers, which disappeared when the mega-wetlands transformed into the modern Amazon River drainage system.

“When we analyzed Gnatusuchus bones and realized that it was probably a head-burrowing and shoveling caiman preying on mollusks living in muddy river and swamp bottoms, we knew it was a milestone for understanding proto-Amazonian wetland feeding dynamics,” said Rodolfo Salas-Gismondi, lead author of the paper and a graduate student at the University of Montpellier, in France, as well as researcher and chief of the paleontology department at the National University of San Marcos’ Museum of Natural History in Lima, Peru.

Besides the blunt-snouted crocodiles like Gnatusuchus, the researchers also recovered the first unambiguous fossil representative of the living smooth-fronted caiman Paleosuchus, which has a longer and higher snout shape suitable for catching a variety of prey, like fish and other active swimming vertebrates.

“We uncovered this special moment in time when the ancient mega-wetland ecosystem reached its peak in size and complexity, just before its demise and the start of the modern Amazon River system,” Salas-Gismondi said. “At this moment, most known caiman groups co-existed: ancient lineages bearing unusual blunt snouts and globular teeth along with those more generalized feeders representing the beginning of what was to come.”

The new research suggests that with the inception of the Amazon River System, mollusk populations declined and durophagous crocodile species went extinct as caimans with a broader palate diversified into the generalist feeders that dominate modern Amazonian ecosystems. Today, six species of caimans live in the whole Amazon basin, although only three ever co-exist in the same area and they rarely share the same habitats. This is in large contrast to their ancient relatives, the seven diverse species that lived together in the same place and time.

Reference:
Rodolfo Salas-Gismondi, John J. Flynn, Patrice Baby, Julia V. Tejada-Lara, Frank P. Wesselingh, Pierre-Olivier Antoine. A Miocene hyperdiverse crocodylian community reveals peculiar trophic dynamics in proto-Amazonian mega-wetlands. Proc. R. Soc. B, 2015 DOI: 10.1098/rspb.2014.2490

Note: The above story is based on materials provided by American Museum of Natural History.

International team of scientists launches fossil database

Fossil calibrations for select groups: Here is a look at the way the new fossil calibration database will help to tell evolutionary time. Credit: The Bruce Museum, Greenwich, CT

Have you ever wondered exactly when a certain group of plants or animals first evolved? This week a groundbreaking new resource for scientists will go live, and it is designed to help answer just those kinds of questions. The Fossil Calibration Database, a free, open-access resource that stores carefully vetted fossil data, is the result of years of work from a worldwide team led by Dr. Daniel Ksepka, Curator of Science at the Bruce Museum in Greenwich, and Dr. James Parham, Curator at the John D. Cooper Archaeological and Paleontological Center in Orange County, California, funded through the National Evolutionary Synthesis Center (NESCent).

“Fossils provide the critical age data we need to unlock the timing of major evolutionary events,” says Dr. Ksepka. “This new resource will provide the crucial fossil data needed to calibrate ‘molecular clocks’ which can reveal the ages of plant and animal groups that lack good fossil records. When did groups like songbirds, flowering plants, or sea turtles evolve? What natural events were occurring that may have had an impact? Precisely tuning the molecular clock with fossils is the best way we have to tell evolutionary time.”

More than twenty paleontologists, molecular biologists, and computer programmers from five different countries contributed to the design and implementation of this new database. The Fossil Calibrations Database webpage launches on Tuesday February 24th, and a series of five peer-reviewed papers and an editorial on the topic will appear in the scientific journal Palaeontologia Electronica, describing the endeavor. Dr. Ksepka is the author of one of the papers and co-author of the editorial.

“This exciting field of study, known as ‘divergence dating,’ is important for understanding the origin and evolution of biodiversity, but has been hindered by the improper use of data from the fossil record,” says Dr. Parham. “The Fossil Calibration Database addresses this issue by providing molecular biologists with paleontologist-approved data for organisms across the Tree of Life.”

The Tree of Life? “Think of it as a family tree of all species,” explains Dr. Ksepka.

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

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