Active faults more accessible to geologists

The October GSA TODAY science article, “Open-source archive of active faults for northwest South America,” by Gabriel Veloza and colleagues, is now online at www.geosociety.org/gsatoday/archive/22/10/. The article introduces the “Active Tectonics of the Andes Database,” which will provide more data to more geoscientists.

Understanding important aspects of how the Earth works — in this case, hazards associated with active seismic fault zones — is greatly improved by free and open access to the many types of spatial and geological data collected by geologists. While some geophysical data, such as that obtained from seismograms of earthquakes, have long been widely available in digital form, the geological information that is needed to better understand the long-term history and evolution of deformation in fault zones is often not widely or freely available.

The diverse range of geological data — rock types and ages, fault locations and orientations, slip-direction from faults, geometry of other features such as folds and bedding planes — are often difficult to compile and assemble into useful digital forms.

Some of the most important questions and issues that can be addressed with these digital compilations of geological data include comparison of the direction and velocity of surface displacement measured by Global Positioning System receivers (GPS) with the location, orientation, and type of fault zone observed in the geological data. While the GPS data provide excellent coverage of the modern-day surface motion associated with plate boundary zones, many faults and fault zones have longer-term histories of displacement. For example, many fault zones have geological records of large earthquakes that have long, and sometimes variable, recurrence rates that cannot be adequately studied using short-term data from GPS.

In order to really understand the seismic hazards associated with faults that have long-term slip histories, evidence from the geological record must be used. In the October 2012 issue of GSA Today, graduate students Gabriel Veloza and Richard Styron, and their faculty advisor, Michael Taylor, from the Dept. of Geology at the University of Kansas, and Andrés Mora from the Instituto Colombiano del Petroleo in Colombia, present a detailed digital compilation of active faults and other geological feature from the NW portion of South America.

Their work — the Active Tectonics of the Andes Database — includes the locations and associated geological information for more than 400 mapped faults in this region. The digital nature of these data allow modern mapping tools, including Google Earth, to depict these faults and to include other forms of data, such as GPS velocities, earthquake locations, and plate motion data. This new database will allow access by many other geoscientists and will promote a better understanding of the different seismic hazards in this region of South America. For example, comparison of fault zone locations and orientations with GPS-based displacements has led Veloza’s team to recognize several zones with different displacement behavior and relate these to changes in plate motions and plate boundary orientation.

Rare great earthquake in April triggers large aftershocks all over the globe

<IMG SRC="/Images/427985608.jpg" WIDTH="350" HEIGHT="371" BORDER="0" ALT="Some 380 seconds into the greatest earthquake to rupture since 1960, the simulated dynamic Coulomb stress waves (red-blue) shed continuously off the 2004 M=9.2 Sumatra rupture front can be seen sweeping through the Andaman Sea, where faults remarkably shut down for the next five years. Earthquakes since 1964 are shown as black dots, and the Sunda trench along which the 1400-km-long earthquake occurred is the arcuate black line on the left (west). Sumatra is on the right, and Myanmar/Burma is at top. Sevilgen et al (Proc. Nat. Acad. Sci, 2012) find that despite the magnitude of thesedynamic stress waves, the much smaller permanent stresses account for the change in seismicity after the main shock.

This graphic accompanies the Sept. 3, 2012 article in Proceedings of the National Academy of Sciences by Volkan Sevilgen, Ross Stein and Fred Pollitz. – U.S. Geological Survey”>

Some 380 seconds into the greatest earthquake to rupture since 1960, the simulated dynamic Coulomb stress waves (red-blue) shed continuously off the 2004 M=9.2 Sumatra rupture front can be seen sweeping through the Andaman Sea, where faults remarkably shut down for the next five years. Earthquakes since 1964 are shown as black dots, and the Sunda trench along which the 1400-km-long earthquake occurred is the arcuate black line on the left (west). Sumatra is on the right, and Myanmar/Burma is at top. Sevilgen et al (Proc. Nat. Acad. Sci, 2012) find that despite the magnitude of thesedynamic stress waves, the much smaller permanent stresses account for the change in seismicity after the main shock.

This graphic accompanies the Sept. 3, 2012 article in Proceedings of the National Academy of Sciences by Volkan Sevilgen, Ross Stein and Fred Pollitz. – U.S. Geological Survey


Large earthquakes can alter seismicity patterns across the globe in very different ways, according to two new studies by U.S. Geological Survey seismologists. Both studies shed light on more than a decade of debate on the origin and prevalence of remotely triggered earthquakes. Until now, distant but damaging “aftershocks” have not been included in hazard assessments, yet in each study, changes in seismicity were predictable enough to be included in future evaluations of earthquake hazards.

In a study published in this week’s issue of “Nature,” USGS seismologist Fred Pollitz and colleagues analyzed the unprecedented increase in global seismic activity triggered by the Magnitude-8.6 East Indian Ocean quake of April 11, 2012, and in a recently published study in the “Proceedings of the National Academy of Sciences,” seismologist Volkan Sevilgen and his USGS colleagues investigated the near-cessation of seismic activity up to 250 miles away caused by the 2004 M9.2 Sumatra earthquake.

While aftershocks have traditionally been defined as those smaller earthquakes that happen after and nearby the main fault rupture, scientists now recognize that this definition is wrong. Instead, aftershocks are simply earthquakes of any size and location that would not have taken place had the main shock not struck.

“Earthquakes are immense forces of nature, involving complex rock physics and failure mechanisms occurring over time and space scales that cannot be recreated in a laboratory environment,” said USGS Director Marcia McNutt. “A large, unusual event such as the East Indian earthquake last April is a once-in-a-century opportunity to uncover first order responses of the planet to sudden changes in state of stress that bring us a little closer to understanding the mystery of earthquake generation.”

Global aftershock study: April 2012: East Indian Ocean quake triggers many distant quakes

An extraordinary number of earthquakes of M4.5 and greater were triggered worldwide in the six days after the M8.6 East Indian Ocean earthquake in April 2012. These large and potentially damaging quakes, occurring as far away as Mexico and Japan, were triggered within days of the passage of seismic waves from the main shock that generated stresses in Earth’s crust.

The East Indian Ocean event was the largest – by a factor of 10 – strike-slip earthquake ever recorded (the San Andreas is perhaps the most famous strike-slip fault). “Most great earthquakes occur along subduction zones and involve large vertical motions. No other recorded earthquake triggered as many large earthquakes elsewhere around the world as this one,” said Pollitz, “probably because strike-slip faults around the globe were more responsive to the seismic waves produced by a giant strike-slip temblor.”

Another clue in the six days of global aftershocks following the M8.6 quake is that the rate of global quakes during the preceding 6-12 days was extremely low. “Imagine an apple tree, with apples typically ripening and then falling at some steady rate,” Stein said. “If a week goes by without any falling, there will be more very ripe apples on the tree. Now shake the trunk, and many more than normal might drop.”

The authors emphasize that the week of global triggering seen after the East Indian Ocean quake has no bearing on the hypothesis advanced by others that the 2004 M9.2 Sumatra, 2010 M8.8 Maule, Chile, and 2011 M9.0 Tohoku, Japan, are related to each other. Instead, the effect of increased earthquakes lasted a week-not a decade.

Sumatra quake affects faults up to 250 miles away

While global triggering of large aftershocks appears very rare, regional triggering is common and important to understand for post-main shock emergency response and recovery. Sevilgen and his USGS colleagues studied the largest quake to strike in 40 years to understand just how great the reach is on aftershock occurrence. After the M9.2 earthquake in Sumatra in 2004, aftershocks larger than M4.5 ceased for five years along part of a distant series of linked faults known as the Andaman back arc fault system. Along a larger segment of the same system, the sideways-slipping transform earthquakes decreased by two-thirds, while the rate of rift events – earthquakes that happen on a spreading center – increased by 800 percent, according to Sevilgen and his colleagues at the USGS. These very large, but distant seismicity rate changes are unprecedented.

The authors investigated two possible causes for the changes in remote seismicity rates: the dynamic stresses imparted by the main shock rupture, which best explain the global triggering in the April 2012 quake case; and the small but permanent stress changes, which best explain this one. The authors found that the main shock brought the transform fault segments about ¼ bar of pressure farther from static failure, and the rift segments about ¼ bar closer to static failure (for comparison, car tires are inflated with about 3 bars of pressure), which matches the seismic observations.

Why it matters

Incorporating the probability of aftershocks into the hazard assessment of an area is important because the damage of even a moderate aftershock sometimes exceeds that wrought by the main event. For example, a M6.3 aftershock five months after the M7.1 New Zealand earthquake in 2010 hit a more populated area, causing 181 deaths and tripling the insured property damage of the main event.

Large bacterial population colonized land 2.75 billion years ago

A drill core from the 2.5 billion-year-old Mount McRae Shale formation in Western Australia, which originally was fine-grained ocean sediment, shows high concentrations of sulfide and molybdenum. That supports the idea that most of the sulfate came from land, likely freed by microbial activity on rocks. Some data for the research came from the Mount McRae formation. -  Roger Buick/U. of Washington
A drill core from the 2.5 billion-year-old Mount McRae Shale formation in Western Australia, which originally was fine-grained ocean sediment, shows high concentrations of sulfide and molybdenum. That supports the idea that most of the sulfate came from land, likely freed by microbial activity on rocks. Some data for the research came from the Mount McRae formation. – Roger Buick/U. of Washington

There is evidence that some microbial life had migrated from the Earth’s oceans to land by 2.75 billion years ago, though many scientists believe such land-based life was limited because the ozone layer that shields against ultraviolet radiation did not form until hundreds of millions years later.

But new research from the University of Washington suggests that early microbes might have been widespread on land, producing oxygen and weathering pyrite, an iron sulfide mineral, which released sulfur and molybdenum into the oceans.

“This shows that life didn’t just exist in a few little places on land. It was important on a global scale because it was enhancing the flow of sulfate from land into the ocean,” said Eva Stüeken, a UW doctoral student in Earth and space sciences.

In turn, the influx of sulfur probably enhanced the spread of life in the oceans, said Stüeken, who is the lead author of a paper presenting the research published Sunday (Sept. 23) in Nature Geoscience. The work also will be part of her doctoral dissertation.

Sulfur could have been released into sea water by other processes, including volcanic activity. But evidence that molybdenum was being released at the same time suggests that both substances were being liberated as bacteria slowly disintegrated continental rocks, she said.

If that is the case, it likely means the land-based microbes were producing oxygen well in advance of what geologists refer to as the “Great Oxidation Event” about 2.4 billion years ago that initiated the oxygen-rich atmosphere that fostered life as we know it.

In fact, the added sulfur might have allowed marine microbes to consume methane, which could have set the stage for atmospheric oxygenation. Before that occurred, it is likely large amounts of oxygen were destroyed by reacting with methane that rose from the ocean into the air.

“It supports the theory that oxygen was being produced for several hundred million years before the Great Oxidation Event. It just took time for it to reach higher concentrations in the atmosphere,” Stüeken said.

The research examined data on sulfur levels in 1,194 samples from marine sediment formations dating from before the Cambrian period began about 542 million years ago. The processes by which sulfur can be added or removed are understood well enough to detect biological contributions, the researchers said.

The data came from numerous research projects during the last several decades, but in most cases those observations were just a small part of much larger studies. In an effort to provide consistent interpretation, Stüeken combed the research record for data that came from similar types of sedimentary rock and similar environments.

“The data has been out there for a long time, but people have ignored it because it is hard to interpret when it is not part of a large database,” she said.

Gas outlets off Spitsbergen are no new phenomenon

Frequent storms and sub-zero temperatures – nature drove the marine researchers that were assessing gas outlets on the sea bed off the coast of Spitsbergen for four and a half weeks to their limits. Nevertheless the participants were very pleased when they returned: “We were able to gather many samples and data in the affected area. With the submersible JAGO we even managed to form an impression of the sea bed and the gas vents” summarized the chief scientist Professor Dr. Christian Berndt from GEOMAR | Helmholtz Centre for Ocean Research Kiel.

The reason for the expedition was the supposition that ice-like methane hydrates stored in the sea bed were dissolving due to rising water temperatures. “Methane hydrate is only stable at very low temperatures and under very high pressure. The gas outlets off Spitsbergen lie approximately at a depth which marks the border between stability and dissolution. Therefore we presumed that a measurable rise in water temperature in the Arctic could dissolve the hydrates from the top downwards” explained Professor Berndt. Methane could then be released into the water or even into the atmosphere, where it would act as a much stronger greenhouse gas than CO2.

In fact, what the researchers found in the area offers a much more differentiated picture. Above all the fear that the gas emanation is a consequence of the current rising sea temperature does not seem to apply. At least some of the gas outlets have been active for longer. Carbonate deposits, which form when microorganisms convert the escaping methane, were found on the vents. “At numerous emergences we found deposits that might already be hundreds of years old. This estimation is indeed only based on the size of the samples and empirical values as to how fast such deposits grow. On any account, the methane sources must be older” says Professor Berndt. The exact age of the carbonates will be determined from samples in GEOMAR’s laboratories.

“Details will only be known in a few months when the data has been analysed; however the observed gas emanations are probably not caused by human influence” says Berndt. There are two other possible explanations instead: Either they are symptoms of a long term temperature rise or they show a seasonal process where gas hydrates continuously melt and reform.

Another interesting observation made on the expedition, was that a very active microbial community that consumes the methane has established itself on the sea bed. “We were able to detect high concentrations of hydrogen sulphide, which is an indication of methane consuming microbes in the sea bed, and, with the help of JAGO, discovered typical biocoenoses that we recognised from other, older methane outlets” explained microbiologist Professor Dr. Tina Treude from GEOMAR, who also took part in the expedition. “Methane consuming microbes grow only slowly in the sea bed, thus their high activity indicates that the methane has not just recently begun effervescing.”

Colleagues from Bremen, Switzerland, Great Britain and Norway worked alongside marine scientists from GEOMAR and from the Cluster of Excellence “The Future Ocean”. “The study of the gas outlets in the Norwegian Sea is a good example for combined European research” stressed Professor Berndt. Hence German scientists recovered an ocean floor observatory, installed by the British research vessel James Clark Ross a year ago during a joint expedition of the National Oceanography Centre Southampton and the Institut français de recherche pour l’exploitation de la mer (Ifremer). “Understanding the ocean as a system is a challenge that only works in international co-operations” emphasized Berndt. The analysis of the gathered data will also be carried out internationally.

Stratosphere targets deep sea to shape climate

Thomas Reichler, a University of Utah atmospheric scientist, led a new study showing that changes in winds 15- to 30-miles high in the stratosphere can influence seawater circulation a mile or more deep in the ocean. He says this effect should be taken into account in forecasting climate change distinct from global warming. -  Lee J. Siegel, University of Utah.
Thomas Reichler, a University of Utah atmospheric scientist, led a new study showing that changes in winds 15- to 30-miles high in the stratosphere can influence seawater circulation a mile or more deep in the ocean. He says this effect should be taken into account in forecasting climate change distinct from global warming. – Lee J. Siegel, University of Utah.

A University of Utah study suggests something amazing: Periodic changes in winds 15 to 30 miles high in the stratosphere influence the seas by striking a vulnerable “Achilles heel” in the North Atlantic and changing mile-deep ocean circulation patterns, which in turn affect Earth’s climate.

“We found evidence that what happens in the stratosphere matters for the ocean circulation and therefore for climate,” says Thomas Reichler, senior author of the study published online Sunday, Sept. 23 in the journal Nature Geoscience.

Scientists already knew that events in the stratosphere, 6 miles to 30 miles above Earth, affect what happens below in the troposphere, the part of the atmosphere from Earth’s surface up to 6 miles or about 32,800 feet. Weather occurs in the troposphere.

Researchers also knew that global circulation patterns in the oceans – patterns caused mostly by variations in water temperature and saltiness – affect global climate.

“It is not new that the stratosphere impacts the troposphere,” says Reichler, an associate professor of atmospheric sciences at the University of Utah. “It also is not new that the troposphere impacts the ocean. But now we actually demonstrated an entire link between the stratosphere, the troposphere and the ocean.”

Funded by the University of Utah, Reichler conducted the study with University of Utah atmospheric sciences doctoral student Junsu Kim, and with atmospheric scientist Elisa Manzini and oceanographer Jürgen Kröger, both with the Max Planck Institute for Meteorology in Hamburg, Germany.

Stratospheric Winds and Sea Circulation Show Similar Rhythms


Reichler and colleagues used weather observations and 4,000 years worth of supercomputer simulations of weather to show a surprising association between decade-scale, periodic changes in stratospheric wind patterns known as the polar vortex, and similar rhythmic changes in deep-sea circulation patterns. The changes are:

– “Stratospheric sudden warming” events occur when temperatures rise and 80-mph “polar vortex” winds encircling the Artic suddenly weaken or even change direction. These winds extend from 15 miles elevation in the stratosphere up beyond the top of the stratosphere at 30 miles. The changes last for up to 60 days, allowing time for their effects to propagate down through the atmosphere to the ocean.

– Changes in the speed of the Atlantic circulation pattern – known as Atlantic Meridional Overturning Circulation – that influences the world’s oceans because it acts like a conveyor belt moving water around the planet.

Sometimes, both events happen several years in a row in one decade, and then none occur in the next decade. So incorporating this decade-scale effect of the stratosphere on the sea into supercomputer climate simulations or “models” is important in forecasting decade-to-decade climate changes that are distinct from global warming, Reichler says.

“If we as humans modify the stratosphere, it may – through the chain of events we demonstrate in this study – also impact the ocean circulation,” he says. “Good examples of how we modify the stratosphere are the ozone hole and also fossil-fuel burning that adds carbon dioxide to the stratosphere. These changes to the stratosphere can alter the ocean, and any change to the ocean is extremely important to global climate.”

A Vulnerable Soft Spot in the North Atlantic


“The North Atlantic is particularly important for global ocean circulation, and therefore for climate worldwide,” Reichler says. “In a region south of Greenland, which is called the downwelling region, water can get cold and salty enough – and thus dense enough – so the water starts sinking.”

It is Earth’s most important region of seawater downwelling, he adds. That sinking of cold, salty water “drives the three-dimensional oceanic conveyor belt circulation. What happens in the Atlantic also affects the other oceans.”

Reichler continues: “This area where downwelling occurs is quite susceptible to cooling or warming from the troposphere. If the water is close to becoming heavy enough to sink, then even small additional amounts of heating or cooling from the atmosphere may be imported to the ocean and either trigger downwelling events or delay them.”

Because of that sensitivity, Reichler calls the sea south of Greenland “the Achilles heel of the North Atlantic.”

From Stratosphere to the Sea


In winter, the stratospheric Arctic polar vortex whirls counterclockwise around the North Pole, with the strongest, 80-mph winds at about 60 degrees north latitude. They are stronger than jet stream winds, which are less than 70 mph in the troposphere below.But every two years on average, the stratospheric air suddenly is disrupted and the vortex gets warmer and weaker, and sometimes even shifts direction to clockwise.

“These are catastrophic rearrangements of circulation in the stratosphere,” and the weaker or reversed polar vortex persists up to two months, Reichler says. “Breakdown of the polar vortex can affect circulation in the troposphere all the way down to the surface.”

Reichler’s study ventured into new territory by asking if changes in stratospheric polar vortex winds impart heat or cold to the sea, and how that affects the sea.

It already was known that that these stratospheric wind changes affect the North Atlantic Oscillation – a pattern of low atmospheric pressure centered over Greenland and high pressure over the Azores to the south. The pattern can reverse or oscillate.

Because the oscillating pressure patterns are located above the ocean downwelling area near Greenland, the question is whether that pattern affects the downwelling and, in turn, the global oceanic circulation conveyor belt.

The study’s computer simulations show a decadal on-off pattern of correlated changes in the polar vortex, atmospheric pressure oscillations over the North Atlantic and changes in sea circulation more than one mile beneath the waves. Observations are consistent with the pattern revealed in computer simulations.

Observations and Simulations of the Stratosphere-to-Sea Link


In the 1980s and 2000s, a series of stratospheric sudden warming events weakened polar vortex winds. During the 1990s, the polar vortex remained strong.

Reichler and colleagues used published worldwide ocean observations from a dozen research groups to reconstruct behavior of the conveyor belt ocean circulation during the same 30-year period.

“The weakening and strengthening of the stratospheric circulation seems to correspond with changes in ocean circulation in the North Atlantic,” Reichler says.

To reduce uncertainties about the observations, the researchers used computers to simulate 4,000 years worth of atmosphere and ocean circulation.

“The computer model showed that when we have a series of these polar vortex changes, the ocean circulation is susceptible to those stratospheric events,” Reichler says.

To further verify the findings, the researchers combined 18 atmosphere and ocean models into one big simulation, and “we see very similar outcomes.”

The study suggests there is “a significant stratospheric impact on the ocean,” the researchers write. “Recurring stratospheric vortex events create long-lived perturbations at the ocean surface, which penetrate into the deeper ocean and trigger multidecadal variability in its circulation. This leads to the remarkable fact that signals that emanate from the stratosphere cross the entire atmosphere-ocean system.”

Research blog: An expedition to the Earth’s fiery heart

Volcanic activity on and around La Réunion is driven by a localized upwelling of hot buoyant magma. Unlike most magma sources, this is not located on the boundary between two tectonic plates, and rises from much greater depths. It is a so-called hotspot, and has left behind on the overlying mobile crust a track of volcanic activity that stretches 5500 km northwards to the Deccan Plateau in India. Some 65 million years ago, in a process that had a massive impact on world climate, the Deccan area was covered with enormous amounts of lava as the Indian Plate passed over the hotspot.

Such a long-lived upwelling of hot molten rock, which penetrates the overlying material like a blowtorch, is referred to as a mantle plume. Where exactly mantle plumes originate is the subject of a controversial debate among geoscientists. During the course of a French-German expedition, LMU geophysicist Dr. Karin Sigloch, leader of the German contingent, wants to find out more about the putative plume under La Réunion. The goal is to determine the depth of the plume and to map the conduits by which the magma reaches the Earth’s surface.

The largest plume survey campaign ever

“We want to look deeper into the Earth’s interior than any previous expedition, down to the bottom of the mantle at a depth of about 2900 km; earlier efforts reached half that depth, at most,” says Sigloch. To achieve this goal, the researchers must deploy a dense array of seismometers over a wide area. On 22 September, the team will board the French research vessel Marion Dufresne on a cruise that will place nearly 60 seismometers on the seabed, dispersed over an area of some 4 million km2. As 30 additional instruments will be installed on land, this will be the largest such campaign ever undertaken. Data from a further 70 or so observatories located along the coasts of the Indian Ocean will complement the results obtained with the new network.

The data collected will be used to create three-dimensional tomographic images that will give us a picture of the Earth from the bottom of the crust to the core, and provide new insights into the structure, dynamics and history of the Earth. As they effectively short-circuit the transport of heat from the core to the surface, plumes may play an important role in the Earth’s heat budget, and are a major force in shaping the Earth’s surface. Analysis of the new data will begin in a year’s time, after the German RV Meteor retrieves the newly deployed seismometers from the seabed.

Did a ‘forgotten’ meteor have a deadly, icy double-punch?

When a huge meteor collided with Earth about 2.5 million years ago and fell into the southern Pacific Ocean it not only could have generated a massive tsunami but also may have plunged the world into the Ice Ages, a new study suggests.

A team of Australian researchers says that because the Eltanin meteor – which was up to two kilometers across – crashed into deep water, most scientists have not adequately considered either its potential for immediate catastrophic impacts on coastlines around the Pacific rim or its capacity to destabilize the entire planet’s climate system.

“This is the only known deep-ocean impact event on the planet and it’s largely been forgotten because there’s no obvious giant crater to investigate, as there would have been if it had hit a landmass,” says Professor James Goff, lead author of a forthcoming paper in the Journal of Quaternary Science. Goff is co-director of UNSW’s Australia-Pacific Tsunami Research Centre and Natural Hazards Research Laboratory.

“But consider that we’re talking about something the size of a small mountain crashing at very high speed into very deep ocean, between Chile and Antarctica. Unlike a land impact, where the energy of the collision is largely absorbed locally, this would have generated an incredible splash with waves literally hundreds of meters high near the impact site

“Some modelling suggests that the ensuing mega-tsunami could have been unimaginably large – sweeping across vast areas of the Pacific and engulfing coastlines far inland. But it also would have ejected massive amounts of water vapour, sulphur and dust up into the stratosphere.
“The tsunami alone would have been devastating enough in the short term, but all that material shot so high into the atmosphere could have been enough to dim the sun and dramatically reduce surface temperatures. Earth was already in a gradual cooling phase, so this might have been enough to rapidly accelerate and accentuate the process and kick start the Ice Ages.”

In the paper, Goff and colleagues from UNSW and the Australian Nuclear Science and Technology Organisation, note that geologists and climatologists have interpreted geological deposits in Chile, Antarctica, Australia, and elsewhere as evidence of climatic change, marking the start of the Quaternary period. An alternative interpretation is that some or all of these deposits may be the result of mega-tsunami inundation, the study suggests.

“There’s no doubt the world was already cooling through the mid and late Pliocene,” says co-author Professor Mike Archer. “What we’re suggesting is that the Eltanin impact may have rammed this slow-moving change forward in an instant – hurtling the world into the cycle of glaciations that characterized the next 2.5 million years and triggered our own evolution as a species.

“As a ‘cene’ changer – that is, from the Pliocene to Pleistocene – Eltanin may have been overall as significant as the meteor that took out the non-flying dinosaurs 65 million years ago. We’re urging our colleagues to carefully reconsider conventional interpretations of the sediments we’re flagging and consider whether these could be instead the result of a mega-tsunami triggered by a meteor.”

Warming ocean could start big shift of Antarctic ice

Fast-flowing and narrow glaciers have the potential to trigger massive changes in the Antarctic ice sheet and contribute to rapid ice-sheet decay and sea-level rise, a new study has found.

Research results published in the journal Proceedings of the National Academy of Sciences reveal in more detail than ever before how warming waters in the Southern Ocean are connected intimately with the movement of massive ice-sheets deep in the Antarctic interior.

“It has long been known that narrow glaciers on the edge of the Antarctica act as discrete arteries termed ice streams, draining the interior of the ice sheet,” says Dr Chris Fogwill, an author of the study and an ARC Future Fellow with the UNSW Climate Change Research Centre.

“However, our results have confirmed recent observations suggesting that ocean warming can trigger increased flow of ice through these narrow corridors. This can cause inland sectors of the ice-sheet – some larger than the state of Victoria – to become thinner and flow faster.”

The researchers, led by Dr Nicholas Golledge from Victoria University of Wellington, New Zealand, tested high-resolution model simulations against reconstructions of the Antarctic ice sheet from 20,000 years ago, during the last glacial maximum.

They used a new model, capable of resolving responses to ice-streams and other fine- scale dynamic features that interact over the entire ice sheet. This had not previously been possible with existing models. They then used this data to analyze the effects of a warming ocean over time.

The results showed that while glacier acceleration triggered by ocean warming is relatively localized, the extent of the resultant ice-sheet thinning is far more widespread. This observation is particularly important in light of recently observed dynamic changes at the margins of Antarctica. It also highlighted areas that are more susceptible than others to changes in ocean temperatures.

The glaciers that responded most rapidly to warming oceans were found in the Weddell Sea, the Admundsen Sea, the central Ross Sea and in the Amery Trough.

The finding is important because of the enormous scale and potential impact the Antarctic ice sheets could have on sea-level rise if they shift rapidly, says Fogwill. “To get a sense of the scale, the Antarctic ice sheet is 3km deep – three times the height of the Blue Mountains in many areas – and it extends across an area that is equivalent to the distance between Perth and Sydney.

“Despite its potential impact, Antarctica’s effect on future sea level was not fully included in the last IPCC report because there was insufficient information about the behavior of the ice sheet. This research changes that. This new, high-resolution modelling approach will be critical to improving future predictions of Antarctica’s contribution to sea level over the coming century and beyond.”

Challengers to Clovis-age impact theory missed key protocols, new study finds

An interdisciplinary team of scientists from seven U.S. institutions says a disregard of three critical protocols, including sorting samples by size, explains why a group challenging the theory of a North American meteor-impact event some 12,900 years ago failed to find iron- and silica-rich magnetic particles in the sites they investigated.

Not separating samples of the materials into like-sized groupings made for an avoidable layer of difficulty, said co-author Edward K. Vogel, a professor of psychology at the University of Oregon.

The new independent analysis — published this week in the online Early Edition of the Proceedings of the National Academy of Sciences — did, in fact, isolate large quantities of the “microspherules” at the involved sites where the challengers previously reported none. Lead author Malcolm A. LeCompte, an astrophysicist at Elizabeth City State University in North Carolina, said the findings support the climate-altering cosmic impact, but his team stopped short of declaring this as proof of the event.

The Clovis-age cosmic-impact theory was proposed in 2007 by a 26-member team led by Richard B. Firestone. That team included University of Oregon archaeologists Douglas J. Kennett and Jon M. Erlandson. While other groups have found corroborating evidence of a potential cosmic event, other groups reported difficulties doing so. One group, led by Todd A Surovell of the University of Wyoming, did not find any microspherule evidence at five of seven sites they tested, including two previously studied locations where Firestone reported large numbers of microspherules.

“In investigating the two common sites and a third tested only by Surovell’s team, we found spherules in equal or greater abundance than did the Firestone team, and the reported enhancement was in strata dated to about 13,000 years before the present,” LeCompte said. “What we’ve done is provide evidence that is consistent with an impact, but we don’t think it proves the impact. We think there’s a mystery contained in the Younger Dryas strata, and that we’ve provided some validation to the original research by Firestone’s group.”

The particles in question, the team concluded, are terrestrial as was claimed by the Firestone group, and not of meteoric origin as claimed by other challengers including Surovell’s group, and are similar to metamorphic material in Earth’s crust. That determination was made using electron microscopy and spectroscopy.

“These spherules have evidence of very high-temperature melting and very rapid cooling, which is characteristic of debris ejected from an impact,” LeCompte said. Speherules would have melted at temperatures approaching 2,000 degrees Celsius (more than 3,000 degrees Fahrenheit), he added. Cosmic materials, including the some microspherules, regularly fall to earth from space due to meteorite ablation, but the spherules found in soils dating to 13,000 years ago are much different, he added. Other researchers had suggested that these spherules were deposited by a cosmic rain or resulted through slow, terrestrial processes occurring under ambient conditions.

LeCompte and some key collaborators wondered why Surovell didn’t find any spherules, and that led them to Vogel. Many of the spherules investigated were tiny, ranging in size from 20 to 50 micrometers (microns); about the diameter of a human hair.

“The inherent difficulty in finding these small, relatively rare magnetic microspherules suggested there may be inherent limitations in human faculties that needed to be addressed, and that’s how and why we sought out UO Professor Ed Vogel. His research into human cognitive capabilities proved so important in understanding both why the search was so difficult and why size-sorting was effective and important in making it easier,” LeCompte said.

Vogel specializes in the ability of people to find specific items amid multiple distractions.

“A visual search is a very error-prone process,” Vogel said. “This was a case of looking at millions of particles from which you are hoping to find something that might be present much less than 0.1 percent of the time.” Size-sorting, he said, is vital because it is easier to find a target item with a characteristic shape and color when all of the many more-distracting objects are very similar. “It is a slow, tedious process to examine such quantities of materials with the human eyes when object sizes are extremely dissimilar.”

“Science is only as good as the humans who conduct it, and this study shows how the minds of researchers can operate in some surprising ways,” said Kimberly Andrews Espy, UO vice president for research and innovation, and dean of the graduate school. “Dr. Vogel’s excellent work, which illustrates the importance of understanding how the human mind processes information and the consequences it can have beyond making everyday computations, reflects the University of Oregon’s strengths in interdisciplinary research.”

LeCompte described Surovell’s study “as possibly the most damning of the reports that had challenged the original theory.”

“Todd had worked very hard and couldn’t find the spherules, but I think he made some fatal errors that need to be pointed out,” LeCompte said. “It is instructive in that we initially made the same mistake and came to the same erroneous conclusion, but then we corrected our mistake. I would say this is a case of a missed opportunity due to their deviations from the protocol.”

Two other critical protocol deviations not followed by the challengers involved the amounts of material examined and the use of microscopy techniques specified in Firestone’s original research. Another two minor aspects of the protocol also were not repeated, reported LeCompte’s team, which, in addition to Vogel, included an archaeologist, two materials scientists, a botanist, a periglacial geographer and an aerospace engineer.

LeCompte’s team — using the protocols of Firestone’s group and electron microscopy — additionally studied a quarry site in Topper, S.C., where Clovis-age people had made stone tools. After removing chert debris associated with tool making in soil at the depth of the Clovis occupation, LeCompte said, researchers observed virtually no spherules below it, while in soil just above the chert fragments they found a spike in the number of telltale spherules.

Further above that level, he noted, the soil layers were essentially “a dead zone” somewhat analogous to the K-T boundary, or “tombstone layer,” from an extinction event that occurred 65 million years ago. At Topper, the dead zone showed almost no trace of human habitation for perhaps as long as 1,000 years duration.

“This suggests that something very dramatic happened,” LeCompte said.

“The effects of such an impact would have been catastrophic on a global scale,” said co-author Barrett Rock, a botanist at the University of New Hampshire. “On the order of 36 ice-age species became extinct, and the Clovis human culture eventually lost. All of this in response to dramatic changes in the vegetation at the base of the faunal food chain.”

The mountain in detail, on your mobile

You could almost say that María Teresa Ruiz-Monzón (Vitoria-Gasteiz, Basque Country, 1988) carries the mountain around in her pocket. The slopes, spurs and drops of this mountain are very realistically represented on the mobile phone of this student who has recently graduated in Computer Sciences at the University of the Basque Country (UPV/EHU). This was in fact her end-of-studies project: to develop an application to be able to use 3D geolocation on android smartphones. “It resembles Google Earth, but has a more specific purpose,” she explains. It has been devised for mountaineers so that when it is foggy they can find their way by looking at their mobile phone screens. When the horizon is fuzzy, ordinary maps cannot really help us to position ourselves or to know whether we could be getting too close to a precipice. This 3D application is designed to meet these needs.

Ruiz has had to combine different knowledge, systems and all kinds of data to be able to develop her project. Apart from mastering Android, she has had to incorporate into it certain programs that are compatible with it, like OpenGL ES (graphic programming interface), LaTeX (text processing system) and Shapefile (geodata file format). She has also learnt from videogames to draw the 3D surfaces, and has obtained relief maps and other geographical data on the Basque Autonomous Community (region) over the www.geoeuskadi.net website of the Government of the Basque Autonomous Community. But it is not enough just to gather the most detailed maps; the application has to know where the user is and therefore which map to display to him or her. For this purpose, this computer scientist has made use of the electronic compass available on smartphones: “I use the compass like a camera. I detect which way the phone is looking and I draw the surface existing on that stretch of terrain so that he or she can see what is there.”

Ruiz explains that it has been no easy task creating the surface, managing all the information, detecting the location and managing to download the right files on the basis of all this. But the biggest difficulties were caused by the limited memory capacity of mobile phones: “A lot of information has to be managed and the most difficult thing was to enter all this without exceeding the memory limits of mobile phones.”

Without the Internet

Naturally, this tool needs the Internet to make the appropriate geolocation consultations at each moment, and downloading such large files (running to several Mbytes) over the Internet can take quite a time. To prevent the application crashing in situations like this, Ruiz has been developing a mechanism; it still needs to be improved further, but it is progressing nicely. “The downloads are done in background mode, so the application can go on working even though not all the files may be available. This is so that you can go on using your mobile during the download, too,” she explains.

In any case, it has to be remembered that in the mountains mobiles often end up out of range and in these cases the Internet cannot be used. For this very reason this application has the option of using it without a connection. But in this case, you have to do your homework before setting off: “If you download the files beforehand at home and on a card, it can be done.”

Now that Ruiz has had her viva on her end-of-studies project, she has completed her degree in Computer Sciences but is planning to go on developing the application she has created. “Some minimal improvements have to be made, but I think there could be a possibility of marketing it. I don’t yet know whether I will sell it, whether I will release the code… But there are possibilities. I’ll see,” she says.