Researchers show how far South American cities moved in quake

This is a map of South America showing movement of points on continent following Chilean earthquake in February. -  University of Hawaii
This is a map of South America showing movement of points on continent following Chilean earthquake in February. – University of Hawaii

The massive magnitude 8.8 earthquake that struck the west coast of Chile last month moved the entire city of Concepcion at least 10 feet to the west, and shifted other parts of South America as far apart as the Falkland Islands and Fortaleza, Brazil.

These preliminary measurements, produced from data gathered by researchers from four universities and several agencies, including geophysicists on the ground in Chile, paint a much clearer picture of the power behind this temblor, believed to be the fifth-most-powerful since instruments have been available to measure seismic shifts.

Buenos Aires, the capital of Argentina and across the continent from the quake’s epicenter, moved about 1 inch to the west. And Chile’s capital, Santiago, moved about 11 inches to the west-southwest. The cities of Valparaiso and Mendoza, Argentina, northeast of Concepcion, also moved significantly.

The quake’s epicenter was in a region of South America that’s part of the so-called “ring of fire,” an area of major seismic stresses which encircles the Pacific Ocean. All along this line, the tectonic plates on which the continents move press against each other at fault zones.

The February Chilean quake occurred where the Nazca tectonic plate was squeezed under, or “subducted,” below the adjacent South American plate. Quakes routinely relieve pent-up geologic pressures in these convergence zones.

The research team deduced the cities’ movement by comparing precise GPS (global positioning satellite) locations known prior to the major quake to those almost 10 days later. The US Geological Survey reported that there have been dozens of aftershocks, many exceeding magnitude 6.0 or greater, since the initial event February 27.

Mike Bevis, professor of earth sciences at Ohio State, has led a project since 1993 that has been measuring crustal motion and deformation in the Central and Southern Andes. The effort, called the Central and Southern Andes GPS Project, or CAP, hopes to perhaps triple its current network of 25 GPS stations spread across the region.

“By reoccupying the existing GPS stations, CAP can determine the displacements, or ‘jumps’, that occurred during the earthquake,” Bevis said. “By building new stations, the project can monitor the postseismic deformations that are expected to occur for many years, giving us new insights into the physics of the earthquake process.”

Ben Brooks, an associate researcher with the School of Ocean and Earth Science and Technology at the University of Hawaii and co-principal investigator on the project, said that the event, tragic as it was, offers a unique opportunity to better understand the seismic processes that control earthquakes.

“The Maule earthquake will arguably become one of the, if not the most important great earthquake yet studied. We now have modern, precise instruments to evaluate this event, and because the site abuts a continent, we will be able to obtain dense spatial sampling of the changes it caused.

“As such the event represents an unprecedented opportunity for the earth science community if certain observations are made with quickly and comprehensively,” Brooks said.

Earthquake in Chile – a complicated fracture

Distribution of the Earthquakes in Southern Chile.
Distribution of the Earthquakes in Southern Chile.

The extremely strong earthquake in Chile on 27 February this year was a complicated rupture process, as scientists from the GFZ German Research Centre for Geosciences found out. Quakes with such magnitude virtually penetrate the entire Earth’s crust. After closer analysis of the seismic waves radiated by this earthquake during the first 134 seconds after start of the rupture, the researchers came to the conclusion that only the region around the actual epicentre was active during the first minutes. In the second minute the active zone moved north towards Santiago. After that the region south of Concepción became active for a short time. This rupturing trend agrees well with the distribution of the aftershocks during the following three days, as observed by the GEOFON-measuring network of the GFZ up to 03.03.2010.

In the year 1960, the strongest earthquake measured at all to date, with a magnitude of M=9.5, had its origin at Valdivia, south of the region affected now. “The quake of 27 February connects directly to the rupture process of Valdivia”, explains Professor Jochen Zschau, Director of the Section “Earthquake Risk and Early Warning” at the GFZ. “With this, one of the last two seismic gaps along the west coast of South America might now be closed. With the exception of one last section, found in North Chile, the entire earth crust before the west coast of South America has been ruptured within the last 150 years.”

The underlying plate tectonic procedure is such that the Nazca-Plate as part of the Pacific Ocean Floor moves eastwards with approximately seventy millimetres per year, collides with South America and thereby pushes under the continent. The hereby developing earthquakes belong to the strongest world-wide. In the course of about one century, the Earth’s ruptures completely in a number of strong quakes from Patagonia in the South to Panama in the North. Even Darwin reported, in his diary, of the strong earthquake in Concepción on 20 February 1835 and the resulting Tsunami.

In order to examine the aftershock activity in the now fractured seismic gap, scientists from the GFZ are travelling to Chile on March 13, 2010 where, together with the Chilean Seismological Service, they will set-up a seismological-geodetic network in the area of Concepción-Santiago. Partners from Germany (IFM Geomar, Kiel; Free University of Berlin) and from abroad (Institut de Physique du Globe, Paris; University of Liverpool; United States Geological Survey; IRIS) are also taking part in this measuring campaign. The mission will last about three months. The results, one expects, will be able to provide an insight into the mechanisms of the fracture in the Earth’s crust. This activity is financed on the German side by the GFZ.

Scientists from the GFZ have been examining the collision of the Nazca plate and the South American continent since 1994. As a result of numerous expeditions and measuring campaigns in this area this Potsdam Helmholtz Centre avails of the probably the most dense data record on such a subduction zone. “Within the framework of the DFG Priority Programme “Deformation processes in the Andes”, and with the Geotechnology Project TIPTEQ we have just been able to collect a unique data record for the southern part of the Andes” says Professor Onno Oncken, Director of the Department Geodynamics and Geomaterials at the GFZ, and leader of these studies. The current quake puts us in the position to precisely compare the tectonics before and afterwards, a unique situation both internationally and in Earth science.

Currently, the GFZ operates a so-called Plate Boundary Observatory PBO in the north of Chile, exactly in the last remaining seismic gap in Chile. This observatory will be handed over to Chilean colleagues by the Chairman of the Board of the GFZ, Professor Reinhard Huettl, within the framework of the cooperation with the Earthquake Service of Chile during a festive event on 15 March.

New evidence hints at global glaciation 716.5 million years ago

In this photo from Canada's Yukon Territory, an iron-rich layer of 716.5-million-year-old glacial deposits (maroon in color) is seen atop an older carbonate reef (gray in color) that formed in the tropics. -  Francis A. Macdonald/Harvard University
In this photo from Canada’s Yukon Territory, an iron-rich layer of 716.5-million-year-old glacial deposits (maroon in color) is seen atop an older carbonate reef (gray in color) that formed in the tropics. – Francis A. Macdonald/Harvard University

Geologists have found evidence that sea ice extended to the equator 716.5 million years ago, bringing new precision to a “snowball Earth” event long suspected to have taken place around that time.

Led by scientists at Harvard University, the team reports on its work this week in the journal Science. The new findings — based on an analysis of ancient tropical rocks that are now found in remote northwestern Canada — bolster the theory that our planet has, at times in the past, been ice-covered at all latitudes.

“This is the first time that the Sturtian glaciation has been shown to have occurred at tropical latitudes, providing direct evidence that this particular glaciation was a ‘snowball Earth’ event,” says lead author Francis A. Macdonald, an assistant professor in the Department of Earth and Planetary Sciences at Harvard. “Our data also suggests that the Sturtian glaciation lasted a minimum of 5 million years.”

The survival of eukaryotic life throughout this period indicates sunlight and surface water remained available somewhere on the surface of Earth. The earliest animals arose at roughly the same time, following a major proliferation of eukaryotes.

Even in a snowball Earth, Macdonald says, there would be temperature gradients on Earth and it is likely that ice would be dynamic: flowing, thinning, and forming local patches of open water, providing refuge for life.

“The fossil record suggests that all of the major eukaryotic groups, with the possible exception of animals, existed before the Sturtian glaciation,” Macdonald says. “The questions that arise from this are: If a snowball Earth existed, how did these eukaryotes survive? Moreover, did the Sturtian snowball Earth stimulate evolution and the origin of animals?”

“From an evolutionary perspective,” he adds, “it’s not always a bad thing for life on Earth to face severe stress.”

The rocks Macdonald and his colleagues analyzed in Canada’s Yukon Territory showed glacial deposits and other signs of glaciation, such as striated clasts, ice rafted debris, and deformation of soft sediments. The scientists were able to determine, based on the magnetism and composition of these rocks, that 716.5 million years ago they were located at sea level in the tropics, at about 10 degrees latitude.

“Because of the high albedo of ice, climate modeling has long predicted that if sea ice were ever to develop within 30 degrees latitude of the equator, the whole ocean would rapidly freeze over,” Macdonald says. “So our result implies quite strongly that ice would have been found at all latitudes during the Sturtian glaciation.”

Scientists don’t know exactly what caused this glaciation or what ended it, but Macdonald says its age of 716.5 million years closely matches the age of a large igneous province stretching more than 1,500 kilometers (932 miles) from Alaska to Ellesmere Island in far northeastern Canada. This coincidence could mean the glaciation was either precipitated or terminated by volcanic activity.

Methane releases from Arctic shelf may be much larger and faster than anticipated

The permafrost of the East Siberian Arctic Shelf (an area of about 2 million kilometers squared) is more porous than previously thought. The ocean on top of it and the heat from the mantle below it warm it and make it perforated like Swiss cheese. This allows methane gas stored under it under pressure to burst into the atmosphere. The amount leaking from this locale is comparable to all the methane from the rest of the world's oceans put together. Methane is a greenhouse gas more than 30 times more potent than carbon dioxide. - Credit: Zina Deretsky, National Science Foundation
The permafrost of the East Siberian Arctic Shelf (an area of about 2 million kilometers squared) is more porous than previously thought. The ocean on top of it and the heat from the mantle below it warm it and make it perforated like Swiss cheese. This allows methane gas stored under it under pressure to burst into the atmosphere. The amount leaking from this locale is comparable to all the methane from the rest of the world’s oceans put together. Methane is a greenhouse gas more than 30 times more potent than carbon dioxide. – Credit: Zina Deretsky, National Science Foundation

A section of the Arctic Ocean seafloor that holds vast stores of frozen methane is showing signs of instability and widespread venting of the powerful greenhouse gas, according to the findings of an international research team led by University of Alaska Fairbanks scientists Natalia Shakhova and Igor Semiletov.

The research results, published in the March 5 edition of the journal Science, show that the permafrost under the East Siberian Arctic Shelf, long thought to be an impermeable barrier sealing in methane, is perforated and is starting to leak large amounts of methane into the atmosphere. Release of even a fraction of the methane stored in the shelf could trigger abrupt climate warming.

“The amount of methane currently coming out of the East Siberian Arctic Shelf is comparable to the amount coming out of the entire world’s oceans,” said Shakhova, a researcher at UAF’s International Arctic Research Center. “Subsea permafrost is losing its ability to be an impermeable cap.”

Methane is a greenhouse gas more than 30 times more potent than carbon dioxide. It is released from previously frozen soils in two ways. When the organic material (which contains carbon) stored in permafrost thaws, it begins to decompose and, under anaerobic conditions, gradually releases methane. Methane can also be stored in the seabed as methane gas or methane hydrates and then released as subsea permafrost thaws. These releases can be larger and more abrupt than those that result from decomposition.

The East Siberian Arctic Shelf is a methane-rich area that encompasses more than 2 million square kilometers of seafloor in the Arctic Ocean. It is more than three times as large as the nearby Siberian wetlands, which have been considered the primary Northern Hemisphere source of atmospheric methane. Shakhova’s research results show that the East Siberian Arctic Shelf is already a significant methane source, releasing 7 teragrams of methane yearly, which is as much as is emitted from the rest of the ocean. A teragram is equal to about 1.1 million tons.

“Our concern is that the subsea permafrost has been showing signs of destabilization already,” she said. “If it further destabilizes, the methane emissions may not be teragrams, it would be significantly larger.”

Shakhova notes that the Earth’s geological record indicates that atmospheric methane concentrations have varied between about .3 to .4 parts per million during cold periods to .6 to .7 parts per million during warm periods. Current average methane concentrations in the Arctic average about 1.85 parts per million, the highest in 400,000 years, she said. Concentrations above the East Siberian Arctic Shelf are even higher.

The East Siberian Arctic Shelf is a relative frontier in methane studies. The shelf is shallow, 50 meters (164 feet) or less in depth, which means it has been alternately submerged or terrestrial, depending on sea levels throughout Earth’s history. During the Earth’s coldest periods, it is a frozen arctic coastal plain, and does not release methane. As the Earth warms and sea level rises, it is inundated with seawater, which is 12-15 degrees warmer than the average air temperature.

“It was thought that seawater kept the East Siberian Arctic Shelf permafrost frozen,” Shakhova said. “Nobody considered this huge area.”

“This study is a testament to sustained, careful observations and to international cooperation in research,” said Henrietta Edmonds of the National Science Foundation, which partially funded the study. “The Arctic is a difficult place to get to and to work in, but it is important that we do so in order to understand its role in global climate and its response and contribution to ongoing environmental change. It is important to understand the size of the reservoir–the amount of trapped methane that potentially could be released–as well as the processes that have kept it “trapped” and those that control the release. Work like this helps us to understand and document these processes.”

Earlier studies in Siberia focused on methane escaping from thawing terrestrial permafrost. Semiletov’s work during the 1990s showed, among other things, that the amount of methane being emitted from terrestrial sources decreased at higher latitudes. But those studies stopped at the coast. Starting in the fall of 2003, Shakhova, Semiletov and the rest of their team took the studies offshore. From 2003 through 2008, they took annual research cruises throughout the shelf and sampled seawater at various depths and the air 10 meters above the ocean. In September 2006, they flew a helicopter over the same area, taking air samples at up to 2,000 meters (6,562 feet) in the atmosphere. In April 2007, they conducted a winter expedition on the sea ice.

They found that more than 80 percent of the deep water and more than 50 percent of surface water had methane levels more than eight times that of normal seawater. In some areas, the saturation levels reached more than 250 times that of background levels in the summer and 1,400 times higher in the winter. They found corresponding results in the air directly above the ocean surface. Methane levels were elevated overall and the seascape was dotted with more than 100 hotspots. This, combined with winter expedition results that found methane gas trapped under and in the sea ice, showed the team that the methane was not only being dissolved in the water, it was bubbling out into the atmosphere.

These findings were further confirmed when Shakhova and her colleagues sampled methane levels at higher elevations. Methane levels throughout the Arctic are usually 8 to 10 percent higher than the global baseline. When they flew over the shelf, they found methane at levels another 5 to 10 percent higher than the already elevated Arctic levels.

The East Siberian Arctic Shelf, in addition to holding large stores of frozen methane, is more of a concern because it is so shallow. In deep water, methane gas oxidizes into carbon dioxide before it reaches the surface. In the shallows of the East Siberian Arctic Shelf, methane simply doesn’t have enough time to oxidize, which means more of it escapes into the atmosphere. That, combined with the sheer amount of methane in the region, could add a previously uncalculated variable to climate models.

“The release to the atmosphere of only one percent of the methane assumed to be stored in shallow hydrate deposits might alter the current atmospheric burden of methane up to 3 to 4 times,” Shakhova said. “The climatic consequences of this are hard to predict.”

Shakhova, Semiletov and collaborators from 12 institutions in five countries plan to continue their studies in the region, tracking the source of the methane emissions and drilling into the seafloor in an effort to estimate how much methane is stored there.

Oldest measurement of Earth’s magnetic field reveals battle between sun and Earth for our atmosphere

The larger auroral oval relative to the modern is the result of a weaker dipole magnetic field and stronger solar wind dynamic pressure. The auroral intensity is brighter due to solar wind
densities many times greater than those today, and the dominant color reflects greater energies of the precipitating particles and the mildly reducing Paleoarchean atmosphere. -  Courtesy J. Tarduno and R. Cottrell. University of Rochester
The larger auroral oval relative to the modern is the result of a weaker dipole magnetic field and stronger solar wind dynamic pressure. The auroral intensity is brighter due to solar wind
densities many times greater than those today, and the dominant color reflects greater energies of the precipitating particles and the mildly reducing Paleoarchean atmosphere. – Courtesy J. Tarduno and R. Cottrell. University of Rochester

Scientists at the University of Rochester have discovered that the Earth’s magnetic field 3.5 billion years ago was only half as strong as it is today, and that this weakness, coupled with a strong wind of energetic particles from the young Sun, likely stripped water from the early Earth’s atmosphere.

The findings, presented in today’s issue of Science, suggest that the magnetopause-the boundary where the Earth’s magnetic field successfully deflects the Sun’s incoming solar wind-was only half the distance from Earth it is today.

“With a weak magnetosphere and a rapid-rotating young Sun, the Earth was likely receiving as many solar protons on an average day as we get today during a severe solar storm,” says John Tarduno, a geophysicist at the University of Rochester and lead author of the study. “That means the particles streaming out of the Sun were much more likely to reach Earth. It’s very likely the solar wind was removing volatile molecules, like hydrogen, from the atmosphere at a much greater rate than we’re losing them today.” Tarduno says the loss of hydrogen implies a loss of water as well, meaning there may be much less water on Earth today than in its infancy.

To find the strength of the ancient magnetic field, Tarduno and his colleagues from the University of KwaZulu-Natal visited sites in Africa that were known to contain rocks in excess of 3 billion years of age. Not just any rocks of that age would do, however. Certain igneous rocks called dacites contain small millimeter-sized quartz crystals, which in turn have tiny nanometer-sized magnetic inclusions. The magnetization of these inclusions act as minute compasses, locking in a record of the Earth’s magnetic field as the dacite cooled from molten magma to hard rock. Simply finding rocks of this age is difficult enough, but such rocks have also witnessed billions of years of geological activity that could have reheated them and possibly changed their initial magnetic record. To reduce the chance of this contamination, Tarduno picked out the best preserved grains of feldspar and quartz out of 3.5 billion-year-old dacite outcroppings in South Africa.

Complicating the search for the right rocks further, the effect of the solar wind interacting with the atmosphere can induce a magnetic field of its own, so even if Tarduno did find a rock that had not been altered in 3.5 billion years, he had to make sure the magnetic record it contained was generated by the Earth’s core and not induced by the solar wind.

Once he isolated the ideal crystals, Tarduno used a device called a superconducting quantum interface device, or SQUID magnetometer, which is normally used to troubleshoot computer chips because it’s extremely sensitive to the smallest magnetic fields. Tarduno pioneered the use of single crystal analyses using SQUID magnetometers. However, for this study, even standard SQUID magnetometers lacked the sensitivity. Tarduno was able to employ a new magnetometer, which has sensors closer to the sample than in previous instruments.

Using the new magnetometer, Tarduno, Research Scientist Rory Cottrell, and University of Rochester students were able to confirm that the 3.5 billion-year-old silicate crystals had recorded a field much too strong to be induced by the solar wind-atmosphere interaction, and so must have been generated by Earth’s core.

“We gained a pretty solid idea of how strong Earth’s field was at that time, but we knew that was only half the picture,” says Tarduno. “We needed to understand how much solar wind that magnetic field was deflecting because that would tell us what was probably happening to Earth’s atmosphere.”

The solar wind can strip away a planet’s atmosphere and bathe its surface in lethal radiation. Tarduno points to Mars as an example of a planet that likely lost its magnetosphere early in its history, letting the bombardment of solar wind slowly erode its atmosphere. To discover what kind of solar wind the Earth had to contend with, Tarduno employed the help of Eric Mamajek, assistant professor of physics and astronomy at the University of Rochester.

“There is a strong correlation between how old a Sun-like star is and the amount of matter it throws off as solar wind,” says Mamajek “Judging from the rotation and activity we expect of our Sun at a billion years of age, we think that it was shedding material at a rate about 100 times stronger than the average rate observed in modern times.”

While the life cycle of stars like our Sun is well known, says Mamajek, astrophysicists have only a handful of stars for which they know the amount of mass lost as solar wind. Mamajek says the amount of X-rays radiated from a star, regardless of its apparent brightness, can give a good estimate of how much material the star is radiating as solar wind. Through the Sun at this age was likely about 23% dimmer than it would appear to us today, it was giving off much more radiation as X-rays, and driving a much more powerful solar wind.

“We estimate the solar wind at that time was a couple of orders of magnitude stronger,” says Mamajek. “With Earth’s weaker magnetosphere, the standoff point between the two was probably less than five Earth radii. That’s less than half of the distance of 10.7 radii it is today.”

Tarduno says that in addition to the smaller magnetopause allowing the solar wind to strip away more water vapor from the early Earth, the skies might have been filled with more polar aurora. The Earth’s magnetic field bends toward vertical at the poles and channels the solar wind toward the Earth’s surface there. When the solar wind strikes the atmosphere, it releases photons that appear as shifting patterns of light at night.

With the weakened magnetosphere, the area where the solar wind is channeled toward the surface-an area called the magnetic polar cap-would have been three times larger than it is today, says Tarduno.

“On a normal night 3.5 billion years ago you’d probably see the aurora as far south as New York,” says Tarduno.

Experts reaffirm asteroid impact caused mass extinction

An artist's rendering of the moment of impact when an enormous space rock struck the Yucatán peninsula at the end of the Cretaceous Period. Credit: Don Davis, NASA.
An artist’s rendering of the moment of impact when an enormous space rock struck the Yucatán peninsula at the end of the Cretaceous Period. Credit: Don Davis, NASA.

Responding to challenges to the hypothesis that an asteroid impact caused a mass extinction on Earth 65 million years, a panel of 41 scientists re-analyzed data and provided new evidence, concluding that an impact in Mexico was indeed the cause of the mass extinction.

Reporters are invited to a live embargoed webcast with one of the study’s co-authors on March 3. Details below.

Thirty years ago, Luis Alvarez, Jan Smit and their coworkers suggested a large meteorite slammed into Earth 65 million years ago and caused one of the most severe mass extinctions in Earth’s history, ending the age of the dinosaurs. In 1991, a more than 200-kilometer-wide impact crater was discovered in Yucatan, Mexico, that coincided with the extinctions. Since then, the impact hypothesis has gained overwhelming acceptance within the scientific community.

Still in recent years, a few scientists have challenged this hypothesis. To address their claims, a panel of 41 experts from Europe, the U.S., Mexico, Canada and Japan provide new data from the analysis of ocean drilling and continental sites and re-analyze the relevant literature in the field, including the most recent research. In a review paper in the March 5 edition of the journal Science, they find that alternative hypotheses are inadequate to explain the abrupt mass extinction and that the impact hypothesis has grown stronger than ever.

The fossil record clearly shows a mass extinction event across the planet at about 65.5 million years ago. Because this change is so dramatic, geologists use it to define the end of the Cretaceous period and the start of the Paleogene period (formerly called the Tertiary period). They refer to the time of the extinctions as the K-Pg boundary.

Some scientists have suggested that the Chicxulub (“chik-shoo-loob”) impact in Mexico happened 300,000 years before the K-Pg boundary and therefore, came too early to have been the major cause of extinctions.

They point to deposits at sites around the Gulf of Mexico with a layer of tiny glass-like blobs of melted impact material that, according to their interpretation, was deposited at about 300,000 years before the K-Pg boundary mass extinction. As an alternative, they suggest the Deccan Traps -unusually active volcanoes in what is now India-led to global cooling and acid rain, and were the major cause of mass extinction, not the Chicxulub impact in Mexico.

However, the reviewers find that what appears to be a series of layers neatly laid down over 300,000 years near the impact site were actually violently churned and then dumped in a thick pile in a very short time. Models suggest the impact at Chicxulub was a million times more energetic than the largest nuclear bomb ever tested. An impact of this size would eject material at high velocity around the world, cause earthquakes of magnitude >10, continental shelf collapse, landslides, gravity flows, mass wasting and tsunamis and produce a relatively thick and complex sequence of deposits close to Chicxulub.

“If we are to unravel the sequence of events across the K-Pg boundary, perhaps the last place in the world we should look is close to the Chicxulub impact site, where the sedimentary deposits will be most disturbed,” write the reviewers.

In addition, the reviewers note, as you go farther from the impact site, these layers become thinner and the amount of ejected material decreases until it becomes one layer that can be found globally exactly at the K-Pg boundary coincident with the mass extinction. Moreover, the ejecta within the global K-Pg layer is compositionally linked to the specific sediments and crystalline rocks at Chicxulub.

The reviewers find that despite evidence for relatively active volcanism in India, marine and terrestrial ecosystems showed only minor changes within the 500,000 years before the K-Pg boundary. Then, precisely at the boundary, there was an abrupt and major decrease in productivity (a measure of the sheer mass of living things) and species diversity.

The Deccan hypothesis is further weakened by a review of models of atmospheric chemistry. Although significant volumes of sulfur may be emitted during each volcanic eruption and form aerosols in the stratosphere, these sulfur aerosols fall out rapidly and any adverse environmental effects are apparently only short-lasting. In comparison, during the Chicxulub impact, much larger volumes of sulfur, dust and soot were released in a much shorter time, leading to extreme environmental perturbations (such as darkening or cooling).

“Combining all available data from different science disciplines led us to conclude that a large asteroid impact 65 million years ago in modern-day Mexico was the major cause of the mass extinctions,” says Peter Schulte, assistant professor at the University of Erlangen in Germany and lead author of the review paper.

Far from Chicxulub, the geologic record clearly shows a single large meteorite hit the Earth exactly at the K-Pg boundary. Thickening of the K-Pg boundary layer towards Chicxulub shows Chicxulub was the impact site. The significant changes in Earth’s ecosystems all occur precisely at this boundary and thus, say the reviewers, a large asteroid impact into the sulfate-rich sediments at Chicxulub remains the most plausible cause for the K-Pg boundary mass extinction.

Several mechanisms have been proposed to explain why the impact was so deadly. In February 2008, Sean Gulick and Gail Christeson, research scientists at The University of Texas at Austin’s Institute for Geophysics, and their colleagues published a study in the journal Nature Geoscience finding that the asteroid landed in deeper water than previously assumed and therefore released more water vapor and sulfate aerosols into the atmosphere. Gulick, a co-author of the new review paper in Science, said this could have made the impact deadlier in two ways: by altering climate (sulfate aerosols in the upper atmosphere can have a cooling effect) and by generating acid rain (water vapor can help to flush the lower atmosphere of sulfate aerosols, causing acid rain). That finding and many others strengthen the case for the impact hypothesis.

Earth-shaking research to predict devastation from earthquakes

The computational science expertise at the Science and Technology Facilities Council’s (STFC) Daresbury Laboratory is playing a key role in enabling researchers at the National Autonomous University of Mexico (UNAM), to develop a tool that will make it possible to estimate the likely impact of large magnitude earthquakes at specific locations, before they happen.

Led and funded by the Institute of Engineering of UNAM, the project has closely studied the propagation of seismic waves through the earth’s crust during a number of major earthquakes, including the Magnitude Scale (Ms) 8 earthquakes that heavily damaged Mexico City in 1985 and the Great Sichuan Earthquake in China in 2008. Using this background experience, Daresbury’s computational scientists have been working with UNAM on the further development and optimisation of the simulation code for use on the world’s leading computer systems. As well as looking at past events, the work is capable of studying ground motions from hypothetical earthquakes in vulnerable regions, and identifying where the ground shaking shocks would be at their greatest, should the earthquake occur.

Dr Mario Chavez, researcher at UNAM said: “Our research means that governments, developers and planners across the world could soon have access to vital earthquake ground motion data that will enable them to assess the strength and impact of large or extreme magnitude earthquake scenarios in their own region. This kind of information could play a major role when working on the risk assessment for a facility site, such as a nuclear power station, or when designing homes, hospitals, schools, or any buildings, in determining how resilient they need to be in order to minimize the damage caused by an earthquake. It could also help to assess how adequate an area’s emergency infrastructure would be in such an event. However, it is important to point out that we are not predicting that an earthquake will actually happen, or when it will happen, but to pose “what if” type scenarios such as, if an earthquake of a given magnitude does hit a specific area, first, how much and how fast the earth surface will move, and second, by using information of the resilience capacity of the existing or planned infrastructure in that region, what is the probable impact of the earthquake. We are very excited to be working with the computational scientists at STFC Daresbury, who are renowned world experts in engineering computing. Daresbury is one of the best computational modeling centers in the world.”

Dr Mike Ashworth, Associate Director of the Computational Science & Engineering Department at STFC Daresbury Laboratory said: “For this project we have made use of the highest levels of performance on parallel machines, allowing Dr Chavez to perform high resolution simulation to an accuracy and magnitude that has not been done before for this kind of research. We were able to optimize and develop a code on Daresbury’s supercomputers which enabled us to run on thousands of processors simultaneously for many hours, where it had previously only been run with a few tens or hundreds for just a few hours at the Kanbalam supercomputer of UNAM. We followed this up by taking our code to HECToR, the UK’s largest, fastest and most powerful academic supercomputer, based at the University of Edinburgh, where we were able to run more than 8000 simultaneous processes. This project required availability of much larger computing resources than is currently available in Mexico and we are therefore thrilled to be able to offer our expertise to Dr Chavez and his team in this very obviously worthwhile research. UNAM performs more than half of the research of that comes out of Mexico and we look forward to continuing to work with Dr Chavez in the future”

This collaboration has been made possible through The Scientific Computing Advanced Training project (SCAT), a European Commission funded project that brings together research groups in 10 world-leading academic and research institutions from six countries. SCAT aims to provide training in computational science for young scientists in Europe and Latin America, and to create long-term research partnerships.

Dr Richard Blake, Director of STFC’s Computational Science and Engineering Department, said: “This kind of research is invaluable to nations worldwide, the UK included. Although we are not considered a country at risk of a large magnitude earthquake, minor ones can occur nearby a site of interest and resulting damage could be significant. This project is a great illustration of the growing importance of modelling and simulation of what happens naturally on Earth and computational science could help governments implement policies and plans to save the lives of many thousands of people across the globe in years to come. We look forward to continuing to work with Dr Chavez in the future, particularly as we gear up for our new Hartree Centre at Daresbury, a unique national center for high performance computing.”

Rapid response science missions assess potential for another major Haiti earthquake

Map of area of January 12 earthquake and aftershocks.  The colors show calculated differences from before and after the earthquake in radar images.  The close bands of color indicate greater deformation. Notice how a set of  colored rings are centered over the offshore region near where the tsunami also occurred.
Map of area of January 12 earthquake and aftershocks. The colors show calculated differences from before and after the earthquake in radar images. The close bands of color indicate greater deformation. Notice how a set of colored rings are centered over the offshore region near where the tsunami also occurred.

To help assess the potential threat of more large earthquakes in Haiti and nearby areas, scientists at The University of Texas at Austin’s Institute for Geophysics are co-leading three expeditions to the country with colleagues from Purdue University, Lamont-Doherty Earth Observatory, the U.S. Geological Survey and five other institutions.

Rapid response missions can be critical for assessing future risks because a fault can continue to displace the ground for weeks and months after a large earthquake. At the same time, natural weathering processes and human activities can erase valuable geologic evidence.

The goal of the Haiti missions, researchers say, is to understand which segments of the earthquake fault ruptured during the Jan. 12 quake and how much fault movement and uplift of coastal features occurred in locations along or near the fault.

  • Expedition 1: Eric Calais of Purdue University led the first expedition, which has ended, collecting Global Positioning System (GPS) data to determine how land moved as a result of the earthquake. A second team participating in the expedition, led by Paul Mann of the Institute for Geophysics and Rich Koehler of the Alaska Division of Geological & Geophysical Surveys, used a helicopter and fieldwork to search for signs of ruptures-cracks at the surface along the main trace of the suspected earthquake fault. They found no signs of surface rupture but evidence for lateral spreading and liquefaction-a phenomenon in which soils behave like a liquid instead of a solid. Earthquakes most likely caused by the same fault and resulting in the same kind of lateral spreading and liquefaction destroyed the Jamaican capital of Kingston in 1692 and 1907. Funding was provided by the Rapid Response Research Program of the National Science Foundation (NSF).

  • Expedition 2: The second expedition, beginning Feb. 24, will for the first time use a scientific research vessel to examine the underwater effects of the quake. Chief scientist for the expedition is Cecilia McHugh at the City University of New York and Lamont-Doherty Earth Observatory with co-chief scientists Sean Gulick of the Institute for Geophysics and Milene Cormier of the University of Missouri. For two weeks, a team onboard the RV Endeavor will use sonar to map shifted sediments on the seafloor and seismic sensors to examine faults beneath the seafloor. The scientists hope to solve a mystery about how the earthquake unleashed a tsunami that killed seven people and to explain why corals along the coast have now been uplifted above sea level. The 185-foot Endeavor is owned by the NSF and operated by the University of Rhode Island. Funding is provided by the NSF and The University of Texas at Austin’s Jackson School of Geosciences.

  • Expedition 3: The third expedition, led by Fred Taylor of the Institute for Geophysics, will focus on large coral heads exposed by coastal uplift during the earthquake. Taylor will use a specialized chainsaw to collect the now dead coral for study of its tree ring-like structure to reveal clues on recent uplift and previous uplifts extending back hundreds of years. He will be assisted by Mann along with Rich Briggs and Carol Prentice of the U.S. Geological Survey (USGS). The Jackson School of Geosciences and USGS are jointly funding the coral study.

The Jackson School places a special emphasis on mounting rapid response missions to the scenes of geo-hazards, supporting previous missions after the earthquake and tsunami in the Solomon Islands (2007) and Hurricane Ike along the Texas Gulf Coast (2008). Few academic organizations have the infrastructure, equipment and expertise to mount a large field expedition on a few weeks’ notice, yet they can yield valuable insights to prepare communities for future hazards.

“We expect a whole raft of studies about the Haiti earthquake coming out based on remote sensing data from satellites and airplanes,” said Sean Gulick of the Institute for Geophysics. “But there’s no substitute for getting on the ground and in the water to look directly at its immediate effects.”

While collecting information that can save lives in the near future is a top priority of the expeditions, the scientists are also working to help cultivate local earthquake expertise. Two Haitian scientists have been invited to participate-Nicole Dieudonne, a representative of the Haitian Bureau of Mines and Energy, and Steeven Smyithe, a student from the State University of Haiti.

“We’re trying to engage the Haitian science community,” said Mann, who will return to Haiti for the second expedition. “They can help us communicate better with Haitian policy makers and people about the geology behind this devastating earthquake and about the risks going forward.”

In 2008, Mann, Calais and colleagues presented a paper at the Caribbean Conference forecasting a 7.2 magnitude earthquake in the area of Haiti, Jamaica and the Dominican Republic. The forecast was based on an integration of geologic information on the Enriquillo-Plantain Garden fault zone with GPS data collected in the region. David Manaker, Calais and colleagues published an article on the same topic in Geophysical Journal International.

Research team breaks the ice with new estimate of glacier melt

This is Northern Arizona University geographer Erik Schiefer in British Columbia studying glacier melt. -  Photo by Karl Schiefer
This is Northern Arizona University geographer Erik Schiefer in British Columbia studying glacier melt. – Photo by Karl Schiefer

The melting of glaciers is well documented, but when looking at the rate at which they have been retreating, a team of international researchers steps back and says not so fast.

Previous studies have largely overestimated mass loss from Alaskan glaciers over the past 40-plus years, according to Erik Schiefer, a Northern Arizona University geographer who coauthored a paper in the February issue of Nature Geoscience that recalculates glacier melt in Alaska.

The research team, led by Étienne Berthier of the Laboratory for Space Studies in Geophysics and Oceanography at the Université de Toulouse in France, says that glacier melt in Alaska between 1962 and 2006 contributed about one-third less to sea-level rise than previously estimated.

Schiefer said melting glaciers in Alaska originally were thought to contribute about .0067 inches to sea-level rise per year. The team’s new calculations put that number closer to .0047 inches per year. The numbers sound small, but as Schiefer said, “It adds up over the decades.”

While the team looked at three-fourths of all the ice in Alaska, Schiefer noted, “We’re also talking about a small proportion of ice on the planet. When massive ice sheets (such as in the Antarctic and Greenland) are added in, you’re looking at significantly greater rates of sea-level rise.”

Schiefer said the team plans to use the same methodologies from the Alaskan study in other glacial regions to determine if further recalibrations of ice melt are in order. These techniques use satellite imagery that spans vast areas of ice cover.

Previous methods estimated melt for a smaller subset of individual glaciers. The most comprehensive technique previously available used planes that flew along the centerlines of selected glaciers to measure ice surface elevations. These elevations were then compared to those mapped in the 1950s and 1960s. From this, researchers inferred elevation changes and then extrapolated this to other glaciers.

Two factors led to the original overestimation of ice loss with this method, Schiefer said. One is the impact of thick deposits of rock debris that offer protection from solar radiation and, thus, melting. The other was not accounting for the thinner ice along the edges of glaciers that also resulted in less ice melt.

Schiefer and his colleagues used data from the SPOT 5 French satellite and the NASA/Japanese ASTER satellite and converted the optical imagery to elevation information. They then compared this information to the topographical series maps of glacial elevations dating back to the 1950s.

While the team determined a lower rate of glacial melt during a greater than 40-year span, Schiefer said other studies have demonstrated the rate of ice loss has more than doubled in just the last two decades.

“With current projections of climate change, we expect that acceleration to continue,” Schiefer said. This substantial increase in ice loss since the 1990s is now pushing up the rise in sea level to between .0098 inches and .0118 inches per year-more than double the average rate for the last 40 years.

Scientists locate apparent hydrothermal vents off Antarctica

A vent spews chemical fluids from the East Pacific Rise, about 5,600 miles from newly suspected vents on the Pacific Antarctic Ridge. -  Woods Hole Oceanographic Institution
A vent spews chemical fluids from the East Pacific Rise, about 5,600 miles from newly suspected vents on the Pacific Antarctic Ridge. – Woods Hole Oceanographic Institution

Scientists at Columbia University’s Lamont-Doherty Earth Observatory have found evidence of hydrothermal vents on the seafloor near Antarctica, formerly a blank spot on the map for researchers wanting to learn more about seafloor formation and the bizarre life forms drawn to these extreme environments.

Hydrothermal vents spew volcanically heated seawater from the planet’s underwater mountain ranges-the vast mid-ocean ridge system, where lava erupts and new crust forms. Chemicals dissolved in those vents influence ocean chemistry and sustain a complex web of organisms, much as sunlight does on land. In recent decades more than 220 vents have been discovered worldwide, but so far no one has looked for them in the rough and frigid waters off Antarctica.

From her lab in Palisades, N.Y., geochemist Gisela Winckler recently took up the search. By analyzing thousands of oceanographic measurements, she and her Lamont colleagues pinpointed six spots on the remote Pacific Antarctic Ridge, about 2,000 miles from New Zealand, the closest inhabited country, and 1,000 miles from the west coast of Antarctica, where they think vents are likely to be found. The sites are described in a paper published THIS WEEK in the journal Geophysical Research Letters.

“Most of the deep ocean is like a desert, but these vents are oases of life and weirdness,” said Winckler. “The Pacific Antarctic ridge is one of the ridges we know least about. It would be fantastic if researchers were to dive to the seafloor to study the vents we believe are there.”

Two important facts helped the scientists isolate the hidden vents. First, the ocean is stratified with layers of lighter water sitting on top of layers of denser water. Second, when a seafloor vent erupts, it spews gases rich in rare helium-3, an isotope found in earth’s mantle and in the magma bubbling below the vent. As helium-3 disperses through the ocean, it mixes into a density layer and stays there, forming a plume that can stretch over thousands of kilometers.

The Lamont scientists were analyzing ocean-helium measurements to study how the deep ocean exchanges dissolved gases with the atmosphere when they came across a helium plume that looked out of place. It was in a southern portion of the Pacific Ocean, below a large and well-known helium plume coming off the East Pacific Rise, one of the best-studied vent regions on earth. But this mystery plume appeared too deep to have the same source.

Suspecting that it was coming from the Pacific Antarctic Ridge instead, the researchers compiled a detailed map of ocean-density layers in that region, using some 25,000 salinity, temperature and depth measurements. After locating the helium plume along a single density layer, they compared the layer to topographic maps of the Pacific Antarctic Ridge to figure out where the plume would intersect.

The sites they identified cover 340 miles of ridge line–the approximate distance between Manhattan and Richmond, Va.–or about 7 percent of the total 4,300 mile-ridge. This chain of volcanic mountains lies about three miles below the ocean surface, and its mile-high peaks are cut by steep canyons and fracture zones created as the sea floor spreads apart. It is a cold and lonely stretch of ocean, far from land or commercial shipping lanes.

“They haven’t found vents, but they’ve narrowed the places to look by quite a bit,” said Edward Baker, a vent expert at the National Oceanic and Atmospheric Administration.

Of course, finding vents in polar waters is not easy, even with a rough idea where to look. In 2007, Woods Hole Oceanographic Institution geophysicist Rob Reves-Sohn led a team of scientists to the Gakkel Ridge between Greenland and Siberia to look for vents detected six years earlier. Although they discovered regions where warm fluids appeared to be seeping from the seafloor, they failed to find the high-temperature, black smoker vents they had come for. In a pending paper, Sohn now says he has narrowed down the search to a 400-kilometer-square area where he expects to find seven new vents, including at least one black smoker.

The search for vents off Antarctica may be equally unpredictable, but the map produced by the Lamont scientists should greatly improve the odds of success, said Robert Newton, a Lamont oceanographer and study co-author. “You don’t have to land right on top of a vent to know it’s there,” he said. “You get a rich mineral soup coming out of these smokers-methane, iron, manganese, sulphur and many other minerals. Once you get within a few tens of kilometers, you can detect these other tracers.”

Since the discovery of the first hydrothermal vents in the late 1970s, scientists have searched for far-flung sites, in the hunt for new species and adaptive patterns that can shed light on how species evolved in different spots. Cindy Van Dover, a deep sea biologist and director of the Duke University Marine Laboratory, says she expects that new species will be found on the Pacific Antarctic Ridge, and that this region may hold important clues about how creatures vary between the Indian and Pacific Oceans, on either end.

“These vents are living laboratories,” said Van Dover, who was not involved in the study. “When we went to the Indian Ocean, we discovered the scaly-foot gastropod, a deep-sea snail whose foot is covered in armor made of iron sulfides. The military may be interested in studying the snail to develop a better armor. The adaptations found in these animals may have many other applications.”