First complete image created of Himalayan fault, subduction zone

Soma Sapkota, of Nepal's Department of Mines and Geology, at a seismic station in barren, wind-swept central Tibet. - Photo Courtesy: OSU's John Nabelek
Soma Sapkota, of Nepal’s Department of Mines and Geology, at a seismic station in barren, wind-swept central Tibet. – Photo Courtesy: OSU’s John Nabelek

An international team of researchers has created the most complete seismic image of the Earth’s crust and upper mantle beneath the rugged Himalaya Mountains, in the process discovering some unusual geologic features that may explain how the region has evolved.

Their findings, published this week in the journal Science, help explain the formation of the world’s largest mountain range, which is still growing.

The researchers discovered that as the Indian and Eurasian tectonic plates collide, the Indian lower crust slides under the Tibetan crust, while the upper mantle peels away from the crust and drops down in a diffuse manner.

“The building of Tibet is not a simple process,” said John Nabelek, an Oregon State University geophysicist and lead author on the Science study. “In part, the mountain building is similar to pushing dirt with a bulldozer except in this case, the Indian sediments pile up into a wedge that is the lesser Himalayan mountains.

“However, an important component of the mass transfer from the upper crust of India to the Himalayas also occurs at depth through viscous processes, while the lower crust continues sliding intact farther north under the Tibet plateau,” Nabelek added.

The findings are important because there has been clear scientific consensus on the boundaries and processes for that region’s tectonic plates. In fact, the piecemeal images gathered by previous research have led to a series of conflicting models of the lithospheric structure and plate movement.

In this study, the international research team – called Hi-CLIMB (Himalayan-Tibetan Continental Lithosphere during Mountain Building) – was able to create new in-depth images of the Earth’s structure beneath the Himalayas.

The researchers go through Chitwan National Park in Nepal after completing the first phase of the network deployment. - Photo Courtesy:OSU's John Nabelek
The researchers go through Chitwan National Park in Nepal after completing the first phase of the network deployment. – Photo Courtesy:OSU’s John Nabelek

The interface between the subducting Indian plate and the upper Himalayan and Tibetan crust is the Main Himalayan thrust fault, which reaches the surface in southern Nepal, Nabelek said. The new images show it extends from the surface to mid-crustal depths in central Tibet, but the shallow part of the fault sticks, leading to historically devastating mega-thrust earthquakes.

“The deep part is ductile,” Nabelek said, “and slips in a continuous fashion. Knowing the depth and geometry of this interface will advance research on a variety of fronts, including the interpretation of strain accumulation from GPS measurements prior to large earthquakes.”

Nabelek, an associate professor in OSU’s College of Oceanic and Atmospheric Sciences, said the lower part of the Indian crust slides about 450 kilometers under the southern Tibetan plate and the mantle appears to shear off and break into sub-parallel segments.

The researchers found evidence that subduction in the fault zone has been occurring from both the north and south sides – likely at different times in its geologic history.

In this project, funded primarily by the National Science Foundation, the researchers deployed and monitored about 230 seismic stations for a period of three years, cutting across 800 kilometers of some of the most remote terrain in the world. The lowest-elevation station was at 12 meters above sea level in Nepal; the highest, nearly 5,500 meters in Tibet. In fact, 30 of the stations were higher than 5,000 meters, or 16,400 feet.

“The research took us from the jungles of Nepal, with its elephants, crocodiles and rhinos, to the barren, wind-swept heights of Tibet in areas where nothing grew for hundreds of miles and there were absolutely no humans around,” Nabelek said. “That remoteness is one reason this region had never previously been completely profiled.”

More oxygen – colder climate

Everybody talks about CO2 and other greenhouse gases as causes of global warming and the large climate changes we are currently experiencing. But what about the atmospheric and oceanic oxygen content? Which role does oxygen content play in global warming?

This question has become extremely relevant now that Professor Robert Frei from the Department of Geography and Geology at the University of Copenhagen, in collaboration with colleagues from Uruguay, England and the University of Southern Denmark, has established that there is a historical correlation between oxygen and temperature fluctuations towards global cooling.

The team of researchers reached their conclusions via analyses of iron-rich stones, so called banded iron formations, from different locations around the globe and covering a time span of more than 3,000 million years. Their discovery was made possible by a new analytical method which the research team developed. This method is based on analysis of chrome isotopes – different chemical variants of the element chrome. It turned out that the chrome isotopes in the iron rich stones reflect the oxygen content of the atmosphere. The method is a unique tool, which makes it possible to examine historical changes in the atmospheric oxygen content and thereby possible climate changes.

“But we can simply conclude that high oxygen content in seawater enables a lot of life in the oceans “consuming” the greenhouse gas CO2, and which subsequently leads to a cooling of the earth’s surface. Throughout history our climate has been dependent on balance between CO2 and atmospheric oxygen. The more CO2 and other greenhouse gases, the warmer the climate has been. But we still don’t know much about the process which drives the earth from a period with a warmer climate towards an “ice age” with colder temperatures – other than that oxygen content plays an important role. It would therefore be interesting to consider atmospheric and oceanic oxygen contents much more in research aiming at understanding and tackling the causes of the current climate change,” says Professor Robert Frei.

The results Professor Frei and his international research team have obtained indicate that there have been two periods in the earth’s 4.5 billion year history where a significant change in the atmospheric and oceanic oxygen content has occurred. The first large increase took place in between 2.45 billion years and 2.2 billion years ago. The second “boost” occurred for only 800 to 542 million years ago and lead to an oxidisation of the deep oceans and thereby the possibility for life to exist at those depths.

“To understand the future, we have to understand the past. The two large increases in the oxygen content show, at the very least, that the temperature decreased. We hope that these results can contribute to our understanding of the complexity of climate change. I don’t believe that humans have a lot of influence on the major process of oxygen formation on a large scale or on the inevitable ice ages or variations in temperature that the Earth’s history is full of. But that doesn’t mean that we cannot do anything to slow down the current global warming trend. For example by increased forestry and other initiatives that help to increase atmospheric and oceanic oxygen levels,” explains Professor Robert Frei, who, along with his research team, has worked on the project for three years so far.

Researchers to explore sacred Maya pools of Belize

The cenotes of central Belize vary in size, depth and accessibility. -  Photo by Lisa Lucero, University of Illinois
The cenotes of central Belize vary in size, depth and accessibility. – Photo by Lisa Lucero, University of Illinois

A team of expert divers, a geochemist and an archaeologist will be the first to explore the sacred pools of the southern Maya lowlands in rural Belize. The expedition, made possible with a grant from the National Geographic Society and led by a University of Illinois archaeologist, will investigate the cultural significance and environmental history and condition of three of the 23 pools of Cara Blanca, in central Belize.

Called cenotes (sen-OH-tays), these groundwater-filled sinkholes in the limestone bedrock were treated as sacred sites by the Maya, said University of Illinois archaeologist Lisa Lucero, who will lead the expedition next spring.

“Any openings in the earth were considered portals to the underworld, into which the ancient Maya left offerings,” said Lucero, who is a professor of anthropology at Illinois. “We know from ethnographic accounts that Maya collected sacred water from these sacred places, mostly from caves.”

Studies of shallow lakes and cenotes in Mexico and Guatemala have found that the Maya also left elaborate offerings in the sacred lakes and pools. Items found on the bottom of lakes in these regions include masks, bells, jade, human remains, figurines and ceramic vessels decorated with animals, plants and the gods of fertility and death.

“Diving the sacred pools of Cara Blanca, in central Belize, is necessary to determine if they have similar sacred qualities,” Lucero said.

Patricia Beddows, a lecturer of earth and planetary sciences at Northwestern University and an expert diver who has explored cenotes on the Yucatan Peninsula of Mexico, will also explore the geochemistry and hydrology of the pools of central Belize.

“Once underwater, we will first have to cut out some of the jungle wood so that we can even reach the bottom,” Beddows said. “After mapping for fragile Maya artifacts, we will also take water data and manually drill sediment cores.”

The sediment samples will provide a record of changes in surface and water conditions, Beddows said.

“Were the Maya challenged by droughts in the area? Did the water quality suddenly go bad due to sulfur or other geologic factors? We hope these cenotes will provide a rich story of linked human and environmental conditions,” she said.

The cenotes vary in depth from 5 to more than 50 meters, Lucero said. The extraordinary depth of some of the pools, their sheer walls, the probable presence of underwater caves that may lead to other pools and the potential for encountering wildlife (a crocodile was spotted in one of the cenotes the team will explore) all add to the complexity and danger of the task, she said. But the team will include some of the most accomplished technical divers in the world and will be in radio contact with British special forces, who train in the region, to coordinate a medical evacuation in the event of a health emergency.

The divers will videotape and map the pools and any artifacts they find.

One of the three pools the researchers will explore has a substantial Maya structure on its edge, likely ceremonial. Preliminary investigations of the structure conducted by archaeologist Andrew Kinkella, of Moorpark College, turned up a lot of jars and the fragments of jars. This could indicate that the site was important for collecting sacred water, Lucero said. She plans to conduct a limited analysis of the structure while the divers explore the pools. Kinkella will join Lucero’s team, and will search the sheer walls of the cenotes for niches, like those carved by the Maya in other pools, where artifacts were deposited.

Lucero has spent more than 20 years studying settlements and sacred sites that were important to the Maya in Belize, and works under the auspices of the Institute of Archeology, which is part of the National Institute of Culture and History, Government of Belize.

Making geothermal more productive

Steam rises from cooling towers as US Geothermal's Raft River geothermal power plant near Malta, Idaho. Researchers from the University of Utah's Energy and Geoscience Institute will inject cool water and pressurized water into a 'dry' geothermal well at the site during a $10.2 million study aimed at making existing power plants more productive and making geothermal power feasible nationwide. -  US Geothermal Inc.
Steam rises from cooling towers as US Geothermal’s Raft River geothermal power plant near Malta, Idaho. Researchers from the University of Utah’s Energy and Geoscience Institute will inject cool water and pressurized water into a ‘dry’ geothermal well at the site during a $10.2 million study aimed at making existing power plants more productive and making geothermal power feasible nationwide. – US Geothermal Inc.

University of Utah researchers will inject cool water and pressurized water into a “dry” geothermal well during a five-year, $10.2 million study aimed at boosting the productivity of geothermal power plants and making them feasible nationwide.

“Using these techniques to increase pathways in the rock for hot water and steam would increase availability of geothermal energy across the country,” says geologist Ray Levey, director of the Energy & Geoscience Institute (EGI), which is part of the university’s College of Engineering.

EGI geologist Joe Moore – who will head the research effort at U.S. Geothermal Inc.’s Raft River power plant in southeast Idaho – says most geothermal power in the United States now is produced west of the Rocky Mountains, where hot rocks are found closest to the surface.

“Hot rock is present across the United States, but new methods have to be developed to use the heat in these rocks to produce geothermal power,” says Moore. “We want to use oil and gas industry techniques to create pathways in the rock so that we can use the heat in the rocks to generate electricity.”

“There’s incredible potential in Utah and other states for geothermal development,” he adds. “Engineered geothermal systems [in which water is injected to enhance natural cracks in the rock] could provide a means of developing these resources much faster.”

The U.S. Department of Energy on Sept. 4 signed an agreement with the University of Utah and EGI to pay almost $7.4 million of the project’s cost.

The University of Utah is providing $1.1 million through the Office of the Vice President for Research. Another $1.7 million will be provided by discounts or cash or in-kind donations by two of EGI’s partners in the project: U.S. Geothermal, Inc. of Boise, and Apex HiPoint, LLC, of Littleton, Colo.

Moore says the university’s contribution will help fund involvement of graduate and undergraduate students from the College of Engineering and College of Mines and Earth Sciences.

Experiment at Raft River

“We’re going to take a geothermal field and improve its productivity,” Moore says. “We’re going to test the techniques on one well at Raft River. We’re testing methods to take wells that are not productive and make them productive.”

Moore says the Department of Energy did geothermal research for three decades at the site, located 11 miles from Interstate 84 in southeast Idaho halfway between Boise and Salt Lake City. Raft River is now a U.S. Geothermal power plant producing 10.5 to 11.5 megawatts of electricity – enough for roughly 10,000 homes. The power is sold to Idaho Power Co.

Some estimate the site may be capable of producing 110 megawatts of power. Researchers believe production can be increased because underground temperatures measure 275 to 300 degrees Fahrenheit at depths of 4,500 to 6,000 feet.

The Raft River plant currently has five “production” wells that produce geothermal energy and four “injection” wells where water from the production wells is returned to the underground geothermal reservoir. Water must be re-injected to maintain pressure in a geothermal power system.

One well drilled in recent years did not produce enough hot water to be used as a production well because it did not connect with enough of the underground cracks that carry the hot water.

“Geothermal wells are like oil wells – some wells produce and some don’t,” Moore says. “Drilling wells is expensive. That is why we need to develop low-cost techniques to improve their productivity.”

If the experiments run by EGI work, U.S. Geothermal eventually will operate the test well and put it into service.

Stimulating Geothermal Power by Cracking Hot Rock

To produce geothermal power, hot rock is not enough. The rock also must be permeable to the flow of water and-or steam, says John McLennan, an engineer at EGI. Many geothermal reservoirs have heat, but the rock is impermeable, which is the problem at the Raft River well known as RRG-9.

The experiment will try to make RRG-9 into an effective injection well because U.S. Geothermal must inject more water into the ground to increase the productivity of its existing production wells. Moore says all the water-injection “stimulations” will be done during 2010, with the well monitored over the rest of the five-year study period. All the water will come from production wells, not from streams.

Researchers will first let cold water flow into the hot rocks around the 6,000-foot-deep well, hoping to crack them extensively, and then pump water into the ground under high pressures to force the cracks to open wider. The goal of this “hydraulic stimulation” is to create a network of underground conduits that connect the well with underground cracks that already carry hot water.

“When the cold water reaches the hot rock it will crackle,” Moore says. “Stimulation is the process of generating new cracks.”

Apex Petroleum Engineering, Inc. of Englewood, Colo., will help design the water injection operations to create “hydraulic fractures.” Apex HiPoint’s monitoring equipment will listen to microseismic activity in the rural area to determine the extent of the cracking and thus the growth of the underground geothermal reservoir. Groundwater flow and pressures will be monitored.

Moore says three “stimulations” will occur. During the first two, relatively cool water (40 to 135 degrees Fahrenheit) will flow into the well to crack the rock at a depth of 6,000 feet. Then, a third “stimulation” will involve pumping large volumes of water into the well at high pressure to expand the cracks and keep them open to the flow of water and steam.

The lower half of the well is uncased by piping. The researchers will insert more piping so that the injected water will flow to the depths where it is needed.

McLennan says semi-sized trucks carrying large pumps will come to the well site and may pump as much as 4,200 gallons of water per minute into the ground during each “stimulation.” The total amount injected “could be on the order of 1 million gallons” for each of three “stimulations,” he adds.

The goal, says Moore, is “to create a complex fracture network over an extensive area.”

The Department of Energy wants to develop methods that can “stimulate” geothermal production in various geological environments with various rock types, Moore says. If the techniques used at Raft River prove effective, they could be used anywhere rock is hot.

“It will definitely be an advantage to Raft River if they can improve the productivity of the well, but the Department of Energy is funding this as a research program because hot rock exists everywhere,” Moore says.

The Energy & Geoscience Institute is a contract research organization. Levey says that in terms of the number of participating companies, EGI is the largest university-based research consortium working with the energy exploration and production industry.

Satellites and submarines give the skinny on sea ice thickness

Patterns of average winter ice thickness from February to March show thicker ice in 1988 (above), compared to thinner ice averaged from 2003-2008 (below). Thickness information in Antarctica is limited to an irregular polygon shape that outlines the area where declassified submarine data are available. Credit: Ronald Kwok/NASA
Patterns of average winter ice thickness from February to March show thicker ice in 1988 (above), compared to thinner ice averaged from 2003-2008 (below). Thickness information in Antarctica is limited to an irregular polygon shape that outlines the area where declassified submarine data are available. Credit: Ronald Kwok/NASA

This summer, a group of scientists and students – as well as a Canadian senator, a writer, and a filmmaker – set out from Resolute Bay, Canada, on the icebreaker Louis S. St-Laurent. They were headed through the Northwest Passage, but instead of opening shipping lanes in the ice, they had gathered to open up new lines of thinking on Arctic science.

Among the participants in the shipboard workshop (hosted by Fisheries and Oceans Canada) was Ron Kwok of NASA’s Jet Propulsion Laboratory in Pasadena, Calif. Kwok has long provided checkups on the health of Arctic sea ice – the frozen sea water floating within the Arctic Ocean basin. He also knows that some important clues about ice changes can’t be seen from a ship.

Extending the Record

While satellites provide accurate and expansive coverage of ice in the Arctic Ocean, the records are relatively new. Satellites have only monitored sea ice extent since 1973. NASA’s Ice, Cloud, and land Elevation Satellite (ICESat) has been on the task since 2003, allowing researchers to estimate ice thickness as well.

To extend the record, Kwok and Drew Rothrock of the University of Washington, Seattle, recently combined the high spatial coverage from satellites with a longer record from Cold War submarines to piece together a history of ice thickness that spans close to 50 years.

Analysis of the new record shows that since a peak in 1980, sea ice thickness has declined 53 percent. “It’s an astonishing number,” Kwok said. The study, published online August 6 in Geophysical Research Letters, shows that the current thinning of Arctic sea ice has actually been going on for quite some time.

“A fantastic change is happening on Earth – it’s truly one of the biggest changes in environmental conditions on Earth since the end of the ice age,” said Tom Wagner, cryosphere program manager at NASA Headquarters. “It’s not an easy thing to observe, let alone predict, what might happen next.”

Sea ice influences the Arctic’s local weather, climate, and ecosystems. It also affects global climate. As sea ice melts, there is less white surface area to reflect sunlight into space. Sunlight is instead absorbed by the ocean and land, raising the overall temperature and fueling further melting. Ice loss puts a damper on the Arctic air conditioner, disrupting global atmospheric and ocean circulation.

To better identify what these changes mean for the future, scientists need a long-term look at past ice behavior. Each year, Arctic ice undergoes changes brought about by the seasons, melting in the summer warmth and refreezing in the cold, dark winter. A single extreme melt or freeze season may be the result of any number of seasonal factors, from storminess to the Arctic Oscillation (variations in atmospheric circulation over the polar regions that occur on time scales from weeks to decades).

But climate is not the same as weather. Climate fluctuates subtly over decades and centuries, while weather changes from day to day and by greater extremes.

“We need to understand the long-term trends, rather than the short-term trends that could be easily biased by short-term changes,” Kwok said. “Long-term trends are more reliable indicators of how sea ice is changing with the global and regional climate.”

That’s why a long-term series of data was necessary. “Even decadal changes can be cyclical, but this decline for more than three decades does not appear to be cyclical,” Rothrock said.

All the Ice Counts

Arctic sea ice records have become increasingly comprehensive since the latter half of the 20th century, with records of sea ice anomalies viewed from satellites, ships, and ice charts collected by various countries. Most of that record, kept in the United States by the National Snow and Ice Data Center at the University of Colorado, Boulder, describes the areal extent of sea ice.

But a complete picture of sea ice requires an additional, vertical measurement: thickness. Melting affects more than just ice area; it can also impact ice above and below the waterline. By combining thickness and extent measurements, scientists can better understand how the Arctic ice cover is changing.

Kwok and other researchers used ICESat’s Geoscience Laser Altimeter System to estimate the height of sea ice above the ocean surface. Knowing the height, scientists can estimate how much ice is below the surface.

Buoyancy causes a fraction (about 10 percent) of sea ice to stick out above the sea surface. By knowing the density of the ice and applying “Archimedes’ Principle” – an object immersed in a fluid is buoyed by a force equal to the weight of the fluid displaced by the object – and accounting for the accumulation of snowfall, the total thickness of the ice can be calculated.

In 2008, Kwok and colleagues used ICESat to produce an ice thickness map over the entire Arctic basin. Then in July 2009, Kwok and colleagues reported that multiyear ‘permanent’ ice in the Arctic Ocean has thinned by more than 40 percent since 2004. For the first time, thin seasonal ice has overtaken thick older ice as the dominant type.

Submarines and Satellites

To put the recent decline in context, Kwok and Rothrock examined the recent five-year record from ICESat in the context of the longer history of ice thickness observed by U.S. Navy submarines.

During the Cold War, the submarines collected upward-looking sonar profiles, for navigation and defense, and converted the information into an estimate of ice thickness. Scientists also gathered profiles during a five-year collaboration between the Navy and academic researchers called the Scientific Ice Expeditions, or “SCICEX,” of which Rothrock was a participant. In total, declassified submarine data span nearly five decades-from 1958 to 2000-and cover a study area of more than 1 million square miles, or close to 40 percent of the Arctic Ocean.

Kwok and Rothrock compared the submarine data with the newer ICESat data from the same study area and spanning 2003 to 2007. The combined record shows that ice thickness in winter of 1980 averaged 3.64 meters. By the end of 2007, the average was 1.89 meters.

“The dramatic decrease in multiyear ice coverage is quite remarkable and explains to a large degree the decrease in total ice area and volume,” Kwok said.

Rothrock, who has worked extensively with the submarine data, agrees. “This paper shows one of the most compelling signals of global warming with one of the greatest and fastest regional environmental impacts.”

Ice Through Human Eyes

While it is critical to keep monitoring the Arctic with satellites and aircraft, Kwok believes there is also a benefit in physically standing in a place and seeing the changes through human eyes-particularly for non-scientists, who do not keep a close watch on sea ice.

The August 2009 workshop in the Northwest Passage brought together an eclectic group of politicians, artists, and scientists to see the ice firsthand. The challenge was to see the problem of a changing Arctic environment from a variety of scientific, political, cultural and human perspectives and to discuss the future of collaborative study in the Arctic. The science of sea ice has implications for people’s livelihoods, for long-established ecosystems, and for opening a new part of the world to exploration and exploitation.

The workshop participants now take their experiences and observations back to warmer climates, where there is sometimes less urgency about ice retreat.

“Sea ice is about more than just hard science; it’s a geopolitical and human issue,” Kwok noted. “There is a big personal impact when you get away from your desk and see it in person.”

Scientists return from first ever riser drilling operations in seismogenic zone

This image shows a worker lowering the tool to measure stress and pore fluid pressure in the subsurface. -  Copyright: JAMSTEC/IODP
This image shows a worker lowering the tool to measure stress and pore fluid pressure in the subsurface. – Copyright: JAMSTEC/IODP

The Deep-sea Drilling Vessel CHIKYU successfully completed riser drilling operations on Aug. 31, for IODP Expedition 319, Stage 2 of the Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE). The CHIKYU is operated by the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) in partnership with the Integrated Ocean Drilling Program. The expedition began with drilling operations at the Kumano Basin, off the Kii Peninsula on May 10, 2009. Expedition 319 marks the first riser drilling in the history of the scientific ocean drilling program, and the first subseafloor observatory operations for NanTroSEIZE. The expedition was led by four Co-Chief Scientists: Eiichiro Araki, Research Scientist of JAMSTEC; Timothy Byrne, Professor of the University of Connecticut, USA; Lisa McNeill of the University of Southampton, UK; and Demian Saffer, Associate Professor of Geosciences at The Pennsylvania State University, and was joined by scientists from eight countries.

Expedition 319 conducted drilling operations at three drill sites in the Nankai Trough. At the first Site C0009, located directly above the seismogenic zone where great earthquakes occur, scientists conducted the first riser drilling in IODP history and successfully drilled down to a depth of 1,603.7 meters beneath the sea floor. Riser-based drilling allowed the scientists to conduct several scientific operations unprecedented in IODP, including 12 successful measurements of stress and pore fluid pressure in the subsurface using the dynamic formation testing tool, a two ship seismic experiment using a dense seismic array in the borehole, real-time mud gas analysis, and laboratory analyses of drill cuttings that are generated as the drill bit penetrates through the formation. In addition, 57.87 meters of core sample (a cylindrical geological sample) were obtained from depths between 1,510 and 1,593.9 meters below the seafloor. The scientific party developed several new techniques for analyzing these materials, which will be essential for future riser-based drilling.

The stress and pore pressure measurements are critical to understanding the mechanics of active tectonic fault zones, but have previously been unavailable in the scientific ocean drilling. Successful deployment of the test tool to measure these quantities deeper within the upper plate and near major fault zones in future riser holes will constitute a major breakthrough in understanding subduction zone fault earthquakes.

Also a walk-away Vertical Seismic Profiling (VSP) involving the CHIKYU and JAMSTEC’s Research Vessel KAIREI was conducted to characterize the structure of the seismogenic plate boundary below the borehole by utilizing an array of seismic sensors temporarily clamped inside the borehole. Air guns towed by the KAIREI generated seismic waves, and reflected seismic waves from the fault system were clearly observed by the borehole sensors. Experience from the VSP experiment will open the way to in-depth study of seismogenic faults that are beyond the reach of drilling.

At a second borehole (Site C0010), drilling crossed one of the major faults in the plate boundary, known as the mega-splay fault, at a depth of about 400 meters below the seafloor. This fault is a prime candidate for tsunami generation, and may have slipped in historical great earthquakes. During the drilling operation, scientists documented rock physical properties and gained information about stresses in the formation. The borehole was then cased and utilized for observatory operations for future long-term borehole monitoring. These included lowering of test instruments, as well as emplacement of a temporary sensor package that will monitor conditions in the fault zone in the next few years.

The new data from Expedition 319 indicate that the stresses in the upper plate reflect the forces acting on the earthquake generating fault zones below. The direction of the maximum stresses follows the direction of tectonic plate motion in most of the region, but rotates drastically in a very narrow region above the mega-splay fault. In addition, the rock units, and in particular the ages of the rocks obtained by examining microfossils and the sediment types observed in the drill cuttings, provide new constraints on the geologic history of the major fault zone and its activity level.

The CHIKYU is now berthed at the Port of Yokkaichi, where it is preparing for IODP Expedition 322 scheduled to sail on Sept. 4. Operations will include core sampling and logging for all layers in the formation, with an aim to better understand the initial state of geological input materials before they are entering the seismogenic zone.

Methane gas likely spewing into the oceans through vents in sea floor

This image at left shows underground methane gas as it begins to invade fine-grain sediment (shown in yellow) by creating a fracture. In the image at right, the blue circles represent pore spaces where the gas has invaded. -  Ruben Juanes, MIT and Antone Jain
This image at left shows underground methane gas as it begins to invade fine-grain sediment (shown in yellow) by creating a fracture. In the image at right, the blue circles represent pore spaces where the gas has invaded. – Ruben Juanes, MIT and Antone Jain

Scientists worry that rising global temperatures accompanied by melting permafrost in arctic regions will initiate the release of underground methane into the atmosphere. Once released, that methane gas would speed up global warming by trapping the Earth’s heat radiation about 20 times more efficiently than does the better-known greenhouse gas, carbon dioxide.

An MIT paper appearing in the Journal of Geophysical Research online Aug. 29 elucidates how this underground methane in frozen regions would escape and also concludes that methane trapped under the ocean may already be escaping through vents in the sea floor at a much faster rate than previously believed. Some scientists have associated the release, both gradual and fast, of subsurface ocean methane with climate change of the past and future.

“The sediment conditions under which this mechanism for gas migration dominates, such as when you have a very fine-grained mud, are pervasive in much of the ocean as well as in some permafrost regions,” said lead author Ruben Juanes, the ARCO Assistant Professor in Energy Studies in the Department of Civil and Environmental Engineering.

“This indicates that we may be greatly underestimating the methane fluxes presently occurring in the ocean and from underground into Earth’s atmosphere,” said Juanes. “This could have implications for our understanding of the Earth’s carbon cycle and global warming.”

Juanes explains that some of the naturally occurring underground methane exists not as gas but as methane hydrate. In the hydrate phase, a methane gas molecule is locked inside a crystalline cage of frozen water molecules. These hydrates exist in a layer of underground rock or oceanic sediments called the hydrate stability zone or HSZ. Methane hydrates will remain stable as long as the external pressure remains high and the temperature low. Beneath the hydrate stability zone, where the temperatures are higher, methane is found primarily in the gas phase mixed with water and sediment.

But the stability of the hydrate stability zone is climate-dependent.

If atmospheric temperatures rise, the hydrate stability zone will shift upward, leaving in its stead a layer of methane gas that has been freed from the hydrate cages. Pressure in that new layer of free gas would build, forcing the gas to shoot up through the HSZ to the surface through existing veins and new fractures in the sediment. A grain-scale computational model developed by Juanes and recent MIT graduate Antone Jain indicates that the gas would tend to open up cornflake-shaped fractures in the sediment, and would flow quickly enough that it could not be trapped into icy hydrate cages en route.

“Previous studies did not take into account the strong interaction between the gas-water surface tension and the sediment mechanics. Our model explains recent experiments of sediment fracturing during gas flow, and predicts that large amounts of free methane gas can bypass the HSZ,” said Juanes.

Using their model, as well as seismic data and core samples from a hydrate-bearing area of ocean floor (Hydrate Ridge, off the coast of Oregon), Juanes and Jain found that methane gas is very likely spewing out of vents in the sea floor at flow rates up to 1 million times faster than if it were migrating as a dissolved substance in water making its way through the oceanic sediment – a process previously thought to dominate methane transport.

“Our model provides a physical explanation for the recent striking discovery by the National Oceanic and Atmospheric Administration of a plume 1,400 meters high at the seafloor off the Northern California Margin,” said Juanes. This plume, which was recorded for five minutes before disappearing, is believed not to be hydrothermal vent, but a plume of methane gas bubbles coated with methane hydrate.

The Jain and Juanes paper in the Journal of Geophysical Research also explains the short-term consequences of injecting carbon dioxide into the ocean’s subsurface, a method proposed by some researchers for reducing atmospheric greenhouse gas. Juanes found that while some of the CO2 would remain trapped as a hydrate, much would likely spew up through fractures just as methane does.

“It is important to keep both methane and carbon dioxide either in the pipeline or underground, because the consequences of escape can be quite dangerous over time,” said Juanes.

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This video shows underground methane gas invading fine-grain sediment (shown in yellow) by creating a fracture. Blue circles represent pore spaces where the gas has invaded. The maroon lines indicate compressive forces between sediment grains. The video shows that the network of compressive forces changes drastically with the evolution of the fracture. The green lines indicate tension between grains, caused by capillary forces that hold the grains together. The network of tension forces also changes with time, as the gas invades the sediment. – Ruben Juanes, MIT

Shrinking Bylot Island glaciers tell story of climate change

This is University of Illinois at Urbana-Champaign geologist William Shilts. -  Photo by L. Brian Stauffer, U.of I. News Bureau.
This is University of Illinois at Urbana-Champaign geologist William Shilts. – Photo by L. Brian Stauffer, U.of I. News Bureau.

The U.S. Geological Survey has released the results of a long-term study of key glaciers in western North America, reporting this month that glacial shrinkage is rapid and accelerating and a result of climate change.

University of Illinois geologist William Shilts spent nearly two decades studying glaciers on Bylot Island, an uninhabited island about 300 miles southwest of Thule, Greenland. He, his students and other geologists who followed in his footsteps have chronicled the decline of several Bylot Island glaciers. Photos of the island from the 1940s to the present offer a vivid picture of the changing glaciers and the forces that shape their retreat.

For a slide show of the glaciers from 1948 to the present, please go to:

“I started working in the late 1970s on Bylot Island, which is about the size of New Jersey,” said Shilts, the executive director of the Institute of Natural Resource Sustainability at Illinois. “Bylot Island is like a miniature North America. It has a very old crystalline rock core that’s covered with ice and glaciers, and it’s surrounded by younger rocks.”

“As time went on it became very evident that the glaciers on Bylot Island were, for the most part, retreating, shrinking, melting faster than ice could be produced,” he said. “For whatever reason, the summer melting was exceeding the winter snowfall.”

With a perspective spanning more than 4 billion years, geologists have a unique point of view on current climate changes. They know that ice ages and glacial retreats are common because these events leave indelible marks on the land.

To a geologist’s eye, the color of rock near a melting glacier, the pattern of scars on its surface or fissures at its edges, the shape of a mound of gravel left behind or the pattern of snow and ice on its surface speak volumes about the glacier’s origin, recent history and age.

Glaciers are perpetually moving, flowing frozen rivers, and like other rivers, they churn up dirt and rocks carry them “downstream.” When a glacier retreats, the mud and rocks are often dumped at its edge, forming moraines. The moraines sometimes grow so large that they inhibit the advance of the glacier and cause the ice to thicken, like water filling a bathtub.

The surface of the rocks also tells a story. When a glacier melts, the newly exposed material becomes an inviting habitat for lichen and other organisms, which gradually darken the stone. Such growth can take 50 or 60 years to start, however, so bare rock inside the moraine signals that a glacier has retreated only within the last few decades. Shilts calls the light-colored moraine below the dark lichen-covered rock the glacier’s “bathtub ring.”

“1948 was the year that the first aerial photographs were taken of Bylot Island and most of northern Canada,” Shilts said. “On those photographs you can see that the glaciers were considerably advanced over what they are now. And any boulders that were involved with glacier activities in the 1940s look as fresh as if they were broken off their outcrops yesterday.

They have no lichen or any sort of growth on them. As soon as you go beyond the 1948 boundary, the boulders are covered with black lichen. You can’t even see the rock. And so it’s a very clear demarcation on the ground.”

Shilts photographed many of the same glaciers in the 1980s and 1990s, and other geologists have chronicled the changes up to the present. These photos show a steady and rapid decline in the extent of several glaciers: Stagnation Glacier, covered in a layer of rock and debris, has shrunk considerably since 1948.

Nearby Fountain Glacier seems more stable, but the outwash plain below it, a zone always coated in a thick layer of ice, even throughout the summer, was completely dry in the summer of 2008.

Aktineq Glacier has shrunk back about a kilometer since 1948, Shilts said. Most of the other glaciers on Bylot Island, and on nearby Baffin Island, also appear to be melting away.

A glacier that shrinks over a period of decades may seem like an overt sign of a warming climate, but other contributors to glacial retreat are less obviously tied to climate change. Warmer temperatures can bring on more frequent freeze-thaw cycles that open fissures in the rock walls above a glacier, dumping debris on the glacier’s surface that hastens melting by absorbing more of the sun’s heat.

A more precise way of timing glacial events involves radiocarbon dating the soil in embankments near glacial moraines. Shilts and his colleagues conducted such studies on Bylot Island, and found that an undisturbed sand bank near a glacial moraine was about 6,800 years old.

“That means at the very least that the glacier that is a couple of feet away from that sand bank has not gone across that sand bank in 6,800 years,” he said.

Another approach, called cosmogenic dating, indicated that the boulders just outside the 1948 moraine were even older. The technique, conducted by Shilts’ former graduate student, Shirley McCuaig, dated those boulders at 55,000 years, plus or minus 5,000 years.

That finding confirmed something that another student, Rod Klassen, had suggested in his PhD thesis at Illinois, Shilts said. “And that is that the glaciers that are now on Bylot Island were as far advanced in the 1940s as they have been in the last 55,000 years. And now they are retreating.”

“My interpretation of what I saw on Bylot Island is that we’re in another cycle of glacial retreat,” Shilts said. “Whether that cycle is primarily driven by human emissions of carbon dioxide in the atmosphere creating a warming trend, or whether it’s driven by natural cycles, which relate to our orbit around the sun, sunspot activity or various things in the earth’s atmosphere in general, I can’t say.”

“My personal opinion is that this is a combination of both factors,” Shilts said. “There’s a normal cycle here – we’re coming out of the ‘Little Ice Age,’ and have been for some time. At the same time, the Industrial Revolution has begun to load the atmosphere with carbon dioxide among other things. There’s a human effect, and there’s a natural effect, and sorting out those two is very difficult.”

Study reveals seismic shift in methods used to track earthquakes

The team, led by scientists from the University of Edinburgh, says that the new method, which uses data collected from earthquakes, potentially allows the Earth’s seismic activity to be mapped more comprehensively.

Scientists currently monitor underground movements, such as earthquakes and nuclear tests, using seismometers – instruments that measure the motion of those events at the Earth’s surface. This helps to indicate where they took place.

Now, by analysing the seismic waves from two different earthquakes, the team has been able to simulate the seismic waves from one of the earthquakes as if they were recorded by a seismometer at the location of the second.

The discovery allows earthquakes themselves to be used as virtual seismometers that record passing waves from tremors that happen elsewhere in the world.

Using earthquakes in this way substantially increases the number of locations that could be used to detect seismic activity. And since earthquakes occur deep inside the Earth, using them also allows scientists to monitor seismic activity from far deeper than previously possible.

The research, published in Nature Geoscience, was carried out in collaboration with the British Geological Survey and Utrecht University.

Andrew Curtis, Professor of Mathematical Geoscience at the University of Edinburgh, said: “This turns the way we listen to seismic movements on its head. By using earthquakes themselves as virtual microphones that record the sound of the Earth’s internal movements, we can listen to the Earth’s stretching and cracking from directly within its most interesting, dynamic places.”

Dr Brian Baptie, Seismology Team Leader at the British Geological Survey, said: “This discovery shows how we can measure strains deep inside the Earth and helps improve our understanding of the processes driving earthquake activity.”

Map characterizes active lakes below Antarctic ice

Lakes in Antarctica, concealed under miles of ice, require scientists to come up with creative ways to identify and analyze these hidden features. Now, researchers using space-based lasers on a NASA satellite have created the most comprehensive inventory of lakes that actively drain or fill under Antarctica’s ice. They have revealed a continental plumbing system that is more dynamic than scientists thought.

“Even though Antarctica’s ice sheet looks static, the more we watch it, the more we see there is activity going on there all the time,” said Benjamin Smith of the University of Washington in Seattle, who led the study.

Unlike most lakes, Antarctic lakes are under pressure from the ice above. That pressure can push melt water from place to place like water in a squeezed balloon. The water moves under the ice in a broad, thin layer, but also through a linked cavity system. This flow can resupply other lakes near and far.

Understanding this plumbing is important, as it can lubricate glacier flow and send the ice speeding toward the ocean, where it can melt and contribute to sea level change. But figuring out what’s happening beneath miles of ice is a challenge.

Researchers led by Smith analyzed 4.5 years of ice elevation data from NASA’s Ice, Cloud and land Elevation satellite (ICESat) to create the most complete inventory to date of changes in the Antarctic plumbing system. The team has mapped the location of 124 active lakes, estimated how fast they drain or fill, and described the implications for lake and ice-sheet dynamics in the Journal of Glaciology.

What Lies Beneath

For decades, researchers flew ice-penetrating radar on airplanes to “see” below the ice and infer the presence of lakes. In the 1990s, researchers began to combine airborne- and satellite-based data to observe lake locations on a continent-wide scale.

Scientists have since established the existence of about 280 “subglacial” lakes, most located below the East Antarctic ice sheet. But those measurements were a snapshot in time, and the question remained as to whether lakes are static or dynamic features. Were they simply sitting there collecting water?

In 2006 Helen Fricker, a geophysicist at the Scripps Institution of Oceanography, La Jolla, Calif., used satellite data to first observe subglacial lakes on the move. Working on a project to map the outline of Antarctica’s land mass, Fricker needed to differentiate floating ice from grounded ice. This time it was laser technology that was up to the task. Fricker used ICESat’s Geoscience Laser Altimeter System and measured how long it took a pulse of laser light to bounce of the ice and return to the satellite, from which she could infer ice elevation. Repeating the measurement over a course of time revealed elevation changes.

Fricker noticed, however, a sudden dramatic elevation change — over land. It turned out this elevation change was caused by the filling and draining of some of Antarctica’s biggest lakes.

“Sub-ice-sheet hydrology is a whole new field that opened up through the discovery of lakes filling and draining on relatively short timescales and involving large volumes of water,” said Robert Bindschadler, a glaciologist at NASA’s Goddard Space Flight Center in Greenbelt, Md., who has used ICESat data in other studies of Antarctica. “ICESat gets the credit for enabling that discovery.”

Networking in the Antarctic

But were active lakes under the ice a common occurrence or a fluke?

To find out, Ben Smith, Fricker and colleagues extended their elevation analysis to cover most of the Antarctic continent and 4.5 years of data from ICESat’s Geoscience Laser Altimeter System (GLAS). By observing how ice sheet elevation changed between the two or three times the satellite flew over a section every year, researchers could determine which lakes were active. They also used the elevation changes and the properties of water and ice to estimate the volume change.

Only a few of the more than 200 previously identified lakes were confirmed active, implying that lakes in East Antarctica’s high-density “Lakes District” are mostly inactive and do not contribute much to ice sheet changes.

Most of the 124 newly observed active lakes turned up in coastal areas, at the head of large drainage systems, which have the largest potential to contribute to sea level change.

“The survey identified quite a few more subglacial lakes, but the locations are the intriguing part,” Bindschadler said. “The survey shows that most active subglacial lakes are located where the ice is moving fast, which implies a relationship.”

Connections between lakes are apparent when one lake drains and another simultaneously fills. Some lakes were found to be connected to nearby lakes, likely through a network of subglacial tunnels. Others appeared to be linked to lakes hundreds of miles away.

The team found that the rate at which lake water drains and fills varies widely. Some lakes drained or filled for periods of three to four years in steady, rather than episodic, changes. But water flow rates beneath the ice sheet can also be as fast as small rivers and can rapidly supply a lubricating film beneath fast-flowing glaciers.

“Most places we looked show something happening on short timescales,” Smith said. “It turns out that those are fairly typical examples of things that go on under the ice sheet and are happening all the time all over Antarctica.”