Creationism creeps into mainstream geology

In almost every way, the “Garden of the Gods at Colorado Springs” excursion at the annual meeting of the Geological Society of America (GSA) last year was a normal – even enjoyable – field trip. Standard geologic terminology was used in the accompanying field trip guide and the guides relied on orthodox geologic thinking to explain geologic features. But in reality, the trip was anything but a normal geology field trip.

Instead, as EARTH explores in its July feature “Creationism Creeps into Mainstream Geology,” the field trip was an example of a new strategy from creationists to interject their ideas into mainstream geology: Creationists lead field trips and present posters and talks at scientific meetings. They avoid overtly stating anything truly contrary to mainstream science. And when the meeting is over, the creationist participants go home and proudly proclaim that mainstream science has accepted their ideas.

It’s a crafty way of giving credence to creationism, but the question mainstream geologists wrestle with is whether there is anything that the conveners of meetings and field trips can or should do to prevent this.

Read what one scientist suggests should be done, and read other stories on topics such as what water officials are doing to try to get ahead of a declining snowpack in the West, how geophysical tools are helping remediation managers at Hanford and other nuclear cleanup sites, and why disasters such as the Japan earthquake and tsunami affect the economies of rich or poor countries disproportionately in the July issue. And don’t miss the story about the middle school student who uncovered an international mineral scandal.

Meltzone 2011: CCNY expedition to track life and death of supraglacial lake

How do you observe signs of climate change in real time? Dr. Marco Tedesco, associate professor of earth and atmospheric sciences at The City College of New York, plans to be the first to catch sight of one dramatic indicator of a warming world on the Greenland ice sheet this summer, and through social media, people will be able to track his progress.

Professor Tedesco arrived in Greenland earlier this month to attempt to witness – for the first time – the entire lifecycle of a supra-glacial lake – from earliest formation to its catastrophic draining. These huge bodies of water form each year atop melting glaciers. They commonly measure a kilometer or more across, but can drain suddenly within a matter of hours.

Professor Tedesco plans to use data he gathers on his expedition to answer lingering questions about these mysterious pools, including: What causes them to drain? Where does the water go? How does this affect the glaciers’ inevitable flow toward the sea?

“This rapid draining is roughly equivalent to emptying a thousand Olympic-sized swimming pools at a rate of a dozen pools per minute,” notes Nick Steiner, a graduate student in Professor Tedesco’s Cryospheric Processes Lab. Mr. Steiner conducted research with Professor Tedesco in Greenland last year.

Professor Tedesco and his team will hike across the Jakobshavn Isbræ glacier in search of a lake to monitor and eventually make camp on the ice in the midst of an unstable landscape of embryonic lakes, streams and sub-glacier drainage.

Rounding out the expedition party are graduate student Patrick Alexander of the CUNY Graduate Center, biologist Christine Foreman of Montana State University, glaciologist Ian Willis and graduate student Alison Banwell of the Scott Polar Research Institute at the University of Cambridge, UK.

With such a large volume of water flowing out of the lakes – at the surface, under the glacier or thundering into deep holes called “moulins” – the surrounding ice is subject to movements that can cause ground-shaking ‘ice quakes’. The team will drill an array of monitoring equipment into the ice to track ice movement as the lakes drain and better understand the drainage. The monitors use DGPS, a high-precision global positioning system that uses satellite and ground stations to give greater positioning accuracy than a car or cellphone GPS.

A radio-controlled mini helicopter fitted with a camera will help the expedition party estimate the size and depth of the lake. Professor Tedesco used a similar craft on a past expedition in Antarctica.

The team will also study the scattered, dark deposits of “cryoconite,” extremely fine wind-borne particles carried to Greenland from around the world. Cryoconite begins life as soot, dust, soil and pollution and collects in depressions on the glacier. It absorbs more solar energy than the surrounding snow and ice, in turn, causing the snow to heat, melt and form small water-filled holes in the ice. Bacteria appear in these microhabitats, a phenomenon Dr. Foreman will study.


Meanwhile, Dr. Tedesco will measure the albedo, or reflected light, of the cryoconite versus clean snow and ice. Getting a baseline albedo for each type of ground coverage will allow them to calibrate satellite data and map coverage types on wide swaths of glacier.


Professor Tedesco will tweet his progress throughout the expedition for an interactive experience, updating his followers and Facebook page with photos, observations and their locations across the glacier. In addition, he will be reachable via satellite phone, and followers will have the chance to name a newborn lake on the glacier. Links to Twitter and Facebook feeds appear below.

Dating an ancient episode of severe global warming

The image shows a location in Longyearbyen, Spisbergen, where the researchers carried out field work. -  Ian Harding
The image shows a location in Longyearbyen, Spisbergen, where the researchers carried out field work. – Ian Harding

Using sophisticated methods of dating rocks, a team including University of Southampton researchers based at the National Oceanography Centre, Southampton, have pinned down the timing of the start of an episode of an ancient global warming known as the Paleocene-Eocene thermal maximum (PETM), with implications for the triggering mechanism.

The early part of the Cenozoic era, which started around 65.5 million years ago witnessed a series of transient global warming events called hyperthermals. The most severe of these was the PETM at the Paleocene-Eocene boundary, around 56 million years ago. Over a period of around 20,000 years, a mere blink of the eye in geological terms, ocean temperatures rose globally by approximately 5°C. There is evidence that the concentration of atmospheric carbon oxide increased, but the phenomena that triggered the event remain controversial.

One possibility is that these hyperthermals were driven by cyclic variations in the eccentricity of the Earth’s orbit around the sun. At the cycle peaks, increased temperatures could have caused methane hydrate deposits in the deep sea to release large amounts of methane. Some of this potent greenhouse gas would have entered the atmosphere resulting in further intensification of the climatic warming, which would have continued as the methane was fairly rapidly converted into carbon dioxide in the atmosphere.

Alternatively, it may have been geological processes, unrelated to variation in the Earth’s orbit, which could have been the culprit for the warming associated with the PETM. In this scenario, magmatism would have caused the baking of marine organic sediments, leading to the massive release of methane and/or carbon dioxide, possibly through hydrothermal vents, thus initiating the global warming which led to the methane release.

“Determining exactly what triggered the PETM requires very accurate dating of the event itself, to determine whether it occurred during a known maximum in the Earth’s orbital eccentricity” explains Adam Charles, a University of Southampton PhD student supervised by Dr Ian Harding, and first author of the newly published report.

To getter a better grip on the numerical age of the Paleocene-Eocene boundary, the researchers measured radio-isotopes of uranium and lead in the mineral zircon, found as crystals in two volcanic ash horizons deposited during the PETM. These rocks were collected from two locations in Spitsbergen, the largest island of the Svalbard Archipelago in the Arctic.

Based on their data, the researchers dated the Paleocene-Eocene boundary at between 55.728 and 55.964 million years ago, which they believe to be the most accurate estimate to date. Their analyses indicated that the onset of the PETM, unlike those of other Eocene hyperthermals, did not occur at the peak of a 400 thousand year cycle in the Earth’s orbital eccentricity. Instead, it occurred on the falling limb of a cycle when warming by the sun would not have been at a maximum.

“Compared to other early Eocene hyperthermals, it appears that the PETM was triggered by a different mechanism, and thus may have involved volcanism. However, a thorough test of this hypothesis will require further detailed dating studies,” Adam concluded.

Earth from space: A gush of volcanic gas

This image shows the huge plume of sulphur dioxide that spewed from Chile's Puyehue-Cordón Caulle Volcanic Complex, which lies in the Andes about 600 km south of Santiago. It was generated on June 6 using data from the Infrared Atmospheric Sounding Interferometer on the MetOp-A satellite and represents sulfur dioxide concentrations within the full vertical column of atmosphere. As the eruption continued, the image shows how strong winds initially swept the broad plume of sulfur dioxide northwards and then eastwards across Argentina and out over the southern Atlantic Ocean. 
The MetOp program was jointly established by ESA and Eumetsat and forms the space segment of Eumetsat's Polar System. -  Université Libre de Bruxelles (ULB)
This image shows the huge plume of sulphur dioxide that spewed from Chile’s Puyehue-Cordón Caulle Volcanic Complex, which lies in the Andes about 600 km south of Santiago. It was generated on June 6 using data from the Infrared Atmospheric Sounding Interferometer on the MetOp-A satellite and represents sulfur dioxide concentrations within the full vertical column of atmosphere. As the eruption continued, the image shows how strong winds initially swept the broad plume of sulfur dioxide northwards and then eastwards across Argentina and out over the southern Atlantic Ocean.
The MetOp program was jointly established by ESA and Eumetsat and forms the space segment of Eumetsat’s Polar System. – Université Libre de Bruxelles (ULB)

This image shows the huge plume of sulphur dioxide that spewed from Chile’s Puyehue-Cordón Caulle Volcanic Complex, which lies in the Andes about 600 km south of Santiago.

After lying dormant for more than 50 years, a series of rumbling earthquakes signalled the beginnings of this major volcanic eruption. On 4 June, a fissure opened, sending a towering plume of volcanic ash and gas over 10 km high.
Several thousand people were evacuated as a thick layer of ash and pumice fell and blanketed a wide area. Airports in Chile and Argentina were closed as a result.

The image was generated on 6 June using data from the Infrared Atmospheric Sounding Interferometer on Eumetsat’s MetOp-A satellite. As the eruption continued, the image shows how strong winds initially swept the broad plume of sulphur dioxide northwards and then eastwards across Argentina and out over the southern Atlantic Ocean.

Strong westerly winds are common in this region because it lies within the belt of the ‘Roaring Forties’. Since there is little land south of 40º, higher wind speeds can develop than at the same latitudes in the Northern Hemisphere.

Interestingly, over the South Atlantic, the plume take a sharp turn to the north as a pressure system causes the wind to change direction.

The Puyehue-Cordón Caulle complex is a chain of volcanoes that includes the Puyehue volcano, the Cordilera Nevada caldera and the Cordón Caulle rift zone. This event appears to have stemmed from the rift zone and is the most serious since the eruption of 1960, also from the same vent.

Chile has more than 3000 volcanoes, of which around 80 are currently active.

The image represents sulphur dioxide concentrations within the full vertical column of atmosphere. It was generated using data from the interferometer, which was developed by the French space agency CNES for MetOp-A.

NASA provides a 2-satellite view and video of the Chilean volcano eruption

NASA’s Aqua satellite and the GOES-13 satellite both captured their own unique views of the eruption of the Puyehue-Cordón Caulle volcano in Chile this week. One satellite provided a high-resolution image of the ash plume while the other provided a video showing the plumes movement over several days.

NASA’s GOES Project released a satellite animation of the Puyehue-Cordón Caulle volcano that shows the movement of the ash plume over several days. The NASA GOES Project, located at NASA’s Goddard Space Flight Center, Greenbelt, Md. created the animation from images obtained by the Geostationary Operational Environmental Satellite, GOES-13. The GOES series of satellites are operated by NOAA.

The GOES-13 animation includes visible and infrared imagery from GOES-13 that runs from June 4 at 1745 UTC (1:45 p.m. EDT) to June 6 at 1445 UTC (10:45 a.m. EDT). On June 4, the plume was blowing to the southeast. Through June 5 and 6, the winds shifted and viewers of the animation can see the plume start turning in a counterclockwise motion to the east, northeast and then north as high pressure moves in (In the south high pressure system winds rotate opposite they way they do in the northern hemisphere, so they shifted the winds from southeast to the north.

A visible image was taken on June 8 at 18:30 UTC (2:30 p.m. EDT) by the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument that flies aboard NASA’s Aqua satellite. The plume from the Puyehue-Cordón Caulle volcano in Chile has now expanded to the south and is now covering a much wider angle than earlier this week. The image shows the plume of ash now blowing to the east over Argentina in what almost appears to be a 90 degree triangle.

The MODIS Rapid Response Team is also located at NASA Goddard, and creates images from the MODIS instrument that flies aboard NASA’s Aqua and Terra satellites.

According to MSNBC on June 8, flights in and out of Chile, Argentina and Buenos Aires, Brazil were suspended or delayed over the last several days and travelers should check with their airlines. The Associated Press and CBS News noted that the organization in Chile that monitors volcanic eruptions: the National Geology and Mines Service considers the eruption moderate so far, but it could change.

Meanwhile, satellite data from NASA and NOAA will help airlines determine the direction of the ash plumes and whether air travel can resume.

Going with the flow: Researchers find compaction bands in sandstone are permeable

Compaction bands at multiple scales ranging from the field scale to the specimen scale to the meso and grain scale. At the field scale, picture shows the presence of narrow tabular structures within the host rock in the Valley of Fire. At the grain scale, images show clear differences in porosity (dark spots) density. This research aims at quantifying the impact of grain scale features in macroscopic physical properties that control behavior all the way to the field scale. -  José Andrade/Caltech
Compaction bands at multiple scales ranging from the field scale to the specimen scale to the meso and grain scale. At the field scale, picture shows the presence of narrow tabular structures within the host rock in the Valley of Fire. At the grain scale, images show clear differences in porosity (dark spots) density. This research aims at quantifying the impact of grain scale features in macroscopic physical properties that control behavior all the way to the field scale. – José Andrade/Caltech

When geologists survey an area of land for the potential that gas or petroleum deposits could exist there, they must take into account the composition of rocks that lie below the surface. Take, for instance, sandstone-a sedimentary rock composed mostly of weakly cemented quartz grains. Previous research had suggested that compaction bands-highly compressed, narrow, flat layers within the sandstone-are much less permeable than the host rock and might act as barriers to the flow of oil or gas.

Now, researchers led by José Andrade, associate professor of civil and mechanical engineering at the California Institute of Technology (Caltech), have analyzed X-ray images of Aztec sandstone and revealed that compaction bands are actually more permeable than earlier models indicated. While they do appear to be less permeable than the surrounding host rock, they do not appear to block the flow of fluids. Their findings were reported in the May 17 issue of Geophysical Research Letters.

The study includes the first observations and calculations that show fluids have the ability to flow in sandstone that has compaction bands. Prior to this study, there had been inferences of how permeable these formations were, but those inferences were made from 2D images. This paper provides the first permeability calculations based on actual rock samples taken directly from the field in the Valley of Fire, Nevada. From the data they collected, the researchers concluded that these formations are not as impermeable as previously believed, and that therefore their ability to trap fluids-like oil, gas, and CO2-should be measured based on 3D images taken from the field.

“These results are very important for the development of new technologies such as CO2 sequestration-removing CO2 from the atmosphere and depositing it in an underground reservoir-and hydraulic fracturing of rocks for natural gas extraction,” says Andrade. “The quantitative connection between the microstructure of the rock and the rock’s macroscopic properties, such as hydraulic conductivity, is crucial, as physical processes are controlled by pore-scale features in porous materials. This work is at the forefront of making this quantitative connection.”

The research team connected the rocks’ 3D micromechanical features-such as grain size distribution, which was obtained using microcomputed tomography images of the rocks to build a 3D model-with quantitative macroscopic flow properties in rocks from the field, which they measured on many different scales. Those measurements were the first ever to look at the three-dimensional ability of compaction bands to transmit fluid. The researchers say the combination of these advanced imaging technologies and multiscale computational models will lead to unprecedentedly accurate measurements of crucial physical properties, such as permeability, in rocks and similar materials.

Andrade says the team wants to expand these findings and techniques. “An immediate idea involves the coupling of solid deformation and chemistry,” he says. “Accounting for the effect of pressures and their potential to exacerbate chemical reactions between fluids and the solid matrix in porous materials, such as compaction bands, remains a fundamental problem with multiple applications ranging from hydraulic fracturing for geothermal energy and natural gas extraction, to applications in biological tissue for modeling important processes such as osteoporosis. For instance, chemical reactions take place as part of the process utilized in fracturing rocks to enhance the extraction of natural gas.”

Novel geothermal technology packs a one-two punch against climate change

Two University of Minnesota Department of Earth Sciences researchers have developed an innovative approach to tapping heat beneath the Earth’s surface. The method is expected to not only produce renewable electricity far more efficiently than conventional geothermal systems, but also help reduce atmospheric carbon dioxide (CO2) — dealing a one-two punch against climate change.

The approach, termed CO2-plume geothermal system, or CPG, was developed by Earth sciences faculty member Martin Saar and graduate student Jimmy Randolph in the university’s College of Science and Engineering. The research was published in the most recent issue of Geophysical Research Letters. The researchers have applied for a patent and plan to form a start-up company to commercialize the new technology.

Established methods for transforming Earth’s heat into electricity involve extracting hot water from rock formations several hundred feet from the Earth’s surface at the few natural hot spots around the world, then using the hot water to turn power-producing turbines. The university’s novel system was born in a flash of insight on a northern Minnesota road trip and jump-started with $600,000 in funding from the U of M Institute on the Environment’s Initiative for Renewable Energy and the Environment (IREE). The CPG system uses high-pressure CO2 instead of water as the underground heat-carrying fluid.

CPG provides a number of advantages over other geothermal systems, Randolph said. First, CO2 travels more easily than water through porous rock, so it can extract heat more readily. As a result, CPG can be used in regions where conventional geothermal electricity production would not make sense from a technical or economic standpoint.

“This is probably viable in areas you couldn’t even think about doing regular geothermal for electricity production,” Randolph said. “In areas where you could, it’s perhaps twice as efficient.”

CPG also offers the benefit of preventing CO2 from reaching the atmosphere by sequestering it deep underground, where it cannot contribute to climate change. In addition, because pure CO2 is less likely than water to dissolve the material around it, CPG reduces the risk of a geothermal system not being able to operate for long times due to “short-circuiting” or plugging the flow of fluid through the hot rocks. Moreover, the technology could be used in parallel to boost fossil fuel production by pushing natural gas or oil from partially depleted reservoirs as CO2 is injected.

Saar and Randolph first hit on the idea behind CPG in the fall of 2008 while driving to northern Minnesota together to conduct unrelated field research. The two had been conducting research on geothermal energy capture and separately on geologic CO2 sequestration.

“We connected the dots and said, ‘Wait a minute – what are the consequences if you use geothermally heated CO2?'” recalled Saar. “We had a hunch in the car that there should be lots of advantages to doing that.”

After batting the idea around a bit, the pair applied for and received a grant from the Initiative for Renewable Energy and the Environment, which disburses funds from Xcel Energy’s Renewable Development Fund to help launch potentially transformative projects in emerging fields of energy and the environment. The IREE grant paid for preliminary computer modeling and allowed Saar and Randolph to bring on board energy policy, applied economics and mechanical engineering experts from the University of Minnesota as well as modeling experts from Lawrence Berkeley National Laboratory. It also helped leverage a $1.5 million grant from the U.S. Department of Energy to explore subsurface chemical interactions involved in the process.

“The IREE grant was really critical,” Saar said. “This is the kind of project that requires a high-risk investment. I think it’s fair to say that there’s a good chance that it wouldn’t have gone anywhere without IREE support in the early days.”

Saar and Randolph have recently applied for additional DOE funding to move CPG forward to the pilot phase.

“Part of the beauty of this is that it combines a lot of ideas but the ideas are essentially technically proven, so we don’t need a lot of new technology developed,” Randolph said.

“It’s combining proven technology in a new way,” Saar said. “It’s one of those things where you know how the individual components work. The question is, how will they perform together in this new way? The simulation results suggest it’s going to be very favorable.”

3 satellites see eruption of Puyehue-Cordón volcano from space

GOES-11 satellite image, taken on June 6 at 0900 UTC (5 a.m. EDT) from the farthest vantage point of any of the satellites, still showed the triangular-shaped plume, even from its position over the western US, despite the large distance. -  NASA/NOAA GOES Project, Dennis Chesters
GOES-11 satellite image, taken on June 6 at 0900 UTC (5 a.m. EDT) from the farthest vantage point of any of the satellites, still showed the triangular-shaped plume, even from its position over the western US, despite the large distance. – NASA/NOAA GOES Project, Dennis Chesters

NASA’s Terra Satellite, the GOES-13 and GOES-11 satellites all captured images of the ash plume from southern Chile’s Puyehue-Cordón Volcano this week. The volcano is located in Puyehue National Park in the Andes of Ranco Province of Chile.

The Terra satellite flew over the volcano on June 6 at 14:25 UTC (10:25 a.m. EDT). The Moderate Resolution Imaging Spectroradiometer (MODIS) instrument captured a visible image of the eruption that showed the large ash plume blowing northeast, then to the southeast and over the Atlantic Ocean. The ash plume went at least as high as six miles on June 4 when it erupted, according to CNN International. Some 3,500 people were evacuated.

The Geostationary Operational Environmental Satellites called GOES-13 and GOES-11 also captured images of the volcano from a different vantage point in space that revealed the plume was visible from even farther away.

GOES-13 monitors the eastern U.S. and the Atlantic Ocean, while GOES-11 monitors the western U.S. and eastern Pacific Ocean. The GOES-11 satellite image, taken from the farthest vantage point of any of the satellites, still showed the triangular-shaped plume, even from its position over the western U.S., despite the large distance.

Tsunami sensor detects mysterious background signal in Panama

Equipment designed to detect tsunamis and earthquakes also detects background sounds including cars and the hum of the earth. -  J. McMillan
Equipment designed to detect tsunamis and earthquakes also detects background sounds including cars and the hum of the earth. – J. McMillan

An unusual signal detected by the seismic monitoring station at the Smithsonian Tropical Research Institute’s research facility on Barro Colorado Island results from waves in Lake Gatun, the reservoir that forms the Panama Canal channel, scientists report. Understanding seismic background signals leads to improved earthquake and tsunami detection in the Caribbean region where 100 tsunamis have been reported in the past 500 years.

As part of a $37.5 million U.S. presidential initiative to improve earthquake monitoring following the devastating tsunami in the Indian Ocean in 2004, a seismic sensor was installed on Barro Colorado Island in 2006. The sensor is one of more than 150 sensors that comprise the U.S. Geological Survey’s Global Seismographic Network.

Barro Colorado Island is a hilltop that was isolated by the waters of the reservoir created when the Chagres River was dammed to form Lake Gatun, a critical part of the Panama Canal. The Barro Colorado seismic monitoring station is a collaboration between the U.S. Geological Survey, the U.S. National Oceanic and Atmospheric Administration, the University of Panama and STRI.

Ultra-sensitive devices at the station pick up a large range of ground motion from felt earthquakes to nanometer-scale seismic background noise. The instruments at the station include very sensitive broadband seismometers used to detect distant earthquakes and low-gain accelerometers that measure ground movement and withstand violent local earthquakes and explosions.

The sensors detect signals from many different sources that include cars, boats and machinery operating up to several kilometers away. They also pick up the background “hum of the Earth” caused by ocean waves breaking on continental shelves around the world.

Scientists noticed that sensors on Barro Colorado recorded an intriguing wave pattern at an intermediate frequency. They suspected that this pattern could be caused by standing waves in Lake Gatun. Standing waves, also known as “seiches,” are common in enclosed bodies of water like lakes and harbors where waves moving in opposite directions interact. By installing a water-level detection meter along the shoreline, researchers confirmed that changes in the water level of the lake correspond to the unusual seismic signal.

This is not the first report of seiches in Lake Gatun. Earlier reports correlated the release of methane gasses in the sediments below the canal to seiches and bottom currents in the lake. The Panama Canal Authority provided data about the depth of the Canal channel and of Lake Gatun that the authors used to model wave patterns in the lake.

Boat traffic and wind speed correlate with the unusual wave pattern, which was more common during the day than it was at night, but more information is needed to confirm what is actually causing the waves.

This report, published in the Journal of Geophysical Research, provides a new method to quantify the impact of water movements as recorded by land-based seismometers. A more exact understanding of the seismic signals resulting from water movements will improve estimates of other phenomena like tsunami impacts.

New map reveals giant fjords beneath East Antarctic ice sheet

Scientists from the U.S., U.K. and Australia have used ice-penetrating radar to create the first high- resolution topographic map of one of the last uncharted regions of Earth, the Aurora Subglacial Basin, an immense ice-buried lowland in East Antarctica larger than Texas.

The map reveals some of the largest fjords or ice cut channels on Earth, providing important insights into the history of ice in Antarctica. The data will also help computer modelers improve their simulations of the past and future Antarctic ice sheet and its potential impact on global sea level.

“We knew almost nothing about what was going on, or could go on, under this part of the ice sheet and now we’ve opened it up and made it real,” said Duncan Young, research scientist at The University of Texas at Austin’s Institute for Geophysics and lead author on the study, which appears in this week’s journal Nature.

“We chose to focus on the Aurora Subglacial Basin because it may represent the weak underbelly of the East Antarctic Ice Sheet, the largest remaining body of ice and potential source of sea-level rise on Earth,” said Donald Blankenship, principal investigator for the ICECAP project, a multinational collaboration using airborne geophysical instruments to study the ice sheet.

Because the basin lies kilometers below sea level, seawater could penetrate beneath the ice, causing portions of the ice sheet to collapse and float off to sea. Indeed, this work shows that the ice sheet has been significantly smaller in the past.

Previous work based on ocean sediments and computer models indicates the East Antarctic Ice Sheet grew and shrank widely and frequently, from about 34 to 14 million years ago, causing sea level to fluctuate by 200 feet . Since then, it has been comparatively stable, causing sea-level fluctuations of less that 50 feet. The new map reveals vast channels cut through mountain ranges by ancient glaciers that mark the edge of the ice sheet at different times in the past, sometimes hundreds of kilometers from its current edge.

“We’re seeing what the ice sheet looked like at a time when Earth was much warmer than today,” said Young. “Back then it was very dynamic, with significant surface melting. Recently, the ice sheet has been better behaved.”

However, recent lowering of major glaciers near the edge detected by satellites has raised concerns about this sector of Antarctica.

Young said past configurations of the ice sheet give a sense of how it might look in the future, although he doesn’t foresee it shrinking as dramatically in the next 100 years. Still, even a small change in this massive ice sheet could have a significant effect on sea level. Scientists at The University of Texas at Austin’s Institute for Computational Engineering and Sciences, and at Australia’s Antarctic Climate and Ecosystems CRC are developing models that will use the new map to forecast how the ice sheet will evolve in the future and how it might affect sea level.

This research is part of ICECAP (Investigating the Cryospheric Evolution of the Central Antarctic Plate), a joint project of The University of Texas at Austin’s Jackson School of Geosciences, the University of Edinburgh and the Australian Antarctic Division. For three field seasons, the team flew an upgraded World War II-era DC-3 aircraft with a suite of geophysical instruments to study the ice and underlying rock in East Antarctica.