Extreme water

Earth is the only known planet that holds water in massive quantities and in all three phase states. But the earthly, omnipresent compound water has very unusual properties that become particularly evident when subjected to high pressure and high temperatures. In the latest issue of the Proceedings of the National Academy of Sciences (PNAS), a German-Finnish-French team published what happens when water is subjected to pressure and temperature conditions such as those found in the deep Earth.

At pressures above 22 MPa and temperatures above 374°C, beyond the critical point, water turns into a very aggressive solvent, a fact that is crucial for the physical chemistry of Earth’s mantle and crust.

“Without water in Earth’s interior there would be no material cycles and no tectonics. But how the water affects processes in the upper mantle and crust is still subject of intense research”, said Dr. Max Wilke from the GFZ German Research Centre for Geosciences, who carried out the experiments along with his colleague Dr. Christian Schmidt and a team from the TU Dortmund. To this end, the research team brought the water to the laboratory. First, the microscopic structure of water as a function of pressure and temperature was studied by means of X-ray Raman scattering. For that purpose, the diamond anvil cells of the GFZ were used at the European Synchrotron Radiation Facility ESRF in Grenoble. Inside the cell, a very small sample of water was enclosed, heated and brought to high temperatures and pressures. The data analysis was based on molecular dynamics simulations by the GFZ scientists Sandro Jahn.

“The study shows that the structure of water continuously develops from an ordered, polymerized structure to a disordered, marginally polymerized structure at supercritical conditions,” explains Max Wilke. “The knowledge of these structural properties of water in the deep earth is an important basis for the understanding of chemical distribution processes during metamorphic and magmatic processes.” This study provides an improved estimate of the behavior of water under extreme conditions during geochemical and geological processes. It is believed that the unique properties of supercritical water also control the behavior of magma.

Well-healed faults produce high-frequency earthquake waves

Much like our voices create sound waves with a variety of low and high pitches, or frequencies, earthquakes produce seismic waves over a broad spectrum. The seismic waves’ frequencies determine, in part, how far they travel and how damaging they are to human-made structures. However, the inaccessibility of fault zones means that very little is known about why and how earthquakes produce different frequencies. With the help of a new tabletop model, scientists have now identified how a process known as fault healing can shape seismic waves and potentially alter their frequencies.

Fault healing, which can occur on all types of faults, is akin to a wound healing. Over time, changes in pressure, temperature and mineralization can increase the contact area between two sides of a fault, essentially welding the two sides together. When the fault finally ruptures, the frequency of seismic waves released is higher than it otherwise would have been, potentially causing much more damage. What factors promote fault healing, and how will it influence seismic hazard assessments in the future? Read the story online at http://bit.ly/YeQGUE and find out!

All shook up? Make sure to check out the other great stories in this month’s issue of EARTH Magazine! Expose yourself to the Buckskin Glacier in Denali National Park; detect underground nuclear explosions with satellites; and discover the dark side of kerosene lamps all in this month’s issue of EARTH.

Breaking the rules for how tsunamis work

The earthquake zones off of certain coasts-like those of Japan and Java-make them especially vulnerable to tsunamis, according to a new study. They can produce a focusing point that creates massive and devastating tsunamis that break the rules for how scientists used to think tsunamis work.

Until now, it was largely believed that the maximum tsunami height onshore could not exceed the depth of the seafloor. But new research shows that when focusing occurs, that scaling relationship breaks down and flooding can be up to 50 percent deeper with waves that do not lose height as they get closer to shore.

“It is as if one used a giant magnifying lens to focus tsunami energy,” said Utku Kanoglu, professor at the Middle East Technical University and senior author of the study. “Our results show that some shorelines with huge earthquake zones just offshore face a double whammy: not only they are exposed to the tsunamis, but under certain conditions, focusing amplifies these tsunamis far more than shoaling and produces devastating effects.”

The team observed this effect both in Northern Japan, which was struck by the Tohoku tsunami of 2011, and in Central Java, which was struck by a tsunami in 2006.

“We are still trying to understand the implications,” said Costas Synolakis, director of the Tsunami Research Center at the USC Viterbi School of Engineering and a co-author of the study. “But it is clear that our findings will make it easier to identify locales that are tsunami magnets, and thus help save lives in future events.”

During an earthquake, sections of the sea floor lift up while others sink. This creates tsunamis that propagate trough-first in one direction and crest-first in the other. The researchers discovered that on the side of the earthquake zone where the wave propagates trough-first, there is a location where focusing occurs – strengthening it before it hits the coastline with an unusual amount of energy that is not seen by the crest-first wave. Based on the shape, location, and size of the earthquake zone, that focal point can concentrate the tsunami’s power right on to the coastline.

In addition, before this analysis, it was thought that tsunamis usually decrease in height continuously as they move away from where they are created and grow close to shore, just as wind waves do. The study’s authors instead suggest that the crest of the tsunami remains fairly intact close to the source.

“While our study does not preclude that other factors may help tsunamis overgrow, we now know when to invoke exotic explanations for unusual devastation: only when the basic classic wave theory we use does not predict focusing, or if the focusing is not high enough to explain observations,” said Vasily Titov, a researcher at NOAA’s Pacific Marine Environmental Laboratory and study co-author.

Fossil CSI: Prehistoric clues to oil, environment revealed

More than 200 delegates from around the world will assemble at the University of Houston (UH) next week to share research and discoveries about oil and the environment at an international conference on the economic and environmental use of fossils.

Specifically examining microfossils, which are invisible to the naked eye, the scientists who participate in this quadrennial gathering represent leaders in various branches of stratigraphy, the branch of geology that studies rock layers in the Earth’s crust. Notable presenters will include the authors of the last decade of geologic time scales, which are a system of chronological measurements that relate stratigraphy to time. These time scales are used by geologists, paleontologists and other earth scientists to describe the timing and relationships between events that have occurred throughout Earth’s history.

The conference, Geologic Problem Solving with Microfossils III, will be held at UH March 10-13. Kicking off the activities will be poster sessions at the Hilton UH Sunday and Monday evening, with oral presentations taking place Monday through noon Wednesday in room 100 of the Science and Engineering Classroom building.

“We will have some of the world leaders in research on global time scales presenting at this conference. They are the keepers of the keys to time for the fossil record over the course of the last 550 million years in sedimentary rocks,” said Don Van Nieuwenhuise, director of Professional Geoscience Programs at UH in the Department of Earth and Atmospheric Sciences. “They also are keeping track of available age data back into the Precambrian age, extending as far back in time as 4.5 billion years ago. The work of hundreds of scientists from all over the world entails integrating data generated from the Earth, Moon, Mars and Venus.”

The various presentations lined up will show how microfossils are used to understand environmental conditions, such as global warming and cooling, from prehistoric times to the present. Talks also will cover how microfossils are used to age-date rocks, as well as provide clues to finding oil and gas resources not only in conventional sand and limestone, but also unconventional shale plays.

In addition to discussions of practical applications in oil and gas exploration and production, Van Nieuwenhuise says basic science about stratigraphy and environmental monitoring will be showcased. Since microfossils are found in abundance in oil and gas well samples, scientists can then link the environmental signals of similar living microscopic organisms, flora and fauna in a region, also called microbiota, to understand the fossil and rock record.

“This has led to the use of these organisms as environmental monitors for various forms of pollution,” he said. “Once researchers determine the baseline abundances and distributions of microbiota in a given habitat, we can then determine if pollutants have disrupted their habitat and populations. Some microbiota develop deformities related to pollutant influences and other environmental stresses.”

Intended to reflect today’s broadening application of micropaleontology, presentations will include talks on the microfossil record of major oceanic events, microfossils and unconventional resources, reconstructing past environments using microfossils, paleoclimatology and paleoceanography related to sea-level change, and new technologies and techniques in microfossil studies.

Sponsored by the North American Micropaleontology Section of the Society for Sedimentary Geology, this conference broadly focuses on the use of microfossils for solving geological problems. Initiated in 2005 and held every four years, this event has been well received and growing in attendance. Attendees of past meetings have said the open problem-solving theme of the conference and the broad participation of specialists from varied disciplines creates a rich environment for collaboration and sharing of ideas and knowledge.

The making of Antarctica’s hidden fjords

This 3-D reconstruction of the topography hidden under Antarctica's two-mile-thick coating of ice was made using data from radar surveys. Glaciers started carving Antarctica into the current mountain-and-fjord landscape 34 million years ago, according to new findings from University of Arizona geoscientist Stuart N. Thomson and his colleagues. -  Courtesy of Stuart N. Thomson/UA department of geosciences
This 3-D reconstruction of the topography hidden under Antarctica’s two-mile-thick coating of ice was made using data from radar surveys. Glaciers started carving Antarctica into the current mountain-and-fjord landscape 34 million years ago, according to new findings from University of Arizona geoscientist Stuart N. Thomson and his colleagues. – Courtesy of Stuart N. Thomson/UA department of geosciences

Antarctica’s topography began changing from flat to fjord-filled starting about 34 million years ago, according to a new report from a University of Arizona-led team of geoscientists.

Knowing when Antarctica’s topography started shifting from a flat landscape to one with glaciers, fjords and mountains is important for modeling how the Antarctic ice sheet affects global climate and sea-level rise.

Although radar surveys have revealed a rugged alpine landscape under Antarctica’s two-mile-thick ice sheet, the surveys tell nothing about when the continent’s deep valleys formed.

“We have worked out how the landscape under the ice has changed through time,” said lead author Stuart N. Thomson.

“People have speculated when the big fjords formed under the ice,” he said. “But no one knows for sure until you sample the rocks or the sediments.”

He and his colleagues sampled East Antarctica’s rocks by examining the sediments that built up off-shore for millions of years as rocks and dirt eroded off the continent into Prydz Bay.

“We use the sediments to trace what was happening under the ice in the past,” said Thomson, a research scientist in the UA department of geosciences.

The team found that between 250 and 34 million years ago, erosion from the region now covered by the huge Lambert Glacier was slow, suggesting the area was relatively flat and drained by slow-moving rivers.

About 34 million years ago, at the same time the climate shifted and Antarctica was becoming covered with ice, the rate of erosion more than doubled, Thomson said.

“The only way that could happen is from glaciers,” he said. “They started grinding and forming deep valleys.”

Co-author Peter W. Reiners, a UA professor of geosciences, said, “East Antarctica’s landscape changed dramatically when big glaciers appeared there.

“Glaciers can carve deep valleys quickly – and did so on Antarctica before it got so cold that the most of it got covered by one or two miles of thick, stationary ice.”

The team’s paper, “The contribution of glacial erosion to shaping the hidden landscape of East Antarctica,” is published in the March issue of Nature Geoscience.

Other co-authors are Sidney R. Hemming of Columbia University’s Lamont-Doherty Earth Observatory in Palisades, N.Y. and UA geoscientist George E. Gehrels. The National Science Foundation funded the research.

Geologists generally figure out a landscape’s history by hiking around to look at the area’s rocks and then toting some of them back to the lab for analysis.

“The trouble is, in Antarctica, 97 percent of the continent is covered in ice, and you can’t directly access the rocks,” Thomson said.

To reconstruct the history of East Antarctica’s landscape, he and his colleagues instead studied bits of Antarctic rocks from cores of sediment taken just offshore of the Lambert Glacier by the Ocean Drilling Program.

The team used 1,400 individual sand-sized grains of minerals from various locations throughout three different cores to figure out how quickly the surface of Antarctica had eroded at various times in the past.

Because other researchers had used microfossils to pinpoint when in geological time each layer of the core had been deposited, Thomson and his colleagues knew when each of those 1,400 samples had been washed from Antarctica’s surface into the sea.

To link a time in the landscape’s history to an erosion rate, geologists can use the “cooling age” of rocks. The cooling age tells how fast the rock was uncovered from a particular depth in the Earth.

As a rock is moved deeper into the Earth, it warms, and as it moves toward the surface of the Earth, it cools. A particular depth in the Earth corresponds to a particular temperature. Minerals in the rock, apatite and zircon, record when they were last at a certain depth/temperature.

For each of the 1,400 samples, Thomson and his UA colleagues used three independent dating techniques to see how fast the mineral grain was exposed by erosion. Thomson’s lab did the fission-track dating; Reiners’ lab did the uranium-thorium-helium dating; and Gehrels’ lab did the uranium-lead dating.

The different methods of analysis all point to the same answer.

Reiners said, “We can say when and in what way this mysterious sub-ice landscape changed and how. East Antarctica’s landscape changed dramatically when big glaciers appeared there.”

Knowing how the ice sheets changes in the past is important for predicting future changes in ice sheet growth, sea-level change and climate, Thomson said.

His next step is looking offshore in other regions of Antarctica to see if they show the same pattern.

Experts to calculate potential of Greenlandic mineral wealth

The University of Greenland/Illsimatusarfik and the University of Copenhagen have agreed to set up a joint committee to determine how best Greenland’s mineral resources can benefit the country. Greenland’s premier, Kuupik Kleist, and the Danish prime minister, Helle Thorning-Schmidt, support the initiative.

The committee will examine Greenland’s opportunities for exploiting its mineral resources and how they can create value for Greenland through, for example, economic growth and employment. The committee will also study how mining, oil drilling and other large-scale raw materials projects can be undertaken as sustainably as possible and with as little impact as possible on the environment or the people of Greenland.

“Greenland and Denmark have historically had a very close relationship and the University of Copenhagen has been sending faculty to conduct research in Greenland for more than 100 years. We have had researchers stationed at the Arctic Station, climatologists studying the ice cap, and the University of Copenhagen offers a programme in Eskimology and Arctic Studies. The joint committee will be able to gather the necessary knowledge to ensure that Greenland’s resources are developed as sustainably as possible and return the maximum yield for future generations,” says University of Copenhagen Rector Ralf Hemmingsen.

Resumed relationship

Denmark’s Interest in Greenland’s mineral resources started as early as 1878 when a commission was established to undertake geological and geographic studies in Greenland. Their study quickly developed into a forum for Danish and Greenlandic scholars to study everything from natural phenomena to Arctic languages, anthropology, culture and history.

With the decision to grant Greenland Home Rule status in 1979, Denmark has gradually reduced its involvement in the country’s affairs. But the importance of maintaining a strong relationship was demonstrated after Greenland, now with Self-Rule status and even more autonomy from Copenhagen, drafted legislation that would make it easier for foreign companies to set up operations in Greenland.

“The extraction of Greenland’s underground resources affects many different interests. Only by collaborating between universities and cultures are we sure to develop a sufficient insight into these interests,” says Illsimatusarfik Rector Tine Pars.

Professor Minik Rosing, from the University of Copenhagen, often collaborates with Illsimatusarfik faculty and will chair the commission. As a geologist he drew international attention when he uncovered some of the world’s oldest rocks at a site north-east of Nuuk.

Ilisimatusarfik Rector Tine Pars

In all, the committee will be made up of nine members, all of whom will be experts in their field and hand selected by the two rectors.

The committee will examine the potential for extracting Greenland’s resources and make recommendations for specific measures that Greenlandic and Danish interests can take. These could consist of initiatives to ensure that Greenland benefits to the greatest extent possible from investments in developing its geological resources.

The committee’s findings will be presented by the end of this year in the hopes that they can form the basis for a public debate. The commission will be jointly administered by Illsimatusarfik and the University of Copenhagen.

Researchers find new information about ‘Snowball Earth’ period

It is rather difficult to imagine, but approximately 635 million years ago, ice may have covered a vast portion of our planet in an event called “Snowball Earth.” According to the Snowball Earth hypothesis, the massive ice age that occurred before animal life appeared, when Earth’s landmasses were most likely clustered near the equator, precipitated relatively rapid changes in atmospheric conditions and a subsequent greenhouse heat wave. This particular period of extensive glaciation and subsequent climate changes might have supplied the cataclysmic event that gave rise to modern levels of atmospheric oxygen, paving the way for the rise of animals and the diversification of life during the later Cambrian explosion.

But if ice covered the earth all the way to the tropics during what is known as the Marinoan glaciation, how did the planet spring back from the brink of an ice apocalypse? Huiming Bao, Charles L. Jones Professor in Geology & Geophysics at LSU, might have some of the answers. Bao and LSU graduate students Bryan Killingsworth and Justin Hayles, together with Chuanming Zhou, a colleague at Chinese Academy of Sciences, had an article published on Feb. 5 in the Proceedings of the National Academy of Sciences, or PNAS, that provides new clues on the duration of what was a significant change in atmospheric conditions following the Marinoan glaciation.

“The story is to put a time limit on how fast our Earth system can recover from a total frozen state,” Bao said. “It is about a unique and rapidly changing post-glacial world, but is also about the incredible resilience of life and life’s remarkable ability to restore a new balance between atmosphere, hydrosphere and biosphere after a global glaciation.”

Bao’s group went about investigating the post-glaciation period of Snowball Earth by looking at unique occurrences of “crystal fans” of a common mineral known as barite (BaSO4), deposited in rocks following the Marinoan glaciation. Out of the three stable isotopes of oxygen, O-16, O-17 and O-18, Bao’s group pays close attention to the relatively scarce isotope O-17. According to Killingsworth, there aren’t many phenomena on earth that can change the normally expected ratio of the scare isotope O-17 to more abundant isotope O-18. However, in sulfate minerals such as barite in rock samples from around 635 million years ago, Bao’s group finds large deviations in the normal ratio of O-17 to O-18 with respect to O-16 isotopes.

“If something unusual happens with the composition of the atmosphere, the oxygen isotope ratios can change,” Killingsworth said. “We see a large deviation in this ratio in minerals deposited around 635 million years ago. This occurred during an extremely odd time in atmospheric history.”

According to Bao’s group, the odd oxygen isotope ratios they find in barite samples from 635 million years ago could have occurred if, following the extensive Snowball Earth glaciation, Earth’s atmosphere had very high levels of carbon dioxide, or CO2. An ultra-high carbon dioxide atmosphere, Killingsworth explains, where CO2 levels match levels of atmospheric oxygen, would grab more O-17 from oxygen. This would cause a depletion of the O-17 isotope in air and subsequently in barite minerals, which incorporate oxygen as they grow. Bao’s group has found worldwide deposits of this O-17 depleted sulfate mineral in rocks dating from the global glaciation event 635 million years ago, indicating an episode of an ultra-high carbon dioxide atmosphere following the Marinoan glaciation.

“Something significant happened in the atmosphere,” Killingsworth said. “This kind of an atmospheric shift in carbon dioxide is not observed during any other period of Earth’s history. And now we have sedimentary rock evidence for how long this ultra-high carbon dioxide period lasted.”

By using available radiometric dates from areas near layers of barite deposits, Bao’s group has been able to come up with an estimate for the duration of what is now called the Marinoan Oxygen-17 Depletion, or MOSD, event. Bao’s group estimates the MOSD duration at 0 – 1 million years.

“This is, so far, really the best estimate we could get from geological records, in line with previous models of how long an ultra-high carbon dioxide event could last before the carbon dioxide in the air would get drawn back into the oceans and sediments,” Killingsworth said.

Normally, carbon dioxide levels in the atmosphere are in balance with levels of carbon dioxide in the ocean. However, if water and air were cut off by a thick layer of ice during Snowball Earth, atmospheric carbon dioxide levels could have increased drastically. In a phenomenon similar to the climate change Earth is witnessing in modern times, high levels of atmospheric carbon dioxide would have created a greenhouse gas warming effect, trapping heat inside the planet’s atmosphere and melting the Marinoan ice. Essentially, the Marinoan glaciation created the potential for extreme changes in atmospheric chemistry that in turn lead to the end of Snowball Earth and the beginning of a new explosion of animal life on Earth.

While previous work by Bao’s group had advanced the interpretation of the strange occurrence of O-17 depleted barite just after the Marinoan glaciation, there was still much uncertainty on the duration of ultra-high CO2 levels after meltdown of Snowball Earth. Bao’s discovery of a field site with many barite layers gave the opportunity to track how oxygen isotope ratios changed through a thickness of sedimentary rock. As the pages in a novel can be thought of as representing time, so layers of sedimentary rock represent geological history. However, these rock “pages” represented an unknown duration of time for the MOSD event. By using characteristic features of the Marinoan rock sequence occurring regionally in South China, Bao’s group linked the barite layer site to other sites in the region that did have precise dates from volcanic ash beds. Bao’s group has succeeded in estimating the duration of the MOSD event, and thus the time it took for Earth to restore “normal” CO2 levels in the atmosphere.

“To some extent, our findings demonstrate that whatever happens to Earth, she will recover, and recover at a rapid pace,” Bao said. “Mother Earth lived and life carried on even in the most devastating situation. The only difference is the life composition afterwards. In other words, whatever humans do to the Earth, life will go on. The only uncertainty is whether humans will still remain part of the life composition.”

Bao says that he had been interested in this most intriguing episode of Earth’s history since Paul Hoffman, Dan Schrag and colleagues revived the Snowball Earth hypothesis in 1998.

“I was a casual ‘non-believer’ of this hypothesis because of the mere improbability of such an Earth state,” Bao said. “There was nothing rational or logic in that belief for me, of course. I remember I even told my job interviewers back in 2000 that one of my future research plans was to prove that the Snowball Earth hypothesis was wrong.”

However, during a winter break in 2006, Bao obtained some unusual data from barite, a sulfate mineral dating from the Snowball Earth period that he received from a colleague in China.

“I started to develop my own method to explore this utterly strange world,” Bao said. “Now, it seems that our LSU group is the one offering the strongest supporting evidence for a ‘Snowball Earth’ back 635 million years ago. I certainly did not see this coming. The finding we published in 2008 demonstrates, again, that new scientific breakthroughs are often brought in by outsiders.”

Bao credits his research ideas, analytical work and pleasure of working on this project to his two graduate students, Killingsworth and Hayles, as well as his long-time Chinese collaborators. Bao brought Killingsworth and Hayles to an interior mountainous region in South China in December 2011, where the group succeeded in finding multiple barite layers in a section of rocks dating to 635 million years ago. This discovery formed a large part of their analysis and subsequent publication in PNAS.

“Nothing can beat the intellectual excitement and satisfaction you get from research in the field and in the laboratory,” Bao said.

Mineral diversity clue to early Earth chemistry

Mineral evolution is a new way to look at our planet’s history. It’s the study of the increasing diversity and characteristics of Earth’s near-surface minerals, from the dozen that arrived on interstellar dust particles when the Solar System was formed to the more than 4,700 types existing today. New research on a mineral called molybdenite by a team led by Robert Hazen at Carnegie’s Geophysical Laboratory provides important new insights about the changing chemistry of our planet as a result of geological and biological processes.

The work is published by Earth and Planetary Science Letters.

Mineral evolution is an approach to understanding Earth’s changing near-surface geochemistry. All chemical elements were present from the start of our Solar System, but at first they formed comparatively few minerals-perhaps no more than 500 different species in the first billion years. As time passed on the planet, novel combinations of elements led to new minerals.

Molybdenite is the most common ore mineral of the critical metallic element molybdenum. Hazen and his team, which includes fellow Geophysical Laboratory scientists Dimitri Sverjensky and John Armstrong, analyzed 442 molybdenite samples from 135 locations and ages ranging from 2.91 billion years old to 6.3 million years old. They specifically looked for trace contamination of the element rhenium in the molybdenite, because rhenium can be used to use to gauge historical chemical reactions with oxygen from the environment.

They found that concentrations of rhenium, a trace element that is sensitive to oxidation reactions, increased significantly-by a factor of eight-over the past three billion years. The team suggests that this change reflects the increasing near-surface oxidation conditions from the Archean Eon more than 2.5 billion years ago to the Phanerozoic Eon less than 542 million years ago. This oxygen increase was a consequence of what’s called the Great Oxidation Event, when the Earth’s atmospheric oxygen levels skyrocketed as a consequence of oxygen-producing photosynthetic microbes.

In addition, they found that the distribution of molybdenite deposits through time roughly correlates with five periods of supercontinent formation, the assemblies of Kenorland, Nuna, Rodinia, Pannotia, and Pangea. This correlation supports previous findings from Hazen and his colleagues that mineral formation increases markedly during episodes of continental convergence and supercontinent assembly and that a dearth of mineral deposits form during periods of tectonic stability.

“Our work continues to demonstrate that a major driving force for mineral evolution is hydrothermal activity associated with colliding continents and the increasing oxygen content of the atmosphere caused by the rise of life on Earth,” Hazen said.