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San Andreas Fault Cores Go Live, Online

bobs — Fri, 30 May 2008 16:00:00 GMT

Larry O'Hanlon, Discovery News

May 30, 2008 -- For the first time ever, the thrashed and jumbled innards of the notorious San Andreas Fault are now available online for anyone to see.

The new Google Maps-based "Core Viewer" allows scientists and the general public to peer at high-resolution images of the rock cores drilled and extracted directly from the steadily slipping section of the infamous fault two kilometers (1.2 miles) beneath Parkfield, Calif.

"That's where all the action is," said U.S. Geological Survey geophysicist Steve Hickman. At Parkfield, that action is already contorting the metal casing installed in the San Andreas Fault Observatory at Depth (SAFOD) borehole at a rate of two centimeters (0.8 inches) per year.

The core viewer shows the fronts and backs of the long cylindrical rocks, marked in centimeters, drilled out with circular drill heads. The cores reveal two sub-faults of the San Andreas where rocks are currently being ground up by the sidewise meeting of the Pacific and the North American tectonic plates.

The most important parts of the core show not only highly ground-up rocks, but rocks that have been polished by the shearing forces in the fault. There are also chunks of green rocks made of a very weak, slippery mineral called serpentine, which has long been a suspect in the lubricating of the San Andreas along this section in central California.

"The serpentine is really an important find for us," said Hickman, referring to a section shown in the Core Viewer under Hole G, Run 2, sections 7 through 9. "It allows the fault to creep. The presence of that serpentine is kind of a smoking gun."

Section 8 of the same area reveals dark rocks that appear to shimmer like opals. These rocks were essentially ground smooth by the fault, like stones polished by a rock tumbler, Hickman explained.

The bright white minerals in the same sections are calcite, a sign that water as been present and plays a role in the fault as well. These and other important sections of the core will be marked with bubbles containing scientific information as more work is done, Hickman told Discovery News.

"The core viewer is to show the scientific community what the core looks like," said Stanford University's Charley Weiland, who serves as SAFOD's data manager. Already there are 800 samples requested from researchers who want to conduct all sorts of research on the rocks.

"The core is a very scarce commodity," Weiland told Discovery News. The actual core is locked away at 4 degrees Centigrade with ocean drilling cores in a store facility in Texas, he said.

SAFOD is one of three "observatories" encompassed by the EarthScope project. The other two are the Plate Boundary Observatory, which measures the ongoing tectonic mangling of the crust throughout the Western United States, and the U.S. Array, which is moving a high-density network of seismic stations across North America to uncover the physical structure of the continent.

http://www.earthscope.org/data/safod_core_viewer

http://dsc.discovery.com/news/2008/05/30/san-andreas-fault.html

posted in Geology - 1 reply

A single boulder..........

bobs — Thu, 17 Jul 2008 22:16:35 GMT

.............may prove that Antarctica and North America were once connected

A lone granite boulder found against all odds high atop a glacier in Antarctica may provide additional key evidence to support a theory that parts of the southernmost continent once were connected to North America hundreds of millions of years ago.

Writing in the July 11 edition of the journal Science, an international team of U.S. and Australian investigators describe their findings, which were made in the Transantarctic Mountains, and their significance to the problem of piecing together what an ancient supercontinent, called Rodinia, looked like. The U.S. investigators were funded by the National Science Foundation (NSF).

Previous lines of scientific evidence led researchers to theorise that about 600-800 million years ago a portion of Rodinia broke away from what is now the southwestern United States and eventually drifted southward to become eastern Antarctica and Australia.

The team's find, they argue, provides physical evidence that confirms the so-called southwestern United States and East Antarctica (SWEAT) hypothesis.

"What this paper does is say that we have three main new lines of evidence that basically confirm the SWEAT idea," said John Goodge, an NSF-funded researcher with the Department of Geological Sciences at the University of Minnesota-Duluth.

Added Scott Borg, director of the division of Antarctic sciences in NSF's Office of Polar Programs, "this is first-rate work and a fascinating example of scientists at work putting together the pieces of a much larger puzzle. Not only do the authors pull together a diverse array of data to address a long-standing question about the evolution of the Earth's crust during a critical time for biological evolution, but the research shows how the ideas surrounding the SWEAT hypothesis have developed over time."

As a field researcher during the late 1980's and early 1990's, Borg authored papers on the SWEAT hypothesis.

The boulder find came by serendipity while the researchers were picking though rubble carried through the Transantarctic Mountains by ice streams-rivers of ice-that flow at literally a glacial pace from East Antarctica.

Goodge and his team were searching for rocks that might provide keys to the composition of the underlying continent crust of Antarctica, which in most places is buried under almost two miles of ice.

"We were picking up boulders in the moraines that looked interesting," Goodge said. "It was basically just a hodge-podge of material."

One rock in particular, small enough to heft in one hand, found atop the Nimrod Glacier, was later determined to be a very specific form of granite with, as Goodge describes it, "a particular type of coarse-grained texture."

Subsequent chemical and isotopic tests conducted in laboratories in the United States revealed that the boulder had a chemistry "very similar to a unique belt of igneous rocks in North America" that stretches from what is now California eastward through New Mexico to Kansas, Illinois and eventually through New Brunswick and Newfoundland in Canada.

That belt of rocks is known to have been a part of what is called Laurentia, which was a component of the supercontinent of Rodinia.

"There is a long, linear belt of these igneous rocks that stretches across Laurentia. But 'bang' it stops, right there at the (western) margin where we knew that something rifted away" from what is now the West Coast of the United States," Goodge said.

"It just ends right where that ancient rift margin is," Goodge said. "And these rocks are basically not found in any other part of the world."

That it should turn up on a glacier high up in the mountains of Antarctica is strong evidence in support of the SWEAT model that parts of North America continue into part of the frozen continent at the bottom of the Earth.

"There's no other explanation for how it got where we found it," Goodge said. "It was bull-dozed over from that interior region of Antarctica."

The find itself is compelling to geologists, Goodge noted, because little other physical evidences exists to allow them directly to put together the jigsaw puzzle of the long-disappeared Rodinia.

But because the supercontinent existed at a key time in the development of multi-cellular life on Earth, it also helps provide a geological context in which this massive biotic change took place.

"During the Cambrian explosion about 520 million years ago we started seeing this huge expansion in the diversity of life forms," Goodge said. "This was also a time when the Earth was undergoing tremendous geologic changes."

He added that "something helped trigger that big radiation in life."

The shifting configuration of the continents, accompanied by collisions between landmasses, erosion and the influx of chemicals into the seas may well have provided the nutrients to that growing diversity of lifeforms.

"There are ideas developing about these connections between the geo-tectonic world on the one hand and biology on the other.

The job of geoscientists in this context, he said "is to reconstruct what the world was like at the time."

Source: National Science Foundation

http://www.physorg.com/news135518754.html

posted in Geology - 0 replies

ETS event happening under Puget Sound

Will The Dancer — Wed, 21 May 2008 00:46:36 GMT

The Episodic Tremor and Slip event is going on now beneath Puget Sound. The estimated energy dissipated by
some of the previous events are equivalent to a 6.7 subduction zone roller, but drawn out over several weeks.
Last tell during this event The Olympic mountains moved west about 5 mm as well.

It is concerning that my neighborhood part of the Cascadia S.Z. is locked, and has been for 300 years or so.

http://www.pnsn.org/WEBICORDER/DEEPTREM/winter2008.html

posted in Geology - 0 replies

Rocks under the northern ocean are found to resemble ones far south

bobs — Wed, 30 Apr 2008 21:23:20 GMT

Scientists probing volcanic rocks from deep under the frozen surface of the Arctic Ocean have discovered a special geochemical signature until now found only in the southern hemisphere. The rocks were dredged from the remote Gakkel Ridge, which lies under 3,000 to 5,000 meters of water; it is Earth’s most northerly undersea spreading ridge. The study appears in the May 1 issue of the leading science journal Nature.

The Gakkel extends some 1,800 kilometers beneath the Arctic ice between Greenland and Siberia. Heavy ice cover prevented scientists from getting at it until the 2001 Arctic Mid-Ocean Ridge Expedition, in which U.S and German ice breakers cooperated. This produced data showing that the ridge is divided into robust eastern and western volcanic zones, separated by an anomalously deep segment. That abrupt boundary contains exposed unmelted rock from earth’s mantle, the layer that underlies the planet’s hardened outer shell, or lithosphere.

By studying chemical trace elements and isotope ratios of the elements lead, neodymium, and strontium, the paper’s authors showed that the eastern lavas, closer to Siberia, display a typical northern hemisphere makeup. However, the western lavas, closer to Greenland, show an isotopic signature called the Dupal anomaly. The Dupal anomaly, whose origin is intensely debated, is found in the southern Indian and Atlantic oceans, but until now was not known from spreading ridges of the northern hemisphere. Lead author Steven Goldstein, a geochemist at Columbia University’s Lamont-Doherty Earth Observatory (LDEO), said that this did not suggest the rocks came from the south. Rather, he said, they might have formed in similar ways. “It implies that the processes at work in the Indian Ocean might have an analog here,” said Goldstein. Possible origins debated in the south include upwelling of material from the deep earth near the core, or shallow contamination of southern hemispheric mantle with certain elements during subduction along the edges of the ancient supercontinent of Pangea.

At least in the Arctic, the scientists say they know what happened. Some 53 million years ago, what are now Eurasia and Greenland began separating, with the Gakkel as the spreading axis. Part of Eurasia’s “keel”—a relatively stable layer of mantle pasted under the rigid continent and enriched in certain elements that are also enriched in the continental crust—got peeled away. As the spreading continued, the keel material got mixed with “normal” mantle that was depleted in these same elements. This formed a mixture resembling the Dupal anomaly. The proof, said Goldstein, is that the chemistry of the western Gakkel lavas appear to be mixtures of “normal” mantle and lavas coming from volcanoes on the Norwegian/Russian island of Spitsbergen. Although Spitsbergen is an island, it is attached to the Eurasian continent, and its volcanoes are fueled by melted keel material.

“This is unlikely to put an end to the debate about the origin of the southern hemisphere Dupal signature, as there may be other viable explanations for it,” said Goldstein. “On the other hand, this study nails it in the Arctic. Moreover, it delineates an important process within Earth’s system, where material associated with the continental lithospheric keel is transported to the deeper convectiing mantle.”

Source: The Earth Institute at Columbia University

http://www.physorg.com/news128778940.html

posted in Geology - 0 replies

How deep is Europe?

bobs — Wed, 30 Apr 2008 21:22:04 GMT

(Also posted at: http://awesomenature.tribe.net/ )

The Earth's crust is, on global average around 40 kilometres deep. In relation to the total diameter of the Earth with approx. 12800 kilometres this appears to be rather shallow, but precisely these upper kilometres of the crust, the human habitat, is of special interest for us.

Europe's crust shows an astonishing diversity: for example the crust under Finland is as deep as one only expects for crust under a mountain range such as the Alps. It is also amazing that the crust under Iceland and the Faroer-Islands is considerably deeper than a typical oceanic crust. This is explained by M. Tesauro und M. Kaban from GeoForschungsZentrum Potsdam (GFZ) and S. Cloetingh from the Vrije Universiteit in Amsterdam in a recent publication in the renowned scientific journal "Geophysical Research Letters". GFZ is the German Research Centre for Geosciences and a member of the Helmholtz Association.

For many years intensive investigation of the Earth's crust has been underway. However, different research groups in Europe have mostly been concentrating on individual regions. Hence, a high-resolution and consistent overall picture has not been available to date. With the present study this gap can now be filled. By incorporating the latest seismological results a digital model of the European crust has been created. This new detailed picture also allows for the minimization of interfering effects of the crust when taking a glance at the deeper Earth's interior.

A detailed model of the Earth's crust, i.e. from the upper layers to approx. a depth of 60 km is essential to understand the many millions of years of development of the European Continent. This knowledge supports the discovery of the commercial importance of ore deposits or crude oil in the continental shelf or in general with the use of the subterranean e.g. for the sequestration of CO2. It also contributes to the identification of geological hazards such as earthquakes.

Citation: Tesauro, M., M. K. Kaban, and S. A. P. L. Cloetingh (2008), EuCRUST-07: A new reference model for the European crust, Geophys. Res. Lett., 35, L05313, doi:10.1029/2007GL032244.

Source: Helmholtz Association of German Research Centres

http://www.physorg.com/news128774944.html

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Discovery sheds light on mantle formation

bobs — Fri, 11 Apr 2008 19:47:53 GMT

Uncovering a rare, two-billion-year-old window into the Earth’s mantle, a University of Houston professor and his team have found our planet’s geological history is more complex than previously thought.

Jonathan Snow, assistant professor of geosciences at UH, led a team of researchers in a North Pole expedition, resulting in a discovery that could shed new light on the mantle, the vast layer that lies beneath the planet’s outer crust. These findings are described in a paper titled “Ancient, highly heterogeneous mantle beneath Gakkel Ridge, Arctic Ocean,” appearing recently in Nature.

These two-billion-year-old rocks that time forgot were found along the bottom of the Arctic Ocean floor, unearthed during research voyages in 2001 and 2004 to the Gakkel Ridge, an approximately 1,000-mile-long underwater mountain range between Greenland and Siberia. This massive underwater mountain range forms the border between the North American and Eurasian plates beneath the Arctic Ocean, where the two plates diverge.

These were the first major expeditions ever undertaken to the Gakkel Ridge, and these latest published findings are the fruit of several years of research and millions of dollars spent to retrieve and analyze these rocks.

The mantle, the rock layer that comprises about 70 percent of the Earth’s mass, sits several miles below the planet’s surface. Mid-ocean ridges like Gakkel, where mantle rock is slowly pushing upward to form new volcanic crust as the tectonic plates slowly move apart, is one place geologists look for clues about the mantle. Gakkel Ridge is unique because it features – at some locations – the least volcanic activity and most mantle exposure ever discovered on a mid-ocean ridge, allowing Snow and his colleagues to recover many mantle samples.

“I just about fell off my chair,” Snow said. “We can’t exaggerate how important these rocks are – they’re a window into that deep part of the Earth.”

Venturing out aboard a 400-foot-long research icebreaker, Snow and his team sifted through thousands of pounds of rocks scooped up from the ocean floor by the ship’s dredging device. The samples were labeled and cataloged and then cut into slices thinner than a human hair to be examined under a microscope. That is when Snow realized he found something that, for many geologists, is as rare and fascinating as moon rocks – mantle rocks devoid of sea floor alteration. Analysis of the isotopes of osmium, a noble metal rarer than platinum within the mantle rocks, indicated they were two billion years old. The use of osmium isotopes underscores the significance of the results, because using them for this type of analysis is still a new, innovative and difficult technique.

Since the mantle is slowly moving and churning within the Earth, geologists believe the mantle is a layer of well-mixed rock. Fresh mantle rock wells up at mid-ocean ridges to create new crust. As the tectonic plates move, this crust slowly makes its way to a subduction zone, a plate boundary where one plate slides underneath another and the crust is pushed back into the mantle from which it came.

Because this process takes about 200 million years, it was surprising to find rocks that had not been remixed inside the mantle for two billion years. The discovery of the rocks suggests the mantle is not as well-mixed or homogenous as geologists previously believed, revealing that the Earth’s mantle preserves an older and more complex geologic history than previously thought. This opens the possibility of exploring early events on Earth through the study of ancient rocks preserved within the Earth’s mantle.

The rocks were found during two expeditions Snow and his team made to the Arctic, each lasting about two months. The voyages were undertaken while Snow was a research scientist at the Max Planck Institute in Germany, and the laboratory study was done by his research team that now stretches from Hawaii to Houston to Beijing.

Since coming to UH in 2005, Snow’s work stemming from the Gakkel Ridge samples has continued, with more research needed to determine exactly why these rocks remained unmixed for so long. Further study using a laser microprobe technique for osmium analysis available only in Australia is planned for next year.

Source: University of Houston

http://www.physorg.com/news127124384.html

posted in Geology - 0 replies

Grand Canyon may be as old as dinosaurs, says new study

bobs — Thu, 10 Apr 2008 22:59:09 GMT

New geological evidence indicates the Grand Canyon may be so old that dinosaurs once lumbered along its rim, according to a study by researchers from the University of Colorado at Boulder and the California Institute of Technology.

The team used a technique known as radiometric dating to show the Grand Canyon may have formed more than 55 million years ago, pushing back its assumed origins by 40 million to 50 million years. The researchers gathered evidence from rocks in the canyon and on surrounding plateaus that were deposited near sea level several hundred million years ago before the region uplifted and eroded to form the canyon.

A paper on the subject will be published in the May issue of the Geological Society of America Bulletin. CU-Boulder geological sciences Assistant Professor Rebecca Flowers, lead author and a former Caltech postdoctoral researcher, collaborated with Caltech geology Professor Brian Wernicke and Caltech geochemistry Professor Kenneth Farley on the study.

"As rocks moved to the surface in the Grand Canyon region, they cooled off," said Flowers. "The cooling history of the rocks allowed us to reconstruct the ancient topography, telling us the Grand Canyon has an older prehistory than many had thought."

The team believes an ancestral Grand Canyon developed in its eastern section about 55 million years ago, later linking with other segments that had evolved separately. "It's a complicated picture because different segments of the canyon appear to have evolved at different times and subsequently were integrated," Flowers said.

The ancient sandstone in the canyon walls contains grains of a phosphate mineral known as apatite -- hosting trace amounts of the radioactive elements uranium and thorium -- which expel helium atoms as they decay, she said. An abundance of the three elements, paired with temperature information from Earth's interior, provided the team a clock of sorts to calculate when the apatite grains were embedded in rock a mile deep -- the approximate depth of the canyon today -- and when they cooled as they neared Earth's surface as a result of erosion.

Apatite samples from the bottom of the Upper Granite Gorge region of the Grand Canyon yield similar dates as samples collected on the nearby plateau, said Caltech's Wernicke. "Because both canyon and plateau samples resided at nearly the same depth beneath the Earth's surface 55 million years ago, a canyon of about the same dimensions of today may have existed at least that far back, and possibly as far back as the time of dinosaurs at the end of the Cretaceous period 65 million years ago."

One of the most surprising results from the study is the evidence showing the adjacent plateaus around the Grand Canyon may have eroded away as swiftly as the Grand Canyon itself, each dropping a mile or more, said Flowers. Small streams on the plateaus appear to have been just as effective at stripping away rock as the ancient Colorado River was at carving the massive canyon.

"If you stand on the rim of the Grand Canyon today, the bottom of the ancestral canyon would have sat over your head, incised into rocks that have since been eroded away," said Flowers. The ancestral Colorado River was likely running in the opposite direction millions of years ago, she said.

When the canyon was formed, it probably looked like a much deeper version of present-day Zion Canyon, which cuts through strata of the Mesozoic era dating from about 250 million to 65 million years ago, Wernicke said. From 28 million to 15 million years ago, a pulse of erosion deepened the already-formed canyon and also scoured surrounding plateaus, stripping off the Mesozoic strata to reveal the Paleozoic rocks visible today, he said.

The prevailing belief is that the canyon was incised by an ancient river about six million years ago as the surrounding plateau began rising from sea level to the current elevation of about 7,000 feet. The new scenario described in the GSA Bulletin by Flowers and her colleagues is consistent with recent evidence by other geologists using radiometric dating techniques indicating the Grand Canyon is significantly older than scientists had long believed.

Source: University of Colorado at Boulder

http://www.physorg.com/news127055332.html

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New Findings From Tibetan Plateau Suggest Uplift Occurred In Stages

bobs — Tue, 25 Mar 2008 07:41:25 GMT

by Staff Writers
Santa Cruz CA (SPX) Mar 25, 2008
The vast Tibetan Plateau--the world's highest and largest plateau, bordered by the world's highest mountains--has long challenged geologists trying to understand how and when the region rose to such spectacular heights. New evidence from an eight-year study by U.S. and Chinese researchers indicates that the plateau rose in stages, with uplift occurring first in the central plateau and later in regions to the north and south.
"The middle part of the plateau was uplifted first at least 40 million years ago, while the Himalayan Range in the south and also the mountains to the north were uplifted significantly later," said Xixi Zhao, a research scientist at the University of California, Santa Cruz.

The team found marine fossils suggesting that the now lofty Himalayas remained below sea level at a time when the central plateau was already at or near its modern elevation, Zhao said. The average elevation of the plateau today is more than 4,500 meters (14,850 feet).

The researchers published their findings in the Proceedings of the National Academy of Sciences (online the week of March 24 and later in print). Zhao, who is affiliated with the Institute of Geophysics and Planetary Physics at UCSC, is the second author of the paper. First author Chengshan Wang of the China University of Geosciences in Beijing has been collaborating with Zhao and other UCSC researchers since 1996.

Known as "the roof of the world," the Tibetan Plateau was created by the ongoing collision of tectonic plates as India plows northward into Asia. Coauthor Robert Coe, a professor of Earth and planetary sciences at UCSC, said ideas about how the uplift of the plateau occurred have been evolving since well before his first visit to Tibet in 1988.

"People used to talk about the whole plateau coming up at once, but it has become clear that different parts of the plateau were elevated at different times," Coe said. "Our work shows that the central part of the plateau was uplifted first, and it seems to fit pretty well with other studies."

The rise of the Tibetan Plateau led to dramatic changes in the climate, both regionally and globally. For climate researchers trying to understand major episodes of global climate change in Earth's past, the timing of the uplift is a crucial piece of information.

"One of the traditional views of when Tibet became a high plateau is that it's a relatively recent phenomenon that happened in the last 15 million years," said coauthor Peter Lippert, a UCSC graduate student who has spent five field seasons studying the geology of the plateau. "The existence of a high plateau at least 40 million years ago could have important climatic implications."

The team of U.S. and Chinese geologists based their findings on extensive field studies conducted mostly in a remote interior region of the Tibetan Plateau. They focused on an area called the Hoh Xil Basin in the north-central part of the plateau. The area's geologic history is recorded in layers of sedimentary rock 5,000 meters thick. Now a part of the high plateau, it was once a basin on the northern edge of the central plateau, Lippert said.

"The structure of the basin and way the sediments were deposited show that it is the type of basin that forms at the base of large mountains. So we've shown that there was high topography to the south of the Hoh Xil Basin at least 40 million years ago," he said.

Several lines of evidence support the team's conclusions. In addition to field studies, the researchers used a variety of laboratory techniques to analyze and date the rocks. Past changes in Earth's magnetic field, recorded in the magnetization of the rocks, provide one method of dating. Called magnetostratigraphy, this analysis was performed in Coe's laboratory at UCSC. Another dating technique used in the study, called apatite fission-track analysis, is based on the damage trails left in apatite crystals by the decay of radiogenic isotopes.

The researchers also discovered volcanic rock in an area of the central plateau south of the Hoh Xil Basin. The flat bed of hardened lava lies on top of tilted and folded layers of sedimentary rocks; geochronology techniques dated it to 40 million years ago.

"The presence of these flat-lying volcanic rocks tells us that the sedimentary rock was deformed prior to the volcanism, and it extends the age of volcanism in this part of Tibet from 15 million to 40 million years ago," Lippert said.

In the Himalayas, the team found fossils of marine plankton called radiolarians that turned out to be 5 million years younger than any previously discovered marine fossils from that area. The discovery narrows the window of time during which the Himalayas could have been uplifted. When the central part of the Tibetan plateau was uplifted more than 40 million years ago, Mount Everest and the rest of the Himalayas were still part of a deep ocean basin, Zhao said.

The Himalayan region is very complicated, however, and other groups are working to determine the timing of its uplift more precisely, said Lippert. "Our main contribution has been the data we gathered from the north-central part of the plateau, which has not been well studied," he said.

Zhao noted that the U.S. researchers could not have gained access to this area without the support of their Chinese colleagues. This long-term collaboration has included exchanges of graduate students between UCSC and Chinese universities, as well as opportunities for UCSC undergraduates to conduct field research in Tibet. "It has been a very good research collaboration, with a strong educational component as well," Zhao said.

http://www.terradaily.com/reports/New_Findings_From_Tibetan_Plateau_Suggest_Uplift_Occurred_In_Stages_999.html

posted in Geology - 0 replies

10 questions shaping 21st-century earth science identified

bobs — Wed, 12 Mar 2008 20:59:42 GMT

Ten questions driving the geological and planetary sciences were identified today in a new report by the National Research Council. Aimed at reflecting the major scientific issues facing earth science at the start of the 21st century, the questions represent where the field stands, how it arrived at this point, and where it may be headed.

"With all the advancements over the last 20 years, we can now get a better picture of Earth by looking at it from micro- to macro-perspectives, such as discerning individual atoms in minerals or watching continents drift and mountains grow," said Donald J. DePaolo, professor of geochemistry at the University of California at Berkeley and chair of the committee that wrote the report. "To keep the field moving forward, we have to look to the past and ask deeper fundamental questions, about the origins of the Earth and life, the structure and dynamics of planets, and the connections between life and climate, for example."

The report was requested by the U.S. Department of Energy, National Science Foundation, U.S. Geological Survey, and NASA. The committee selected the question topics, without regard to agency-specific issues, and covered a variety of spatial scales -- subatomic to planetary -- and temporal scales -- from the past to the present and beyond.

The committee canvassed the geological community and deliberated at length to arrive at 10 questions. Some of the questions present challenges that scientists may not understand for decades, if ever, while others are more tractable, and significant progress could be made in a matter of years, the report says. The committee did not prioritize the 10 questions -- listed with associated illustrative issues below -- nor did it recommend specific measures for implementing them.

HOW DID EARTH AND OTHER PLANETS FORM?
While scientists generally agree that this solar system's sun and planets came from the same nebular cloud, they do not know enough about how Earth obtained its chemical composition to understand its evolution or why the other planets are different from one other. Although credible models of planet formation now exist, further measurements of solar system bodies and extrasolar objects could offer insight to the origin of Earth and the solar system.

WHAT HAPPENED DURING EARTH'S "DARK AGE" (THE FIRST 500 MILLION YEARS)?
Scientists believe that another planet collided with Earth during the latter stages of its formation, creating debris that became the moon and causing Earth to melt down to its core. This period is critical to understanding planetary evolution, especially how the Earth developed its atmosphere and oceans, but scientists have little information because few rocks from this age are preserved.

HOW DID LIFE BEGIN?
The origin of life is one of the most intriguing, difficult, and enduring questions in science. The only remaining evidence of where, when, and in what form life first appeared springs from geological investigations of rocks and minerals. To help answer the question, scientists are also turning toward Mars, where the sedimentary record of early planetary history predates the oldest Earth rocks, and other star systems with planets.

HOW DOES EARTH'S INTERIOR WORK, AND HOW DOES IT AFFECT THE SURFACE?
Scientists know that the mantle and core are in constant convective motion. Core convection produces Earth's magnetic field, which may influence surface conditions, and mantle convection causes volcanism, seafloor generation, and mountain building. However, scientists can neither precisely describe these motions, nor calculate how they were different in the past, hindering scientific understanding of the past and prediction of Earth's future surface environment.

WHY DOES EARTH HAVE PLATE TECTONICS AND CONTINENTS?
Although plate tectonic theory is well established, scientists wonder why Earth has plate tectonics and how closely it is related to other aspects of Earth, such as the abundance of water and the existence of the continents, oceans, and life. Moreover, scientists still do not know when continents first formed, how they remained preserved for billions of years, or how they are likely to evolve in the future. These are especially important questions as weathering of the continental crust plays a role in regulating Earth's climate.

HOW ARE EARTH PROCESSES CONTROLLED BY MATERIAL PROPERTIES?
Scientists now recognize that macroscale behaviors, such as plate tectonics and mantle convection, arise from the microscale properties of Earth materials, including the smallest details of their atomic structures. Understanding materials at this microscale is essential to comprehending Earth's history and making reasonable predictions about how planetary processes may change in the future.

WHAT CAUSES CLIMATE TO CHANGE -- AND HOW MUCH CAN IT CHANGE?
Earth's surface temperature has remained within a relatively narrow range for most of the last 4 billion years, but how does it stay well-regulated in the long run, even though it can change so abruptly" Study of Earth's climate extremes through history -- when climate was extremely cold or hot or changed quickly -- may lead to improved climate models that could enable scientists to predict the magnitude and consequences of climate change.

HOW HAS LIFE SHAPED EARTH -- AND HOW HAS EARTH SHAPED LIFE?
The exact ways in which geology and biology influence each other are still elusive. Scientists are interested in life's role in oxygenating the atmosphere and reshaping the surface through weathering and erosion. They also seek to understand how geological events caused mass extinctions and influenced the course of evolution.

CAN EARTHQUAKES, VOLCANIC ERUPTIONS, AND THEIR CONSEQUENCES BE PREDICTED?
Progress has been made in estimating the probability of future earthquakes, but scientists may never be able to predict the exact time and place an earthquake will strike. Nevertheless, they continue to decipher how fault ruptures start and stop and how much shaking can be expected near large earthquakes. For volcanic eruptions, geologists are moving toward predictive capabilities, but face the challenge of developing a clear picture of the movement of magma, from its sources in the upper mantle, through Earth's crust, to the surface where it erupts.

HOW DO FLUID FLOW AND TRANSPORT AFFECT THE HUMAN ENVIRONMENT?
Good management of natural resources and the environment requires knowledge of the behavior of fluids, both below ground and at the surface, and scientists ultimately want to produce mathematical models that can predict the performance of these natural systems. Yet, it remains difficult to determine how subsurface fluids are distributed in heterogeneous rock and soil formations, how fast they flow, how effectively they transport dissolved and suspended materials, and how they are affected by chemical and thermal exchange with the host formations.

Source: The National Academies

http://www.physorg.com/news124539902.html

posted in Geology - 4 replies

Scientist answers how Peruvian meteorite made it to Earth

bobs — Tue, 11 Mar 2008 21:51:18 GMT

It made news around the world: On Sept. 15, 2007, an object hurtled through the sky and crashed into the Peruvian countryside. Scientists dispatched to the site near the village of Carancas found a gaping hole in the ground.

Peter Schultz, professor of geological sciences at Brown University and an expert in extraterrestrial impacts, went to Peru to learn more. For the first time, he will present findings from his travels at the 39th annual Lunar and Planetary Science Conference in League City, Texas, in a talk scheduled for 2 p.m. on March 11, 2008. Brown graduate student Robert “Scott” Harris collaborated on the research, joined by Jose Ishitsuka, a Peruvian astrophysicist, and Gonzalo Tancredi, an astronomer from Uruguay.

What Schultz and his team found is surprising. The object that slammed into a dry riverbed in Peru was a meteorite, and it left a 49-foot-wide crater. Soil ejected from the point of impact was found nearly four football fields away. When Schultz’s team analyzed the soil where the fireball hit, he found “planar deformation features,” or fractured lines in sand grains found in the ground. Along with evidence of debris strewn over a wide area, the shattered sand grains told Schultz that the meteorite had maintained a high rate of speed as it shot through the atmosphere. Scientists think it was traveling at roughly 15,000 miles per hour at the moment of impact.

“Normally with a small object like this, the atmosphere slows it down, and it becomes the equivalent of a bowling ball dropping into the ground,” Schultz said. “It would make a hole in the ground, like a pit, but not a crater. But this meteorite kept on going at a speed about 40 to 50 times faster than it should have been going.”

Scientists have determined the Carancas fireball was a stony meteorite – a fragile type long thought to be ripped into pieces as it enters the Earth’s atmosphere and then leaves little more than a whisper of its journey.

Yet the stony meteorite that struck Peru survived its passage mostly intact before impact.

“This just isn’t what we expected,” Schultz said. “It was to the point that many thought this was fake. It was completely inconsistent with our understanding how stony meteorites act.”

Schultz said that typically fragments from meteorites shoot off in all directions as the object speeds to Earth. But he believes that fragments from the Carancas meteorite may have stayed within the fast-moving fireball until impact. How that happened, Schultz thinks, is due to the meteorite’s high speed. At that velocity, the fragments could not escape past the “shock-wave” barrier accompanying the meteorite and instead “reconstituted themselves into another shape,” he said.

That new shape may have made the meteorite more aerodynamic – imagine a football passing through air versus a cinderblock – meaning it encountered less friction as it sped toward Earth, hitting the surface as one large chunk.

“It became very streamlined and so it penetrated the Earth’s atmosphere more efficiently,” Schultz said.

Schultz’s theory could upend the conventional wisdom that all small, stony meteorites disintegrate before striking Earth. If correct, it could change the thinking about the size and type of extraterrestrial objects that have bombarded the Earth for eons and could strike our planet next.

“You just wonder how many other lakes and ponds were created by a stony meteorite, but we just don’t know about them because when these things hit the surface they just completely pulverize and then they weather,” said Schultz, director of the Northeast Planetary Data Center and the NASA/Rhode Island University Space Grant Consortium.

Schultz’s research could have implications for Mars, where craters have been discovered in recent missions. “They could have come from anything,” he said. “It would be interesting to study these small craters and see what produced them. Perhaps they also will defy our understanding.”

Source: Brown University

http://www.physorg.com/news124466115.html

posted in Geology - 0 replies

Rock: Electrons Run Through It

bobs — Tue, 11 Mar 2008 09:51:45 GMT

ScienceDaily (Mar. 11, 2008) — If the Flintstones had electricity, their wires might have been made of rock. New results in Science Express show that a chunk of hematite can conduct electrons under certain chemical conditions. In addition, the current causes some mineral surfaces to build up while others degrade. These results with iron oxide might be important for water quality, soil evolution, and environmental cleanup.

"Considering iron as an important nutrient, the finding could help us understand how soils evolve from nutrient rich to nutrient poor," says lead investigator Kevin Rosso, a chemist at the Department of Energy's Pacific Northwest National Laboratory. "And it has implications for other common minerals such as pyrite and manganese oxides -- even particles in the atmosphere."

Mineral surfaces are linked by electrons traveling through mineral's bulk. Scientists have long known that electrons can travel through some iron oxides when a voltage is applied, but they have assumed that electrons stemming from chemical reactions alone won't move spontaneously through the mineral's bulk. That long-standing assumption has caused chemists to treat different faces of a hunk of mineral as independent entities that don't 'communicate' with each other. New results, published online March 6, 2008 in Science Express, suggest otherwise.

"Now we know reactions at different faces of these minerals can couple together and yield behavior unique to semiconducting minerals," says Rosso.

Minerals often exist as individual crystals in rocks at a stream's bottom, where they keep busy reacting with the water flowing around them. Understanding this chemistry is central to understanding how elements move through sediments, maintaining good water quality, and cleaning up pollution. To elicit the details, scientists study what effect acids and other forms of chemicals have on mineral surfaces.

When Rosso and PNNL colleague Svetlana Yanina immersed a cube-shaped hematite crystal in an acid solution in the absence of oxygen, they expected all surfaces to degrade. But when the chemists examined the surfaces at high magnification, they found one surface that didn't. This surface grew pyramid-like mounds rising from the top. "The whole crystal wants to dissolve, thermodynamically," says Rosso. "So we didn't expect to see that growth."

No one had previously reported this buildup, so the team modified their experiments to try to prevent the pyramids from growing. "In fact, we spent a year trying to get rid of it," Rosso says.

One path to getting rid of something is to understand how it got there in the first place, so they decided to explore how the pyramids formed. The researchers performed atomic force, scanning electron and transmission electron microscopy at the DOE's Environmental Molecular Sciences Laboratory on the PNNL campus, as well as electrical potential measurements of the individual surfaces.

Because hematite is a crystal of iron oxide, the sides and the top (and bottom) are structurally different, and therefore have different chemical properties. The team wondered if the iron being deposited on the top came from iron dissolving from the sides, building up in solution, and then redepositing.

To test this, they separated the six cube surfaces into groups: They took two cubes, protected four sides from the solution on one, and on the other, protected the top and bottom. The acidic solution chewed away the unprotected surfaces, as expected. But the chemists didn't see any buildup on the unprotected top and bottom faces and instead saw degradation. This indicated the breakdown and buildup were not independent of each other.

"The hematite won't grow pyramids without that surface being connected to the dissolving ones," says Rosso.

The required physical connection hinted at electron conduction. Iron in solution, or Fe(II), contains one more electron than the iron in the crystal, Fe(III). If Fe(II) landed on the top, it might react with the surface, incorporate into the crystal and give up its electron. The electron could then flow through the crystal to the sides, where an atom of Fe(III) could pick up the electron and dissolve into the solution.

To prove this, the chemists connected the electron flow with a wire. When they repeated the first experiment but connected the two cubes with a dab of silver, the team restored the pyramid buildup. Additional experiments allowed them to measure the electrical potential driving the current flow, which came out to 200 millivolts -- about 6% of the power needed for a keychain LED light, or about twice as much as in a nerve cell.

Reference: S. V. Yanina and K. M. Rosso, "Linked reactivity at mineral-water interfaces through bulk crystal conduction," published online at Science Express, March 6, 2008, 10.1126/science.1151614.

This work was supported by the Department of Energy's Office of Basic Energy Sciences Geosciences Program.

Adapted from materials provided by DOE/Pacific Northwest National Laboratory.

http://www.sciencedaily.com/releases/2008/03/080306183140.htm

posted in Geology - 0 replies

Researchers confirm discovery of Earth's inner, innermost core

bobs — Mon, 10 Mar 2008 22:16:05 GMT

Geologists at the University of Illinois have confirmed the discovery of Earth’s inner, innermost core, and have created a three-dimensional model that describes the seismic anisotropy and texturing of iron crystals within the inner core.

“For many years, we have been like blind men touching different parts of an elephant,” said U. of I. geologist Xiaodong Song. “Now, for the fist time, we have a sense of the entire elephant, and see what the inner core of Earth really looks like.”

Using both newly acquired data and legacy data collected around the world, Song and postdoctoral research associate Xinlei Sun painstakingly probed the shape of Earth’s core. The researchers report their findings in a paper accepted for publication in the journal Earth and Planetary Science Letters.

Composed mainly of iron, Earth’s core consists of a solid inner core about 2,400 kilometers in diameter and a fluid outer core about 7,000 kilometers in diameter. The inner core plays an important role in the geodynamo that generates Earth’s magnetic field.

The solid inner core is elastically anisotropic; that is, seismic waves have different speeds along different directions. The anisotropy has been found to change with hemisphere and with radius. In the latest work, Sun and Song describe another anomaly – a global structure – found within the inner core.

“To constrain the shape of the inner core anisotropy, we needed a uniform distribution of seismic waves traveling in all directions through the core,” Sun said. “Since the seismic waves we studied were generated by earthquakes, one challenge was acquiring enough seismic waves recorded at enough stations.”

In their analysis, Sun and Song used a three-dimensional tomography technique to invert the anisotropy of the inner core. They parameterized the anisotropy of the inner core in both radial and longitudinal directions. The researchers then used a three-dimensional ray tracing method to trace and retrace the seismic waves through the inner core iteratively.

What they found was a distinct change in the inner core anisotropy, clearly marking the presence of an inner inner core with a diameter of about 1,180 kilometers, slightly less than half the diameter of the inner core.

The layering of the core is interpreted as different texturing, or crystalline phase, of iron in the inner core, the researchers say.

“Our results suggest the outer inner core is composed of iron crystals of a single phase with different degrees of preferred alignment along Earth’s spin axis,” Sun said. “The inner inner core may be composed of a different phase of crystalline iron or have a different pattern of alignment.”

Although the anisotropy of the inner core was proposed 20 years ago, “this is the first time we have been able to piece everything together to create a three-dimensional view,” Song said. “This view should help us better understand the character, mineral properties and evolution of Earth’s inner core.”

Source: University of Illinois at Urbana-Champaign

http://www.physorg.com/news124372414.html

posted in Geology - 0 replies

You Can't Make This Stuff Up....

Badger — Tue, 26 Feb 2008 00:29:04 GMT

Well, actually it seems you can. From the same folks who bring us the Creation Museum in Knuckle Drag, Kentucky we now have a peer reviewed journal of Scientific papers anchored in creationist science.

"I’m not making this up, I swear. “Answers in Genesis,” the same nonsensical outlet that has given us Ken Ham’s “Creation Museum,” recently launched a “peer reviewed” “technical” journal, called, of course, “Answers Research Journal.” The idea, we learn from the “About” section of the journal’s web page, is to provide an outlet for “interdisciplinary scientific and other relevant research from the perspective of the recent Creation and the global Flood within a biblical framework.” See, apparently “there has been a pressing need for such a journal,” because “people want to know they can trust what is published on the Internet,” and they “can give you absolute assurance that the papers we will be publishing in Answers Research Journal are of the highest scientific and theological standard.” Of course, a high theological standard is a bit of an oxymoron, but let’s not quibble on the details."

I checked out the web site and the first thing I stumble across here: http://www.answersingenesis.org/arj/

is a paper on Catastrophic Granite Formation ( http://www.answersingenesis.org/articles/arj/v1/n1#catastrophic-granite-formation) which suggests - no PROVES - that batholithic granites can emplace into country rock and cool in periods of hundred of years.

With this in mind have a laugh. The reading's worth it.

posted in Geology - 4 replies

Tiny pieces of 'deep time' brought to the surface

bobs — Mon, 03 Mar 2008 22:19:20 GMT

Three-billion-year-old zircon microcrystals found in northern Ontario are proving to be a new record of the processes that form continents and their natural resources, including gold and diamonds.

The discovery was made recently by an international research team led by Earth Sciences professor Desmond Moser at The University of Western Ontario. Measuring no more than the width of a human hair, the 200-million-year growth span of these ancient microcrystals is longer than any previously discovered.

The findings provide a new record of planetary evolution and contradict previous experimental predictions that the crystals would change when exposed to heat and pressure upon burial in the deep Earth. Instead, they have an incredible ‘memory’ of their time below volcanoes, of transport to the shores of ancient oceans and of their burial beneath now-extinct mountain ranges billions of years before the time of dinosaurs. “This research shows that these crystals are incredibly resistant to change and proves for the first time that the growth zones we see inside them contain an accurate record of their movements through and around the Earth,” says Moser.

Containing trace amounts of uranium, the crystals continued to grow over hundreds of millions of years, even as the planet evolved and underwent a series of dramatic shifts. “The oldest pieces of our planet are crystals of zircon,” says Moser. “These crystals are the memory cells of the Earth and with our study we can now say they are an accurate recorder of planetary evolution over eons – in the same way that rings on an old growth tree can record changes in a forest over hundreds of years.”

Keeping with the tree analogy, Moser found that these crystals had roughly circular growth zones that he was able to date and analyze with specialized ion probes. These zones track the formation of the early North American continent, from its beginning as a series of volcanic island chains, to its eventual fusion into a large, thick continental plate that became the core of North America.

As the crystals formed around the same time as gold, diamond and other metal deposits, this research provides not only insight into the formation of Earth itself, it can also help answer the question, “Did plate tectonics operate early in our planet’s history or did some other process create the large metal and diamond deposits of the Canadian Shield?” “It also provides a new tool for dating the appearance of oceans on other rocky planets like Mars, where Rover results indicate zircon crystals should exist” says Moser.

Over the course of millions of years, the crystals have been pushed back to the surface from depths of 30 kilometres by a series of pushes on the edges of the original continent, which give us globally-rare exposures in northern Ontario. “It’s not every day you find a piece of the deep Earth that you can walk around on and explore,” Moser says.

Moser’s findings are further detailed in the March issue of Geology, published by the Geological Society of America.

Source: University of Western Ontario

http://www.physorg.com/news123768995.html

posted in Geology - 0 replies

Earthquake theory stretched in Central Asia study

bobs — Mon, 25 Feb 2008 23:38:06 GMT

(Also posted in : http://awesomenature.tribe.net/ )

The entrenched political instability in Pakistan and Afghanistan is of grave concern to many in the West – but now geologists at ANU have suggested a new cause for the seismic instability that regularly rocks the region.

Scientists from the Research School of Earth Sciences at ANU argue that the frequent and dramatic earthquakes in the Hindu Kush mountain range are likely to be the result of a slow, elastic stretching of a sub-surface feature called a boudin. Their findings, published in the journal Nature Geoscience today, run contrary to the theory that earthquakes usually result from the abrasive collisions between tectonic plates.

“We’ve always thought of earthquakes as being brittle, but our research that the slow, ductile stretching of certain geological features can build up energy that is then suddenly released, causing major seismic upheaval,” said lead author Professor Gordon Lister.

Using computer modelling, the researchers were able to show that the long, hard boudin that sits vertically beneath the Hindu Kush is being stretched as its lower parts are pulled into the Earth’s mantle. “It’s like a metal rod that is being pulled at both ends,” Professor Lister explained. “Eventually the stretching will suddenly accelerate, releasing energy in the process.”

The boudin is thought to be a remnant of the oceanic plate that was pushed into the Earth’s mantle when India collided with Asia. Professor Lister said that eventually it too will eventually drop into the deeper mantle, but that is likely to take thousands, if not millions, of years.

“This is important work, as it suggests a new way of understanding how earthquakes happen. It feeds into the potential for us to eventually develop new and innovative long-range forecasting techniques” Professor Lister said.

“It’s no accident that nations like Afghanistan and Pakistan are places of unrest, because the people there are living in constant hardship, and this results in part from periodic catastrophe’s they must endure, for example related to earthquakes. If we don’t put more effort into understanding the how and why, and also into how we might eventually better forecast earthquakes, humankind is forever doomed to deal with the consequences.”

The researchers have developed a software program called eQuakes that allows them to model earthquake patterns against geological features.

Source: Australian National University

http://www.physorg.com/news123171934.html

posted in Geology - 0 replies

Request: Modeling textbook

Inaras — Tue, 05 Feb 2008 02:53:01 GMT

I'm looking for a good textbook on glacial modeling. Anyone have any recommendations?

posted in Geology - 1 reply

Man-made changes bring about new epoch in Earth's history

bobs — Sat, 26 Jan 2008 14:16:30 GMT

"Geologists from the University of Leicester propose that humankind has so altered the Earth that it has brought about an end to one epoch of Earth’s history and marked the start of a new epoch.

Jan Zalasiewicz and Mark Williams at the University of Leicester and their colleagues on the Stratigraphy Commission of the Geological Society of London have presented their research in the journal GSA Today.

In it, they suggest humans have so changed the Earth that on the planet the Holocene epoch has ended and we have entered a new epoch - the Anthropocene.

They have identified human impact through phenomena such as:

-- Transformed patterns of sediment erosion and deposition worldwide
-- Major disturbances to the carbon cycle and global temperature
-- Wholesale changes to the world’s plants and animals
-- Ocean acidification

The scientists analysed a proposal made by Nobel Prize-winning chemist Paul Crutzen in 2002. He suggested the Earth had left the Holocene and started the Anthropocene era because of the global environmental effects of increased human population and economic development.

The researchers argue that the dominance of humans has so physically changed Earth that there is increasingly less justification for linking pre- and post-industrialized Earth within the same epoch - the Holocene.

The scientists said their findings present the scholarly groundwork for consideration by the International Commission on Stratigraphy for formal adoption of the Anthropocene as the youngest epoch of, and most recent addition to, the Earth's geological timescale.

They state: “Sufficient evidence has emerged of stratigraphically significant change (both elapsed and imminent) for recognition of the Anthropocene—currently a vivid yet informal metaphor of global environmental change—as a new geological epoch to be considered for formalization by international discussion.”

Source: University of Leicester

http://www.physorg.com/news120484292.html

posted in Geology - 1 reply

fault maps

Chili_Bonbons — Sat, 19 Jan 2008 21:02:37 GMT

does anyone know of any links to world (quake/plate) fault maps besides the ones through the usgs website that they would recommend?

posted in Geology - 6 replies

Hot springs microbes hold key to dating sedimentary rocks, researchers say

bobs — Tue, 22 Jan 2008 22:22:02 GMT

Scientists studying microbial communities and the growth of sedimentary rock at Mammoth Hot Springs in Yellowstone National Park have made a surprising discovery about the geological record of life and the environment.

Their discovery could affect how certain sequences of sedimentary rock are dated, and how scientists might search for evidence of life on other planets.

“We found microbes change the rate at which calcium carbonate precipitates, and that rate controls the chemistry and shape of calcium carbonate crystals,” said Bruce Fouke, a professor of geology and of molecular and cellular biology at the University of Illinois.

In fact, the precipitation rate can more than double when microbes are present, Fouke and his colleagues report in a paper accepted for publication in the Geological Society of America Bulletin.

The researchers’ findings imply changes in calcium carbonate mineralization rates in the rock record may have resulted from changes in local microbial biomass concentrations throughout geologic history.

A form of sedimentary rock, calcium carbonate is the most abundant mineral precipitated on the surface of Earth, and a great recorder of life.

“As calcium carbonate is deposited, it leaves a chemical fingerprint of the animals and environment, the plants and bacteria that were there,” said Fouke, who also is affiliated with the university’s Institute for Genomic Biology.

The extent to which microorganisms influence calcium carbonate precipitation has been one of the most controversial issues in the field of carbonate sedimentology and geochemistry. Separating biologically precipitated calcium carbonate from non-biologically precipitated calcium carbonate is difficult.

Fouke’s research team has spent 10 years quantifying the physical, chemical and biological aspects of the hot springs environment. The last step in deciphering the calcium carbonate record was performing an elaborate field experiment, which drew water from a hot springs vent and compared deposition rates with and without microbes being present.

“Angel Terrace at Mammoth Hot Springs in Yellowstone National Park is an ideal, natural laboratory because of the high precipitation rates and the abundance of microbes,” Fouke said. “Calcium carbonate grows so fast – millimeters per day – we can examine the interaction between microorganisms and the calcium-carbonate precipitation process.”

The researchers found that the rate of precipitation drops drastically – sometimes by more than half – when microbes are not present.

“So one of the fingerprints of calcium carbonate deposition that will tell us for sure if there were microbes present at the time it formed is the rate at which it formed,” Fouke said. “And, within the environmental and ecological context of the rock being studied, we can now use chemistry to fingerprint the precipitation rate.”

In a second paper, to appear in the Journal of Sedimentary Research, Fouke and colleagues show how the calcium carbonate record in a spring’s primary flow path can be used to reconstruct the pH, temperature and flux of ancient hot springs environments. The researchers also show how patterns in calcium carbonate crystallization can be used to differentiate signatures of life from those caused by environmental change.

“This means we can go into the rock record, on Earth or other planets, and determine if calcium carbonate deposits were associated with microbial life,” Fouke said.

Source: University of Illinois at Urbana-Champaign

http://www.physorg.com/news120228971.html

posted in Geology - 1 reply

Shrinking ice means Greenland is rising fast

bobs — Fri, 02 Nov 2007 21:45:50 GMT

18:06 02 November 2007
NewScientist.com news service
Catherine Brahic

Greenland appears to be floating upwards – its landmass is rising up to 4 centimetres each year, scientists reveal.
And the large country's new-found buoyancy is a symptom of Greenland's shrinking ice cap, they add.
"The Earth is elastic and if you put a load on top of it, then the surface will move down; if you remove the load, then the surface will start rising again," explains Shfaqat Khan of the Danish National Space Center in Copenhagen.
In the case of Greenland, the "load" is its ice cap, he says.
Such uplift is not an unknown phenomenon. Relic "raised beaches" are relatively common in some areas, where the loss of ice after the last Ice Age caused the land to rise, leaving beaches often metres above the water.
Khan and his team detected the country's uplift using measurements from GPS stations located on the bedrock, underneath the ice.
Khan and his colleagues have been monitoring data from these stations since 2001 and have found that the southeastern tip of the country is definitely rising upwards. They have also found that the rate of rise has dramatically accelerated in recent years.
Sudden acceleration"Before 2004, the uplift was about 0.5 cm to 1 cm per year," Khan told New Scientist. Since then, however, the land has been rising four times faster. "This means that since 2004, Greenland has been losing four times more ice than before," he says.
These figures roughly correspond to other measurements of how much ice is being lost by the ice sheet.
In 2006, a team led by Eric Rignot from NASA's Jet Propulsion Laboratory in Pasadena, California, US, published findings suggesting that there had been a sudden acceleration in the rate at which Greenland was losing ice during 2004.
Khan says they are unsure what caused the acceleration and cautions that it is impossible to say if this speedy loss will be maintained in the long-term.
"It could be that more melt water is flowing into crevasses, which is making the glaciers flow into the ocean faster," he says. Research done at NASA has shown that warmer temperatures due to global warming are melting ice at the surface of Greenland's glaciers.
Vertical riversThe warm water is boring holes through the glaciers, creating vertical rivers whose water lubricates the bottom of the glaciers once it reaches the bedrock. This process makes glaciers speed faster towards the sea, where they break off and eventually melt.
Calculations by Khan and his team land suggest the uplift is mostly due to glaciers flowing out to the sea and breaking off. They calculated that some ice is also lost through melting, however.
This is consistent with a review of the polar meltdown which was published in March 2007.
At the time, Duncan Wingham of University College London in the UK had told New Scientist: "It has become very clear over the past 5 years that these sheets are not losing most of their mass through melting. They are losing it because the ice is flowing into the ocean faster than the snow is replacing it."

Journal reference: Geophysical Research Letters (DOI: 10.1029/2007GL031468)

http://technology.newscientist.com/channel/tech/dn12872-shrinking-ice-means-greenland-is-rising-fast.html?feedId=online-news_rss20

posted in Geology - 0 replies

Nano-coatings grease earthquake zones

bobs — Wed, 31 Oct 2007 22:48:48 GMT

Samples of rock from deep inside the San Andreas Fault could shake up scientists' notions about why some fault zones move slowly and steadily while others balk for a time and then shift suddenly and violently, producing major earthquakes.

'There's been strong interest in finding signatures in rocks that would characterize a fault as creeping or seismic,' said University of Michigan geological sciences professor Ben van der Pluijm, who will discuss recent findings today (Oct. 30) in a symposium during the 119th annual meeting of the Geological Society of America in Denver.

Some scientists have speculated that fluids facilitate slippage; others have focused on bits of serpentine—a greenish mineral that can crystallize as slippery talc under certain conditions—which were found in core samples retrieved from the San Andreas Fault.

But van der Pluijm and coworkers at U-M and the University of Strasbourg in France aren't convinced of those explanations for slippery fault behavior. 'We think the answer is in clay,' he said.

He bases his opinion on analyses of material brought up from a depth of two miles below the fault's surface as part of the San Andreas Fault Observatory at Depth (SAFOD) project. SAFOD, which is establishing the world's first underground earthquake observatory, is a major research component of EarthScope, an ambitious, $197-million federal program to investigate the forces that shape the North American continent and the physical processes controlling earthquakes and volcanic eruptions.

Earth scientists are especially interested in the San Andreas Fault—that notorious fracture running 800 miles along the length of California—because major earthquakes occur on such plate boundaries. The SAFOD site, near Parkfield, Calif., sits on a creeping section of the fault that moves regularly and incrementally, but does not produce large earthquakes.

Van der Pluijm's samples are 'not glamorous to look at. They're not spectacular to showcase; they just look like dirt.' But it's how the 'dirt' forms and behaves in active fault zones that makes it noteworthy. Through a combination of chemical and mechanical processes, the grains making up the rock develop 'nano-coatings' of clay on their surfaces, which act something like grease on ball bearings.

'We can show that these nano-coatings, which are only a few hundred nanometers thick, occur all around broken-up, fractured grains, and they occur exactly in the places where they can affect the 'weakness' of the fault,'—how easily it moves. We think that as these grains move past one another, the coatings facilitate the displacement.'

By dating the first suite of samples collected in 2005, the researchers show that these coatings are relatively recent. 'They form in actively creeping fault zones,' van der Pluijm said, 'creating a dynamic environment where rocks change while faulting occurs,' Finding signatures that reveal whether a fault is creeping or seismic won't immediately aid in earthquake prediction, van der Pluijm said. 'But it will help us understand what processes govern this behavior.'

Source: University of Michigan

http://www.physorg.com/news113067833.html

posted in Geology - 0 replies

Seismologists see Earth's interior as interplay........

bobs — Thu, 25 Oct 2007 21:42:36 GMT

.......... between temperature, pressure and chemistry.

Seismologists in recent years have recast their understanding of the inner workings of Earth from a relatively benign homogeneous environment to one that is highly dynamic and chemically diverse. This new view of Earth’s inner workings depicts the planet as a living organism where events that happen deep inside can affect what happens at its surface, like the rub and slip of tectonic plates and the rumble of the occasional volcano.

New research into these dynamic inner workings are now showing that Earth’s upper mantle (an area that extends down to 660 km) exhibits how far more than just temperature and pressure play a role in the dynamics of the deep interior.

A study by Nicholas Schmerr, a doctoral student in Arizona State University’s School of Earth and Space Exploration is shedding light on these processes and showing that they are not just temperature driven. His work helps assess the role chemistry plays in the structure of Earth’s mantle.

The simplest model of the mantle — the layer of the Earth’s interior just beneath the crust — is that of a convective heat engine. Like a pot of boiling water, the mantle has parts that are hot and welling up, as in the mid-Atlantic rift, and parts that are cooler and sinking, as in subduction zones. There, crust sinks into the Earth, mixing and transforming into different material “phases,” like graphite turning into diamond.

“A great deal of past research on mantle structure has interpreted anomalous seismic observations as due to thermal variations within the mantle,” Schmerr said. “We’re trying to get people to think about how the interior of the Earth can be not just thermally different in different regions but also chemically different.”

The research, which Schmerr conducted with Edward Garnero, a professor in ASU’s School of Earth and Space Exploration, was published in the October 26 issue of the journal Science. Their article is titled “Upper Mantle Discontinuity Topography from Thermal and Chemical Heterogeneity.”

Schmerr’s work shows that Earth’s interior is far from homogeneous, as represented in traditional views, but possesses an exotic brew of down and upwelling material that goes beyond simply hot and cold convection currents. His work demonstrates the need for a chemical component in the convection process.

At key depths within Earth, rock undergoes a compression to a denser material where its atoms rearrange due to the ever-increasing pressure. Earth scientists have long known that the dominant mineral olivine in Earth’s outer shell, compresses into another mineral named wadsleyite at 410 km (255 mile) depth, which then changes into ringwoodite around 520 km (325 mile) depth and then again into perovskite + magnesiowüstite at 660 km (410 mile) depth.

These changes in crystal structure, called phase transitions, are sensitive to temperature and pressure, and the transition depth moves up and down in the mantle in response to relatively hot or cold material.

Beneath South America, Schmerr’s research found the 410 km phase boundary bending the wrong way. The mantle beneath South America is predicted to be relatively cold due to cold and dense former oceanic crust and the underlying tectonic plate sinking into the planet from the subduction zone along the west coast. In such a region, the 410 km boundary would normally be upwarped, but using energy from far away earthquakes that reflect off the deep boundaries in this study area, Schmerr and Garnero found that the 410 km boundary significantly deepened.

“Our discovery of the 410 boundary deflecting downwards in this region is incompatible with previous assumptions of upper mantle phase boundaries being dominantly modulated by the cold temperature of the subducting crust and plate,” Garnero said.

Geologists and geochemists have long suspected that subduction processes are driven by more than temperature alone. A sinking oceanic plate is compositionally distinct from the mantle, and brings with it minerals rich in elements that can alter the range of temperatures and pressures at which a phase change takes place.

“We’re not the first to suggest chemical heterogeneities in the mantle, however, we are the first to suggest hydrogen or iron as an explanation for an observation at this level of detail and over a geographical region spanning several thousands of kilometers,” Schmerr said.

Hydrogen from ocean water can be bonded to minerals within the crust and carried down as it is subducted into the mantle, Schmerr explained. When the plate reaches the 410 km phase boundary, the hydrogen affects the depth of the olivine to wadsleyite phase transition, reducing the density of the newly formed wadsleyite, and making it relatively more buoyant than its surrounding material. This hydrated wadsleyite then “pools” below the 410 km boundary, and the base of the wet zone reflects the seismic energy observed by Schmerr.

Alternatively, subduction can bring the iron-poor and magnesium-enriched residues of materials that melted near the surface to greater depths. Mantle mineral compositions enriched in magnesium are stable to greater depths than usual, resulting in a deeper phase transition.

“Either hypothesis explains our observation of a deep 410-km boundary beneath South American subduction, and both ideas invoke chemical heterogeneity,” Schmerr said. “However, if we look deeper, at the 660-km phase transition, we find it at a depth consistent with the mantle being colder there. This tells us that the mantle beneath South America is both thermally cold and chemically different.”

To make their observations, Schmerr and Garnero used data from the USArray, which is part of the National Science Foundation-funded EarthScope project.

“The USArray essentially is 500 seismometers that are deployed in a movable grid across the United States,” Schmerr said. “It’s an unheard of density of seismometers.”

Schmerr and Garnero used seismic waves from earthquakes to measure where phase transitions occur in the interior of Earth by looking for where waves reflect off these boundaries. In particular, they used a set of seismic waves that reflect off the underside of phase transitions halfway between the earthquake and the seismometer. The density and other characteristics of the material they travel through affect how the waves move, and this gives geologists an idea of the structure of the inner Earth.

“Seismic discontinuities are abrupt changes in density and seismic wave speeds that usually occur where a mineral undergoes a phase change -- such as when olivine transitions to wadsleyite, or ringwoodite transforms into perovskite and magnesiowüstite. The transformed mineral is generally denser, and typically seismic waves travel faster through it as well. Discontinuities reflect seismic energy, which allows us to figure out how deep they are. They are found throughout the world at certain average depths -- in this case, at 410 and 660 km,” Schmerr said. “Because these phase transitions are not always uniform, these layers are bumpy with ridges and troughs.”

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“Right now the big question that we have is about Earth’s thermal state and its chemical state, and there are a lot of ways we can go about getting at that information,” Schmerr said. “This study lets us look at one particular area in Earth and constrain the temperature and composition to a certain degree, imaging this structure inside the Earth and saying, These are not just thermal effects -- there’s also some sort of chemical aspect to it as well.”

Source: Arizona State University

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