Asteroid impacts significantly altered ancient Earth

August 1, 2014

This is an artistic conception of the early Earth, showing a surface pummeled by large impacts, resulting in extrusion of deep seated magma onto the surface. At the same time, distal portion of the surface could have retained liquid water. Credit: Simone Marchi

New research shows that more than four billion years ago, the surface of Earth was heavily reprocessed — or mixed, buried and melted — as a result of giant asteroid impacts. A new terrestrial bombardment model based on existing lunar and terrestrial data sheds light on the role asteroid bombardments played in the geological evolution of the uppermost layers of the Hadean Earth (approximately 4 to 4.5 billion years ago).
An international team of researchers published their findings in the July 31, 2014 issue of Nature.

“When we look at the present day, we have a very high fidelity timeline over the last about 500 million years of what’s happened on Earth, and we have a pretty good understanding that plate tectonics and volcanism and all these kinds of processes have happened more or less the same way over the last couple of billion years,” says Lindy Elkins-Tanton, director of the School of Earth and Space Exploration at Arizona State University.

But, in the very beginning of Earth’s formation, the first 500 million years, there’s a less well-known period which has typically been called the Hadean (meaning hell-like) because it was assumed that it was wildly hot and volcanic and everything was covered with magma — completely unlike the present day.

Terrestrial planet formation models indicate Earth went through a sequence of major growth phases: accretion of planetesimals and planetary embryos over many tens of millions of years; a giant impact that led to the formation of our Moon; and then the late bombardment, when giant asteroids, dwarfing the one that presumably killed the dinosaurs, periodically hit ancient Earth.

While researchers estimate accretion during late bombardment contributed less than one percent of Earth’s present-day mass, giant asteroid impacts still had a profound effect on the geological evolution of early Earth. Prior to four billion years ago Earth was resurfaced over and over by voluminous impact-generated melt. Furthermore, large collisions as late as about four billion years ago, may have repeatedly boiled away existing oceans into steamy atmospheres. Despite heavy bombardment, the findings are compatible with the claim of liquid water on Earth’s surface as early as about 4.3 billion years ago based on geochemical data.

A key part of Earth’s mysterious infancy period that has not been well quantified in the past is the kind of impacts Earth was experiencing at the end of accretion. How big and how frequent were those incoming bombardments and what were their effects on the surface of the Earth? How much did they affect the ability of the now cooling crust to actually form plates and start to subduct and make plate tectonics? What kind of volcanism did it produce that was different from volcanoes today?”

“We are increasingly understanding both the similarities and the differences to present day Earth conditions and plate tectonics,” says Elkins-Tanton. “And this study is a major step in that direction, trying to bridge that time from the last giant accretionary impact that largely completed the Earth and produced the Moon to the point where we have something like today’s plate tectonics and habitable surface.”

The new research reveals that asteroidal collisions not only severely altered the geology of the Hadean Earth, but likely played a major role in the subsequent evolution of life on Earth as well.

“Prior to approximately four billion years ago, no large region of Earth’s surface could have survived untouched by impacts and their effects,” says Simone Marchi, of NASA’s Solar System Exploration Research Virtual Institute at the Southwest Research Institute. “The new picture of the Hadean Earth emerging from this work has important implications for its habitability.”

Large impacts had particularly severe effects on existing ecosystems. Researchers found that on average, Hadean Earth could have been hit by one to four impactors that were more than 600 miles wide and capable of global sterilization, and by three to seven impactors more than 300 miles wide and capable of global ocean vaporization.

“During that time, the lag between major collisions was long enough to allow intervals of more clement conditions, at least on a local scale,” said Marchi. “Any life emerging during the Hadean eon likely needed to be resistant to high temperatures, and could have survived such a violent period in Earth’s history by thriving in niches deep underground or in the ocean’s crust.”

Note : The above story is based on materials provided by Arizona State University.

Antarctic ice sheet is result of carbon dioxide decrease, not continental breakup

August 1, 2014

Antarctic Peninsula. Credit: © adfoto / Fotolia

Climate modelers from the University of New Hampshire have shown that the most likely explanation for the initiation of Antarctic glaciation during a major climate shift 34 million years ago was decreased carbon dioxide (CO2) levels. The finding counters a 40-year-old theory suggesting massive rearrangements of Earth’s continents caused global cooling and the abrupt formation of the Antarctic ice sheet. It will provide scientists insight into the climate change implications of current rising global CO2 levels.
In a paper published today in Nature, Matthew Huber of the UNH Institute for the Study of Earth, Oceans, and Space and department of Earth sciences provides evidence that the long-held, prevailing theory known as “Southern Ocean gateway opening” is not the best explanation for the climate shift that occurred during the Eocene-Oligocene transition when Earth’s polar regions were ice-free.

“The Eocene-Oligocene transition was a major event in the history of the planet and our results really flip the whole story on its head,” says Huber. “The textbook version has been that gateway opening, in which Australia pulled away from Antarctica, isolated the polar continent from warm tropical currents, and changed temperature gradients and circulation patterns in the ocean around Antarctica, which in turn began to generate the ice sheet. We’ve shown that, instead, CO2-driven cooling initiated the ice sheet and that this altered ocean circulation.”

Huber adds that the gateway theory has been supported by a specific, unique piece of evidence — a “fingerprint” gleaned from oxygen isotope records derived from deep-sea sediments. These sedimentary records have been used to map out gradient changes associated with ocean circulation shifts that were thought to bear the imprint of changes in ocean gateways.

Although declining atmospheric levels of CO2 has been the other main hypothesis used to explain the Eocene-Oligocene transition, previous modeling efforts were unsuccessful at bearing this out because the CO2 drawdown does not by itself match the isotopic fingerprint. It occurred to Huber’s team that the fingerprint might not be so unique and that it might also have been caused indirectly from CO2 drawdown through feedbacks between the growing Antarctic ice sheet and the ocean.

Says Huber, “One of the things we were always missing with our CO2 studies, and it had been missing in everybody’s work, is if conditions are such to make an ice sheet form, perhaps the ice sheet itself is affecting ocean currents and the climate system — that once you start getting an ice sheet to form, maybe it becomes a really active part of the climate system and not just a passive player.”

For their study, Huber and colleagues used brute force to generate results: they simply modeled the Eocene-Oligocene world as if it contained an Antarctic ice sheet of near-modern size and shape and explored the results within the same kind of coupled ocean-atmosphere model used to project future climate change and across a range of CO2 values that are likely to occur in the next 100 years (560 to 1200 parts per million).

“It should be clear that resolving these two very different conceptual models for what caused this huge transformation of the Earth’s surface is really important because today as a global society we are, as I refer to it, dialing up the big red knob of carbon dioxide but we’re not moving continents around.”

Just what caused the sharp drawdown of CO2 is unknown, but Huber points out that having now resolved whether gateway opening or CO2 decline initiated glaciation, more pointed scientific inquiry can be focused on answering that question.

Huber notes that despite his team’s finding, the gateway opening theory won’t now be shelved, for that massive continental reorganization may have contributed to the CO2 drawdown by changing ocean circulation patterns that created huge upwellings of nutrient-rich waters containing plankton that, upon dying and sinking, took vast loads of carbon with them to the bottom of the sea.

Note :The above story is based on materials provided by University of New Hampshire.

Tidal forces gave moon its shape early in its history, new analysis finds

August 1, 2014

NASA’s Lunar Reconnaissance Orbiter Camera acquired this image of the nearside of the moon in 2010. Credit: NASA/GSFC/Arizona State University

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The shape of the moon deviates from a simple sphere in ways that scientists have struggled to explain. A new study by researchers at UC Santa Cruz shows that most of the moon’s overall shape can be explained by taking into account tidal effects acting early in the moon’s history.
The results, published July 30 in Nature, provide insights into the moon’s early history, its orbital evolution, and its current orientation in the sky, according to lead author Ian Garrick-Bethell, assistant professor of Earth and planetary sciences at UC Santa Cruz.

As the moon cooled and solidified more than 4 billion years ago, the sculpting effects of tidal and rotational forces became frozen in place. The idea of a frozen tidal-rotational bulge, known as the “fossil bulge” hypothesis, was first described in 1898. “If you imagine spinning a water balloon, it will start to flatten at the poles and bulge at the equator,” Garrick-Bethell explained. “On top of that you have tides due to the gravitational pull of the Earth, and that creates sort of a lemon shape with the long axis of the lemon pointing at the Earth.”

But this fossil bulge process cannot fully account for the current shape of the moon. In the new paper, Garrick-Bethell and his coauthors incorporated other tidal effects into their analysis. They also took into account the large impact basins that have shaped the moon’s topography, and they considered the moon’s gravity field together with its topography.

Impact craters

Efforts to analyze the moon’s overall shape are complicated by the large basins and craters created by powerful impacts that deformed the lunar crust and ejected large amounts of material. “When we try to analyze the global shape of the moon using spherical harmonics, the craters are like gaps in the data,” Garrick-Bethell said. “We did a lot of work to estimate the uncertainties in the analysis that result from those gaps.”

Their results indicate that variations in the thickness of the moon’s crust caused by tidal heating during its formation can account for most of the moon’s large-scale topography, while the remainder is consistent with a frozen tidal-rotational bulge that formed later.

A previous paper by Garrick-Bethell and some of the same coauthors described the effects of tidal stretching and heating of the moon’s crust at a time 4.4 billion years ago when the solid outer crust still floated on an ocean of molten rock. Tidal heating would have caused the crust to be thinner at the poles, while the thickest crust would have formed in the regions in line with the Earth. Published in Science in 2010, the earlier study found that the shape of one area of unusual topography on the moon, the lunar farside highlands, was consistent with the effects of tidal heating during the formation of the crust.

“In 2010, we found one area that fits the tidal heating effect, but that study left open the rest of the moon and didn’t include the tidal-rotational deformation. In this paper we tried to bring all those considerations together,” Garrick-Bethell said.

Tidal heating and tidal-rotational deformation had similar effects on the moon’s overall shape, giving it a slight lemon shape with a bulge on the side facing the Earth and another bulge on the opposite side. The two processes left distinct signatures, however, in the moon’s gravity field. Because the crust is lighter than the underlying mantle, gravity signals reveal variations in the thickness of the crust that were caused by tidal heating.

Gravity field

Interestingly, the researchers found that the moon’s overall gravity field is no longer aligned with the topography, as it would have been when the tidal bulges were frozen into the moon’s shape. The principal axis of the moon’s overall shape (the long axis of the lemon) is now separated from the gravity principal axis by about 34 degrees. (Excluding the large basins from the data, the difference is still about 30 degrees.)

“The moon that faced us a long time ago has shifted, so we’re no longer looking at the primordial face of the moon,” Garrick-Bethell said. “Changes in the mass distribution shifted the orientation of the moon. The craters removed some mass, and there were also internal changes, probably related to when the moon became volcanically active.”

The details and timing of these processes are still uncertain. But Garrick-Bethell said the new analysis should help efforts to work out the details of the moon’s early history. While the new study shows that tidal effects can account for the overall shape of the moon, tidal processes don’t explain the topographical differences between the near side and the far side.

In addition to Garrick-Bethell, the coauthors of the paper include Viranga Perera, who worked on the study as a UCSC graduate student and is now at Arizona State University; Francis Nimmo, professor of Earth and planetary sciences at UCSC; and Maria Zuber, a planetary scientist at the Massachusetts Institute of Technology. This work was funded by the Ministry of Education of Korea through the National Research Foundation.

Note : The above story is based on materials provided by University of California – Santa Cruz. The original article was written by Tim Stephens.

Mercury’s bizzare magnetic field tells scientists how its interior is different from Earth’s

July 31, 2014

Mercury, with colors enhanced to emphasize the chemical, mineralogical and physical differences among the rocks that make up its surface. Credit: NASA

Earth and Mercury are both rocky planets with iron cores, but Mercury’s interior differs from Earth’s in a way that explains why the planet has such a bizarre magnetic field, UCLA planetary physicists and colleagues report.
Measurements from NASA’s Messenger spacecraft have revealed that Mercury’s magnetic field is approximately three times stronger at its northern hemisphere than its southern one. In the current research, scientists led by Hao Cao, a UCLA postdoctoral scholar working in the laboratory of Christopher T. Russell, created a model to show how the dynamics of Mercury’s core contribute to this unusual phenomenon.

The magnetic fields that surround and shield many planets from the sun’s energy-charged particles differ widely in strength. While Earth’s is powerful, Jupiter’s is more than 12 times stronger, and Mercury has a rather weak magnetic field. Venus likely has none at all. The magnetic fields of Earth, Jupiter and Saturn show very little difference between the planets’ two hemispheres.

Within Earth’s core, iron turns from a liquid to a solid at the inner boundary of the planet’s liquid outer core; this results in a solid inner part and liquid outer part. The solid inner core is growing, and this growth provides the energy that generates Earth’s magnetic field. Many assumed, incorrectly, that Mercury would be similar.

“Hao’s breakthrough is in understanding how Mercury is different from the Earth so we could understand Mercury’s strongly hemispherical magnetic field,” said Russell, a co-author of the research and a professor in the UCLA College’s department of Earth, planetary and space sciences. “We had figured out how the Earth works, and Mercury is another terrestrial, rocky planet with an iron core, so we thought it would work the same way. But it’s not working the same way.”

Mercury’s peculiar magnetic field provides evidence that iron turns from a liquid to a solid at the core’s outer boundary, say the scientists, whose research currently appears online in the journal Geophysical Research Letters and will be published in an upcoming print edition.

“It’s like a snow storm in which the snow formed at the top of the cloud and middle of the cloud and the bottom of the cloud too,” said Russell. “Our study of Mercury’s magnetic field indicates iron is snowing throughout this fluid that is powering Mercury’s magnetic field.”

The research implies that planets have multiple ways of generating a magnetic field.

Hao and his colleagues conducted mathematical modeling of the processes that generate Mercury’s magnetic field. In creating the model, Hao considered many factors, including how fast Mercury rotates and the chemistry and complex motion of fluid inside the planet.

The cores of both Mercury and Earth contain light elements such as sulfur, in addition to iron; the presence of these light elements keeps the cores from being completely solid and “powers the active magnetic field-generation processes,” Hao said.

Hao’s model is consistent with data from Messenger and other research on Mercury

and explains Mercury’s asymmetric magnetic field in its hemispheres. He said the first important step was to “abandon assumptions” that other scientists make.

“Planets are different from one another,” said Hao, whose research is funded by a NASA fellowship. “They all have their individual character.”

Co-authors include Jonathan Aurnou, professor of planetary science and geophysics in UCLA’s Department of Earth, Planetary and Space Sciences, and Johannes Wicht, a research scientist at Germany’s Max Planck Institute for Solar System Research.

Note : The above story is based on materials provided by University of California – Los Angeles.

Fossils found in Siberia suggest all dinosaurs could have been feathered

July 30, 2014

Kulindadromeus zabaikalicus in its lacustrine environment. Credit: Andrey Atuchin

The first ever example of a plant-eating dinosaur with feathers and scales has been discovered in Russia. Previously only flesh-eating dinosaurs were known to have had feathers, so this new find raises the possibility that all dinosaurs could have been feathered.
The new dinosaur, named Kulindadromeus zabaikalicus as it comes from a site called Kulinda on the banks of the Olov River in Siberia, is described in a paper recently published in Science.

Kulindadromeus shows epidermal scales on its tail and shins, and short bristles on its head and back. The most astonishing discovery, however, is that it also has complex, compound feathers associated with its arms and legs.

Birds arose from dinosaurs over 150 million years ago so it was no surprise when dinosaurs with feathers were found in China in 1996. But all those feathered dinosaurs were theropods, flesh-eating dinosaurs that include the direct ancestors of birds.

Lead author Dr Pascal Godefroit from the Royal Belgian Institute of Natural History in Brussels said: “I was really amazed when I saw this. We knew that some of the plant-eating ornithischian dinosaurs had simple bristles, and we couldn’t be sure whether these were the same kinds of structures as bird and theropod feathers. Our new find clinches it: all dinosaurs had feathers, or at least the potential to sprout feathers.”

The Kulinda site was found in summer 2010 by Professor Dr Sofia Sinitsa from the Institute of Natural Resources, Ecology and Cryology SB RAS in Chita, Russia. In 2013, the Russian-Belgian team excavated many dinosaur fossils, as well as plant and insect fossils.

The feathers were studied by Dr Maria McNamara (University of Bristol and University College, Cork) and Professor Michael Benton (University of Bristol), who has also worked on the feathers of Chinese dinosaurs, and Professor Danielle Dhouailly (Université Joseph Fourier in Grenoble, France) who is a specialist on the development of feathers and scales in modern reptiles and birds.

Dr McNamara said: “These feathers are really very well preserved. We can see each filament and how they are joined together at the base, making a compound structure of six or seven filaments, each up to 15mm long.”

Professor Dhouailly said: “Developmental experiments in modern chickens suggest that avian scales are aborted feathers, an idea that explains why birds have scaly legs. The astonishing discovery is that the molecular mechanisms needed for this switch might have been so clearly related to the appearance of the first feathers in the earliest dinosaurs.”

Kulindadromeus was a small plant-eater, only about 1m long. It had long hind legs and short arms, with five strong fingers. Its snout was short, and its teeth show clear adaptations to plant eating. In evolutionary terms, it sits low in the evolutionary tree of ornithischian dinosaurs. There are six skulls and several hundred partial skeletons of this new dinosaur at the Kulinda locality.

This discovery suggests that feather-like structures were likely widespread in dinosaurs, possibly even in the earliest members of the group. Feathers probably arose during the Triassic, more than 220 million years ago, for purposes of insulation and signalling, and were only later co-opted for flight. Smaller dinosaurs were probably covered in feathers, mostly with colourful patterns, and feathers may have been lost as dinosaurs grew up and became larger.

Journal Reference:
P. Godefroit, S. M. Sinitsa, D. Dhouailly, Y. L. Bolotsky, A. V. Sizov, M. E. McNamara, M. J. Benton, P. Spagna. A Jurassic ornithischian dinosaur from Siberia with both feathers and scales. Science, 2014; 345 (6195): 451 DOI: 10.1126/science.1253351

Note : The above story is based on materials provided by Bristol University.

From finding Nemo to minerals: What riches lie in the deep sea?

July 30, 2014

Deep sea riches. Credit: Image courtesy of European Geosciences Union (EGU)

As fishing and the harvesting of metals, gas and oil have expanded deeper and deeper into the ocean, scientists are drawing attention to the services provided by the deep sea, the world’s largest environment. “This is the time to discuss deep-sea stewardship before exploitation is too much farther underway,” says lead-author Andrew Thurber. In a review published today in Biogeosciences, a journal of the European Geosciences Union (EGU), Thurber and colleagues summarise what this habitat provides to humans, and emphasise the need to protect it.
“The deep sea realm is so distant, but affects us in so many ways. That’s where the passion lies: to tell everyone what’s down there and that we still have a lot to explore,” says co-author Jeroen Ingels of Plymouth Marine Laboratory in the UK.

“What we know highlights that it provides much directly to society,” says Thurber, a researcher at the College of Earth, Ocean and Atmospheric Sciences at Oregon State University in the US. Yet, the deep sea is facing impacts from climate change and, as resources are depleted elsewhere, is being increasingly exploited by humans for food, energy and metals like gold and silver.

“We felt we had to do something,” says Ingels. “We all felt passionate about placing the deep sea in a relevant context and found that there was little out there aimed at explaining what the deep sea does for us to a broad audience that includes scientists, the non-specialists and ultimately the policy makers. There was a gap to be filled. So we said: ‘Let’s just make this happen’.”

In the review of over 200 scientific papers, the international team of researchers points out how vital the deep sea is to support our current way of life. It nurtures fish stocks, serves as a dumping ground for our waste, and is a massive reserve of oil, gas, precious metals and the rare minerals we use in modern electronics, such as cell phones and hybrid-car batteries. Further, hydrothermal vents and other deep-sea environments host life forms, from bacteria to sponges, that are a source of new antibiotics and anti-cancer chemicals. It also has a cultural value, with its strange species and untouched habitats inspiring books and films from “20,000 Leagues Under the Sea” to “Finding Nemo.”

“From jewellery to oil and gas and future potential energy reserves as well as novel pharmaceuticals, deep-sea’s worth should be recognised so that, as we decide how to use it more in the future, we do not inhibit or lose the services that it already provides,” says Thurber.

The deep sea (ocean areas deeper than 200m) represents 98.5% of the volume of our planet that is hospitable to animals. It has received less attention than other environments because it is vast, dark and remote, and much of it is inaccessible to humans. But it has important global functions. In the Biogeosciences review the team shows that deep-sea marine life plays a crucial role in absorbing carbon dioxide from the atmosphere, as well as methane that occasionally leaks from under the seafloor. In doing so, the deep ocean has limited much of the effects of climate change.

This type of process occurs over a vast area and at a slow rate. Thurber gives other examples: manganese nodules, deep-sea sources of nickel, copper, cobalt and rare earth minerals, take centuries or longer to form and are not renewable. Likewise, slow-growing and long-lived species of fish and coral in the deep sea are more susceptible to overfishing. “This means that a different approach needs to be taken as we start harvesting the resources within it.”

By highlighting the importance of the deep sea and identifying the traits that differentiate this environment from others, the researchers hope to provide the tools for effective and sustainable management of this habitat.

“This study is one of the steps in making sure that the benefits of the deep sea are understood by those who are trying to, or beginning to, regulate its resources,” concludes Thurber. “We ultimately hope that it will be a useful tool for policy makers.”

Journal Reference:
A. R. Thurber, A. K. Sweetman, B. E. Narayanaswamy, D. O. B. Jones, J. Ingels, R. L. Hansman. Ecosystem function and services provided by the deep sea. Biogeosciences Discussions, 2013; 10 (11): 18193 DOI: 10.5194/bgd-10-18193-2013

Note : The above story is based on materials provided by European Geosciences Union (EGU).

Gasses from Kilauea volcano affected tropical storm Flossie formation

July 30, 2014

Model predictions show gasses and particles from Kilauea entrained in Tropical Storm Flossie. Credit: Pattantyus and Businger, 2014.

One might assume that a tropical storm moving through volcanic smog (vog) would sweep up the tainted air and march on, unchanged. However, a recent study from atmospheric scientists at the University of Hawai’i — Mānoa (UHM) revealed that, though microscopic, gasses and particles from Kilauea volcano exerted an influence on Tropical Storm Flossie — affecting the formation of thunderstorms and lightning in the sizeable storm.

In July 2013, as Flossie approached the Hawaiian Islands, satellites steadily monitored lightning, rainfall, cloud cover, temperature and winds. In addition, UHM graduate assistant Andre Pattantyus and UHM Atmospheric Science Professor Dr. Steven Businger dutifully maintained their vog model — a forecasting tool Businger has operated since 2010 to provide guidance on the location of the vog plume and the concentrations of sulfur dioxide (SO2) and sulfate aerosol for Hawaiian Island communities.

In assessing the vog model, “We noticed the curious spiral pattern of vog being entrained into Hurricane Flossie and decided to dig deeper by looking at satellite and lightning data sets,” said Businger, co-author of the study.

He and lead author Pattantyus found that prior to Flossie’s passage over the island of Hawai’i, the observation network detected no lightning in the storm. Though one hour later, vigorous lightning flashed in the vicinity of the Island of Hawaii as Flossie approached. Further, as volcanic emissions were wrapped into this moist environment, sulfate aerosols promoted the formation of a greater number of smaller than normal cloud droplets, which favored charge separation in the upper cloud region and the occurrence of lightning.

Sulfate aerosols have previously been identified as a principal component of cloud condensation nuclei (CCN), a necessary ingredient for forming raindrops. But, said Businger, “This is the first interaction between an active, vigorously degassing volcano and a tropical cyclone captured by a vog model run over the Hawaiian Islands — providing a unique opportunity to analyze the influence of robust volcanic emissions entrained into a tropical storm system.”

Taken together, the observations and the vog model highlight an intimate interaction between Tropical Storm Flossie and Kilauea’s vog plume during the passage of the storm. The observations of Flossie’s changing dynamics as it encountered Kilauea’s vog has implications for the impact on hurricanes of polluted air as they approach the US mainland coast.

“The Hawaiian Islands provide a unique environment to study this interaction in relative isolation from other influences,” according to Businger. He plans to model the interaction of the vog plume and Hurricane Flossie with a more complex model that integrates chemistry into the predictions to better understand the processes at work in this unique confluence.

Journal Reference:
Andre Pattantyus, Steven Businger. On the interaction of Tropical Cyclone Flossie and emissions from Hawaii’s Kilauea volcano. Geophysical Research Letters, 2014; 41 (11): 4082 DOI: 10.1002/2014GL060033

Note : The above story is based on materials provided by University of Hawaii ‑ SOEST.

Time to reappraise how we interpret minerals

July 30, 2014

Professor John Wheeler: “These calculations show that we need to reappraise how we interpret minerals which grew within the Earth”

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A study by the University of Liverpool has provided new insight into how minerals grow under the Earth’s surface.

Using new calculations, a researcher in the School of Environmental Sciences was able to predict that the difference in stress acting on a rock in various directions has played a more significant role in influencing the growth of minerals in the Earth’s crust and mantle than was previously supposed.

Basis of our understanding

Minerals are formed under the earth’s surface as a result of geological influences such as heat, pressure and fluid interaction and therefore provide the basis of our understanding of the science of the earth.

They can be used to fingerprint the temperature and pressure at the time they grew. A diamond, for example, can grow only at pressures of greater than 40,000 atmospheres – in the same way that ice can form from water only below 0 degrees Celsius.

Liverpool geologist Professor John Wheeler, who undertook the research, said: “These calculations show that we need to reappraise how we interpret minerals which grew within the Earth”

“It has previously been assumed the effects of differential stress on mineral growth are small. But now I have shown that changing the stress (applied force per unit area on which it acts) in
one direction by, say, 500 atmospheres might have an effect equivalent to changing the overall pressure by 5000 atmospheres”.

“These calculations mean that current estimates made by geologists for burial depths could be 20 km or more above or below their true values, and temperature estimates could be 100 degrees C above or below the actual values when minerals grew. So we need to revitalise our approach to what minerals tell us”.

Density differences

Stresses result from density differences within the Earth and movement of tectonic plates and can be hundreds of atmospheres different in value, depending on the direction of the stress. As stress is applied slowly over time, rocks deform and change shape forming aligned mineral textures which are very common.

The theory also has an impact on the understanding of metals which, like rocks, are interlocked crystals of different chemistries and are often processed by deformation which, as in rocks, occurs in parallel with chemical change.

More information:
The complete study is available online: geology.gsapubs.org/content/ea… 5718.1.full.pdf+html

Note : The above story is based on materials provided by University of Liverpool

Dinosaurs fell victim to perfect storm of events, study shows

July 29, 2014

Stegosaurus illustration (stock image). “The dinosaurs were victims of colossal bad luck. Not only did a giant asteroid strike, but it happened at the worst possible time, when their ecosystems were vulnerable,” said Dr Steve Brusatte, lead author of a new paper. Credit: © Elenarts / Fotolia

Dinosaurs might have survived the asteroid strike that wiped them out if it had taken place slightly earlier or later in history, scientists say.
A fresh study using up-to-date fossil records and improved analytical tools has helped palaeontologists to build a new narrative of the prehistoric creatures’ demise, some 66 million years ago.

They found that in the few million years before a 10km-wide asteroid struck what is now Mexico, Earth was experiencing environmental upheaval. This included extensive volcanic activity, changing sea levels and varying temperatures.

At this time, the dinosaurs’ food chain was weakened by a lack of diversity among the large plant-eating dinosaurs on which others preyed. This was probably because of changes in the climate and environment.

This created a perfect storm in which dinosaurs were vulnerable and unlikely to survive the aftermath of the asteroid strike.

The impact would have caused tsunamis, earthquakes, wildfires, sudden temperature swings and other environmental changes. As food chains collapsed, this would have wiped out the dinosaur kingdom one species after another. The only dinosaurs to survive were those who could fly, which evolved to become the birds of today.

Researchers suggest that if the asteroid had struck a few million years earlier, when the range of dinosaur species was more diverse and food chains were more robust, or later, when new species had time to evolve, then they very likely would have survived.

An international team of palaeontologists led by the University of Edinburgh studied an updated catalogue of dinosaur fossils, mostly from North America, to create a picture of how dinosaurs changed over the few million years before the asteroid hit. They hope that ongoing studies in Spain and China will aid even better understanding of what occurred.

Their study, published in Biological Reviews, was supported by the US National Science Foundation and the European Commission. It was led by the Universities of Edinburgh and Birmingham in collaboration with the University of Oxford, Imperial College London, Baylor University, and University College London. The world’s top dinosaur museums — The Natural History Museum, the Smithsonian Institution, the Royal Ontario Museum, the American Museum of Natural History and the New Mexico Museum of Natural History and Science — also took part.

Dr Steve Brusatte, of the University of Edinburgh’s School of GeoSciences, said: “The dinosaurs were victims of colossal bad luck. Not only did a giant asteroid strike, but it happened at the worst possible time, when their ecosystems were vulnerable. Our new findings help clarify one of the enduring mysteries of science.”

Dr Richard Butler of the School of Geography, Earth and Environmental Sciences at the University of Birmingham, said: “There has long been intense scientific debate about the cause of the dinosaur extinction. Although our research suggests that dinosaur communities were particularly vulnerable at the time the asteroid hit, there is nothing to suggest that dinosaurs were doomed to extinction. Without that asteroid, the dinosaurs would probably still be here, and we very probably would not.”

Note : The above story is based on materials provided by University of Edinburgh.

Mineral magic? Common mineral capable of making and breaking bonds

July 29, 2014

A team of ASU researchers has demonstrated that a particular mineral, sphalerite, can affect the most fundamental process in organic chemistry: carbon-hydrogen bond breaking and making. This is a sample of gem-quality sphalerite in a quartz matrix. Credit: Tom Sharp

Reactions among minerals and organic compounds in hydrothermal environments are critical components of Earth’s deep carbon cycle, they provide energy for the deep biosphere, and may have implications for the origins of life. However, very little is known about how minerals influence organic reactions. A team of researchers from Arizona State University have demonstrated how a common mineral acts as a catalysts for specific hydrothermal organic reactions — negating the need for toxic solvents or expensive reagents.
At the heart of organic chemistry, aka carbon chemistry, is the covalent carbon-hydrogen bond (C-H bond) ─ a fundamental link between carbon and hydrogen atoms found in nearly every organic compound.

The essential ingredients controlling chemical reactions of organic compounds in hydrothermal systems are the organic molecules, hot pressurized water, and minerals, but a mechanistic understanding of how minerals influence hydrothermal organic reactivity has been virtually nonexistent.

The ASU team set out to understand how different minerals affect hydrothermal organic reactions and found that a common sulfide mineral (ZnS, or Sphalerite) cleanly catalyzes a fundamental chemical reaction — the making and breaking of a C-H bond.

Their findings are published in the July 28 issue of the Proceedings of the National Academy of Sciences. The paper was written by a transdisciplinary team of ASU researchers that includes: Jessie Shipp (2013 PhD in Chemistry & Biochemistry), Ian Gould, Lynda Williams, Everett Shock, and Hilairy Hartnett.

“Typically you wouldn’t expect water and an organic hydrocarbon to react. If you place an alkane in water and add some mineral it’s probably just going to sit there and do nothing,” explains first author Shipp. “But at high temperature and pressure, water behaves more like an organic solvent, the thermodynamics of reactions change, and suddenly reactions that are impossible on the bench-top start becoming possible. And it’s all using naturally occurring components at conditions that can be found in past and present hydrothermal systems.”

A mineral in the mix

Previously, the team had found they could react organic molecules in hot pressurized water to produce many different types of products, but reactions were slow and conversions low. This work, however, shows that in the presence of sphalerite, hydrothermal reaction rates increased dramatically, the reaction approached equilibrium, and only one product formed. This very clean, very simple reaction was unexpected.

“We chose sphalerite because we had been working with iron sulfides and realized that we couldn’t isolate the effects of iron from the effects of sulfur. So we tried a mineral with sulfur but not iron. Sphalerite is a common mineral in hydrothermal systems so it was a pretty good choice. We really didn’t expect it to behave so differently from the iron sulfides,” says Hartnett, an associate professor in the School of Earth and Space Exploration, and in the Department of Chemistry and Biochemistry at ASU.

This research provides information about exactly how the sphalerite mineral surface affects the breaking and making of the C-H bond. Sphalerite is present in marine hydrothermal systems i.e., black smokers, and has been the focus of recent origins-of-life investigations.

For their experiments, the team needed high pressures (1000 bar — nearly 1000 atm) and high temperatures (300°C) in a chemically inert container. To get these conditions, the reactants (sphalerite, water, and an organic molecule) are welded into a pure gold capsule and placed in a pressure vessel, inside a furnace. When an experiment is done, the gold capsule is frozen in liquid nitrogen to stop the reaction, opened and allowed to thaw while submerged in dichloromethane to extract the organic products.

“This research is a unique collaboration because Dr. Gould is an organic chemist and you combine him with Dr. Hartnett who studies carbon cycles and environmental geochemistry, Dr. Shock who thinks in terms of thermodynamics and about high temperature environments, and Dr. Williams who is the mineral expert, and you get a diverse set of brains thinking about the same problems,” says Shipp.

Hydrothermal organic reactions affect the formation, degradation, and composition of petroleum, and provide energy and carbon sources for microbial communities in deep sedimentary systems. The results have implications for the carbon cycle, astrobiology, prebiotic organic chemistry, and perhaps even more importantly for Green Chemistry (a philosophy that encourages the design of products and processes that minimize the use and generation of hazardous substances).

“This C-H bond activation is a fundamental step that is ultimately necessary to produce more complex molecules — in the environment those molecules could be food for the deep biosphere — or involved in the production of petroleum fuels,” says Hartnett. “The green chemistry side is potentially really cool — since we can conduct reactions in just hot water with a common mineral that ordinarily would require expensive or toxic catalysts or extremely harsh — acidic or oxidizing — conditions.”

The work was funded by the National Science Foundation.

Note : The above story is based on materials provided by Arizona State University.

New research suggests Saharan dust is key to the formation of Bahamas’ Great Bank

July 29, 2014

Distribution of insoluble material in the sediments and collection sites are shown. The insoluble material is derived from atmospheric dust. Credit: Peter Swart, Ph.D., UM Rosenstiel School of Marine and Atmospheric Science

A new study suggests that Saharan dust played a major role in the formation of the Bahamas islands. Researchers from the University of Miami (UM) Rosenstiel School of Marine and Atmospheric Science showed that iron-rich Saharan dust provides the nutrients necessary for specialized bacteria to produce the island chain’s carbonate-based foundation.

UM Rosenstiel School Lewis G. Weeks Professor Peter Swart and colleagues analyzed the concentrations of two trace elements characteristic of atmospheric dust – iron and manganese – in 270 seafloor samples collected along the Great Bahama Bank over a three-year period. The team found that the highest concentrations of these trace elements occurred to the west of Andros Island, an area which has the largest concentration of whitings, white sediment-laden bodies of water produced by photosynthetic cyanobacteria.

“Cyanobacteria need 10 times more iron than other photosynthesizers because they fix atmospheric nitrogen,” said Swart, lead author of the study. “This process draws down the carbon dioxide and induces the precipitation of calcium carbonate, thus causing the whiting. The signature of atmospheric nitrogen, its isotopic ratio is left in the sediments.”

Swart’s team suggests that high concentrations of iron-rich dust blown across the Atlantic Ocean from the Sahara is responsible for the existence of the Great Bahama Bank, which has been built up over the last 100 million years from sedimentation of calcium carbonate. The dust particles blown into the Bahamas’ waters and directly onto the islands provide the nutrients necessary to fuel cyanobacteria blooms, which in turn, produce carbonate whitings in the surrounding waters.

Persistent winds across Africa’s 3.5-million square mile Sahara Desert lifts mineral-rich sand into the atmosphere where it travels the nearly 5,000-mile northwest journey towards the U.S. and Caribbean. The paper, titled “The fertilization of the Bahamas by Saharan dust: A trigger for carbonate precipitation?” was published in the early online edition of the journal Geology. The paper’s authors include Swart, Amanda Oehlert, Greta Mackenzie, Gregor Eberli from the UM Rosenstiel School’s Department of Marine Geosciences and John Reijmer of VU University Amsterdam in the Netherlands.

Note : The above story is based on materials provided by University of Miami

Japan volcanic island smouldering and growing

July 29, 2014

Picture taken by Japan Coast Guard on July 23, 2014 shows a newly created islet (R) and Nishinoshima island (L), which are conjoined by erupting lava at the Ogasawara island chain, 1,000 kilometres south of Tokyo

A volcanic island off Japan’s southern coast continues to smoulder with lava flowing from its craters into the sea, new aerial images showed Friday.Nishinoshima, some 1,000 kilometres (620 miles) south of Tokyo, joined up with a small volcanic islet formed in November and the new mass now measures 1.26 square kilometres (0.49 square miles) around, the Japanese coastguard said.

The agency’s images showed a few craters on Nishinoshima spewing columns of smoke 1,500-2,000 metres (4,900-6,600 feet) high as molten lava flowed into the sea, sending clouds of white steam into the sky.

Nishinoshima is estimated to be 10 million years old.

Leaf-mining insects destroyed with the dinosaurs, others quickly appeared

July 25, 2014

This is a mine produced by a micromoth larva on Platanus raynoldski, a sycamore. Credit: Michael Donovan, Penn State

After the asteroid impact at the end of the Cretaceous period that triggered the dinosaurs’ extinction and ushered in the Paleocene, leaf-mining insects in the western United States completely disappeared. Only a million years later, at Mexican Hat, in southeastern Montana, fossil leaves show diverse leaf-mining traces from new insects that were not present during the Cretaceous, according to paleontologists.
“Our results indicate both that leaf-mining diversity at Mexican Hat is even higher than previously recognized, and equally importantly, that none of the Mexican Hat mines can be linked back to the local Cretaceous mining fauna,” said Michael Donovan, graduate student in geosciences, Penn State.

Insects that eat leaves produce very specific types of damage. One type is from leaf miners — insect larvae that live in the leaves and tunnel for food, leaving distinctive feeding paths and patterns of droppings.

Donovan, Peter Wilf, professor of geosciences, Penn State, and colleagues looked at 1,073 leaf fossils from Mexican Hat for mines. They compared these with more than 9,000 leaves from the end of the Cretaceous, 65 million years ago, from the Hell Creek Formation in southwestern North Dakota, and with more than 9,000 Paleocene leaves from the Fort Union Formation in North Dakota, Montana and Wyoming. The researchers present their results in today’s (July 24) issue of PLOS ONE.

“We decided to focus on leaf miners because they are typically host specific, feeding on only a few plant species each,” said Donovan. “Each miner also leaves an identifiable mining pattern.”

The researchers found nine different mine-damage types at Mexican Hat attributable to the larvae of moths, wasps and flies, and six of these damage types were unique to the site.

The researchers were unsure whether the high diversity of leaf miners at Mexican Hat compared to other early Paleocene sites, where there is little or no leaf mining, was caused by insects that survived the extinction event in refugia — areas where organisms persist during adverse conditions — or were due to range expansions of insects from somewhere else during the early Paleocene.

However, with further study, the researchers found no evidence of the survival of any leaf miners over the Cretaceous-Paleocene boundary, suggesting an even more total collapse of terrestrial food webs than has been recognized previously.

“These results show that the high insect damage diversity at Mexican Hat represents an influx of novel insect herbivores during the early Paleocene and not a refugium for Cretaceous leaf miners,” said Wilf. “The new herbivores included a startling diversity for any time period, and especially for the classic post-extinction disaster interval.”

Insect extinction across the Cretaceous-Paleocene boundary may have been directly caused by catastrophic conditions after the asteroid impact and by the disappearance of host plant species. While insect herbivores constantly need leaves to survive, plants can remain dormant as seeds in the ground until more auspicious circumstances occur.

The low-diversity flora at Mexican Hat is typical for the area in the early Paleocene, so what caused the high insect damage diversity?

Insect outbreaks are associated with a rapid population increase of a single insect species, so the high diversity of mining damage seen in the Mexican Hat fossils makes the possibility of an outbreak improbable.

The researchers hypothesized that the leaf miners that are seen in the Mexican Hat fossils appeared in that area because of a transient warming event, a number of which occurred during the early Paleocene.

“Previous studies have shown a correlation between temperature and insect damage diversity in the fossil record, possibly caused by evolutionary radiations or range shifts in response to a warmer climate,” said Donovan. “Current evidence suggests that insect herbivore extinction decreased with increasing distance from the asteroid impact site in Mexico, so pools of surviving insects would have existed elsewhere that could have provided a source for the insect influx that we observed at Mexican Hat.”

Note : The above story is based on materials provided by Penn State. The original article was written by A’ndrea Eluse Messer.

Four-billion-year-old chemistry in cells today

July 25, 2014

3-D rendering of a mitochondrium. Credit: © Mopic / Fotolia

Parts of the primordial soup in which life arose have been maintained in our cells today according to scientists at the University of East Anglia.

Research published today in the Journal of Biological Chemistry reveals how cells in plants, yeast and very likely also in animals still perform ancient reactions thought to have been responsible for the origin of life — some four billion years ago.

The primordial soup theory suggests that life began in a pond or ocean as a result of the combination of metals, gases from the atmosphere and some form of energy, such as a lightning strike, to make the building blocks of proteins which would then evolve into all species.

The new research shows how small pockets of a cell — known as mitochondria — continue to perform similar reactions in our bodies today. These reactions involve iron, sulfur and electro-chemistry and are still important for functions such as respiration in animals and photosynthesis in plants.

Lead researcher Dr Janneke Balk, from UEA’s school of Biological Sciences and the John Innes Centre, said: “Cells confine certain bits of dangerous chemistry to specific compartments of the cell.

“For example small pockets of a cell called mitochondria deal with electrochemistry and also with toxic sulfur metabolism. These are very ancient reactions thought to have been important for the origin of life.

“Our research has shown that a toxic sulfur compound is being exported by a mitochondrial transport protein to other parts of the cell. We need sulfur for making iron-sulfur catalysts, again a very ancient chemical process.

“The work shows that parts of the primordial soup in which life arose has been maintained in our cells today, and is in fact harnessed to maintain important biological reactions.”

The research was carried out at UEA and JIC in collaboration with Dr Hendrik van Veen at the University of Cambridge. It was funded by the Biotechnology and Biological Sciences Research Council (BBSRC).

‘A Conserved Mitochondrial ATB-Binding Cassette Transporter Exports Glutathione Polysufide for Cytosolic Metal Cofactor Assembly’ is published in the Journal of Biological Chemistry.

Note : The above story is based on materials provided by University of East Anglia.

Parched West is using up underground water

July 25, 2014

U.S. Bureau of Reclamation Surface-water depletion in the Colorado River Basin has left this “bathtub ring” of mineral deposits on Lake Mead, but groundwater loss is invisible. Credit: U.S. Bureau of Reclamation

A new study by University of California, Irvine and NASA scientists finds more than 75 percent of the water loss in the drought-stricken Colorado River Basin since late 2004 came from underground resources. The extent of groundwater loss may pose a greater threat to the water supply of the western United States than previously thought.
This study is the first to quantify the amount that groundwater contributes to the water needs of western states. According to the U.S. Bureau of Reclamation, the federal water management agency, the basin has been suffering from prolonged, severe drought since 2000 and has experienced the driest 14-year period in the last hundred years.

The research team used data from NASA’s Gravity Recovery and Climate Experiment (GRACE) satellite mission to track changes in the mass of the Colorado River Basin, which are related to changes in water amount on and below the surface. Monthly measurements in the change in water mass from December 2004 to November 2013 revealed the basin lost nearly 53 million acre feet (65 cubic kilometers) of freshwater, almost double the volume of the nation’s largest reservoir, Nevada’s Lake Mead. More than three-quarters of the total — about 41 million acre feet (50 cubic kilometers) — was from groundwater.

“We don’t know exactly how much groundwater we have left, so we don’t know when we’re going to run out,” said Stephanie Castle, a water resources specialist at UC Irvine and the study’s lead author. “This is a lot of water to lose. We thought that the picture could be pretty bad, but this was shocking.”

Water above ground in the basin’s rivers and lakes is managed by the U.S. Bureau of Reclamation, and its losses are documented. Pumping from underground aquifers is regulated by individual states and is often not well documented.

“There’s only one way to put together a very large-area study like this, and that is with satellites,” said senior author Jay Famiglietti, senior water cycle scientist at JPL on leave from UC Irvine, where he is an Earth system science professor. “There’s just not enough information available from well data to put together a consistent, basin-wide picture.”

Famiglietti said GRACE is like having a giant scale in the sky. Within a given region, the change in mass due to rising or falling water reserves influences the strength of the local gravitational attraction. By periodically measuring gravity regionally, GRACE reveals how much a region’s water storage changes over time.

The Colorado River is the only major river in the southwest part of the United States. Its basin supplies water to about 40 million people in seven states, as well as irrigating roughly four million acres of farmland.

“The Colorado River Basin is the water lifeline of the western United States,” said Famiglietti. “With Lake Mead at its lowest level ever, we wanted to explore whether the basin, like most other regions around the world, was relying on groundwater to make up for the limited surface-water supply. We found a surprisingly high and long-term reliance on groundwater to bridge the gap between supply and demand.”

Famiglietti noted that the rapid depletion rate will compound the problem of short supply by leading to further declines in streamflow in the Colorado River.

“Combined with declining snowpack and population growth, this will likely threaten the long-term ability of the basin to meet its water allocation commitments to the seven basin states and to Mexico,” Famiglietti said.

The study has been accepted for publication in the journal Geophysical Research Letters, which posted the manuscript online July 24. Coauthors included other scientists from NASA’s Goddard Space Flight Center, Greenbelt, Md.; and the National Center for Atmospheric Research, Boulder, Colo. The research was funded by NASA and the University of California.

Note : The above story is based on materials provided by University of California – Irvine.

Synchronization of North Atlantic, North Pacific preceded abrupt warming, end of ice age

July 25, 2014

This image depicts the Hubbard Glacier ice front, with floating ice ‘growlers’ in August 2004. Credit: Photo courtesy of Oregon State University

Scientists have long been concerned that global warming may push Earth’s climate system across a “tipping point,” where rapid melting of ice and further warming may become irreversible — a hotly debated scenario with an unclear picture of what this point of no return may look like.
A newly published study by researchers at Oregon State University probed the geologic past to understand mechanisms of abrupt climate change. The study pinpoints the emergence of synchronized climate variability in the North Pacific Ocean and the North Atlantic Ocean a few hundred years before the rapid warming that took place at the end of the last ice age about 15,000 years ago.

The study suggests that the combined warming of the two oceans may have provided the tipping point for abrupt warming and rapid melting of the northern ice sheets.

Results of the study, which was funded by the National Science Foundation, appear this week in Science.

This new discovery by OSU researchers resulted from an exhaustive 10-year examination of marine sediment cores recovered off southeast Alaska where geologic records of climate change provide an unusually detailed history of changing temperatures on a scale of decades to centuries over many thousands of years.

“Synchronization of two major ocean systems can amplify the transport of heat toward the polar regions and cause larger fluctuations in northern hemisphere climate,” said Summer Praetorius, a doctoral student in marine geology at Oregon State and lead author on the Science paper. “This is consistent with theoretical predictions of what happens when Earth’s climate reaches a tipping point.”

“That doesn’t necessarily mean that the same thing will happen in the future,” she pointed out, “but we cannot rule out that possibility.”

The study found that synchronization of the two regional systems began as climate was gradually warming. After synchronization, the researchers detected wild variability that amplified the changes and accelerated into an abrupt warming event of several degrees within a few decades.

“As the systems become synchronized, they organized and reinforced each other, eventually running away like screeching feedback from a microphone,” said Alan Mix, a professor in OSU’s College of Earth, Ocean, and Atmospheric Sciences and co-author on the paper. “Suddenly you had the combined effects of two major oceans forcing the climate instead of one at a time.”

“The example that we uncovered is a cause for concern because many people assume that climate change will be gradual and predictable,” Mix added. “But the study shows that there can be vast climate swings over a period of decades to centuries. If such a thing happened in the future, it could challenges society’s ability to cope.”

What made this study unusual is that the researchers had such a detailed look at the geologic record. While modern climate observations can be made every day, the length of instrumental records is relatively short — typically less than a century. In contrast, paleoclimatic records extend far into the past and give good context for modern changes, the researchers say. However, the resolution of most paleo records is low, limited to looking at changes that occur over thousands of years.

In this study, the researchers examined sediment cores taken from the Gulf of Alaska in 2004 during an expedition led by Mix. The mountains in the region are eroding so fast that sedimentation rates are “phenomenal,” he said. “Essentially, this rapid sedimentation provides a ‘climate tape recorder’ at extremely high fidelity.”

Praetorius then led an effort to look at past temperatures by slicing the sediment into decade-long chunks spanning more than 8,000 years — a laborious process that took years to complete. She measured ratios of oxygen isotopes trapped in fossil shells of marine plankton called foraminifera. The isotopes record the temperature and salinity of the water where the plankton lived.

When the foraminifera died, their shells sank to the sea floor and were preserved in the sediments that eventually were recovered by Mix’s coring team.

The researchers then compared their findings with data from the North Greenland Ice Core Project to see if the two distinct high-latitude climate systems were in any way related.

Most of the time, the two regions vary independently, but about 15,500 years ago, temperature changes started to line up and then both regions warmed abruptly by about five degrees (C) within just a few decades. Praetorius noted that much warmer ocean waters likely would have a profound effect on northern-hemisphere climates by melting sea ice, warming the atmosphere and destabilizing ice sheets over Canada and Europe.

A tipping point for climate change “may be crossed in an instant,” Mix noted, “but the actual response of the Earth’s system may play out over centuries or even thousands of years during a period of dynamic adjustment.”

“Understanding those dynamics requires that we look at examples from the past,” Mix said. “If we really do cross such a boundary in the future, we should probably take a long-term perspective and realize that change will become the new normal. It may be a wild ride.”

Added Praetorius: “Our study does suggest that the synchronization of the two major ocean systems is a potential early warning system to begin looking for the tipping point.”

Note : The above story is based on materials provided by Oregon State University.

How much magma is hiding beneath our feet? Mysteries of Earth’s crust pierced

July 24, 2014

How much magma is hiding beneath our feet? Credit: © naypong / Fotolia

Table of Contents

Molten rock (or magma) has a strong influence on our planet and its inhabitants, causing destructive volcanic eruptions and generating some of the giant mineral deposits. Our understanding of these phenomena is, however, limited by the fact that most magma cools and solidifies several kilometres beneath our feet, only to be exposed at the surface, millions of years later, by erosion. Scientists have never been able to track the movements of magma at such great depths… that is, until a team from the University of Geneva (UNIGE) discovered an innovative technique, details of which will be published in the next issue of the journal Nature.

It is a story of three scientists: a modelling specialist, an expert in a tiny mineral known as “zircon,” and a volcanologist. Following a casual conversation, the researchers stumbled upon an idea, and eventually a new method to estimate the volume and flow of magma required for the construction of magma chambers was shaped. The technique they developed makes it possible to refine predictions of future volcanic eruptions as well as identifying areas of the planet that are rich in magma-related natural resources.

Zircon: a valuable mineral for scientists

Professor Urs Schaltegger has been studying zircon for more than ten years in his laboratory at UNIGE, one of the world’s few labs in this field. “The zircon crystals that are found in solidified magma hold key information about the injection of molten rock into a magma chamber before it freezes underground,” explains the professor. Zircon contains radioactive elements that enable researchers to determine its age. As part of the study, the team from the Section of Earth and Environmental Sciences of UNIGE paired data collected using natural samples and numerical simulation. As Guy Simpson, a researcher at UNIGE further explains: “Modelling meant that we could establish how the age of crystallised zircon in a cooled magma reservoir depends on the flow rate of injected magma and the size of the reservoir.”

Applications for society and industry

In the Nature article, the researchers propose a model that is capable of determining with unprecedented accuracy the age, volume and injection rate of magma that has accumulated at inaccessible depths. As a result, they have established that the formation of Earth’s crust, volcanic super eruptions and mineral deposits occur under very specific yet different conditions. Professor Luca Caricchi adds: “When we determine the age of a family of zircons from a small sample of solidified magmatic rock, using results from the mathematical model we have developed, we can tell what the size of the entire magma chamber was, as well as how fast the magma reservoir grew.” The professor continues: “This information means that we can determine the probability of an explosive volcanic eruption of a certain size to occur. In addition, the model will be of interest to industry because we will be able to identify new areas of our planet that are home to large amounts of natural resources such as copper and gold.”

Journal Reference:

Luca Caricchi, Guy Simpson, Urs Schaltegger. Zircons reveal magma fluxes in the Earth’s crust. Nature, 2014; 511 (7510): 457 DOI: 10.1038/nature13532

Note : The above story is based on materials provided by Université de Genève.

3-D image of Paleolithic child’s skull reveals trauma, brain damage

July 24, 2014

This is a 3-D reconstruction of skull compound fracture and endocranial surface changes. Credit: Coqueugniot H, Dutour O, Arensburg B, Duday H, Vandermeersch B, et al. (2014) Earliest Cranio-Encephalic Trauma from the Levantine Middle Palaeolithic: 3D Reappraisal of the Qafzeh 11 Skull, Consequences of Pediatric Brain Damage on Individual Life Condition and Social Care. PLoS ONE 9(7): e102822. doi:10.1371/journal.pone.0102822

Three-dimensional imaging of a Paleolithic child’s skull reveals potentially violent head trauma that likely lead to brain damage, according to a study published July 23, 2014 in the open-access journal PLOS ONE by Hélène Coqueugniot and colleagues from CNRS — Université de Bordeaux and EPHE.
A Paleolithic child that lived ~100 thousand years ago found at Qafzeh in lower Galilee, was originally thought to have a skull lesion that resulted from a trauma that healed. The child died at about 12-13 years old, but the circumstances surround the child’s death remain mysterious. To better understand the injury, the authors of this study aimed to re-appraise the child’s impact wound using 3D imaging, which allows scientists to better to explore inner bone lesions, to evaluate their impact on soft tissues, and to estimate brain size to reconstruct the events surrounding the skull trauma.

3D reconstruction reveals that the child’s skull fracture appears to be compound, with a broken piece depressed in the skull, surrounded by linear fractures. The authors suggest that this fracture type generally results from a blunt force trauma, often a result of interpersonal violence, but can also occur accidentally. The depressed fracture was likely caused a moderate traumatic brain injury, possibly resulting in personality changes, trouble controlling movements, and difficulty in social communication. The authors conclude that, the child represents the oldest documented human case of severe skull trauma available from south-western Asia. Furthermore, the child appears to have received special social attention after death, as the body positioning seems intentional with two deer antlers lying on the upper part of the adolescent’s chest, likely suggesting a deliberate ceremonial burial.

Hélène Coqueugniot added, “Digital imaging and 3D reconstruction evidenced the oldest traumatic brain injury in a Paleolithic child. Post-traumatic neuropsychological disorders could have impaired social life of this individual who was buried, when teenager, with a special ritual raising the question of compassion in Prehistory.”

Journal Reference:

Coqueugniot H, Dutour O, Arensburg B, Duday H, Vandermeersch B, et al. Earliest Cranio-Encephalic Trauma from the Levantine Middle Palaeolithic: 3D Reappraisal of the Qafzeh 11 Skull, Consequences of Pediatric Brain Damage on Individual Life Condition and Social Care. PLoS ONE, 2014 DOI: 10.1371/journal.pone.0102822

Note : The above story is based on materials provided by PLOS.

Oso disaster had its roots in earlier landslides

July 24, 2014

An aerial view of the slide site at Oso, Washington, from March 31, 2014. Credit: Gordon Farquharson / UW

The disastrous March 22 landslide that killed 43 people in the rural Washington state community of Oso involved the “remobilization” of a 2006 landslide on the same hillside, a new federally sponsored geological study concludes.
The research indicates the landslide, the deadliest in U.S. history, happened in two major stages. The first stage remobilized the 2006 slide, including part of an adjacent forested slope from an ancient slide, and was made up largely or entirely of deposits from previous landslides. The first stage ultimately moved more than six-tenths of a mile across the north fork of the Stillaguamish River and caused nearly all the destruction in the Steelhead Haven neighborhood.

The second stage started several minutes later and consisted of ancient landslide and glacial deposits. That material moved into the space vacated by the first stage and moved rapidly until it reached the trailing edge of the first stage, the study found.

The report, released Tuesday on the four-month anniversary of the slide, details an investigation by a team from the Geotechnical Extreme Events Reconnaissance Association, or GEER. The scientists and engineers determined that intense rainfall in the three weeks before the slide likely was a major issue, but factors such as altered groundwater migration, weakened soil consistency because of previous landslides and changes in hillside stresses played key roles.

The extreme events group is funded by the National Science Foundation, and its goal is to collect perishable data immediately in the wake of extreme events such as earthquakes, hurricanes, tsunamis, landslides or floods. Recent events for which reports have been filed include earthquakes in New Zealand and Haiti, the 2011 earthquake and tsunami in Japan, and Hurricane Sandy on the U.S. Eastern Seaboard in 2012.

“Perhaps the most striking finding is that, while the Oso landslide was a rare geologic occurrence, it was not extraordinary,” said Joseph Wartman, a University of Washington associate professor of civil and environmental engineering and a team leader for the study.

“We observed several other older but very similar long-runout landslides in the surrounding Stillaguamish River Valley. This tells us these may be prevalent in this setting over long time frames. Even the apparent trigger of the event — several weeks of intense rainfall — was not truly exceptional for the region,” Wartman said.

Team co-leader Jeffrey Keaton, a principal engineering geologist with AMEC Americas, an engineering consultant and project management company, said another important finding is that spring of 2014 was not a big time for landslides in Northwest Washington.

“The Oso landslide was the only major one that occurred in Snohomish County or the Seattle area this spring,” Keaton said.

Other team members are Scott Anderson of the Federal Highway Administration, Jean Benoit of the University of New Hampshire, John deLaChapelle of Golder Associates Inc., Robert Gilbert of the University of Texas and David Montgomery of the University of Washington.

The team was formed and approved within days of the landslide, but it began work at the site about eight weeks later, after search and recovery activities were largely completed. The researchers documented conditions and collected data that could be lost over time. Their report is based largely on data collected during a four-day study of the entire landslide area in late May. It focuses on data and observations directly from the site, but also considers information such as local geologic and climate conditions and eyewitness accounts.

The researchers reviewed evidence for a number of large landslides in the Stillaguamish Valley around Oso during the previous 6,000 years, many of them strongly resembling the site of the 2014 slide. There is solid evidence, for example, of a slide just west of this year’s slide that also ran out across the valley. In addition, they reviewed published maps showing the entire valley bottom in the Oso area is made up of old landslide deposits or areas where such deposits have been reworked by the river and left on the flood plain.

The team estimated that large landslides such as the March event have happened in the same area as often as every 400 years (based on 15 mapped large landslides) to every 1,500 years (based on carbon dating of what appears to be the oldest of four generations of large slides) during the last six millennia.

The researchers found that the size of the landslide area grew slowly starting in the 1930s until 2006, when it increased dramatically. That was followed by this year’s catastrophically larger slide.

Studies in previous decades indicated a high landslide risk for the Oso area, the researchers found, but they noted that it does not appear there was any publicly communicated understanding that debris from a landslide could run as far across the valley as it did in March. In addition to the fatalities, that event seriously injured at least 10 people and caused damage estimated at more than $50 million.

“For me, the most important finding is that we must think about landslides in the context of ‘risk’ rather than ‘hazard,'” Wartman said. “While these terms are often used interchangeably, there is a subtle but important difference. Landslide hazard, which was well known in the region, tells us the likelihood that a landslide will occur, whereas landslide risk tells us something far more important — the likelihood that human losses will occur as a result of a landslide.

“From a policy perspective, I think it is very important that we begin to assess and clearly communicate the risks from landslides,” he said.

Other study conclusions include:

• That past landslides and associated debris deposited by water should be carefully investigated when mapping areas for zoning purposes.

• That the influence of precipitation on destabilizing a slope should consider both cumulative amounts and short-duration intensities in assessing the likelihood of initial or renewed slope movement.

• That methods to identify and delineate potential landslide runout zones need to be revisited and re-evaluated.

The report is available at http://www.geerassociation.org/GEER_Post%20EQ%20Reports/Oso_WA_2014/index.html

Note : The above story is based on materials provided by University of Washington. The original article was written by Vince Stricherz.

Researchers figure out how oddly shaped sandstone landform structures come about

July 23, 2014

Delicate Arch, Arches National Park, Utah, USA. Credit: Jaroslav Soukup

A team of researchers with members from facilities in the Czech Republic and one from the U.S. has discovered the mechanism by which unique sandstone landforms take shape. In their paper published in Nature Geoscience, the team describes how their studies of sandstone in their lab led to insights about how both gravity and erosion contribute to the creation of such unique structures as Delicate Arch at Arches National Park in Utah. Chris Paola of the University of Minnesota offers a News & Views piece on the research done by the team in the same journal issue.
For many years, scientists have assumed it was wind and rain along with freezing and thawing that accounted for uniquely shaped sandstone landforms—they occur in many places and generally cause those who see them to take a second—or third look. Many believed they came about because some of the rock was just naturally harder than other parts. The results were sometimes awe inspiring structures that at times appeared to defy gravity. But now, new research suggests that it’s actually gravity that allows the structures to form in the first place.

Curious as to the real mechanism by which sandstone landforms take shape, the researchers took several samples into their lab and subjected them to intense scrutiny—after cutting the samples into cubes, they used pressure plates to simulate the loads of real structures while also subjecting them to simulated wind and rain. As the cubes were deformed, close inspection revealed that in the parts of the sandstone subjected to direct pressure (simulated gravity) individual grains tended to lock together creating sections of stone that were more resilient to wind and rain. That led to the creation of pillars within the sandstone that stood strong as the grains around them were swept away. As more free grains were swept away, more pressure was exerted on the column causing the grains in them to lock even tighter.

The team found that when pressure was applied from above to different parts of a cube, and artificial cracks and other perturbations were also introduced to the sandstone, it led to the development of interesting and unique shapes when subjected to simulated erosion. The researchers believe this same action applies to sandstone in its natural state, and accounts for the remarkable shapes that have left those beholding them wondering how they could have formed and then withstood the ravages of wind and rain—it’s because their columns have been made strong enough to withstand further weathering.

More information:
Sandstone landforms shaped by negative feedback between stress and erosion, Nature Geoscience (2014) DOI: 10.1038/ngeo2209

Abstract

Weathering and erosion of sandstone produces unique landforms1, 2 such as arches, alcoves, pedestal rocks and pillars. Gravity-induced stresses have been assumed to not play a role in landform preservation3 and to instead increase weathering rates4, 5. Here we show that increased stress within a landform as a result of vertical loading reduces weathering and erosion rates, using laboratory experiments and numerical modelling. We find that when a cube of locked sand exposed to weathering and erosion processes is experimentally subjected to a sufficiently low vertical stress, the vertical sides of the cube progressively disintegrate into individual grains. As the cross-sectional area under the loading decreases, the vertical stress increases until a critical value is reached. At this threshold, fabric interlocking of sand grains causes the granular sediment to behave like a strong, rock-like material, and the remaining load-bearing pillar or pedestal landform is resistant to further erosion. Our experiments are able to reproduce other natural shapes including arches, alcoves and multiple pillars when planar discontinuities, such as bedding planes or fractures, are present. Numerical modelling demonstrates that the stress field is modified by discontinuities to make a variety of shapes stable under fabric interlocking, owing to the negative feedback between stress and erosion. We conclude that the stress field is the primary control of the shape evolution of sandstone landforms.

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Researchers figure out how oddly shaped sandstone landform structures come about

Abstract

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