As much as two-thirds of Earth’s carbon may be hidden in the inner core, making it the planet’s largest carbon reservoir, according to a new model that even its backers acknowledge is “provocative and speculative.”
In a paper scheduled for online publication in the Proceedings of the National Academy of Sciences this week, University of Michigan researchers and their colleagues suggest that iron carbide, Fe7C3, provides a good match for the density and sound velocities of Earth’s inner core under the relevant conditions.
The model, if correct, could help resolve observations that have troubled researchers for decades, according to authors of the PNAS paper.
The first author is Bin Chen, who did much of the work at the University of Michigan before taking a faculty position at the University of Hawaii at Manoa. The principal investigator of the project, Jie Li, is an associate professor in U-M’s Department of Earth and Environmental Sciences.
“The model of a carbide inner core is compatible with existing cosmochemical, geochemical and petrological constraints, but this provocative and speculative hypothesis still requires further testing,” Li said. “Should it hold up to various tests, the model would imply that as much as two-thirds of the planet’s carbon is hidden in its center sphere, making it the largest reservoir of carbon on Earth.”
It is now widely accepted that Earth’s inner core consists of crystalline iron alloyed with a small amount of nickel and some lighter elements. However, seismic waves called S waves travel through the inner core at about half the speed expected for most iron-rich alloys under relevant pressures.
Some researchers have attributed the S-wave velocities to the presence of liquid, calling into question the solidity of the inner core. In recent years, the presence of various light elements—including sulfur, carbon, silicon, oxygen and hydrogen—has been proposed to account for the density deficit of Earth’s core.
Iron carbide has recently emerged as a leading candidate component of the inner core. In the PNAS paper, the researchers conclude that the presence of iron carbide could explain the anomalously slow S waves, thus eliminating the need to invoke partial melting.
“This model challenges the conventional view that the Earth is highly depleted in carbon, and therefore bears on our understanding of Earth’s accretion and early differentiation,” the PNAS authors wrote.
In their study, the researchers used a variety of experimental techniques to obtain sound velocities for iron carbide up to core pressures. In addition, they detected the anomalous effect of spin transition of iron on sound velocities.
They used diamond-anvil cell techniques in combination with a suite of advanced synchrotron methods including nuclear resonant inelastic X-ray scattering, synchrotron Mössbauser spectroscopy and X-ray emission spectroscopy.
Laguna del Maule, Chile, is at the center of a volcanic field that has erupted 36 times during the last 25,000 years, and is now experiencing significant uplift due to magma intrusion. Photos: David Tenenbaum/University of Wisconsin
MADISON, Wis. — If Brad Singer knew for sure what was happening three miles under an odd-shaped lake in the Andes, he might be less eager to spend a good part of his career investigating a volcanic field that has erupted 36 times during the last 25,000 years. As he leads a large scientific team exploring a region in the Andes called Laguna del Maule, Singer hopes the area remains quiet.
But the primary reason to expend so much effort on this area boils down to one fact: The rate of uplift is among the highest ever observed by satellite measurement for a volcano that is not actively erupting.
That uplift is almost definitely due to a large intrusion of magma — molten rock — beneath the volcanic complex. For seven years, an area larger than the city of Madison has been rising by 10 inches per year.
That rapid rise provides a major scientific opportunity: to explore a mega-volcano before it erupts. That effort, and the hazard posed by the restless magma reservoir beneath Laguna del Maule, are described in a major research article in the December issue of the Geological Society of America’s GSA Today.
“We’ve always been looking at these mega-eruptions in the rear-view mirror,” says Singer. “We look at the lava, dust and ash, and try to understand what happened before the eruption. Since these huge eruptions are rare, that’s usually our only option. But we look at the steady uplift at Laguna del Maule, which has a history of regular eruptions, combined with changes in gravity, electrical conductivity and swarms of earthquakes, and we suspect that conditions necessary to trigger another eruption are gathering force.”
Laguna del Maule looks nothing like a classic, cone-shaped volcano, since the high-intensity erosion caused by heavy rain and snow has carried most of the evidence to the nearby Pacific Ocean. But the overpowering reason for the absence of “typical volcano cones” is the nature of the molten rock underground. It’s called rhyolite, and it’s the most explosive type of magma on the planet.
The eruption of a rhyolite volcano is too quick and violent to build up a cone. Instead, this viscous, water-rich magma often explodes into vast quantities of ash that can form deposits hundreds of yards deep, followed by a slower flow of glassy magma that can be tens of yards tall and measure more than a mile in length.
The next eruption could be in the size range of Mount St. Helens — or it could be vastly bigger, Singer says. “We know that over the past million years or so, several eruptions at Laguna del Maule or nearby volcanoes have been more than 100 times larger than Mount St. Helens,” he says. “Those are rare, but they are possible.” Such a mega-eruption could change the weather, disrupt the ecosystem and damage the economy.
Trying to anticipate what Laguna del Maule holds in store, Singer is heading a new $3 million, five-year effort sponsored by the National Science Foundation to document its behavior before an eruption. With colleagues from Chile, Argentina, Canada, Singapore, and Cornell and Georgia Tech universities, he is masterminding an effort to build a scientific model of the underground forces that could lead to eruption. “This model should capture how this system has evolved in the crust at all scales, from the microscopic to basinwide, over the last 100,000 years,” Singer says. “It’s like a movie from the past to the present and into the future.”
Over the next five years, Singer says he and 30 colleagues will “throw everything, including the kitchen sink, at the problem — geology, geochemistry, geochronology and geophysics — to help measure, and then model, what’s going on.”
One key source of information on volcanoes is seismic waves. Ground shaking triggered by the movement of magma can signal an impending eruption. Team member Clifford Thurber, a seismologist and professor of geoscience at UW-Madison, wants to use distant earthquakes to locate the underground magma body.
As many as 50 seismometers will eventually be emplaced above and around the magma at Laguna del Maule, in the effort to create a 3-D image of Earth’s crust in the area.
By tracking multiple earthquakes over several years, Thurber and his colleagues want to pinpoint the size and location of the magma body — roughly estimated as an oval measuring five kilometers (3.1 miles) by 10 kilometers (6.2 miles).
Each seismometer will record the travel time of earthquake waves originating within a few thousand kilometers, Thurber explains. Since soft rock transmits sound less efficiently than hard rock, “we expect that waves that pass through the presumed magma body will be delayed,” Thurber says. “It’s very simple. It’s like a CT scan, except instead of density we are looking at seismic wave velocity.”
As Singer, who has been visiting Laguna del Maule since 1998, notes, “The rate of uplift — among the highest ever observed — has been sustained for seven years, and we have discovered a large, fluid-rich zone in the crust under the lake using electrical resistivity methods. Thus, there are not many possible explanations other than a big, active body of magma at a shallow depth.”
The expanding body of magma could freeze in place — or blow its top, he says. “One thing we know for sure is that the surface cannot continue rising indefinitely.”
Twin-satellites GRACE with the earth’s gravity field (vertically enhanced) calculated from CHAMP data. Credit: GFZ
People tend to think of gravity here on Earth as a uniform and consistent thing. Stand anywhere on the globe, at any time of year, and you’ll feel the same downward pull of a single G. But in fact, Earth’s gravitational field is subject to variations that occur over time. This is due to a combination of factors, such as the uneven distributions of mass in the oceans, continents, and deep interior, as well as climate-related variables like the water balance of continents, and the melting or growing of glaciers.
And now, for the first time ever, these variations have been captured in the image known as the “Potsdam Gravity Potato” – a visualization of the Earth’s gravity field model produced by the German Research Center for Geophysics’ (GFZ) Helmholtz’s Center in Potsdam, Germany.
And as you can see from the image above, it bears a striking resemblance to a potato. But what is more striking is the fact that through these models, the Earth’s gravitational field is depicted not as a solid body, but as a dynamic surface that varies over time.This new gravity field model (which is designated EIGEN-6C) was made using measurements obtained from the LAGEOS, GRACE, and GOCE satellites, as well as ground-based gravity measurements and data from the satellite altimetry.
Compared to the previous model obtained in 2005 (shown above), EIGEN-6C has a fourfold increase in spatial resolution.
“Of particular importance is the inclusion of measurements from the satellite GOCE, from which the GFZ did its own calculation of the gravitational field,” says Dr. Christoph Foerste who directs the gravity field work group at GFZ along with Dr. Frank Flechtner.
The ESA mission GOCE (Gravity Field and Steady-State Ocean Circulation Explorer) was launched in mid-March 2009 and has since been measuring the Earth’s gravitational field using satellite gradiometry – the study and measurement of variations in the acceleration due to gravity.
“This allows the measurement of gravity in inaccessible regions with unprecedented accuracy, for example in Central Africa and the Himalayas,” said Dr. Flechtner. In addition, the GOCE satellites offers advantages when it comes to measuring the oceans.
Within the many open spaces that lie under the sea, the Earth’s gravity field shows variations. GOCE is able to better map these, as well as deviations in the ocean’s surface – a factor known as “dynamic ocean topography” – which is a result of Earth’s gravity affecting the ocean’s surface equilibrium.
Long-term measurement data from the GFZ’s twin-satellite mission GRACE (Gravity Recovery And Climate Experiment) were also included in the model. By monitoring climate-based variables like the melting of large glaciers in the polar regions and the amount of seasonal water stored in large river systems, GRACE was able to determine the influence of large-scale temporal changes on the gravitational field.
Given the temporal nature of climate-related processes – not to mention the role played by Climate Change – ongoing missions are needed to see how they effect our planet long-term. Especially since the GRACE mission is scheduled to end in 2015.
In total, some 800 million observations went into the computation of the final model which is composed of more than 75,000 parameters representing the global gravitational field. The GOCE satellite alone made 27,000 orbits during its period of service (between March 2009 and November 2013) in order to collect data on the variations in the Earth’s gravitational field.
The final result achieved centimeter accuracy, and can serve as a global reference for sea levels and heights. Beyond the “gravity community,” the research has also piqued the interest of researchers in aerospace engineering, atmospheric sciences, and space debris.
But above all else, it offers scientists a way of imaging the world that is different from, but still complimentary to, approaches based on light, magnetism, and seismic waves. And it could be used for everything from determining the speed of ocean currents from space, monitoring rising sea levels and melting ice sheets, to uncovering hidden features of continental geology and even peeking at the convection force driving plate tectonics.
Large oviraptorosauruses arranged their nests so that the adult dinosaur could put its weight in the middle and avoid crushing the eggs. Image Credit : Kohei Tanaka, University of Calgary
It must have been a weighty question for dinosaurs, some of which were dutiful parents that brooded their eggs like birds: How could they sit on their eggs without breaking them? According to new research presented at the Society of Vertebrate Paleontology annual meeting here, some rhinoceros-sized dinosaurs successfully brooded in open-air nests by arranging the eggs so they wouldn’t break. The study shows that even the largest dinosaurs in this group probably provided some parental care.
Researchers have found a number of fossilized nests from the group of dinosaurs called oviraptorosaurs, fairly close relatives of early birds. (The name means “egg-thief lizards,” because researchers originally assumed the creatures ate the eggs that were so often found with them. But scientists now realize the animals were nesting, not feasting.) Several fossil nests include an adult, apparently a brooding parent buried alongside its eggs. Those specimens were about the size of a modern ostrich—about 100 kilograms. But some oviraptorosaurs weighed 3000 kilograms, as much as a modern rhinoceros. Whether those largest oviraptorosaurs, with eggs up to 40 centimeters in diameter, had open nests and brooded like their smaller cousins or buried their eggs more like modern crocodiles has been an open question.
Open nests require less porous eggshells to prevent water from escaping. Previous studies used indirect calculations to estimate how much water could have escaped through the shells and concluded that they were too porous to be stored in open nests. But Kohei Tanaka of the University of Calgary in Canada took a closer look. He calculated the porosity of the oviraptorosaurus eggs and compared them with the porosity of modern eggs in buried nests and open nests. The results showed that the oviraptorosaur eggs were less porous than the earlier studies had indicated. That suggests that even the largest “ovis” built open nests, Tanaka says.
Tanaka then calculated how much weight the eggs could bear before they cracked. He found that the eggs of small and medium-sized oviraptorosaurs could have borne the weight of an adult sitting on a nest of a dozen or so tightly packed eggs. But the eggs of the largest animals would have broken.
Finally, he analyzed nest shape. The smaller dinosaurs built nests with the eggs arranged like the petals of a daisy, closely packed together. The nests of the larger oviraptorosauruses, however, have eggs arranged in a larger ring around an open space. An adult could have plopped into the middle, keeping most of its weight on the ground instead of on the eggs, Tanaka says. He concludes that the dinosaurs’ egg-laying behavior seems to have evolved to allow even the largest animals to sit in their nests.
Given the precise arrangement of eggs in fossil nests, the eggs could have been partially buried—or at least nestled—in sediment, even when a parent was brooding them in an “open” nest, says David Varricchio, a paleontologist at Montana State University, Bozeman. But he finds Tanaka’s calculations persuasive and agrees that even the biggest oviraptorosaurs probably sat on their eggs.
Since 2000, minor volcanic eruptions (such as Russia’s Sarychev Peak, seen erupting in this image taken from the International Space Station on 12 June 2009) have slowed Earth’s warming as a result of carbon dioxide and other greenhouse gases. Image Credit : NASA
Minor volcanic eruptions substantially slowed Earth’s warming between 2000 and 2013, a new study suggests. The small particles, or aerosols, were spewed high into the atmosphere and scattered sunlight back into space, preventing the global average temperature from rising from 0.05°C to 0.12°C. That cooling effect represents between 25% and 50% of the expected temperature rise during that period because of rising atmospheric concentrations of greenhouse gases, the scientists say, so the finding helps explain the so-called hiatus in global warming over the last 15 years.
“This is an important paper,” says Brian Toon, an atmospheric scientist at the University of Colorado, Boulder. The team’s results “help us understand why Earth didn’t warm as much as expected by climate models in the past decade or so.”
Scientists have long known of the cooling effect of major volcanic eruptions, which spew large amounts of light-scattering aerosols into the stratosphere. The Philippines’ Mount Pinatubo, for example, cooled Earth by a few tenths of a degree Celsius for months after it blew its top in June 1991. But the chilling effect of minor eruptions has been hotly debated, says David Ridley, an atmospheric scientist at the Massachusetts Institute of Technology in Cambridge. That’s because scientists have presumed that most of the aerosols from minor eruptions do not rise beyond the troposphere, the layer of Earth’s atmosphere where weather occurs and where natural processes quickly clear particles from the atmosphere.
As a result, scientists typically ignore satellite data for altitudes lower than 15 kilometers, Ridley says. That’s because the individual droplets or ice particles in clouds (which are, after all, aerosols themselves) in those layers of the atmosphere can confuse the tally, he notes. In the tropics, the boundary between the stratosphere and the troposphere is about 15 kilometers. But in temperate and polar regions, the boundary can be as low as 10 kilometers, Ridley says. That leaves a gap as much as 5 km thick in the lower stratosphere where climate-cooling aerosols can persist, yet not show up, in satellite data.
So, Ridley and his colleagues scoured data from other sources. Some came from ground-based lasers that probed the atmosphere from four sites in the Northern Hemisphere. By measuring the amount of laser light reflected back to Earth, the researchers could estimate the concentrations of aerosols at various altitudes. Data gathered by high-flying balloons and satellites helped provide crosschecks on the laser measurements. Also, a worldwide network of sensors measured the total amount of sunlight reaching the ground, which gave the scientists a sense of how much radiation was being scattered back into space by atmospheric aerosols at all levels.
The team’s analysis reveals that the lower stratosphere indeed contains many untallied aerosols from minor eruptions. Data gathered at a site near Tsukuba, Japan, show that about a third of stratospheric aerosols—much of them from small volcanoes—sit below 15 kilometers. A site near Tomsk, Russia, found that, on average, about half of the stratospheric aerosols resided below 15 kilometers, the researchers will report in a forthcoming issue of Geophysical Research Letters. In these lower layers of the stratosphere, aerosol concentrations rose after known volcanic eruptions and then dropped off, Ridley says.
“What they’ve found makes sense, and it’s important to quantify,” says Alan Robock, a climate scientist at Rutgers University in New Brunswick, New Jersey. The better scientists can pin down natural influences on climate, he says, the better they can understand the impact of human activities.
Yet the cooling effect of these minor eruptions does not completely account for the global warming hiatus in which the rise in Earth’s average temperature has slowed since the late 1990s, Toon says. Scientists increasingly believe that most of the rest of the missing heat has gone into deep ocean waters. Another source of cooling is suspected to be aerosols from industry in East Asia.
In any case, Robock suggests, scientists should develop new sets of sensors or analytical techniques to measure stratospheric aerosols. Whereas some of those instruments could be space-based, others could be borne by high-flying balloons. The latter type of sensors, Robock notes, could directly measure the size distribution of aerosols, which could help researchers better model their effects on climate.
(From left) John Waldron with graduate students Shawna White and Ryan Lacombe examining sea-floor sediments formed during the closing of the Iapetus Ocean, now uplifted and exposed at the foot of the steep cliffs of the Port au Port Peninsula in western Newfoundland.
Pangea, the supercontinent that contained most of the Earth’s landmass until about 180 million years ago, endured an apocalyptic undoing during the Jurassic period, when the Atlantic Ocean opened up. This is well understood. But what is less clear is how Pangea came into being in the first place.
Earth and atmospheric sciences professor John Waldron in the University of Alberta’s Faculty of Science, along with three colleagues in Atlantic Canada and the United Kingdom, recently described a new model for the events that led to the closing of ancient oceans and the formation of Pangea. The scientists outline their findings in a paper published in the journal Geology.
According to Waldron and his fellow authors, the answers may be found in the best known of the ancient oceans, Iapetus, which lay between the ancient core of North America and parts of what are now Europe, Africa and South America.
The Iapetus Ocean opened up about 600 million years ago by rifting between these continents. But just how oceans transition from opening to closing is a long-standing unsolved problem in tectonics.
*Fig(2)
Using the modern Caribbean Sea as an analogy, Waldron and his co-authors observed that at its eastern edge, the Caribbean Plate is overriding the floor of the Atlantic Ocean in a process known as subduction, which produces a zone of earthquakes and volcanoes extending from Barbados to Haiti. In another example, the zone between South America and Antarctica is also overriding the Atlantic Ocean floor.
“Most geologists have assumed that the ancient Iapetus Ocean stopped getting wider and started to shrink when subduction somehow spontaneously started up along its margins. Looking at the history of the oceans formed since Pangea, we think that just doesn’t happen,” explains Waldron. “It’s much more likely that a small plate, like the modern Caribbean, came into the Iapetus from the east, bringing with it many small continental fragments. This helps to explain many odd features of the Appalachian and Caledonide mountain belts that are otherwise very difficult to understand.”
Waldron and his colleagues suggest that the Iapetus Ocean contained a region that looked like a mirror image of the Caribbean. They have named this the Sea of Exploits, after the Bay of Exploits in Newfoundland, where fragments of this plate are preserved. A subduction zone along its edge advanced westward into the Iapetus Ocean, overriding its floor and producing earthquakes and chains of island volcanoes.
Once “infected” with subduction, the floor of the Iapetus Ocean was progressively consumed, leading to collisions between the surrounding continents that built the Appalachians of North America and the Caledonide Mountains of Scotland and Norway—and the assembly of Pangea.
Fragments of these ancient island volcanoes are preserved in Atlantic Canada and the British Isles, with folded and faulted sedimentary rocks squeezed by the ensuing collisions, which Waldron has studied with a succession of graduate students since the 1990s.
The modern Atlantic may be similarly doomed to close, in the distant future. If subduction zones like those around the Caribbean Plate continue to consume the floor of the Atlantic Ocean, eventually the continents around the Atlantic may collide to form a mountain range and a new supercontinent.
However, notes Waldron, the process is likely to take another 100 million years, so we may not be around to see it happen.
*Fig(2) : This graphic shows the possible geography of the Iapetus Ocean in a series of snapshots from the Cambrian Period (about 530 million years ago) until the Late Ordovician Period (about 450 million years ago). The continent Laurentia, which formed the core of modern North America, is shown in blue. Yellow colours represent Baltica, which became Scandinavia and Eastern Europe. Shades of pink and magenta represent parts of Gondwana, which was located over the South Pole in the Cambrian Period and included modern South America and Africa. The red and orange fragments are pieces of Gondwana that found their way into the Appalachian and Caledonide mountain ranges, including much of Atlantic Canada and portions of Great Britain and Ireland.
Reference:
“How was the Iapetus Ocean infected with subduction?” Geology, December 2014, v. 42, p. 1095-1098, first published on October 24, 2014, DOI: 10.1130/G36194.1
Forty-seven million years ago, a pregnant mare and its unborn foal lost their lives, perhaps chased into a lake, where they drowned. Where they died, however, was a stroke of luck for 21st century paleontologists. Their fossilized remains were discovered in the Messel Pit, a former coal and oil shale mine near Frankfurt, Germany, that is famous for its exquisitely preserved fossils.
The mare and her fetus are now giving scientists an unprecedented glimpse into the anatomy and reproduction of this early horse species, Eurohippus messelensis. Like other early horses, the mare was small, only about the size of a fox terrier, says Jens Franzen, a paleontologist at the Senckenberg Research Institute and Natural History Museum in Frankfurt, who presented the prepared fossil for the first time yesterday at the Society of Vertebrate Paleontology annual meeting here.
Not only were most of the bones of the mare and fetus intact, but scientists can also detect the placenta. This organ was not fossilized directly, but is visible as a dark shadow left by bacteria that consumed the tissue and then were fossilized. Researchers can also see the broad ligament that helps attach the uterus to the backbone. (Although the skull of the fetus was crushed, its ribs and legs are clearly visible.) Under a scanning electron microscope, scientists could see the cellular structure of the colon and the plant remains of the mare’s final meals.
The position of the foal suggests that it wasn’t fully in position to be born, but was close to mature, and suggests that ancient horses gave birth in a similar way to their modern cousins. It is only the second example of a fossil where the placenta can be identified, Franzen says.
Coccolithophores. Credit: University of Southampton
A study of ancient marine algae, led by the University of Southampton, has found that climate change affected their growth and skeleton structure, which has potential significance for today’s equivalent microscopic organisms that play an important role in the world’s oceans.
Coccolithophores, a type of marine algae, are prolific in the ocean today and have been for millions of years. These single-celled plankton produce calcite skeletons that are preserved in seafloor sediments after death. Although coccolithophores are microscopic, their abundance makes them key contributors to marine ecosystems and the global carbon cycle.
There is, therefore, much current interest in how coccolithophore calcification might be affected by climate change and ocean acidification, both of which occur as atmospheric carbon dioxide increases.
The research, published in Nature Communications, examined preserved fossil remains of coccolithophores from a period of climate warming and ocean acidification that occurred around 56 million years ago – the Paleocene Eocene Thermal Maximum (PETM) – and provides a much-needed long-term perspective of coccolithophore response to ocean acidification.
Dr Sarah O’Dea, from Ocean and Earth Science at the University of Southampton and lead author of the study, says: “Our results show that climate change significantly altered coccolithophore calcification rates at the PETM and has the potential to be just as significant, perhaps even more so, today. Ultimately then, it is the factors that influence where species live, their abundance, how fast they grow and their ability to adapt to environmental change that is likely to control future coccolithophore calcite production.”
The study investigated two key PETM coccolithophores, Coccolithus pelagicus and Toweius pertusus, both of which are directly related to species that dominate the modern ocean.
It found that calcification rates of C. pelagicus and T. pertusus halved during the PETM, due to changes in environmental factors that influenced their growth. The response of each species was, however, different, and involved intervals of slowed growth in C. pelagicus and an overall reduction in the size of the skeletal components – coccoliths – in T. pertusus. Intriguingly though, there was very little evidence for any response to ocean acidification, other than perhaps a slight thinning of C. pelagicus coccoliths..
Dr Samantha Gibbs, from Ocean and Earth Science at the University of Southampton, who was Dr O’Dea’s PhD supervisor and co-author of the study, says: “A key objective was to record calcification in fossil coccolithophores in a way that enabled direct comparison with measurements from living specimens. Our novel technique involved analysing coccolithophore skeletal remains and applying observations from modern specimens to estimate, for the first time, calcification rates of fossil coccolithophores.”
This image, based on the final GOCE gravity model, charts current velocities in the Gulf Stream in meters per second. Credit: TUM IAPG
Just four months after the final data package from the GOCE satellite mission was delivered, researchers are laying out a rich harvest of scientific results, with the promise of more to come. A mission of the European Space Agency (ESA), the Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) provided the most accurate measurements yet of Earth’s gravitational field.
The GOCE Gravity Consortium, coordinated by the Technische Universität München (TUM), produced all of the mission’s data products including the fifth and final GOCE gravity model. On this basis, studies in geophysics, geology, ocean circulation, climate change, and civil engineering are sharpening the picture of our dynamic planet – as can be seen in the program of the 5th International GOCE User Workshop, taking place Nov. 25-28 in Paris.
The GOCE satellite made 27,000 orbits between its launch in March 2009 and re-entry in November 2013, measuring tiny variations in the gravitational field that correspond to uneven distributions of mass in Earth’s oceans, continents, and deep interior. Some 800 million observations went into the computation of the final model, which is composed of more than 75,000 parameters representing the global gravitational field with a spatial resolution of around 70 kilometers. The precision of the model improved over time, as each release incorporated more data. Centimeter accuracy has now been achieved for variations of the geoid – a gravity-derived figure of Earth’s surface that serves as a global reference for sea level and heights – in a model based solely on GOCE data.
The fifth and last data release benefited from two special phases of observation. After its first three years of operation, the satellite’s orbit was lowered from 255 to 225 kilometers, increasing the sensitivity of gravity measurements to reveal even more detailed structures of the gravity field. And through most of the satellite’s final plunge through the atmosphere, some instruments continued to report measurements that have sparked intense interest far beyond the “gravity community” – for example, among researchers concerned with aerospace engineering, atmospheric sciences, and space debris.
Moving on: new science, future missions
Through the lens of Earth’s gravitational field, scientists can image our planet in a way that is complementary to approaches that rely on light, magnetism, or seismic waves. They can determine the speed of ocean currents from space, monitor rising sea level and melting ice sheets, uncover hidden features of continental geology, even peer into the convection machine that drives plate tectonics. Topics like these dominate the more than 100 talks scheduled for the 5th GOCE User Workshop, with technical talks on measurements and models playing a smaller role. “I see this as a sign of success, that the emphasis has shifted decisively to the user community,” says Prof. Roland Pail, director of the Institute for Astronomical and Physical Geodesy at TUM.
This shift can be seen as well among the topics covered by TUM researchers, such as estimates of the elastic thickness of the continents from GOCE gravity models, mass trends in Antarctica from global gravity fields, and a scientific roadmap toward worldwide unification of height systems. For his part Pail – who was responsible for delivery of the data products – chose to speak about consolidating science requirements for a next-generation gravity field mission.
Reference :
“EGM_TIM_RL05: An Independent Geoid with Centimeter Accuracy Purely Based on the GOCE Mission,” Jan Martin Brockmann, Norbert Zehentner, Eduard Höck, Roland Pail, Ina Loth, Torsten Mayer-Gürr, and Wolf-Dieter Shuh. Geophysical Research Letters 2014, doi:10.1002/2014GL061904.
Soil fauna from a soil in Alabama, USA is depicted. Credit: Valerie Behan-Pelletier/TheUniversity of Manchester
A new study has pulled together research into the most diverse place on earth to demonstrate how the organisms below-ground could hold the key to understanding how the worlds ecosystems function and how they are responding to climate change.
Published in Nature, the paper by Professor Richard Bardgett from The University of Manchester and Professor Wim van der Putten of the Netherlands Institute of Ecology, brings together new knowledge on this previously neglected area. The paper not only highlights the sheer diversity of life that lives below-ground, but also how rapid responses of soil organisms to climate change could have far reaching impacts on future ecosystems. The paper also explores how the below-ground world can be utilised for sustainable land management.
Professor Bardgett explains: “The soil beneath our feet arguably represents the most diverse place on Earth. Soil communities are extremely complex with literally millions of species and billions of individual organisms within a single grassland or forest, ranging from microscopic bacteria and fungi through to larger organisms such as earthworms, ants and moles. Despite this plethora of life the underground world had been largely neglected by research, it certainly used to be a case of out of sight out of mind, although over the last decade we have seen a significant increase in work in this area.”
The increase in research on below-ground organisms has helped to explain how they interact with each other and crucially how they influence the above-ground flora and fauna.
Professor van der Putten says: “For example, an increasing number of studies show that above-ground pest control is influenced by organisms in the soil. This supports the view that a healthy crop requires healthy soil.”
Professor Bardgett says there have been some other fascinating results: “Recent soil biodiversity research has revealed that below-ground communities not only play a major role in shaping plant biodiversity and the way that ecosystems function, but it can also determine how they respond to environmental change.”
He continues: “One of the key areas for future research will be to integrate what has been learnt about soil diversity into decisions about sustainable land management. There is an urgent need for new approaches to the maintenance and enhancement of soil fertility for food, feed and biomass production, the prevention of human disease and tackling climate change. As we highlight in this paper, a new age of research is needed to meet these scientific challenges and to integrate such understanding into future land management and climate change mitigation strategies.”
With the publication of this paper Professor Bardgett is optimistic for the future: “Soil biodiversity research is now entering a new era; awareness is growing among scientists and policy makers of the importance of soil biodiversity for the supply of ecosystem goods and services to human society. New technologies are allowing us to study underground ecosystems in situ and a new generation of tools are available to properly investigate the biology of soil and its ecological and evolutionary role.”
Terrestrial LiDAR scanning of the lava dome, Soufriere Hills Volcano, Montserrat.
We live on an ever-changing planet. Volcanoes emerge from the oceans; landslides transport millions of tonnes of material down hills and mountains causing billions of pounds of damage; coastlines and glaciers retreat at almost visible rates. But can we do anything about it? Lee Jones says we can.
Geomatics is the science of measuring, storing and processing information about the Earth that is accurate in both space and time. It uses a variety of specialised equipment, including Terrestrial Light Detection and Ranging (LiDAR) Scanners (TLS) and Global Navigation Satellite Systems (GNSS) to produce images, maps and 3D models of these rapidly-changing environments that are geo-referenced – accurately positioned in physical space.
The British Geological Survey (BGS) has been using geomatic techniques, both in the UK and overseas, since 2000. Applications have been many and varied. Scientists have monitored the actively-growing volcanic lava dome of the Soufriere Hills Volcano, on the Caribbean island of Montserrat. They have mapped and modelled several UK landslide locations, both inland and on the coast
They have tracked eroding coastlines on England’s eastern and southern coasts, and carried out rock stability analysis in places from Brotton in North Yorshire to the Rock of Gibraltar. They have even been involved with geo-conservation – caring for sites which make a special contribution to our Earth heritage – at Hutton’s Unconformity* at Siccar Point in Berwickshire and other sites across the UK.
BGS has a field laboratory site on the Holderness coast, at Aldbrough in North Yorkshire. The 300m-long site includes a 17m-high section of cliff made up of glacial till, a mixture of clay, sand, gravel and boulders left behind by retreating glaciers during the last ice age. The cliff has been monitored since 2001 and is disappearing at a rate of 3m a year. This erosion is caused by both landslides and the direct action of the sea crashing against it.
Between 2001 and 2013, researchers carried out 19 terrestrial LiDAR surveys on the same section of cliff and beach. Varying weather and tide conditions meant that not all the surveys had the same coverage, but the scans gave us enough information to create 3D terrain models – digital representations of the ground surface without any objects like plants and buildings. We could then model how the ground was changing over time.
In 2012, BGS established a weather station at the site to record rainfall, wind-speed and direction, temperature and atmospheric pressure. Two pairs of 20m-deep boreholes were drilled 10m and 20m back from the cliff edge, which we used to place instruments for measuring changes in slope angle and water pressure. This information helps us model future changes in the cliff that may warn of landslides. Putting instruments in active slopes and retreating coastlines in this way may give us enough forewarning of slope failure or coastal collapse to allow time for evacuation and specialist repairs, potentially saving lives and millions of pounds.
Tracking glaciers’ retreat
BGS also has a field observatory site at Virkisjökull in south-east Iceland, studying the evolution of the glacier and the surrounding landscape, and their responses to regional climate. Repeated, highly detailed surveys monitor how both the glacier and land surface, and the rock and earth beneath, change over time. Cutting-edge technologies, not used in such a combination anywhere else in the world, give us unique insights into how the landscape is formed and how the glacial system responds to climate change. Virkisjökull is retreating quickly, like most glaciers in Iceland. Since 1996, the glacier margin has retreated nearly 500m and it has accelerated over the last five years.
No single location has a view of the entire glacier, so since 2009 we have used different combinations of instruments at different sites to get a picture of its whole surface. The enormity of this task should not be underestimated; transporting over 50kg of surveying kit across the glacial foreland is hard enough, but moving it onto the glacier itself while wearing crampons was extremely treacherous.
In terms of data-storage and processing, these LiDAR scans were massive, with over 300 million points recorded in the 2012 survey alone. The data produced by the laser scan survey were turned into a virtual 3D surface of the glacier and its margin; from this we could create change models from year to year and determine how quickly the glacier is retreating over time.
In 2010 we set up three weather stations and four seismometers to locate and measure the size of the ground movement under and around the glacier. Two years later, we installed six GNSS units on the glaciers of Virkisjökull and Falljökull, with another unit as a permanently recording base-station on stable ground away from the ice, to let us accurately monitor the rate of glacial movement.
This shows us that the top of the glacier, where it drops over the edge of the cliff (the ice-fall), is being pushed forwards by newly-formed ice from the ice-cap that feeds it, by more than 70m a year. However, the front edge of the glacier – its snout – is melting back at a rate of over 10m a year. This is happening even in the winter, telling us the glacier is now in terminal decline.
This type of monitoring has importance far beyond the glacier itself. By finding out how the Earth is changing in a particular place, we can gain insights into much broader trends in the environment. Tracking the glacier’s retreat at Virkisjökull gives us a better understanding of what effect climate change is having on our planet. Monitoring the coast at Aldbrough shows us how our coastlines are reacting to changes in sea levels and weather patterns. When we need to understand the big picture, sometimes it pays to think small.
*This is a rocky promontory where in 1788 James Hutton made one of the fundamental breakthroughs in the history of geology. He realised that rock formations created at different times and by different forces came together here, providing compelling evidence for his theories on the Earth’s age and on the forces that shape it.
Remnants of one of the largest landslides ever to occur on land covers a 3400-square-kilometer swath of southwestern Utah that lies generally southeast of a line between Beaver (top center) and Cedar City (lower left). (Beaver lies about 77 km from Cedar City.)
For decades, geologists have noted the signs of ancient landslides in southwestern Utah. Although many parts of the landscape don’t look that odd at first glance, certain layers include jumbled masses of fractured rock sandwiched among thick veins of lava, ash, and mud. Now, new fieldwork suggests that many of those ancient debris flows are the result of one of Earth’s largest known landslides, which covered an area nearly 39 times the size of Manhattan.
Between 20 million and 30 million years ago, southwestern Utah was home to active volcanoes. It isn’t clear how many peaks were erupting during that time, but together they left behind lava, ash, and other material that geologists have dubbed the Marysvale volcanic field.
Previously, scientists had noted that large volumes of broken rock—including everything from boulder-sized bits to mountain-sized chunks—covered as much as 500 square kilometers of the region. Many of those masses were presumed to come from different sources at different times, says Robert Biek, a geologist with the Utah Geological Survey in Salt Lake City. But now, an analysis by Biek and his colleagues hints that the ancient slumps were all part of one massive, catastrophic collapse.
Material from that landslide is sandwiched between volcanic ash that has been well dated, Biek says. The slide debris sits on top of a now-hardened layer of ash that fell about 22 million years ago. The ash layer atop the masses of broken rock fell about 21.6 million years ago. So, the researchers contend, the immense landslide happened sometime between those two dates.
Altogether, the broken rock can be found across 3400 square kilometers of the region. The volume of rock involved, somewhere between 1700 and 2000 cubic kilometers of material, makes the ancient slide one of the largest known to have occurred on land anywhere in the world, the researchers report in the current issue of Geology.
The ancient event has been dubbed the Markagunt gravity slide, Biek says. (Markagunt, the name of a plateau in the region, means “highland of the trees” in the language of the Paiute Indians who are native to the area.) Geological evidence gives scientists an idea of how the event occurred. First, the terrain at the time of the slide sloped, in general, slightly toward the south. Second, there’s a relatively thin layer of heavily weathered volcanic ash on the lower edge of many flows, Biek says. After long exposure to the elements, some of that material had degraded into slick clay, which acted as a lubricant for the landslide once it began.
Eventually, the accumulation of massive volumes of volcanic material on top of the region’s slick, sloping terrain led to a slide of almost unimaginable proportions. About one-fourth of the volcanic plateau collapsed and gave way during the event, Biek says. The front end of the slide, where material is dozens of meters thick, spilled southward more than 30 kilometers. In some places, the friction generated by the surging slide produced so much heat that it melted the surfaces of rocks into 2- to 5-centimeter-thick layers of glass.
What specifically triggered the Markagunt gravity slide is still a mystery, Biek says. It’s possible that molten rock rising toward Earth’s surface pushed the flanks of the area’s volcanoes upward as well as sideways, fracturing their rocks and creating an increasingly unstable pile of material ripe for a landslide, he notes.
Geologists have long suspected that a similarly large slide occurred in northwestern Wyoming millions of years ago, says Gary Smith, a geologist at the University of New Mexico, Albuquerque. That event, often called the Heart Mountain slide, was previously considered the largest landslide known to have taken place on land. “So while these [large] events are not common, they’re not unique,” he notes.
Ongoing fieldwork suggests that the Markagunt slide is substantially larger than first estimated, Biek says. That would dethrone the Heart Mountain slide as the world’s largest, he notes.
But the size of the Markagunt gravity slide isn’t the only interesting thing about the new study, Smith says: “It never ceases to amaze me how geologists can go into an area we think we know well and find new things.”
A palaeontologist from our University studying fossils that were kept in a museum in Canada for over 75 years has discovered a new species of dinosaur.
Dr Nick Longrich from our University studied the fossilised bones of two horned dinosaurs from the ceratopsian family and found that they were in fact two previously unknown species. The findings reveal that the dinosaur species from this region were much more diverse than first thought.
“We thought we had discovered most of the species, but it seems there are many undiscovered dinosaurs left,” said Dr Nick Longrich from the University’s Department of Biology & Biochemistry. “There are lots of species out there. We’ve really only just scratched the surface.”
One of the new species represents a new species of Pentaceratops, named Pentaceratops aquilonius. Pentaceratops, a smaller cousin of Triceratops, belong to the Chasmosaurinae, a group of large, horned dinosaurs characterised by long brow horns and elongate frills. Around the size of a buffalo, they were a major group of plant eating dinosaurs in western North America at the end of the Cretaceous Period, around 75 million years ago. The other appears to represent a new species of Kosmoceratops.
Western North America hosted a remarkable diversity of dinosaurs during the Campanian period. Among the most diverse clades was the Chasmosaurinae. Up until now, ten chasmosaur species have been recognised from the upper Campanian of western North America, with distinct species occurring in the northern and southern parts of the continent.
The fossils studied by Longrich were previously classified as Anchiceratops and Chasmosaurus, species known from Canada, but after re-analysing the skeletons, he realised they more closely resembled dinosaurs from the American Southwest. One was closely related to Pentaceratops sternbergii from New Mexico, but is a more primitive species, named Pentaceratops aquilonius. It was smaller, and differed in the shape of the frill and arrangement of the hornlets on the back. The other seems to be related to Kosmoceratops from Utah. It seems to be a new species as well, but more complete fossils are needed to be certain.
Published in the academic journal Cretaceous Research, Longrich proposes that distinct northern and southern provinces existed during the Campanian, but that there was exchange between them. The dinosaurs would spread from one part of the continent to the other and then diverge to form new species. Competition between the different species then prevented the dinosaurs from moving between the northern and southern regions.
Longrich added: “The distribution of dinosaur species was very different from the patterns seen in living mammals.
“In living mammals, there tend to be relatively few large species, and they have large ranges. With Cretaceous dinosaurs, we see a lot of large species in a single habitat. They also tend to be very regional – as you move from one habitat to another, you get a completely different set of species.”
These patterns help explain why palaeontologists keep finding more species – when they sample different habitats, they find different species.
Longrich speculates that dinosaur biology may cause these patterns. He said: “In this sense dinosaur biology seems quite different from mammal biology. It could be that mammals are more intelligent and so they tend to have more flexible behaviour, and adapt their behaviour to their habitats.
“On the other hand, dinosaurs may have had to adapt themselves physically to survive in a different habitat, and evolved new species. Perhaps that’s the reason why there are so many species.”
Reference :
Nicholas R. Longrich, “The horned dinosaurs Pentaceratops and Kosmoceratops from the upper Campanian of Alberta and implications for dinosaur biogeography,” Cretaceous Research, Volume 51, September 2014, Pages 292-308, ISSN 0195-6671, dx.doi.org/10.1016/j.cretres.2014.06.011.
Note : The above story is based on materials provided by University of Bath
The familiar continents of Earth are embedded in tectonic plates on the planet’s surface that slowly collide with each over time.
Geological processes shape the planet Earth and are in many ways essential to our planet’s habitability for life. One important geological process is plate tectonics – the drifting, colliding and general movement of continental plates. This slow movement of mass has a role in causing all kinds of activity at the planet’s surface, from earthquakes to the formation of mountains.
A new review published by the Geological Society of London examines questions about the continental crust of Earth, which is the primary repository for information about Earth’s geological history (as well as many natural resources of value to humankind).
In the volume, scientists explore when and how continental crust formed and how it evolved through time. These are important questions for astrobiologists, and could provide clues about whether or not crustal formation is essential for the habitability of distant worlds.
Note : The above story is based on materials provided by Astrobio.net This story is republished courtesy of NASA’s Astrobiology Magazine. Explore the Earth and beyond at www.astrobio.net .
The mineral that makes up more than a third of our planet finally has a name, thanks to tiny samples found, ironically, in a meteorite that fell to Earth in Australia in 1879. Under the rules of the International Mineralogical Association, scientists can name a mineral (a solid material with a distinct chemical composition and crystalline structure) only once they’ve analyzed a natural sample.
But because the newly named mineral typically is stable only at pressures found more than 660 kilometers below Earth’s surface, natural versions of the mineral remained stubbornly out of reach. So scientists looked for another source of incredibly high pressures: collisions between asteroids in space, such as the one that created the Australian meteorite hundreds of millions of years ago.
Analyzing a slice of the meteorite (see image above), researchers discovered that the crash briefly subjected the rock to hellish temperatures of about 2100°C and pressures about 240,000 times sea-level air pressure, they report online today in Science. In dark veins within the once-shattered sample, the researchers also found tiny 20- to 30-micrometer-wide blobs of the mineral. The frigid cold of space locked the mineral’s atoms in place, and slightly elevated pressures due to stresses inside the meteorite also helped preserve its crystalline structure.
The mineral’s new name, bridgmanite, honors 1946 Nobel Prize winner Percy Bridgman, a physicist who pioneered the analyses of minerals and other materials under high pressure. Previous estimates suggest that 70% of Earth’s lower mantle—which falls between depths of 660 and 2900 kilometers—is bridgmanite, the researchers say. That means the new mineral accounts for a whopping 38% of Earth’s entire volume.
Note : The above story is based on materials provided by American Association for the Advancement of Science . The original article was written by Sid Perkins .
Aerial photo of the San Andreas Fault in the Carrizo Plain, northwest of Los Angeles. Credit: Wikipedia.
Geologists may be close to cracking one of the biggest seismological mysteries in the Pacific Northwest: the origin of a powerful earthquake that rattled seven states and provinces when Ulysses S. Grant was president.
Preliminary evidence points to a newly discovered fault near the town of Entiat in Chelan County, Wash. The find adds to a growing body of evidence that Central and Eastern Washington are more quake-prone than previously thought, and will help refine seismic risks in an area that’s home to 1.5 million people, more than a dozen hydropower dams and the Hanford nuclear reservation, said Craig Weaver, regional chief of the U.S. Geological Survey’s earthquake programs.
“For more than four decades, people have been guessing where the 1872 earthquake was,” Weaver said. “To be able to finally pinpoint this thing on a map would be really important in helping us get the seismic hazard assessment correct in that part of the state.”
The quake struck on the evening of Dec. 14, 1872, long before the first seismometer was installed in the Northwest.
The fact that chimneys cracked in Olympia, trees toppled in Puyallup and fissures split the ground south of Seattle led early observers to assume the quake was centered under Puget Sound.
But windows also shattered as far away as Victoria, British Columbia, and people were knocked off their feet at Snoqualmie Pass. The first analysis of newspaper reports from the time put the epicenter not far from Vancouver, British Columbia.
The most compelling eyewitness accounts, though, trickled in from east of the Cascades, in the sparsely populated hills near Wenatchee. Settlers and Native Americans reported a massive slide that briefly dammed the Columbia River. Some claimed that geysers spouted from the ground and gushed for months. Throughout Washington and Oregon, strong aftershocks kept the populace on edge for more than a year.
Subsequent studies proposed epicenters in the North Cascades and near Lake Chelan. Estimates of the quake’s size have ranged from magnitude 6.5 to 7.5, which would make it one of the biggest in recorded state history.
“No matter how you define it, that’s a big earthquake,” said USGS researcher Brian Sherrod, who led the modern-day hunt for the quake’s source. “It was felt from Montana and British Columbia down into Oregon and Northern California.”
In the 1970s, legions of consultants employed by utilities with nuclear ambitions attempted to pin down the location of the quake. One consortium wanted to build three reactors at Hanford, while another proposed a pair on the Skagit River near Sedro-Woolley. Neither project wanted to be near where the 1872 quake was centered.
The result was a series of reports that put the epicenter back and forth across the Cascades. A Seattle politician called it “the earthquake that wouldn’t stay put.”
No one was able to find the fault.
Beginning six years ago, Sherrod brought a new tool called LiDAR to bear on the puzzle. The technique allows scientists to virtually strip away vegetation and generate detailed topographic maps by beaminglaser pulses from an airplane and analyzing the way the signals bounce back.
The area near Entiat was already a prime suspect as the source of the quake, based on eyewitness reports and recurring swarms of small quakes.The first LiDARimages didn’t show much, though, so the USGS commissioned another sweep in 2013.
“When I looked at those, it just popped out,” Sherrod said in late October as he led a team of geologists down a fire-blackened hillside in the Okanogan-Wenatchee National Forest and into a small valley that drains into the Columbia River.
He pointed to a faint ridgeline a few feet high that snaked across the landscape like an oversized mole track. “That’s the scarp.”
A scarp is a scar created when an earthquake ruptures the ground surface. This one extends at least 3.5 miles, bearing witness to a major upheaval in the recent past, Sherrod said.
“Clearly we have a fault. There’s no doubt about it,” he said, scrambling into a 15-foot-long trench cut perpendicularly across the scarp. He named it the Spencer Canyon fault, after the drainage where it’s located.
The steep terrain and winding road ruled out the use of a backhoe, so Sherrod and his team dug two trenches by hand.
In the exposed dirt walls, Sherrod traced the diagonal line that marks the fault. Soil layers on one side are higher than on the other, he explained, revealing the way the ground jerked during past quakes.
Scraping the walls of the trenches and using colored pins to delineate layers, the geologists have uncovered evidence of at least two quakes, and perhaps as many as four.
But did the most recent one strike in 1872?
The evidence isn’t definitive, but it points in that direction, Sherrod said.
The fault isn’t far from Ribbon Cliffs, the scar of a huge landslide along the Columbia River that is likely the one reported by witnesses in 1872. Highway 97 runs below the cliff, and islands in the river are remnants of the slide.
In Spencer Canyon, the fault scarp itself is buried in one spot under a much smaller landslide. When Sherrod and his colleagues dated trees growing on the slide, they found the oldest sprouted sometime around 1880. The slide impounded a stream, forming small ponds that drowned several trees. Tree-ring dating showed those trees died around the same time period.
For geologist Jim Miller, of the consulting firm GeoEngineers, that’s almost slam-dunk evidence that the fault was responsible for the 1872 quake. “The information I’ve got right now gets me to the 98 percent confidence level,” said Miller, who helped Sherrod excavate the trenches and examine the scarp.
Sherrod is still hedging his bets.
He and his colleagues collected bits of charcoal, wood and volcanic ash from the trenches. Radiocarbon dating and chemical analysis of the ash should help them establish the oldest possible age of the most recent quake, he explained. They also hope to determine roughly when earlier quakes occurred, to get some idea of how frequently the fault might snap in the future.
The results will be of keen interest to Columbia River dam operators, Miller said. He has been working with Douglas County Public Utility District, which operates Wells Dam, to re-evaluate the risk posed by earthquakes. Similar reviews are under way for several other dams in the area.
The possibility of an 1872-type quake was factored into the safety equation when the dams were built. But knowing exactly where the fault is will provide a better picture of how the ground is expected to shake the next time it snaps, Weaver said.
“The more certain you can be about the hazard and ground motions, the more certain the engineering solutions can be.”
Weaver said it’s not clear what, if any, implications the Spencer Canyon Fault might have for nuclear-waste-storage facilities and the Columbia Generating Station, Washington’s sole nuclear-power plant. Both are located more than 100 miles away at Hanford.
Seismic safety at the nuclear-power plant is under review, with a report expected next year.
Over the past decade, Sherrod and his colleagues have discovered several other new faults east of the Cascades, along with evidence that some known faults are larger-and therefore more dangerous-than geologists used to think.
Collectively, the new evidence shows that while the region isn’t as seismically active as Western Washington, it’s far from immune from damaging quakes.
Locating the source of the 1872 quake would help fill in that picture, Sherrod said.
And for a geologist, what could be cooler than playing sleuth in a 142-year-old mystery story?
“This is pretty exciting stuff for us,” Sherrod said.
“For more than four decades, people have been guessing where the 1872 earthquake was. To be able to finally pinpoint this thing on a map would be really important in helping us get the seismic hazard assessment correct in that part of the state. “For more than four decades, people have been guessing where the 1872 earthquake was. To be able to finally pinpoint this thing on a map would be really important in helping us get the seismic hazard assessment correct in that part of the state. ”
Note : The above story is based on materials provided by The Seattle Times Distributed by Tribune Content Agency, LLC
Field Work in the Arctic sea ice. Credit: Thomas A. Brown and Simon T. Belt
“We have not seen an ice free period in the Arctic Ocean for 2,6 million years. However, we may see it in our lifetime,” says marine geologist Jochen Knies. In an international collaborative project, Knies has studied the historic emergence of the ice in the Arctic Ocean. The results are published in Nature Communications.
The extent of sea ice cover in Arctic was much less than it is today between four and five million years ago. The maximum winter extent did not reaching its current location until around 2.6 million years ago. This new knowledge can now be used to improve future climate models.
“We have not seen an ice free period in the Arctic Ocean for 2,6 million years. However, we may see it in our lifetime. The new IPCC report shows that the expanse of the Arctic ice cover has been quickly shrinking since the 70-ies, with 2012 being the year of the sea ice minimum”, Jochen Knies.
He is marine geologist at the Geological Survey of Norway (NGU) and Centre for Arctic Gas Hydrate, Climate and Environment, UiT The Arctic Univeristy of Norway.
In an international collaborative project, Jochen Knies has studied the trend in the sea ice extent in the Arctic Ocean from 5.3 to 2.6 million years ago. That was the last time the Earth experienced a long period with a climate that, on average, was warm before cold ice ages began to alternate with mild interglacials.
Fossils reveal past sea ice extent
“When we studied molecules from certain plant fossils preserved in sediments at the bottom of the ocean, we found that large expanses of the Arctic Ocean were free of sea ice until four million years ago,” Knies tells us.
“Later, the sea ice gradually expanded from the very high Arctic before reaching, for the first time, what we now see as the boundary of the winter ice around 2.6 million years ago ,” says Jochen Knies, who is also attached to CAGE, the Centre for Arctic Gas Hydrate, Environment and Climate at the University of Tromsø, the Arctic University of Norway.
Arctic Ocean likely to be completely free of sea ice
The research is of great interest on the international stage because present-day global warming is strongly tied to a shrinking ice cover in the Arctic Ocean. By the end of the present century, the Arctic Ocean seems likely to be completely free of sea ice, especially in summer.
This may have major significance for the entire planet ‘s climate system. Polar oceans , their temperature and salinity, are important drivers for world ocean circulation that distributes heat in the oceans. It also affects the heat distribution in the atmosphere. Trying to anticipate future changes in this finely tuned system, is a priority for climate researchers. For that they use climate modeling , which relies on good data.
“Our results can be used as a tool in climate modelling to show us what kind of climate we can expect at the turn of the next century. There is no doubt that this will be one of many tools the UN Climate Panel will make use of, too. The extent of the ice in the Arctic has always been very uncertain but, through this work, we show how the sea ice in the Arctic Ocean developed before all the land-based ice masses in the Northern Hemisphere were established,” Jochen Knies explains.
Seabed samples from Spitsbergen
A deep well into the ocean floor northwest of Spitsbergen was the basis for this research. It was drilled as part of the International Ocean Drilling Programme, (IODP), to determine the age of the ocean-floor sediments in the area. Then, by analysing the sediments for chemical fossils made by certain microscopic plants that live in sea ice and the surrounding oceans, Knies and his co-workers were able to fingerprint the environmental conditions as they changed through time.
“One thing these layers of sediment enable us to do is to “read” when the sea ice reached that precise point,” Jochen Knies tells us.
The scientists believe that the growth of sea ice until 2.6 million years ago was partly due to the considerable exhumation of the land masses in the circum-Arctic that occurred during this period. “Significant changes in altitudes above sea level in several parts of the Arctic, including Svalbard and Greenland, with build-up of ice on land, stimulated the distribution of the sea ice,” Jochen Knies says.
“In addition, the opening of the Bering Strait between America and Russia and the closure of the Panama Cannel in central America at the same time resulted in a huge supply of fresh water to the Arctic, which also led to the formation of more sea ice in the Arctic Ocean,” Jochen Knies adds.
All the large ice sheets in the Northern Hemisphere existed around 2.6 million years ago.
Scientists at Norwegian Geological Survey (NGU), CAGE, UiT The Arctic University of Norway,University of Plymouth, Universitat Autònoma de Barcelona, Stellenbosch University in South Africa and Institució Catalana de Recerca i Estudis Avançats in Barcelona have collaborated in this work.
Reference:
The emergence of modern sea ice cover in the Arctic Ocean, Jochen Knies, Patricia Cabedo-Sanz, Simon T. Belt, Soma Baranwal, Susanne Fietz & Antoni Rosell-Melé, Nature Communications 5, Article number: 5608 DOI: 10.1038/ncomms6608
The cranium of Lantian Homo erectus. Credit: HUANG Weiwen
According to paper published online November 20 in the Journal of Human Evolution, the age of the Lantian Homo erectus cranium from Gongwangling, Lantian County, Shaanxi Province, China, is likely half a million years older than previously thought. Earlier estimates dated this important fossil, which was found in 1964, to 1.15 million years ago. A research team of Chinese and British scientists, have provided compelling evidence that the fossil should be dated to 1.63 million years ago, making it the oldest fossil hominin cranium known in northeast Asia, and the second oldest site with cranial remains outside Africa. Only the Dmanisi crania from Georgia that, like Lantian, are relatively small-brained, are older, at around 1.75 million years old.
The new date for the Lantian cranium provides good evidence that small-brained hominins moved rapidly eastwards in a warm period just after 1.75 million years ago. The presence of fossils much further south, in Indonesia, that are only slightly younger (c. 1.5 – 1.6 million years ago), also opens up the possibility that hominins followed northern and southern dispersal routes from Africa into Asia.
The research team, of scientists from the Guangzhou Institute of Geochemistry of Chinese Academy of Sciences, University of Exeter in United Kingdom and the Institute of Vertebrate Paleontology and Paleoanthropology of Chinese Academy of Sciences (IVPP), led by Professors ZHU Zhaoyu, Robin Dennell and HUANG Weiwen used a range of methods including loess-palaeosol stratigraphy, tectonic-geomorphology, sedimentology and mineralogy, geochemistry, palaeontology, paleomagnetism and rock magnetic methods to re-date the skull. Over 12 years (2001–2013) of research, they investigated some key geological sections by using high-resolution sampling, such as the Gongwangling and Jiacun sections in the Lantian basin of North China immediately north of the Qinling Mountains, and measured thousands of samples.
Based on reference and analysis of previous literature, four lines of new evidence from this research have been established to support a re-dating of the Gongwangling hominin from 1.15 to ca. 1.63 million years ago. First, the fossiliferous horizon cannot be attributed, as previously thought, to the 15th loess unit (L15), but lies below L15 and an underlying erosional surface, and there is therefore a stratigraphic break between L15 and the hominin horizon. Second, the fossil horizon is situated between the Gilsa Event (average age c. 1.62 million years ago) and the Olduvai Subchron (top age 1.77 million years ago) of the geomagnetic zones in the section, and thus the fossil horizon should correspond to the 22-23rd palaeosol units (S22~S23). Thirdly, the same type of subtropical faunal assemblage was found at both the Gongwangling sections and at Jiacun, and in the same stratigraphic position, i.e., S22–S23, between the Gilsa Event and the Olduvai Subchron. Fourthly, based on the palaeomagnetic time scale and the astronomical timescale of the Chinese loess-paleosol sequence, the age of the horizon of the Gongwangling fossil cranium should be about 1.63 million years ago, which was also a warm climatic period.
“This age is consistent with the geological context and the subtropical fossil fauna at Gongwangling, and also the small-brain size of the Gongwangling Homo erectus cranium, similar to that seen in Georgia and Indonesia”, said HUANG Weiwen, a professor of the IVPP in Beijing.
“The revised age extends its age by about half a million years and makes the Gongwangling site a crucial benchmark in establishing the framework of the origin, migration and dispersal of early man in the Old World”, said Robin Dennell of University of Exeter in United Kingdom, “It also provides reasonable evidence for re-evaluating the status of other early and controversial human fossils in China and Java. In addition, this new research rewrites the history of the Lantian hominin and provides additional knowledge of human evolution for the public”.
The new dating of the Gongwangling cranium is a multi-disciplinary research based on the fine correlation between the Chinese loess strata (the loess-palaeosol sequence over a period of 2.5 million year) and marine oxygen isotope stages, and the results demonstrate again that the Chinese loess-palaeosol sequence should and will play an important role in studies of Quaternary global change and early human evolution over the last two million years.
This research was mainly supported by the National Basic Research Program of China and the Knowledge Innovation Program of CAS.
Sean Bemis put his hands together side by side to demonstrate two plates of the earth’s crust with a smooth boundary running between them. But that boundary is not always smooth and those plates do not always sit together neatly, which makes the earth’s crust a dynamic and complex surface.
As a structural geologist and paleoseismologist, Bemis often uses visual and three dimensional (3-D) models to explain his studies of the earth’s crust; sometimes that entails sophisticated 3-D digital imagery, maps and diagrams of fault lines, the rocks he processes in his lab, or, as in this case, his own hands.
These techniques not only help Bemis demonstrate his research, they also represent the multidimensional nature of his work.
Bemis, an assistant professor in UK’s Department of Earth and Environmental Sciences, studies the deformation of the tectonic plates that make up Earth’s crust. When these plates move, they slide past each other, with most of the motion occurring across relatively narrow zones.
Due to the large amount of crushing required for the Earth’s crust to move, the zones between plates, called plate boundaries, are sites of frequent, often damaging earthquakes and the formation of dramatic mountain ranges. Some of these plate boundaries are also very well-known faults, such as the San Andreas fault in California.
Bemis simplifies some key terminology when he says, “A fault is just a break in rock; an active fault is one that has moved recently and has the potential to move again in the near future.” In particular, he researches the San Andreas fault in California and the Denali fault in Alaska.
By excavating faults in California and Alaska, Bemis and his team identify plate deformation recorded as prehistoric earthquakes. With the rocks, soil and organic matter they examine, they can use radiocarbon dating to identify when an earthquake occurred.
With these findings, Bemis can determine the character of a fault, which helps scientists forecast the likelihood and size of possible future earthquakes. “Understanding how earthquakes recur through time,” Bemis explained, “can tell us how the surface of the Earth is evolving in terms of the deformation as well as community-related hazards and hazard mitigation needs.”
While in graduate school at the University of Alaska Fairbanks, Bemis did field work in Denali. He even discovered and named several previously unknown active faults in the region. In 2002, there was a major earthquake on the Denali fault—the largest in the world that year. At the time it occurred, Bemis recalled, “I was a hundred miles away from the earthquake, but I could barely stand up, that’s how strong it was.”
Bemis likens the earthquake process (in its simplest form) to breaking a rubber band that you stretch, building up pressure until it snaps. But with an earthquake, the pressure builds in miles of crust moving at rates of kilometer per second. “That’s a lot of energy,” he remarked. “The spot where I’m standing could jump instantaneously to other side of the room.”
Later, Bemis went out to the fault and could see the effects of the earthquake on the earth’s surface. “The earthquake had sheared the ground surface for hundreds of kilometers and this shearing had opened up large fissures that rotated during the rapid deformation,” Bemis remembered.
These fissures, or openings in the earth’s surface, were so big, Bemis remembered, that he could stand in them and hold his arms up over head and still be below the ground surface. He also saw trees with huge chunks of roots torn off and slipped several meters away.
Over time, the fissures and shearing Bemis observed in Denali would fill in with soil, rocks and organic material, so the surface would eventually come to look like it had before the earthquake. “These observations of recent earthquakes,” like the 2002 Denali earthquake, “help us understand what we need to look for to find evidence for prehistoric earthquakes.” To see buried records of earthquakes, “we go play in the dirt,” Bemis said, laughing.
Even though Bemis has a renovated lab in the Slone Research Building, one might say that his primary lab is in the field, playing in the dirt, so to speak. He and his team excavate a fault, exposing a flat plane or wall in the earth. They can see evidence of earthquakes and deformation in the dirt wall where the color or layers of sediment are inconsistent.
Images of these excavations are helpful for showing what Bemis looks for in his analysis of the earth’s surface.
“You have to be able to visualize that what you’re seeing isn’t actually a 2-D plane, it’s actually something that extends back into space. It’s hard to teach this part,” said Bemis. It’s especially hard in a region like Kentucky where students can’t go out to a nearby active fault like Bemis did at the University of Alaska Fairbanks and at the University of Oregon.
Bemis’s undergraduate and graduate students at UK, however, sometimes have the opportunity to travel to California or Alaska with their professor to excavate a fault. He tries to help his graduate students develop projects out of facets of his research so they are working toward their own research while contributing to his. Therefore, his mentorship is embedded in his research.
For people who won’t get such a first-hand look at a fault excavation, Bemis makes use of digital, high-resolution 3-D imaging that lets a viewer appreciate the greater scope and depth of plate displacement. He especially likes his students to not only look at a 3-D model but to use the mouse to turn it and truly interact with it themselves.
Even in graduate school, Bemis was exploring new ways of demonstrating his study of plate deformation because “as we’re collecting more and more data about these prehistoric earthquakes, all of the simple models are falling apart—they don’t work because the earth is a complex place—there’s a lot of interacting parts.”
From playing in the dirt, to sample processing in the lab, to presenting his findings, Bemis’s research could also be said to have “a lot of interacting parts,” and he continues to explore the new effective means of representing it. Of course, he can always resort to his own hands.
Note : The above story is based on materials provided by University of Kentucky
Scientists have discovered an invisible shield roughly 7,200 miles above Earth. Credit: Andy Kale, University of Alberta
A team led by the University of Colorado Boulder has discovered an invisible shield some 7,200 miles above Earth that blocks so-called “killer electrons,” which whip around the planet at near-light speed and have been known to threaten astronauts, fry satellites and degrade space systems during intense solar storms.
The barrier to the particle motion was discovered in the Van Allen radiation belts, two doughnut-shaped rings above Earth that are filled with high-energy electrons and protons, said Distinguished Professor Daniel Baker, director of CU-Boulder’s Laboratory for Atmospheric and Space Physics (LASP). Held in place by Earth’s magnetic field, the Van Allen radiation belts periodically swell and shrink in response to incoming energy disturbances from the sun.
As the first significant discovery of the space age, the Van Allen radiation belts were detected in 1958 by Professor James Van Allen and his team at the University of Iowa and were found to be composed of an inner and outer belt extending up to 25,000 miles above Earth’s surface. In 2013, Baker — who received his doctorate under Van Allen — led a team that used the twin Van Allen Probes launched by NASA in 2012 to discover a third, transient “storage ring” between the inner and outer Van Allen radiation belts that seems to come and go with the intensity of space weather.
The latest mystery revolves around an “extremely sharp” boundary at the inner edge of the outer belt at roughly 7,200 miles in altitude that appears to block the ultrafast electrons from breeching the shield and moving deeper towards Earth’s atmosphere.
“It’s almost like theses electrons are running into a glass wall in space,” said Baker, the study’s lead author. “Somewhat like the shields created by force fields on Star Trek that were used to repel alien weapons, we are seeing an invisible shield blocking these electrons. It’s an extremely puzzling phenomenon.”
A paper on the subject was published in the Nov. 27 issue of Nature.
The team originally thought the highly charged electrons, which are looping around Earth at more than 100,000 miles per second, would slowly drift downward into the upper atmosphere and gradually be wiped out by interactions with air molecules. But the impenetrable barrier seen by the twin Van Allen belt spacecraft stops the electrons before they get that far, said Baker.
The group looked at a number of scenarios that could create and maintain such a barrier. The team wondered if it might have to do with Earth’s magnetic field lines, which trap and control protons and electrons, bouncing them between Earth’s poles like beads on a string. The also looked at whether radio signals from human transmitters on Earth could be scattering the charged electrons at the barrier, preventing their downward motion. Neither explanation held scientific water, Baker said.
“Nature abhors strong gradients and generally finds ways to smooth them out, so we would expect some of the relativistic electrons to move inward and some outward,” said Baker. “It’s not obvious how the slow, gradual processes that should be involved in motion of these particles can conspire to create such a sharp, persistent boundary at this location in space.”
Another scenario is that the giant cloud of cold, electrically charged gas called the plasmasphere, which begins about 600 miles above Earth and stretches thousands of miles into the outer Van Allen belt, is scattering the electrons at the boundary with low frequency, electromagnetic waves that create a plasmapheric “hiss,” said Baker. The hiss sounds like white noise when played over a speaker, he said.
While Baker said plasmaspheric hiss may play a role in the puzzling space barrier, he believes there is more to the story. “I think the key here is to keep observing the region in exquisite detail, which we can do because of the powerful instruments on the Van Allen probes. If the sun really blasts Earth’s magnetosphere with a coronal mass ejection (CME), I suspect it will breach the shield for a period of time,” said Baker, also a faculty member in the astrophysical and planetary sciences department.
“It’s like looking at the phenomenon with new eyes, with a new set of instrumentation, which give us the detail to say, ‘Yes, there is this hard, fast boundary,'” said John Foster, associate director of MIT’s Haystack Observatory and a study co-author.
Reference:
D. N. Baker, A. N. Jaynes, V. C. Hoxie, R. M. Thorne, J. C. Foster, X. Li, J. F. Fennell, J. R. Wygant, S. G. Kanekal, P. J. Erickson, W. Kurth, W. Li, Q. Ma, Q. Schiller, L. Blum, D. M. Malaspina, A. Gerrard, L. J. Lanzerotti. An impenetrable barrier to ultrarelativistic electrons in the Van Allen radiation belts. Nature, 2014; 515 (7528): 531 DOI: 10.1038/nature13956
Note : The above story is based on materials provided by University of Colorado at Boulder.
