Earth’s Sediments Record a Falling Sky


A new publication by The Geological Society of America illustrates the sedimentary record of meteorite impacts on Earth. Senior volume editor Kevin R. Evans of Missouri State University notes that “up until the 1960s, the geologic community largely regarded meteorite impacts as geologic sideshows and curiosities, and inherently controversial. Today, it is widely recognized that large impacts have played a pivotal role in the evolution of Earth’s biota and sculpted the surface of the planet.”



Large meteorite impacts are agents of sedimentation; sedimentary particles are generated through brecciation, which then are transported, emplaced, and deposited. In addition to the deformation of sedimentary target rocks, the record of meteorite impacts also includes ejecta and tsunami deposits, both of which typically are preserved in sedimentary successions.


“Although the future holds risks of impact,” Evans explains, “ancient impact structures may also be viewed as resources, where breccia bodies and peripheral strata host accumulations of hydrocarbons and ore deposits.”



Currently, says Evans, “Nearly all known terrestrial meteorite impacts are on continents or continental shelves, but many, including most of the examples detailed in this volume, actually occurred in marine settings.” The impact-related structures examined in this book include Chesapeake Bay, Gardnos, Lockne, Mjølnir, and Weaubleau, and distal deposits from the Alamo, Avak, and Chicxulub impacts.

Stress Buildup Precedes Large Sumatra Quakes





Sumatra is the sixth largest island in the world and is the largest island in Indonesia
Sumatra is the sixth largest island in the world and is the largest island in Indonesia

The island of Sumatra, Indonesia, has shaken many times with powerful earthquakes since the one that wrought the infamous 2004 Indian Ocean tsunami. Now, scientists from the California Institute of Technology and the Indonesian Institute of Sciences are harnessing information from these and earlier quakes to determine where the next ones will likely occur, and how big they will be.



Mohamed Chlieh, the lead author of a new report, looked at the region during his postdoctoral studies at Caltech with Jean-Philippe Avouac, professor of geology and director of Caltech’s Tectonics Observatory (TO) and Kerry Sieh, Sharp Professor of Geology. They found that in the time between great earthquakes, some portions of the fault zone locked up while others crept along steadily, and the portions that were locked in the past few decades coincided with portions that rupture to produce large-magnitude quakes. The correlation was especially strong for two temblors of magnitude 8.7 that struck the region in 1861 and again in 2005.



The study also reveals which part of the Sumatra megathrust is storing strain that will be released during future large earthquakes.



Earthquakes in Sumatra are the manifestation of a sudden release of strain that constantly builds as the plates beneath the Indian Ocean creeps steadily toward southeast Asia and dive into the subduction zone under the island. If the total tectonic plate motion in the region is not taken up by fault slip during earthquakes, then a deficit builds until the next earthquake rupture. The patch of the fault where slip is greatest during an earthquake and releases the most pent-up strain, known as an asperity, also gets stuck between quakes. The scientists were interested in what was happening at the land surface, above these asperities, between big earthquakes.



Investigations by Caltech scientists in the region began when Sieh and his students started documenting the history of subsidence and emergence of the islands offshore Sumatra using the record provided by coral heads. Later on, a network of geodetic stations was deployed by the TO. To measure how strain built up in the calm interseismic period between earthquakes, Chlieh and his colleagues analyzed GPS measurements collected since 1991 and annual banding in corals from the past 50 years. Coral growth bands indicate vertical land motion because as the seafloor on which corals live shifts down or up, the creatures either grow to chase sunlight from below water or die back when elevated above water. Both the bands and the GPS data record small land-position shifts in interseismic periods. In contrast, they show drastic shifts during an earthquake, as the corals typically die when they are thrust high enough above or sunk too deep below sea level to survive.


The data provide a record of unevenly distributed deformation of the land surface directly above the subduction zone during the interseismic period. Modeling further indicates that this results from the asperities along the plate interface, while other parts remain smoothly slipping. These interseismic asperities are 10 times as wide–up to 175 kilometers–in the region where great earthquakes have occurred in the past.



“Our model shows asperities exactly at the same places that the 2005 Nias and the 1797 and 1833 earthquakes in the Mentawai islands occurred, indicating that aperities seem to be persistent features from one seismic cycle to another,” Chlieh remarks. Avouac adds, “This is clear indication that the characteristics of large earthquakes are somewhat determined by properties of the plate interface that can be gauged in advance from measuring interseismic deformation.



“A priori, large earthquakes should not be expected where the plate interface is creeping, but are inescapable where it is locked. So it seems that we can, with interseismic observations, see these asperities before the earthquake occurs,” he says. “The question now is, ‘How well are we able to estimate the characteristics of the earthquakes that these asperities could produce?'”



The implications of the study are major, according to Chlieh. “Using the asperity locations, we may be able to construct some more realistic earthquake and tsunami models following different scenarios. Then we will have a good idea of the risk induced by these locked fault zones.”



The study appears in the May issue of the Journal of Geophysical Research. Other authors on the paper are Danny Natawidjaja, a former Caltech grad student who is now at the Indonesian Institute of Sciences, and John Galetzka, staff geodesist with the TO.



Abstract: http://www.agu.org/pubs/crossref/2008/2007JB004981.shtml

Large methane release could cause abrupt climate change as happened 635 million years ago





Geologists Chris von der Borch (front) and David Mrofka (back) look for evidence of ancient methane seepage within tidal sediments seen in sea cliff exposures at Marino Rocks, South Australia. - Credit: M. Kennedy, UC Riverside.
Geologists Chris von der Borch (front) and David Mrofka (back) look for evidence of ancient methane seepage within tidal sediments seen in sea cliff exposures at Marino Rocks, South Australia. – Credit: M. Kennedy, UC Riverside.

UCR-led research team says methane-triggered global warming ended last ‘snowball’ ice age; dramatically reorganized Earth system



An abrupt release of methane, a powerful greenhouse gas, about 635 million years ago from ice sheets that then extended to Earth’s low latitudes caused a dramatic shift in climate, triggering a series of events that resulted in global warming and effectively ended the last “snowball” ice age, a UC Riverside-led study reports.



The researchers posit that the methane was released gradually at first and then in abundance from clathrates – methane ice that forms and stabilizes beneath ice sheets under specific temperatures and pressures. When the ice sheets became unstable, they collapsed, releasing pressure on the clathrates which began to degas.



“Our findings document an abrupt and catastrophic means of global warming that abruptly led from a very cold, seemingly stable climate state to a very warm also stable climate state with no pause in between,” said Martin Kennedy, a professor of geology in the Department of Earth Sciences, who led the research team.



“This tells us about the mechanism, which exists, but is dormant today, as well as the rate of change,” he added. “What we now need to know is the sensitivity of the trigger: how much forcing does it take to move from one stable state to the other, and are we approaching something like that today with current carbon dioxide warming.”



Study results appear in the May 29 issue of Nature.





Dolomite cement, formed from oxidized methane as it evolved from melting methane hydrates at the end of the snowball Earth glaciation, present in wave-cut platforms at Marino Rocks, South Australia. The dolomite is orange-red and formed vertical plumbing of tubes and vugs as methane passed upward and disrupted overlying sediment. - Credit: M. Kennedy, UC Riverside.
Dolomite cement, formed from oxidized methane as it evolved from melting methane hydrates at the end of the snowball Earth glaciation, present in wave-cut platforms at Marino Rocks, South Australia. The dolomite is orange-red and formed vertical plumbing of tubes and vugs as methane passed upward and disrupted overlying sediment. – Credit: M. Kennedy, UC Riverside.

According to the study, methane clathrate destabilization acted as a runaway feedback to increased warming, and was the tipping point that ended the last snowball Earth. (The snowball Earth hypothesis posits that the Earth was covered from pole to pole in a thick sheet of ice for millions of years at a time.)



“Once methane was released at low latitudes from destabilization in front of ice sheets, warming caused other clathrates to destabilize because clathrates are held in a temperature-pressure balance of a few degrees,” Kennedy said. “But not all the Earth’s methane has been released as yet. These same methane clathrates are present today in the Arctic permafrost as well as below sea level at the continental margins of the ocean, and remain dormant until triggered by warming.



“This is a major concern because it’s possible that only a little warming can unleash this trapped methane. Unzippering the methane reservoir could potentially warm the Earth tens of degrees, and the mechanism could be geologically very rapid. Such a violent, zipper-like opening of the clathrates could have triggered a catastrophic climate and biogeochemical reorganization of the ocean and atmosphere around 635 million years ago.”



Today, the Earth’s permafrost extends from the poles to approximately 60 degrees latitude. But during the last snowball Earth, which lasted from 790 to 635 million years ago, conditions were cold enough to allow clathrates to extend all the way to the equator.



According to Kennedy, the abruptness of the glacial termination, changes in ancient ocean-chemistry, and unusual chemical deposits in the oceans that occurred during the snowball Earth ice age have been a curiosity and a challenge to climate scientists for many decades.



“The geologic deposits of this period are quite different from what we find in subsequent deglaciation,” he said. “Moreover, they immediately precede the first appearance of animals on earth, suggesting some kind of environmental link. Our methane hypothesis is capable also of accounting for this odd geological, geochemical and paleooceanographic record.”



Also called marsh gas, methane is a colorless, odorless gas. As a greenhouse gas, it is about 30 times more potent than carbon dioxide, and has largely been held responsible for a warming event that occurred about 55 million years ago, when average global temperatures rose by 4-8 degrees Celsius.



When released into the ocean-atmosphere system, methane reacts with oxygen to form carbon dioxide and can cause marine dysoxia, which kills oxygen-using animals, and has been proposed as an explanation for major oceanic extinctions.



“One way to look at the present human influence on global warming is that we are conducting a global-scale experiment with Earth’s climate system,” Kennedy said. “We are witnessing an unprecedented rate of warming, with little or no knowledge of what instabilities lurk in the climate system and how they can influence life on Earth. But much the same experiment has already been conducted 635 million years ago, and the outcome is preserved in the geologic record. We see that strong forcing on the climate, not unlike the current carbon dioxide forcing, results in the activation of latent controls in the climate system that, once initiated, change the climate to a wholly different state.”



As part of their research, Kennedy and his colleagues collected hundreds of marine sediment samples in South Australia for stable isotope analysis, an important tool used in climate reconstruction. At UCR, the researchers analyzed the samples and found the broadest range of oxygen isotopic variation ever reported from marine sediments that they attribute to melting waters in ice sheets as well as destabilization of clathrates by glacial meltwater.



Next in their research, Kennedy and his colleagues will work on estimating how much of the temperature change that occurred 635 million years ago was due solely to methane.

World’s fastest-growing mud volcano is collapsing, says new research


The world’s fastest-growing mud volcano is collapsing and could subside to depths of more than 140 metres with consequences for the surrounding environment, according to new research.



As the second anniversary (May 29) of the eruption on the Indonesian island of Java approaches, scientists have also found that the centre of the volcano – named Lusi – is collapsing by up to three metres overnight.



Such sudden collapses could be the beginning of a caldera – a large basin-shaped volcanic depression – according to the research team, from Durham University UK, and the Institute of Technology Bandung, in Indonesia.



Their findings, based on Global Positioning System (GPS) and satellite measurements, are due to be published in the journal Environmental Geology.



Lusi first erupted on May 29, 2006, in the Porong sub-district of Sidoarjo, close to Indonesia’s second city of Surabaya, East Java, and now covers seven square kilometres and is 20 metres thick.



In January 2007 Durham University published the first scientific report into the causes and impact of Lusi, revealing that the eruption was almost certainly manmade and caused by the drilling of a nearby exploratory borehole(1) looking for gas.



Fourteen people have been killed and 30,000 people have been evacuated from the area. More than 10,000 homes have been destroyed while schools, offices and factories have also been wiped out and a major impact on the wider marine and coastal environment is expected.


The researchers say the subsidence data could help determine how much of the local area will be affected by Lusi.



Their research used GPS and satellite data recorded between June 2006 and September 2007 that showed the area affected by Lusi had subsided by between 0.5 metres and 14.5 metres per year.



The scientists found that if Lusi continued to erupt for three to 10 years at the constant rates measured during 2007 then the central part of the volcano could subside by between 44 metres and 146 metres – 26 metres longer than a football pitch.



They propose the subsidence is due to the weight of mud and collapse of rock strata due to the excavation of mud from beneath the surface.



Their study has also found that while some parts of Sidoarjo are subsiding others are rising suggesting that the Watukosek fault system has been reactivated due to the eruption.



Co-author Professor Richard Davies, of Durham University’s Centre for Research into Earth Energy Systems (CeREES), said: “In the two years since she first erupted Lusi has continued to grow. Our research is fundamental if we are to understand the long-term effects of the mud volcano on the local and wider environment and population.



“Sidoarjo is a populated region and is collapsing as a result of the birth and growth of Lusi. This could continue to have a significant environmental impact on the surrounding area for years to come.



“If we establish how long the volcano will continue to erupt for then the subsidence data will allow us to assess the area that will ultimately be affected by this disaster. This could have implications for future plans aimed at minimising the volcano’s overall impact.”

Geoengineering could slow down the global water cycle


As fossil fuel emissions continue to climb, reducing the amount of sunlight hitting the Earth would definitely have a cooling effect on surface temperatures.



However, a new study from Lawrence Livermore National Laboratory, led by atmospheric scientist Govindasamy Bala, shows that this intentional manipulation of solar radiation also could lead to a less intense global water cycle. Decreasing surface temperatures through “geoengineering” also could mean less rainfall.



The reduction in sunlight can be accomplished by geoengineering schemes. There are two classes: the so-called “sunshade” geoengineering scheme, which would mitigate climate change by intentionally manipulating the solar radiation on the earth’s surface; the other category removes atmospheric CO2 and sequesters it into the terrestrial vegetation, oceans or deep geologic formations.



In the new climate modeling study, which appears in the May 27-30 early online edition of the Proceedings of the National Academy of Sciences, Bala and his colleagues Karl Taylor and Philip Duffy demonstrate that the sunshade geoengineering scheme could slow down the global water cycle.



The sunshade schemes include placing reflectors in space, injecting sulfate or other reflective particles into the stratosphere, or enhancing the reflectivity of clouds by injecting cloud condensation nuclei in the troposphere. When CO2 is doubled as predicted in the future, a 2 percent reduction in sunlight is sufficient to counter the surface warming.



This new research investigated the sensitivity of the global mean precipitation to greenhouse and solar forcings separately to help understand the global water cycle in a geoengineered world.



While the surface temperature response is the same for CO2 and solar forcings, the rainfall response can be very different.


“We found that while climate sensitivity can be the same for different forcing mechanisms, the hydrological sensitivity is very different,” Bala said.



The global mean rainfall increased approximately 4 percent for a doubling of CO2 and decreases by 6 percent for a reduction in sunlight in his modeling study.



“Because the global water cycle is more sensitive to changes in solar radiation than to increases in CO2, geoengineering could lead to a decline in the intensity of the global water cycle” Bala said.



A recent study showed that there was a substantial decrease in rainfall over land and a record decrease in runoff and discharge into the ocean following the eruption of Mount Pinatubo in 1991. The ash emitted from Pinatubo masked some of the sunlight reaching the earth and therefore decreased surface temperatures slightly, but it also slowed down the global hydrologic cycle.



“Any research in geoengineering should explore the response of different components of the climate system to forcing mechanisms,” Bala said.



For instance, Bala said, sunshade geoengineering would not limit the amount of CO2 emissions. CO2 effects on ocean chemistry, specifically, could have harmful consequences for marine biota because of ocean acidification, which is not mitigated by geoengineering schemes.



“While geoengineering schemes would mitigate the surface warming, we still have to face the consequences of CO2 emissions on marine life, agriculture and the water cycle,” Bala said.

Sunshade World – a global warming solution?


Placing a ‘sunshade’ in space in order to counteract global warming was first proposed in 1989. More recent studies concluded that such a scheme could be developed and deployed in about 25 years time at a cost of several trillion dollars.



Recent research at the University of Bristol indicates that contrary to popular conception, this kind of geoengineering would not re-establish a ‘natural’ pre-industrial climate. The results are published online in Geophysical Research Letters.



For the first time, Dr Dan Lunt and the team at Bristol investigated the magnitude and nature of climate change in a Sunshade World using a climate model capable of simulating changes to both atmosphere and ocean circulation, developed at the UK Met Office.



Using this climate modelling approach, they exactly cancelled out the global warming caused by increased atmospheric carbon dioxide, by decreasing the amount of sunlight reaching Earth from the sun. They then examined the regional effects this would have on other aspects of the climate.


“We found significant cooling of the Tropics, a warming of the polar regions and related sea ice reduction,” said Lunt. “We also found important differences in the hydrological cycle, with Sunshade World being generally drier than the pre-industrial ‘natural’ world. Average precipitation decreased by five percent with the largest decreases being in the Tropics.”



Despite these problems, when compared to possible scenarios of ‘uncontrolled’ future climate change, the predicted changes are relatively small. In this respect, the research found sunshade geoengineering to be highly successful.



Other problems, however, remain unsolved by this form of geoengineering. In particular, the potential effects of ocean acidification on certain types of plankton – the base of the ocean food chain – could lead to an unforeseen impact on ecosystems in Sunshade World.



As a result, the team could not recommend sunshade geoengineering as an alternative to the reduction of carbon emissions. This is even before the high cost and possible ethical considerations of a sunshade geoengineering scheme have been considered.

Big quakes spark jolts worldwide





This map of the world shows seismic stations that detected more than twice the normal number of small, nearby earthquakes after the passage of what are known as 'surface waves' from major quakes that were centered hundreds to thousands of miles away and occurred from 1992 through 2006. A new study co-authored by University of Utah seismologist Kris Pankow found that at least 12 of the 15 major earthquakes (greater than magnitude-7) during 1992-2006 triggered small quakes in distant parts of the world. Scientists once believed big quakes could not trigger distant tremors. - Credit: Aaron Velasco, University of Texas at El Paso.
This map of the world shows seismic stations that detected more than twice the normal number of small, nearby earthquakes after the passage of what are known as ‘surface waves’ from major quakes that were centered hundreds to thousands of miles away and occurred from 1992 through 2006. A new study co-authored by University of Utah seismologist Kris Pankow found that at least 12 of the 15 major earthquakes (greater than magnitude-7) during 1992-2006 triggered small quakes in distant parts of the world. Scientists once believed big quakes could not trigger distant tremors. – Credit: Aaron Velasco, University of Texas at El Paso.

Triggered tremors occur even on the opposite side of the Earth



Until 1992, when California’s magnitude-7.3 Landers earthquake set off small jolts as far away as Yellowstone National Park, scientists did not believe large earthquakes sparked smaller tremors at distant locations. Now, a definitive study shows large earthquakes routinely trigger smaller jolts worldwide, including on the opposite side of the planet and in areas not prone to quakes.



“Previously it was thought seismically active regions or geothermal areas were most vulnerable to large earthquake triggers,” says Kris Pankow, a seismologist at the University of Utah Seismograph Stations and a co-author of the new study.



But Pankow and colleagues analyzed 15 major earthquakes stronger than magnitude-7.0 since 1992, and found that at least 12 of them triggered small quakes hundreds and even thousands of miles away, according to the findings published online Sunday, May 25, 2008 in the journal Nature Geoscience.



“We conclude that dynamic triggering is a ubiquitous phenomenon,” they wrote.



Pankow conducted the study with seismologist Aaron Velasco and undergraduate student Stephen Hernandez, both at the University of Texas at El Paso; and seismologist Tom Parsons, of U.S. Geological Survey in Menlo Park, Calif.



They analyzed data from more than 500 seismic recording stations five hours before and five hours after earthquakes that registered more than 7.0 on the “moment magnitude” scale, which scientists say is the most accurate scale for large earthquakes. (The frequently cited Richter scale measures only relatively small, nearby quakes).



The data – obtained from the Incorporated Research Institutions for Seismology, a consortium of universities – included 15 major earthquakes from 1992 through 2006, including the 1992 Landers quake in California 800 miles southwest of Yellowstone, the magnitude-7.9 Denali fault quake in Alaska in 2002, and the magnitude-9.2 Sumatra-Andaman Islands quake near Indonesia in 2004 that generated a catastrophic tsunami blamed for most of the quake’s 227,898 deaths in South Asia and East Africa.



Scientists previously noted that those three major quakes triggered not only nearby aftershocks, but small quakes at great distances. The new study is the first to systematically analyze all the world’s big quakes during 1992-2006 and find that most of them triggered distant, smaller tremors. These are different than aftershocks, which occur fairly close to the main quake. After the devastating 2004 Sumatra earthquake, triggered quakes even occurred in Ecuador, on the opposite side of the Earth.

Earthquakes Release Waves of Energy



When an earthquake begins, energy is released in the form of shock waves that move through the ground. The first waves are called P or pressure waves, which move at high speed with an up-and-down motion. The next waves are S or shear waves. These move from side to side, causing much damage from an earthquake. The next waves are two types of surface waves: Love waves move in a shearing fashion, followed by Rayleigh waves, which have a rolling motion.



Pankow and colleagues showed that magnitude-4 or smaller seismic events often are triggered when either Love or Rayleigh waves from a major quake pass a given point.



“We can recognize the different kinds of waves as they pass and can filter out everything except the small seismic events, which are presumed to be local small earthquakes,” says Pankow.



There are about 600 small seismic events around the Earth every five minutes. For five hours after the arrival of Love waves from a major quake, the researchers saw a 37 percent increase in the number of small quakes worldwide. And after Rayleigh waves from the same large quake followed the Love waves, the number of small quakes worldwide shot up by 60 percent during the five hours after the major quake.



“It is interesting that Rayleigh and Love waves, two very different types of surface waves, are both able to trigger these events,” says Pankow.



In addition to the 1992 Landers, 2002 Denali and 2004 Sumatra-Andaman Islands quakes, the other 12 major quakes in the study (and their moment magnitudes) were: 1998 Balleny Island near Antarctica (8.1), 1999 Izmit, Turkey (7.6), 1999 Hector Mine, Calif. (7.1), 2000 New Ireland, Papua New Guinea (8.0), 2001 Peru (8.4), 2001 Kunlun, China (7.8), 2003 Hokkaido, Japan (8.3), 2003 Siberia, Russia (7.3), 2004 Macquarie Ridge, near New Zealand (8.1), 2005 Sumatra, Indonesia (8.7), 2006 Java, Indonesia (7.7) and 2006 Kuril Islands, Russia (8.3).



Only the Hector Mine, Siberia, and Kuril Islands quakes did not show triggering events in the study. But it is known from previous studies that the Hector Mine earthquake indeed triggered smaller quakes near California’s Salton Sea. Those were not included in the study, because they were within about 680 miles of the main shock’s epicenter. Researchers excluded triggered quakes within that distance to avoid counting aftershocks in the same category as more distant triggered quakes.



How do the surface waves trigger small earthquakes at distant locations?



“The physical mechanism is not known,” says Pankow. “It has been proposed that the passage of the waves may change the water flow in a fault, possibly increasing the number of conduits that water can flow through which could cause the fault to slip.”



Other theories are that surface waves may increase the strain on a fault, or loosen a fault so that it prematurely breaks or slides, she adds.



The study was funded by the United States Geological Survey and the National Science Foundation, Pankow says.

New 6 million research centre to create the mine of the future


Advanced mining and mineral processing techniques to extract minerals from deep within the Earth will be developed thanks to the establishment of a new £6 million research centre, announced today.



The centre is a partnership between Imperial College London and mining company Rio Tinto aimed at developing the mine of the future. It will push forward the development of innovative mining technologies and techniques to improve the extraction of minerals, whilst minimising environmental impacts.



Minerals used to produce valuable metals such as copper, used in electrical wiring, or nickel, used to make stainless steel, are becoming increasingly hard to find and recover using traditional mining methods. Because of this extracting these minerals efficiently from deeper underground is becoming an important focus for mining research.



The Rio Tinto Centre for Advanced Mineral Recovery will develop a range of new mining technologies that use less energy to mine more minerals from hard to reach places deep underground.



Scientists will be developing more efficient techniques for block caving. This exploits the natural fractures in rocks so that they break under gravity rather than by using explosives, making the mining process cheaper and safer.



Research will be undertaken to develop a deeper understanding behind the fundamental science of rock fracturing so that mines can be developed and operated with increased confidence.



Researchers will also design new sensing technology for use in block caving to measure the underground area containing minerals and the size and shape of these deposits, which would increase the efficiency of this mining process.



New ways of mining minerals which use acids to dissolve metals in rocks below the Earth’s surface will also be explored. These dissolved metals could then be pumped above ground and extracted from the acids.



Researchers believe this method would use less energy and remove the need to disturb land in open cut mines. It would also allow for minerals to be extracted from harder to reach places making it safer for miners who would not need to venture deep below the surface to carry out the extraction process.


Scientists will also work on improvements to current froth flotation technology which is a process for separating the valuable minerals from waste rock. This process uses bubbles to pick up the fine mineral particles, which separates them from the rock and lifts them into a foaming froth on the tank’s surface for collection.



Currently, it requires large amounts of energy to crush rocks finely enough in order for the minerals to separate. Researchers hope to develop a froth flotation system in which coarser rock particles can be separated, which would reduce the amount of energy needed, lowering costs and increasing efficiency levels.



Lead scientist, Professor Jan Cilliers, Rio Tinto Chair in Mineral Processing at Imperial’s Department of Earth Science and Engineering, says in a world where resources are dwindling, research carried out by the Centre will lead to improvements in the way mining is done. He says:



“If we found copper close to a major city tomorrow then the associated environmental and social concerns would make it impossible for us to mine this resource. However, research to be developed by the Rio Tinto Centre for Advanced Mineral Recovery could make this a reality without any adverse impacts to the environment.”



Sir Richard Sykes, Rector of Imperial College London, says:



“This long-term research and development collaboration is a great example of how industry and academia can work together to drive economic competitiveness and to benefit the environment. Imperial and Rio Tinto have different but complementary strengths. By pooling them in this way we can develop innovative technological solutions and implement them speedily.”



John McGagh, Head of Innovation at Rio Tinto, adds:



“The alliance with Imperial College is a key element in delivering the Rio Tinto mine of the future. This approach is based around optimising all stages of the mineral extraction process, resulting in maximum recovery rates while minimising the mining footprint. We aim to work with the best research groups in the world, and Imperial College are an obvious partner in the field.”



The £ 6 million funds will be used over a 5-year period and will see six postdocs and 12 researchers employed at Imperial’s Department of Earth Science and Engineering to carry out research in this field.

Arctic explorer delivers unique snow-depth data for CryoSat





CryoSat can distinguish between altimetry signals returned from sea ice and open water - the difference between the two is known as the 'freeboard', and can be used to derive ice thickness. Over topographic surfaces, the first radar echo comes from the nearest point to the satellite. CryoSat can measure the angle from which this echo originates, so that the source point can be located on the ground. This, in turn, allows the height of that point to be determined. - Credits: ESA - AOES Medialab
CryoSat can distinguish between altimetry signals returned from sea ice and open water – the difference between the two is known as the ‘freeboard’, and can be used to derive ice thickness. Over topographic surfaces, the first radar echo comes from the nearest point to the satellite. CryoSat can measure the angle from which this echo originates, so that the source point can be located on the ground. This, in turn, allows the height of that point to be determined. – Credits: ESA – AOES Medialab

Following a formidable 106-day trek across the Arctic, which ended with the two Arctic Arc expedition members relying on Envisat images to guide them safely through disintegrating sea-ice, intrepid polar explorer Alain Hubert recently visited ESA to handover a unique set of snow-depth measurements.



To coincide with the launch of the International Polar Year (IPY) 2007-2008, Alain Hubert and fellow explorer Dixie Dansercoer ventured out onto the sea-ice to embark upon a trek from Siberia to northern Greenland via the North Pole – a route never before attempted. Throughout the expedition, the polar explorers had to endure temperatures down to -40ºC, encounters with polar bears and the incredible physical demand of having to drag heavy sledges across pressure ridges of sea-ice piled up several metres high as well as cross open water where the ice had fractured. Nevertheless, Alain and Dixie took time out every 50 km to make snow-depth measurements for the CryoSat mission.



“It wasn’t really difficult to take these measurements for CryoSat,” said Alain, “It became part of our routine. The difficult part of the expedition was putting one foot in front of the other when the ice is breaking up around you. As co-founder of the International Polar Foundation, a scientist as well as a seasoned explorer – I aim to form a kind of ‘bridge’ between science and society. Observing the changes that are occurring in the fragile Arctic environment will help lead to a better understanding of the effects of climate change, and ultimately the Earth system as a whole. CryoSat is an exciting mission that will help answer questions about the polar ice so we were very happy to contribute through our Arctic Arc expedition.”


Since the Earth Explorer CryoSat mission, which is due for launch next year, is designed to measure tiny variations in the thickness of floating sea-ice and ice on land, understanding the effects that the overlying snow can have on the measurement of ice elevation is of huge importance. To this end, ESA has in place a dedicated validation programme that involves a number of field campaigns in the polar regions. Measurements collected on the ice and from the air are crucial to fully understand and characterise the geophysical uncertainties in the CryoSat products so that the data CryoSat delivers is interpreted as accurately as possible.



During a presentation held this week at ESA-ESTEC in the Netherlands Alain handed over the dataset to Richard Francis ESA’s Project Manager for CryoSat, who commented that, “While snow-depth information holds the key to producing accurate maps of ice-thickness change over time, there are relatively few basic ground-measurements readily available. So when Alain offered to take measurements during his expedition, the CryoSat project was extremely grateful.”



In turn, Alain and Dixie were also grateful for help provided by an existing ESA satellite. Under the ongoing ESA Project Polar View, which is delivering logistical support to IPY, they were able to rely on images from Envisat to guide them through some dangerous ice-break up. Alain explained, “As we approached the coast of northern Greenland, the sea ice in the Lincoln Sea began to break up chaotically – something we really weren’t expecting. We realised there was no way we could take our planned route to reach land. Fortunately, however, we were guided by expedition router who relied on information provided by the Danish Technical University using data from ESA’s Envisat satellite to help us circumnavigate the open waters and eventually reach land safely.”



Malcolm Davidson ESA’s CryoSat Validation Manager noted that, “ESA has now released the snow-depth data collected by the Arctic Arc expedition to the CryoSat Validation and Retrieval Team. The team has been quite eager to get the data and start the analysis. Ultimately we expect that – in conjunction with the core ESA-sponsored airborne campaigns and similar initiatives from other polar expeditions – the data will help us better measure ice-thickness changes over time from space with CryoSat-2.”

Scorched Earth Millenium Map Shows ‘Fire Scars’





This map shows the occurrence of fire activity in sub-Saharan Africa, determined by detection of the fire scar, for a seven year period 2000-2007. The frequency of fire occurrence is shown in the map, colour coded from regions that burnt once in the seven year period shown in green to regions that burnt during every year of the project shown in purple.
This map shows the occurrence of fire activity in sub-Saharan Africa, determined by detection of the fire scar, for a seven year period 2000-2007. The frequency of fire occurrence is shown in the map, colour coded from regions that burnt once in the seven year period shown in green to regions that burnt during every year of the project shown in purple.

A geographer from the University of Leicester has produced for the first time a map of the scorched Earth for every year since the turn of the Millennium.



Dr Kevin Tansey, of the Department of Geography, a leading scientist in an international team, created a visual impression of the fire scars on our planet between 2000 and 2007. The work was funded by the Joint Research Centre of the European Commission.



The map reveals that between 3.5 and 4.5 million km2 of vegetation burns on an annual basis. This is an area equivalent to the European Union (EU27) and larger than the country of India that is burnt every year.



The information is vital for scientists and agencies involved in monitoring global warming, measuring and understanding pollutants in the atmosphere, managing forests and controlling fire and even for predicting future fire occurrence.



The research has been published in the journal Geophysical Research Letters.



Dr Tansey, a Lecturer in Remote Sensing at the University of Leicester, said: “We have produced, for the first time, a global data base and map of the occurrence of fire scars covering the period 2000-2007. Prior to this development, data were only available for the year 2000. With seven years of data, it is not possible to determine if there is an increasing trends in the occurrence of fire, but we have significant year-to-year differences, of the order of 20%, in the area that is burnt.


“The work was undertaken with colleagues from the Joint Research Centre of the European Commission (Italy) and the Université catholique de Louvain (Belgium).



“This unique data set is in much demand by a large community of scientists interested in climate change, vegetation monitoring, atmospheric chemistry and carbon storage and flows.



“We have used the VEGETATION instrument onboard the SPOT European satellite, which collects reflected solar energy from the Earth’s surface, providing global coverage on almost a daily basis.



“When vegetation burns the amount of reflected energy is altered, long enough for us to make an observation of the fire scar. Supercomputers located in Belgium were used to process the vast amounts of satellite data used in the project. At the moment, we have users working towards predicting future fire occurrence and fire management issues in the Kruger Park in southern Africa”.



“The majority of fires occur in Africa. Large swathes of savannah grasslands are cleared every year, up to seven times burnt in the period 2000-2007 (see Figure 1). The system is sustainable because the grass regenerates very quickly during the wet season. From a carbon perspective, there is a net balance due to the regenerating vegetation acting as a carbon sink. Fires in forests are more important as the affected area becomes a carbon source for a number of years.



“The forest fires last summer in Greece and in Portugal a couple of years back, remind us that we need to understand the impact of fire on the environment and climate to manage the vegetation of the planet more effectively. Probably 95% of all vegetation fires have a human source; crop stubble burning, forest clearance, hunting, arson are all causes of fire across the globe. Fire has been a feature of the planet in the past and under a scenario of a warmer environment will certainly be a feature in the future”.