Water was present during birth of Earth

New research by The University of Manchester and the Carnegie Institution of Washington is to make scientists rethink their understanding of how Earth formed.
New research by The University of Manchester and the Carnegie Institution of Washington is to make scientists rethink their understanding of how Earth formed.

New research by The University of Manchester and the Carnegie Institution of Washington is to make scientists rethink their understanding of how Earth formed.

The team have found that volatile elements – most likely to include water – were present during the violent process of the Earth’s birth between 30 and 100 million years after the solar system was created – a minute period in geological terms

The findings mean that comets and asteroids were unlikely to have brought the bulk of volatile elements to Earth – as commonly thought.

Lead scientist Dr Maria Schonbachler from The University of Manchester, publishes her research in Science, the prestigious weekly American journal today.

The scientist based at the University’s School of Earth, Atmospheric and Environmental Sciences hit upon the findings by using high precision equipment to measure abundances of Silver isotopes contained in rocks.

The readings show that the moderately volatile element Silver was present in relatively large amounts towards the final stages of the Earth’s formation.

The radioactive isotope Palladium 107 decays to Silver 107, which was present during the formation of the solar system.

The decay of Palladium 107 creates anomalies in the abundances of Silver isotopes, which can be measured and used for dating, even though Palladium 107 is no longer present on Earth.

The findings give a new boost to a 30 year old model, which suggests that volatile elements were already present in the final stages of the Earth’s birth.

How much of these elements were lost during impacts like the one that formed the moon, however, is still not well known.

Dr Schonbachler said: “The sensitive equipment we use works in much the same way as when you might carbon date a rock or artifact – but on a scale which enables us to go back billions of years.

“And those measurements allow us to detect a transition from volatile-depleted to volatile-enriched building blocks as the accumulation of Earth proceeded.

“Because we know what happened to the moderately volatile Silver, it’s very likely that the same thing happened to the highly volatile water.

“Though I accept that about 85 per cent of the Earth’s mass was built without volatile elements the rest of it was- and that’s quite an important difference in our understanding of the Earth’s geological history.”

“We don’t now need any theories about how water came to Earth – such as comets and asteroids – it was most likely here almost from the beginning. And water is, what made Earth habitable for life. “

A new science project on the historical and natural heritage of the Pyrenees

Six Spanish and French institutions are working jointly to put into action “The Origins Route”, a scientific dissemination project to develop a quality sustainable model for tourism in the Pyrenees. Participating is also the Centre for the Studies of Archaeological and Prehistoric Heritage (CEPAP) of Universitat Autònoma de Barcelona (UAB). The initiative comprises a set of activities to inform society about the origins of the Pyrenees in fields related to astronomy, geology, palaeontology and human evolution.

In the next three years, the project will be promoting an innovative and experimental model of tourism, respectful with the environment and at the same time valuing the natural and historical heritage and related scientific knowledge.

To do so participating institutions will create permanent science-tourism cooperation structures. In addition to UAB, taking part in the project are two institutions from La Noguera County, the Montsec Consortium and La Noguera Historical Heritage Research and Dissemination Association, and three from the French Midi-Pyrénées region: the astronomy and space centres Cité de l’Espace (Toulouse) and À Ciel Ouvert (Fleurance), and the Museum of Natural History of Toulouse.

“The Origins Route” proposes to create the basic elements needed for routes through the Pyrenees Mountains, offering visitors different itineraries to help them discover and understand many of the questions formulated today by scientists concerning both the universe and the first inhabitants of the region. Each stage of the itinerary will focus on a specific period. Thus the full route will offer a global vision of its origins, from the Big Bang to the birth of humanity. Proposed activities will allow participants to experience different situations such as palaentological or archaeological digs, skywatching or studying the mountain’s biodiversity.

The project will also include an itinerant exhibition coordinated by la Cité de l’Space which will last approximately ten years and will be on display at each of the participating institution headquarters and in different cities and towns of the region. A website will also be created to disseminate and promote information and activities carried out under the project. Users will also be able to view an online exhibition of the full itinerary.

Universitat Autònoma de Barcelona not only is taking part in these joint initiatives. It will also be in charge of the museumification of the prehistoric archaeological site Roca dels Bous, located near the town of Sant Llorenç de Montgai (La Noguera), where CEPAP researchers have been studying the origins and evolution of Neanderthals in the eastern Pyrenees. Known as ArkeoTic, this project will be the first to use innovative museographies based on information and communication technologies (ICT) to display the archaeological findings uncovered. The site and its surroundings will be prepared for visiting school groups and the public in general and will include wireless connections to complement on-site visits and interactive itineraries. The facilities will be completed by the end of this summer.

CEPAP-UAB researchers participating in the project are Rafael Mora, director of the Centre, Paloma González, Jorge Martínez, Antoni Bardavio and Mònica López. According to Rafael Mora, “we intend to show the construction of science and at the same time bring it closer to the public. By being able to see how researchers work and establishing direct contact with them we aim to foster young people’s interest in science”.

The total cost of the project is ?2,606,897. Almost two-thirds of the funding (65%) came from the Operational Programme Spain-France-Andorra 2007-2013 (POCTEFA) belonging to the European Regional Development Fund. All other funding came from participating institutions.

The POCTEFA programme, coordinated by the Pyrenees Work Community (CTP), with headquarters in Jaca, Huesca, aims to strengthen the economic and social integration of the cross-border area between Spain, Andorra and France.

Mining programs, research at University of Nevada, Reno, receive $2.4 million from industry

The University of Nevada, Reno, received $2.4 million from the mining industry in Nevada to enhance its mineral processing and extractive metallurgy programs and research.
Carl Nesbitt, Assoc. Professor of Metallurgical-Minerals Engineering in Mackay School of Earth Sciences and Engineering, teaches undergraduate students during a mineral process lab class in the crushing and grinding lab on campus. -  Photo by Jean Dixon, University of Nevada, Reno.
The University of Nevada, Reno, received $2.4 million from the mining industry in Nevada to enhance its mineral processing and extractive metallurgy programs and research.
Carl Nesbitt, Assoc. Professor of Metallurgical-Minerals Engineering in Mackay School of Earth Sciences and Engineering, teaches undergraduate students during a mineral process lab class in the crushing and grinding lab on campus. – Photo by Jean Dixon, University of Nevada, Reno.

The mining industry has stepped up its long-term support with a $2.4 million boost to the University of Nevada, Reno’s mining engineering program and research; and instructors, students and administrators are pleased with the resulting real-world applications that come with a strengthened program.

Two new endowed professorships, made possible by the industry support, contribute to an expanded research base for environmental solutions while the classroom has expanded beyond the walls, reaching across the state and world-wide through technology-based distance education.

“The first semester went tremendously well,” Carl Nesbitt, associate professor and Goldcorp Chair of Mineral Engineering in the Mackay School of Earth Sciences and Engineering said. “The industry support made it all possible. We’re offering two new classes in the fall semester.”

Thom Seal, recently named the Barrick Professor of Mining Engineering, teaches with Nesbitt in the metallurgical engineering program. He said students, both in the classroom and web-based, responded positively and are looking forward to more classes.

The generous gifts for the program came to the Mackay School from Newmont Mining, Goldcorp and Barrick Gold to fund the new faculty positions, student scholarships and grants to further strengthen teaching and research in extractive metallurgy and minerals processing.

The two faculty members bring extensive and important research experience from both higher education and industry.

“By endowing these professorships, the mining industry has strongly signaled its commitment to its future workforce and environmental sustainability,” said Jeff Thompson, dean of the College of Science and interim director of the Mackay School. “Carl and Thom bring the expertise to advance these mining industry commitments.”

Nesbitt, who earned his doctorate from the Mackay School, has been teaching metallurgical engineering courses for more than 20 years and has conducted research for more than 18 years, resulting in a number of patents. Thom Seal, who earned his doctorate from the University of Idaho, spent more than 30 years working in the mining industry, retiring from Newmont in 2008 as manager of metallurgy technology.

“Hiring two faculty members at once helped us get to a critical mass quickly,” Nesbitt said. “We can brainstorm and we trust each other. It’s nice to have someone who speaks the same hydrometallurgy language.”

Nesbitt’s research forte is in carbon and recovering metals, such as removing mercury from processing streams, while Seal’s research is in enhanced metal extraction. They envision offering all of the program’s required undergraduate classes online.

“Eventually, we’re hoping to team up online with experts at other universities who could teach their specialties in mineral processing,” Seal said. “And ultimately, we’re hoping to build the program into a leader preparing metallurgical engineers for the mining industry well into the future.”

In another measure of support last year, the mining industry initiated an increase to the mining claim fee in Nevada to support higher education in Nevada. The additional fee, collected through the Nevada State Bureau of Mining, now supports the University’s mining engineering program. With the program’s continuation solidified, Newmont Mining, Goldcorp and Barrick Gold embraced the opportunity to take it to the next level through the additional, capacity-building gifts.

“We’re grateful for the wonderful and continued support we have from these mining companies, and the industry as a whole,” Thompson said. “All of their contributions have lead to a successful beginning of building the mining engineering portion of our academic offerings, with more to come for the future. It’s successful partnerships such as this between higher education and the mining industry that help build the education base and sustain local and state economies.”

Contributions include:

  • Barrick Gold Corporation: A $300,000 gift funds the Barrick Gold of North America Visiting Professorship and Scholarship. Over time, Barrick Gold has given more than $2.1 million to the Mackay School.
  • Goldcorp, Inc.: A $1.25 million gift funds the Goldcorp Endowed Chair in Minerals Engineering, and an additional $50,000 supports operating expenses. Over time, Goldcorp has given more than $1.3 million to the Mackay School.
  • Newmont Mining Corporation: Gifts totaling $875,000 include the Newmont Endowed Professorship in Minerals Engineering and Newmont Mining Corporation Scholarship. Over time, Newmont has given nearly $5 million to the Mackay School.

Quantum mechanics reveals new details of deep earth

Kevin Driver
Kevin Driver

Scientists have used quantum mechanics to reveal that the most common mineral on Earth is relatively uncommon deep within the planet.

Using several of the largest supercomputers in the nation, a team of physicists led by Ohio State University has been able to simulate the behavior of silica in a high-temperature, high-pressure form that is particularly difficult to study firsthand in the lab.

The resulting discovery — reported in this week’s early online edition of the Proceedings of the National Academy of Sciences (PNAS) — could eventually benefit science and industry alike.

Silica makes up two-thirds of the Earth’s crust, and we use it to form products ranging from glass and ceramics to computer chips and fiber optic cables.

“Silica is all around us,” said Ohio State doctoral student Kevin Driver, who led this project for his doctoral thesis. “But we still don’t understand everything about it. A better understanding of silica on a quantum-mechanical level would be useful to earth science, and potentially to industry as well.”

Silica takes many different forms at different temperatures and pressures — not all of which are easy to study, Driver said.

“As you might imagine, experiments performed at pressures near those of Earth’s core can be very challenging. By using highly accurate quantum mechanical simulations, we can offer reliable insight that goes beyond the scope of the laboratory.”

Over the past century, seismology and high-pressure laboratory experiments have revealed a great deal about the general structure and composition of the earth. For example, such work has shown that the planet’s interior structure exists in three layers called the crust, mantle, and core. The outer two layers — the mantle and the crust — are largely made up of silicates, minerals containing silicon and oxygen.

Still, the detailed structure and composition of the deepest parts of the mantle remain unclear. These details are important for geodynamical modeling, which may one day predict complex geological processes such as earthquakes and volcanic eruptions.

Even the role that the simplest silicate — silica — plays in Earth’s mantle is not well understood.

“Say you’re standing on a beach, looking out over the ocean. The sand under your feet is made of quartz, a form of silica containing one silicon atom surrounded by four oxygen atoms. But in millions of years, as the oceanic plate below becomes subducted and sinks beneath the Earth’s crust, the structure of the silica changes dramatically,” Driver said.

As pressure increases with depth, the silica molecules crowd closer together, and the silicon atoms start coming into contact with oxygen atoms from neighboring molecules. Several structural transitions occur, with low-pressure forms surrounded by four oxygen atoms and higher-pressure forms surrounded by six. With even more pressure, the structure collapses into a very dense form of the mineral, which scientists call alpha-lead oxide.

It’s this form of silica that likely resides deep within the earth, in the lower part of the mantle, just above the planet’s core, Driver said.

When scientists try to interpret seismic signals from that depth, they have no direct way of knowing what form of silica they are dealing with. So they must simulate the behavior of different forms on computer, and then compare the results to the seismic data. The simulations rely on quantum mechanics.

In PNAS, Driver, his advisor John Wilkins, and their coauthors describe how they used a quantum mechanical method to design computer algorithms that would simulate the silica structures. When they did, they found that the behavior of the dense, alpha-lead oxide form of silica did not match up with any global seismic signal detected in the lower mantle.

This result indicates that the lower mantle is relatively devoid of silica, except perhaps in localized areas where oceanic plates have subducted, Driver explained.

Wilkins, Ohio Eminent Scholar and professor of physics at Ohio State, cited Driver’s determination and resourcefulness in making this study happen. The physicists used a method called quantum Monte Carlo (QMC), which was developed during atomic bomb research in World War II. To earn his doctorate, Driver worked to show that the method could be applied to studying minerals in the planet’s deep interior.

“This work demonstrates both the superb contributions a single graduate student can make, and that the quantum Monte Carlo method can compute nearly every property of a mineral over a wide range of pressure and temperatures,” Wilkins said. He added that the study will “stimulate a broader use of quantum Monte Carlo worldwide to address vital problems.”

While these algorithms have been around for over half a century, applying them to silica was impossible until recently, Driver said. The calculations were simply too labor-intensive.

Even today, with the advent of more powerful supercomputers and fast algorithms that require less computer memory, the calculations still required using a number of the largest supercomputers in the United States, including the Ohio Supercomputer Center in Columbus.

“We used the equivalent of six million CPU hours or more, to model four different states of silica” Driver said.

He and his colleagues expect that quantum Monte Carlo will be used more often in materials science in the future, as the next generation of computers goes online.

GOCE satellite determines gravitational force in the Himalayas

This Envisat Medium Resolution Imaging Spectrometer (MERIS) reduced resolution image was acquired on 16 October 2004 along the southern rim of the Himalayas defining the edge of the Tibetan Plateau.
This Envisat Medium Resolution Imaging Spectrometer (MERIS) reduced resolution image was acquired on 16 October 2004 along the southern rim of the Himalayas defining the edge of the Tibetan Plateau.

ESA’s GOCE satellite has been orbiting the Earth for more than a year and surveying its gravitational field more accurately than any instrument previously. The goal of the researchers – including scientists at the Technische Universitaet Muenchen (TUM) – is to determine the gravitational force in precise detail even in pathless places like the Himalayas. Evaluations of the first data from the satellite indicate that current models of the gravitational field in some regions can be fundamentally revised. On that basis, researchers expect to develop a better understanding of many geophysical processes, including for example earthquakes and ocean circulation. Another success: The satellite will probably manage to work in space for a much longer period than intended.

Gravitation is one of the fundamental forces of nature, but it is by no means the same everywhere. Earth’s rotation, height differences of the surface, and the composition of the crust cause significant differences in the global gravitational field. Measuring the field with previously unattainable precision – thereby contributing to the understanding of its effects – is the task of GOCE (Gravity Field and Steady-State Ocean Circulation Explorer), which lifted into earth’s orbit on March 17, 2009. In addition, GOCE is expected to provide the basis for the most accurate calculation of the “geoid” possible. Geoid is the name given to the virtual sea level of a global ocean at rest, which is used, for example, as a height reference for construction projects.

In recent months, researchers from the GOCE Gravity Consortium, a group of ten European institutes from seven countries, have processed data from the satellite in such a way that it can be used for model calculations. They can already see that GOCE will enable significant progress to be made in mapping. “It is becoming clear that we are receiving good information for the regions that are of interest from a geophysical point of view,” says TUM geodesist Prof. Reiner Rummel, chairman of the consortium, who presented the first interim results of the mission on May 7 at the General Assembly of the European Geosciences Union in Vienna.

The scientists had suspected that there were large inaccuracies in the previous models, calculated on the basis of conventional methods, particularly in the Himalayas, parts of Africa, and the Andes The initial evaluations of the GOCE data do indeed confirm this hypothesis. “Measurements made from the surface of the Earth in regions that are difficult to get to carry a high risk of errors,” explains Rummel. “This is not a problem for the satellite, of course.”

Not only the data, but also the satellite itself is proving to be very robust. It was originally intended to carry out the actual measurements for one year from October, with a break after six months. However, GOCE’s energy supply is operating so well and its stability is so high that this rest phase was not necessary. “We hope we can continue to measure for even three to four years,” says Rummel – and this despite the extremely challenging track the satellite is on: Its working height of 255 kilometers is the lowest Earth orbit ever for a scientific satellite. Its path must be continuously corrected with an electric ion propulsion system so that it does not crash to Earth. “This works extremely well,” says Rummel with delight. The Sun, which has been behaving extremely peacefully in recent months, is aiding the mission. Stronger solar activity would increase the aerodynamic drag and thus make control more difficult.

The scientists expect the mission to enable better understanding of many processes both on and below the surface of the Earth. Because gravitation is directly correlated with the distribution of mass in the Earth’s interior, mapping gravitation in detail can contribute to better understanding of dynamics in Earth’s crust. Understanding better why and where the movement of tectonic plates causes earthquakes is of great significance, particularly for regions on plate boundaries such as the Himalayas and the Andes. The researchers hope that the mission could eventually contribute to development of an early warning system for earthquakes.

With the aid of the new data, scientists also want to measure ocean circulation globally, precisely, and in detail for the first time. The ability to measure changes to ocean circulation and sea level is crucial for all global climate studies. Until now, ocean circulation has mainly been derived from mathematical model calculations.

Surveying should also profit enormously from the GOCE data. The exact reference planes can be used to correctly compare the heights of the Earth’s surface on different continents. Through coordination with measurements from satellite navigation systems (e.g. GPS or GALILEO), it will be possible in the future to make such data available with centimeter accuracy to every user. And last but not least, it also will become simpler to plan the construction of roads, tunnels, and bridges.

The consortium scientists, coordinated at the TU Muenchen, will now use the pre-processed data to develop an initial global model of the gravitational field. It will be presented at the Living Planet Symposium of the European Space Agency ESA at the end of June in Bergen, Norway.

Did phosphorus trigger complex evolution — and blue skies?

Paleoproterozoic phosphate deposit from Rajasthan,India
Paleoproterozoic phosphate deposit from Rajasthan,India

The evolution of complex life forms may have gotten a jump start billions of years ago, when geologic events operating over millions of years caused large quantities of phosphorus to wash into the oceans. According to this model, proposed in a new paper by Dominic Papineau of the Carnegie Institution for Science, the higher levels of phosphorus would have caused vast algal blooms, pumping extra oxygen into the environment which allowed larger, more complex types of organisms to thrive.

“Phosphate rocks formed only sporadically during geologic history,” says Papineau, a researcher at Carnegie’s Geophysical Laboratory, “and it is striking that their occurrences coincided with major global biogeochemical changes as well as significant leaps in biological evolution.”

In his study, published in the journal Astrobiology, Papineau focused on the phosphate deposits that formed during an interval of geologic time known as the Proterozoic, from 2.5 billion years ago to about 540 million years ago. “This time period is very critical in the history of the Earth, because there are several independent lines of evidence that show that oxygen really increased during its beginning and end,” says Papineau. The previous atmosphere was possibly methane-rich, which would have given the sky an orangish color. “So this is the time that the sky literally began to become blue.”

During the Proterozoic, oxygen levels in the atmosphere rose in two phases: first ranging from 2.5 to 2 billion years ago, called the Great Oxidation Event, when atmospheric oxygen rose from trace amounts to about 10% of the present-day value. Single-celled organisms grew larger during this time and acquired cell structures called mitochondria, the so-called “powerhouses” of cells, which burn oxygen to yield energy. The second phase of oxygen rise occurred between about 1 billion and 540 million years ago and brought oxygen levels to near present levels. This time intervals is marked by the earliest fossils of multi-celled organisms and climaxed with the spectacular increase of fossil diversity known as the “Cambrian Explosion.”

Papineau found that these phases of atmospheric change corresponded with abundant phosphate deposits, as well as evidence for continental rifting and extensive glacial deposits. He notes that both rifting and climate changes would have changed patterns of erosion and chemical weathering of the land surface, which would have caused more phosphorous to wash into the oceans. Over geologic timescales the effect on marine life, he says, would have been analogous to that of high-phosphorus fertilizers washed into bodies of water today, such as the Chesapeake Bay, where massive algal blooms have had a widespread impact.

“Today, this is happening very fast and is caused by us,” he says, “and the glut of organic matter actually consumes oxygen. But during the Proterozoic this occurred over timescales of hundreds of millions of years and progressively led to an oxygenated atmosphere.”

“This increased oxygen no doubt had major consequences for the evolution of complex life. It can be expected that modern changes will also strongly perturb evolution,” he adds. “However, new lineages of complex life-forms take millions to tens of millions of years to adapt. In the meantime, we may be facing significant extinctions from the quick changes we are causing.”

How does ice flow?

The seismic snow streamer is laid out. -  Olaf Eisen, Alfred Wegener Institute
The seismic snow streamer is laid out. – Olaf Eisen, Alfred Wegener Institute

Currently the yearly General Assembly of the European Geological Union takes place in Vienna, Austria. Dr. Olaf Eisen from the German Alfred Wegener Institute presents results from an environmentally friendly measurement method that he and his colleagues used on an Antarctic ice-shelf for the first time in early 2010. It supplies data that are input to models for the ice mass balance and thus permit better forecasting of future changes in the sea level.

The quality of scientific models depends to a decisive degree on the available database. Therefore members of a young investigators group supported by the German Research Foundation (DFG) now applied a special geophysical measurement method, vibroseismics, for data collection in the Antarctic for the first time. “By means of vibroseismic measurements, we would like to find out more about the structure of the ice and thus about the flow characteristics of the Antarctic ice sheet,” explains Dr. Olaf Eisen from the Alfred Wegener Institute for Polar and Marine Research in the Helmholtz Association. He is head of the LIMPICS young investigators group (Linking micro-physical properties to macro features in ice sheets with geophysical techniques).

Eisen now presents first results from geophysical measurement campaign in the Antarctic on the international conference. The objective of the expedition was to determine the internal structure of an ice sheet from its surface by means of geophysical methods. The cooperation partners are the Universities of Bergen (Norway), Swansea (Wales, UK), Innsbruck (Austria) and Heidelberg (Germany) and the Commission for Glaciology of the Bavarian Academy of Sciences and Humanities. For test purposes vibroseismics was used along with proven explosive seismic methods for the first time on an ice sheet

One of the problems involved in the application of seismic methods on ice sheets is the very porous firn layer, which may be 50 to 100 meters thick. Explosive seismics involves drilling a hole, approximately 10 to 20 metres deep, into the firn to achieve a better coupling between the explosive charge and the surrounding firn or ice. Drilling takes a lot of time and permits only slow progress along the seismic profiles. Vibroseismics entails the generation of seismic waves directly on the surface. For this purpose the vibrator pad of a 16-ton vibroseis truck of the University of Bergen is pressed onto the precompressed firn and set into operation at a defined vibration rate. In contrast to explosive seismic methods, the excited seismic signal is known and can be repeatedly generated as frequently as desired, leading in the end to improved data quality. However, the loss of seismic energy in the porous firn is a disadvantage. Therefore, the scientists compare the explosive seismic and vibroseismic methods quantitatively and in this way want determine how much energy is propagating from the surface through the ice and reflected back to the surface. First data analysis show that vibroseismics is coequal to the classic explosive seismics concerning the amplitude of the waves sent into deeper snow and ice layers. An explicit advantage is the lower effort and thus less time and energy the scientists spend to measure seismic profiles now.

Yngve Kristoffersen, professor of geophysics at the University of Bergen, who provides the vibroseismic equipment, explains: “The successful pilot study opens up a new era for efficient and more environmentally friendly methods for obtaining seismic information on the internal structure of the ice and the bedrock underneath it. This would extend our knowledge about how the ice sheet moves across the bedrock and about the geological structure of the rock under the ice.” Furthermore, in the coming years this method will be applied during pre-site surveys of future geological drill sites under ice shelves, which will contribute to a better understanding of climate history.

Envisat captures renewed volcanic activity

New eruptions from Iceland's Eyjafjallajoekull volcano have produced a 1600 km-wide ash cloud over the Atlantic. The brownish plume, traveling east and then south, is clearly visible in stark contrast to white clouds framing this Envisat image from May 6, 2010. -  ESA
New eruptions from Iceland’s Eyjafjallajoekull volcano have produced a 1600 km-wide ash cloud over the Atlantic. The brownish plume, traveling east and then south, is clearly visible in stark contrast to white clouds framing this Envisat image from May 6, 2010. – ESA

New eruptions from Iceland’s Eyjafjallajoekull volcano have produced a 1600 km-wide ash cloud over the Atlantic. The brownish plume, travelling east and then south, is clearly visible in stark contrast to white clouds framing this Envisat image from 6 May.

The volcano began emitting steam and ash on 20 March, wreaking havoc on European aviation last month. Renewed activity earlier this week caused some flights to be suspended to and from Ireland, Northern Ireland and Scotland.

Authorities are monitoring the position and height of the ash cloud as well as the direction of prevailing Atlantic winds, which pose a problem when they blow south towards Ireland, located 1500 km southeast of the volcano.

Envisat’s Medium Resolution Imaging Spectrometer (MERIS) acquired this image. To see the latest MERIS images of the ash cloud, visit our MIRAVI website. MIRAVI, which is free and requires no registration, generates images from the raw data collected by MERIS and provides them online quickly after acquisition.

Stream water study detects thawing permafrost

The Storflaket  permafrost plateau bog near Abisko in northern Sweden  shows cracks at its borders due to thawing of the permafrost.
The Storflaket permafrost plateau bog near Abisko in northern Sweden shows cracks at its borders due to thawing of the permafrost.

Among the worrisome environmental effects of global warming is the thawing of Arctic permafrost—soil that normally remains at or below the freezing point for at least a two-year period and often much longer. Monitoring changes in permafrost is difficult with current methods, but a study by University of Michigan researchers offers a new approach to assessing the extent of the problem.

The new study approach, which relies on chemical tracers in stream water, is described in the journal Chemical Geology.

Overlying permafrost is a thin “active layer” that thaws every summer, and increases in the thickness of this layer over the years indicate thawing of permafrost. Both physical measurements and modeling suggest that active layer thickness has increased in some areas over the 20th century and that if present warming trends continue, increases of up to 40 percent could occur by the end of the 21st century.

Although the full effects of thawing are yet to be determined, coastal erosion and damage to the roads, buildings and pipelines that have been built on permafrost are likely outcomes. In addition, thawing permafrost may release the greenhouse gases carbon dioxide and methane into the atmosphere, triggering further warming and more permafrost thawing.

Currently, the main method for determining thaw depth is with a graduated steel probe. “You stick it in the ground and see when it hits frozen material,” said geochemist Joel Blum, who with ecologist George Kling and former graduate student Katy Keller undertook the new study.

“We were studying the chemistry of soils in the area around Toolik Field Station in northern Alaska, and we found that once we got below the thickness that typically would thaw during summer, the soil chemistry changed dramatically,” said Blum, who is the John D. MacArthur Professor of Geological Sciences. “Material that has not thawed since it was deposited by glaciers 10,000 to 20,000 years ago is now beginning to thaw, and when it does, it reacts strongly with water, which it’s encountering for the first time. This soil is much more reactive than soils higher up that interact with soil water every summer.”

In particular, the amount of calcium, relative to sodium and barium, is higher in the newly-thawed permafrost, and the ratio of the strontium isotope 87Sr to its counterpart 86Sr is lower. The researchers wondered if these chemical signatures of increasing thaw depth could be seen in local stream water.

Kling, who is the Robert G. Wetzel Collegiate Professor of Ecology and Evolutionary Biology, has conducted research at Toolik Lake for many years and obtained stream water samples that had been collected over an 11-year period.

When the samples were analyzed, “we saw really significant changes from year to year that were consistent with what you would predict from increasing thaw depth,” Kling said.

Although the method can’t reveal precisely how much permafrost thawing is occurring in particular localities, it still can be a useful adjunct to current methods, Blum said. “We’d love to be able to say that we see an increase in thickness of, say, 1 centimeter over the entire watershed, but we simply can’t say where in the watershed thawing is occurring. Nevertheless, we think it’s important to monitor streams in Arctic regions to keep track of these kinds of changes and follow the rate of change.”

Peruvian tectonic plates move by earthquakes and non-seismic slip

Just a few years ago, Dan Farber happened to be doing field work in Peru with students when the 8.0 Pisco earthquake struck.As a scientist working in the active tectonics of the Peruvian Andes – funded through the Lawrence Livermore National Laboratory’s Institute for Geophysics and Planetary Physics – Farber was asked by colleagues if he could participate in a rapid response team to map the damage of the seismic deformation and install a system of geodetic stations.

He jumped at the opportunity to install a Global Positioning System (GPS) network to capture the post-seismic response and collected critical geological data for the understanding of the inter-plate dynamics of one of the Earth’s largest subduction zones – the Central Peru Megathrust.

In a new paper appearing in the May 6 edition of the journal Nature, Farber and international colleagues determined that the seismic slip on the Central Peru Megathrust is not dependent on earthquakes alone. As it turns out, movement along this subduction zone is caused by earthquakes as well as non-seismic (aseismic) related slip from steady or transient creep between or directly after earthquakes.

“Active faults are made up of areas that slip mostly during earthquakes and areas that mostly slip aseismically,” Farber said. “The size, location and frequency of earthquakes that a megathrust can generate depend on where and when aseismic creep is taking place.”

The 8.0 Pisco earthquake that occurred in 2007 ruptured the subduction interface – where load-bearing flat surfaces butt up – between the Nazca plate and the South American plate, an area that subducts about 6 centimeters per year. In this event, two distinct areas moved 60 seconds apart in a zone that had remained locked in between earthquakes. The event also triggered aseismic frictional afterslip on two adjacent areas.

The most prominent afterslip coincides with the Nazca ridge subduction, which seems to have repeatedly acted as a barrier to seismic rupture propagation in the past.

To sum up, aseismic (non-earthquake producing) slip accounts for as much as 50 percent to 70 percent of the slip on this portion of the megathrust in central Peru. Because much of the interface displacement is taken up aseismically, an earthquake the size of the 2007 earthquake is estimated to occur only every 250 years.