New aid to biogeochemical research slated for materials characterization lab

A mass spectrometer that will help researchers interpret and understand the history of the Earth system will join other instruments in the Penn State’s multi-user Materials Characterization Laboratory, thanks to a $724,000 grant through the National Science Foundation’s Major Research Instrumentation Program.

Matthew Fantle, assistant professor of geoscience, is the principal investigator on this grant, which is funded under the American Recovery and Reinvestment Act of 2009. Geoscientists and biochemists will use the Multiple Collector Inductively-Coupled Mass Spectrometer (MC-ICP-MS) to measure isotope ratios of elements such as calcium, copper, iron, lithium and molybdenum in natural materials. The isotopic composition of various elements aid researchers in tracing important processes in the Earth system, helping them to understand connections in the weathering-climate system and developing methods to interpret the history of the Earth as recorded in the rock record.

The MC-ICP-MS will be in a state-of-the-art clean room in the College of Earth and Mineral Sciences and will be run daily by a specialist who will train new users and help incorporate the new equipment into courses focused on data collection and analysis. The instrument represents the most advanced technology in the field of isotope chemistry and can ionize liquid samples extremely efficiently, stripping electrons from individual atoms to produce the positively charged ions measured. Those ions are filtered into a uniform energy beam, which passes through a magnetic field that separates the ions based on their mass-to-charge ratio. The separated atoms are then sent to a series of sensitive collectors that respond to discrete masses and convert each impact produced by the ion beam into voltages. The voltages measured at each collector are compared to each other to create isotope ratios.

The new spectrometer will benefit Penn State in a variety of ways. Those who are already involved in isotope research will increase the speed at which they do research by eliminating the need to travel to or send samples to external laboratories. This instrument will also support development of new isotopic systems, expand the use of isotope techniques to new fields across the University, promote mult-disciplinary collaboration and beyond and train graduate and undergraduate students in cutting-edge analytical techniques.

The dawn of a new epoch?

Dr. Jan Zalasiewicz is a researcher at the University of Leicester. -  University of Leicester
Dr. Jan Zalasiewicz is a researcher at the University of Leicester. – University of Leicester

Geologists from the University of Leicester are among four scientists- including a Nobel prize-winner – who suggest that the Earth has entered a new age of geological time.

The Age of Aquarius? Not quite – It’s the Anthropocene Epoch, say the scientists writing in the journal Environmental Science & Technology. (web issue March 29; print issue April 1)

And they add that the dawning of this new epoch may include the sixth largest mass extinction in the Earth’s history.

Jan Zalasiewicz and Mark Williams from the University of Leicester Department of Geology; Will Steffen, Director of the Australian National University’s Climate Change Institute and Paul Crutzen the Nobel Prize-winning atmospheric chemist of Mainz University provide evidence for the scale of global change in their commentary in the American Chemical Society’s’ bi-weekly journal Environmental Science & Technology.

The scientists propose that, in just two centuries, humans have wrought such vast and unprecedented changes to our world that we actually might be ushering in a new geological time interval, and alter the planet for millions of years.

Zalasiewicz, Williams, Steffen and Crutzen contend that recent human activity, including stunning population growth, sprawling megacities and increased use of fossil fuels, have changed the planet to such an extent that we are entering what they call the Anthropocene (New Man) Epoch.

First proposed by Crutzen more than a decade ago, the term Anthropocene has provoked controversy. However, as more potential consequences of human activity – such as global climate change and sharp increases in plant and animal extinctions – have emerged, Crutzen’s term has gained support. Currently, the worldwide geological community is formally considering whether the Anthropocene should join the Jurassic, Cambrian and other more familiar units on the Geological Time Scale.

The scientists note that getting that formal designation will likely be contentious. But they conclude, “However these debates will unfold, the Anthropocene represents a new phase in the history of both humankind and of the Earth, when natural forces and human forces became intertwined, so that the fate of one determines the fate of the other. Geologically, this is a remarkable episode in the history of this planet.”

Expedition heads for world’s deepest undersea volcanoes

The robot submarine Autosub6000 can dive 3.73 miles (6,000 m) deep and was developed at the National Oceanography Centre, Southampton. -  NOCS
The robot submarine Autosub6000 can dive 3.73 miles (6,000 m) deep and was developed at the National Oceanography Centre, Southampton. – NOCS

A British scientific expedition is heading into the world’s deepest volcanic rift, more than three miles beneath the waves in the Caribbean, to hunt for the deepest “black smoker” vents detected so far on the ocean floor. The team, working aboard the Royal Research Ship James Cook, will use a robot submarine called Autosub6000 and a remotely-controlled deep-sea vehicle called HyBIS to reveal the features and inhabitants of the world’s undersea volcanoes for the first time.

The expedition is being run by Drs Doug Connelly, Jon Copley, Bramley Murton, Kate Stansfield and Professor Paul Tyler, all from the National Oceanography Centre in Southampton, UK. They will explore the Cayman Trough – a rift in the seafloor of the Caribbean that reaches more than three miles deep. In November last year, a US-led survey of the waters of the Cayman Trough detected signs of deep-sea vents on the ocean floor below – and now the British expedition is heading out to investigate them.

Deep-sea vents are undersea volcanic springs that erupt mineral-rich water hot enough to melt lead. They were discovered in the Pacific three decades ago, but most are found one to two miles deep, dotted along chains of undersea volcanoes around the world. Scientists are fascinated by these vents because they support lush colonies of deep-sea creatures that thrive in the otherwise sparsely-populated abyss. The vent creatures feed on microbes that are nourished by minerals in the superheated water, creating an ecosystem that is not reliant on sunlight as its energy source.

For this expedition, the RRS James Cook is equipped with Autosub6000, a robot submarine developed by engineers at the National Oceanography Centre in Southampton, UK. Autosub6000 can dive 3.73 miles (6000 m) deep to map the ocean floor in detail, survey the currents and chemistry of deep waters, and take photographs. The team also plan to use a deep-sea vehicle called HyBIS, built by engineering company Hydro-Lek Ltd in Berkshire, UK. HyBIS can be remotely-controlled from the ship to film the ocean floor and collect samples of rocks and deep-sea creatures.

The researchers hope to compare the marine life at the bottom of the Cayman Trough with that known from other deep-sea vents, thereby shedding light on the web of life that spans the deep ocean. “Studying the species that thrive in such unlikely havens gives us insights into patterns of marine life around the world, and even the possibility of life on other planets,”, says Copley, a marine biologist at the University of Southampton and leader of the research programme.

In addition, the team will investigate the geology of the area and the hot water that gushes from deep-sea vents. “Because deep-sea vents get hotter at greater depths, we expect these vents to be the hottest yet,” says geochemist Connelly, who will be the Principal Scientist aboard the ship. The current world-record temperature for a deep-sea vent is 403ºC, at a vent 2.67 miles (4300 metres) deep in the middle of the Atlantic.

The expedition will also leave instruments on the ocean floor to monitor the little-known deep-sea currents of the Cayman Trough, and deploy experiments to investigate how deep-sea creatures colonize new habitats. The scientists will board the RRS James Cook in Trinidad on 21st March, to prepare for the ship’s departure on 25th March. The expedition is scheduled to arrive at the Cayman Trough around 31st March, and will end in Jamaica on 24th April. During the voyage, the scientists will be posting updates about their progress live from the ship at www.noc.soton.ac.uk “We look forward to sharing the excitement of our expedition with people around
the world”, says Copley.

Greenland ice sheet losing mass on northwest coast

New research indicates ice loss in Greenland is moving up the northwest coast. -  Greenland
New research indicates ice loss in Greenland is moving up the northwest coast. – Greenland

Ice loss from the Greenland ice sheet, which has been increasing during the past decade over its southern region, is now moving up its northwest coast, according to a new international study.

Led by the Denmark Technical Institute’s National Space Institute in Copenhagen and involving the University of Colorado at Boulder, the study indicated the ice-loss acceleration began moving up the northwest coast of Greenland starting in late 2005. The team drew their conclusions by comparing data from NASA’s Gravity and Recovery Climate Experiment satellite system, or GRACE, with continuous GPS measurements made from long-term sites on bedrock on the edges of the ice sheet.

The data from the GPS and GRACE provided the researchers with monthly averages of crustal uplift caused by ice-mass loss. The team combined the uplift measured by GRACE over United Kingdom-sized chunks of Greenland while the GPS receivers monitor crustal uplift on scales of just tens of miles. “Our results show that the ice loss, which has been well documented over southern portions of Greenland, is now spreading up along the northwest coast,” said Shfaqat Abbas Khan, lead author on a paper that will appear in Geophysical Research Letters.

The team found that uplift rates near the Thule Air Base on Greenland’s northwest coast rose by roughly 1.5 inches, or about 4 centimeters, from October 2005 to August 2009. Although the low resolution of GRACE — a swath of about 155 miles, or 250 kilometers across — is not precise enough to pinpoint the source of the ice loss, the fact that the ice sheet is losing mass nearer to the ice sheet margins suggests the flows of Greenland outlet glaciers there are increasing in velocity, said the study authors.

“When we look at the monthly values from GRACE, the ice mass loss has been very dramatic along the northwest coast of Greenland,” said CU-Boulder physics Professor and study co-author John Wahr, also a fellow at CU-Boulder’s Cooperative Institute for Research in Environmental Sciences.

“This is a phenomenon that was undocumented before this study,” said Wahr. “Our speculation is that some of the big glaciers in this region are sliding downhill faster and dumping more ice in the ocean.”

Other co-authors on the new GRL study included Michael Bevis and Eric Kendrick from Ohio State University and Isabella Velicogna of the University of California-Irvine, who also is a scientist at NASA’s Jet Propulsion Laboratory. GRL is published by the American Geophysical Union.

A 2009 study published in GRL by Velicogna, who is a former CU-Boulder research scientist, showed that between April 2002 and February 2009, the Greenland ice sheet shed roughly 385 cubic miles of ice. The mass loss is equivalent to about 0.5 millimeters of global sea-level rise per year.

“These changes on the Greenland ice sheet are happening fast, and we are definitely losing more ice mass than we had anticipated, ” said Velicogna. “We also are seeing this ice mass loss trend in Antarctica, a sign that warming temperatures really are having an effect on ice in Earth’s cold regions.”

Researchers have been gathering data from GRACE since NASA launched the system in 2002. Two GRACE satellites whip around Earth 16 times a day separated by 137 miles and measure changes in Earth’s gravity field caused by regional shifts in the planet’s mass, including ice sheets, oceans and water stored in the soil and in underground aquifers.

“GRACE is unique in that it allows us to see changes in the ice mass in almost real time,” said Velicogna. “Combining GRACE data with the separate signals from GPS stations gives us a very powerful tool that improves our resolution and allows us to better understand the changes that are occurring.”

In addition to monitoring the Thule GPS receiver in northwest Greenland as part of the new GRL study, the team also is taking data from GPS receivers in southern Greenland near the towns of Kellyville and Kulusuk. An additional 51 permanent GPS stations recently set up around the edges of the Greenland ice sheet should be useful to measure future crustal uplift and corresponding ice loss, said Wahr.

“If this activity in northwest Greenland continues and really accelerates some of the major glaciers in the area — like the Humboldt Glacier and the Peterman Glacier — Greenland’s total ice loss could easily be increased by an additional 50 to 100 cubic kilometers (12 to 24 cubic miles) within a few years,” said Khan.

A thesis characterizes marine conditions of Aralar mountain range of 120 million years ago

The Early Aptian (120 million years ago) was an age of intense volcanic activity on Earth, eruptions that emitted large amounts of CO2 into the atmosphere, thus causing a revolution in the carbon cycle. As a consequence, great changes happened in the whole of the terrestrial system. Researcher María Isabel Millán has studied how these changes happened in the marine environment of the Aralar mountain range (at that time it was under the sea) in the Basque Country, and found more than one surprise. She presented her conclusions in her PhD thesis at the University of the Basque Country (UPV/EHU).

Ms Millán’s thesis is entitled Record of Palaeoceanographic changes during the Early Aptian of the Aralar mountain range. Given its geological characteristics, Ms Millán suspected that the changes that took place in the Early Aptian period must have left traces in the sediments of the Aralar mountain range, which straddles the Basque provinces of Gipuzkoa and Navarre. She began to study the outcrops in detail. The researcher observed that the materials representing this period in Aralar are more significant than those studied to date, and this was the first surprise of this thesis. While in other parts of the world the sedimentary series of the Early Aptian that can be studied are some 20 metres thick, Ms Millán found up to 1,000 meters in Aralar.

An unparalleled event

One of the principal global changes that took place in the oceans of the Early Aptian was that known as OAE1a (Oceanic Anoxic Event 1a); that is, a sudden reduction in maritime oxygen at the ocean beds. In order to show that this phenomenon also occurred in Aralar, Ms Millán employed a number of methodologies. On the one hand, she used ammonite fossils, which give very precise dates and which have been found in abundance in these sediments. She also made use of analytical techniques for identifying rock enriched with organic material. In fact, when something important happened in the atmosphere or in the ocean during that period, rocks known as black shales were deposited at the bottom of the sea. These rocks were enriched with organic material, leaving remains thereof in the sedimentary layers. Ms Millán also made use of stable isotopes of carbon, as their proportion depends on the origin and concentration of CO2 present at the time. It is precisely in the Early Aptian that a huge increase of volcanic-origin CO2 took place. She found evidence amongst the sedimentary rocks which were significant in terms of an OAE1 event, thus demonstrating that this phenomenon also had taken place in Aralar.

While looking for the OAE1, Ms Millán also came across another event which, to date, has only been found on Aralar. The point here is that she discovered an interval of rock enriched with organic material, which indicates an enormously significant geological event. However, the ammonites found in this interval show that this event does not correspond exactly to the period in which the OAE1 event occurred, but is a somewhat later (younger) event; from the Upper Early Aptian to be exact. Ms Millán believes it could be a sub-event within the more wide-ranging OAE1 one. It would be, therefore, a regional or local event, given that nothing similar has been found anywhere else to date, and it remains to be seen if anything equivalent does, in fact, exist.

Sudden collapse of the reef platform of Madotz

The biocalcification crisis is another of the representative phenomena of the changes in the Early Aptian. Specifically, in Madotz, in the south-east of the mountain range, there was a reef platform, equivalent to, for example, what is found in the coral reefs of Australia today. As the researcher explained, the biocalcification that commonly occurred on the reefs suddenly collapsed on this platform, coinciding with the OAE1a event and probably responding to an acidification of the oceans (as is happening today due to industrial-origin CO2). This, according to Ms Millán, is a clear reflection of the biocalcification crisis, given that the carbonated composition of the platform was drastically modified.

Tectonics: Precision is hallmark of 20-year study

Richard Gordon and his colleagues have just put the finishing touches on a 20-year effort to precisely describe the relative movements of the interlocking tectonic plates that make up about 97 percent of Earth's surface. -  Jeff Fitlow/Rice University
Richard Gordon and his colleagues have just put the finishing touches on a 20-year effort to precisely describe the relative movements of the interlocking tectonic plates that make up about 97 percent of Earth’s surface. – Jeff Fitlow/Rice University

When it comes to three-dimensional puzzles, Rubik’s Cube pales in comparison with the latest creation of Rice University geoscientist Richard Gordon. Gordon and collaborators Chuck DeMets of the University of Wisconsin-Madison and Donald Argus of NASA’s Jet Propulsion Laboratory in Pasadena, Calif., have just put the finishing touches on a 20-year labor of love, a precise description of the relative movements of the interlocking tectonic plates that account for about 97 percent of Earth’s surface.

The 25 tectonic plates that form Earth’s surface are rigid, but they are in constant motion because they float atop the planet’s interior. The plates constantly grind together and slide past one another. When two plates crash into each other, they form mountain ranges like the Himalayas. When they slide past one another, they cause earthquakes like the one that struck Haiti this year.

“We live on a dynamic planet, and it’s important to understand how the surface of the planet changes,” said Gordon, Rice’s W.M. Keck Foundation Chair in Geophysics. “The frequency and magnitude of earthquakes depend upon how the tectonic plates move. Understanding how plates move can help researchers understand surface processes like mountain-building and subsurface processes like mantle convection.”

The new model of Earth, dubbed “MORVEL” for “mid-ocean ridge velocities,” was developed by Gordon and longtime collaborators DeMets and Argus. A paper describing MORVEL is available online and due to appear in next month’s issue of Geophysical Journal International (GJI). In creating MORVEL, DeMets, Gordon and Argus are essentially one-upping themselves: Their 1990 paper on tectonic plate velocities has been cited more than 2,000 times by other scientists.

“At the time that one came out, Chuck and I were out on an airplane in the Indian Ocean collecting more than 60,000 kilometers of new magnetic profiles south and southwest of the Maldives,” Gordon said. “At that point, we’d already decided to do another model, but we didn’t want to do one that was just an incremental improvement. To make it worthwhile, it had to be a whole lot better, and that’s why it took so long.”

Gordon said MORVEL offers a marked improvement on the previous work they did because it’s based on more — and more precise — data, like the profiles he and DeMets collected in the Indian Ocean in 1990.

“This model can be used to predict the movement of one plate relative to any other plate on the Earth’s surface,” said DeMets, the lead author of the MORVEL paper. “Plate tectonics describes almost everything about how the Earth’s surface moves and deforms, but it’s remarkably simple in a mathematical way.”

About three-quarters of the MORVEL data come from Earth’s mid-ocean ridges, undersea boundaries between tectonic plates. At these ridges, new crust forms constantly as magma wells up from beneath the planet’s surface while the plates spread apart.

To judge how fast the plates are spreading, the team uses data from scanners that look at the magnetic profile of the crust that’s formed at mid-ocean ridges. When Earth’s magnetic field changes polarity, it leaves a magnetic mark in the crust that’s akin to a tree ring. These polarity changes occur at irregular intervals — the last being about 780,000 years ago. By matching up the marks from the polarity shifts at different points along mid-ocean ridges worldwide, the team can judge how quickly new crust is being formed.

MORVEL’s a study in contrasting scales. It estimates exactly how fast plates are spreading apart along mid-ocean ridges. These rates are typically a few inches a year at most. And MORVEL does this for plate boundaries along a continuous string of mid-ocean ridges more than 40,000 miles long.

Twenty years ago, DeMets, Argus and Gordon used spreading rates that were based on magnetic reversal timescales developed from potassium-argon dating, but more precise methods have since been developed. Using the newer data, the team was able to improve the resolution of its model, particularly in parts of the world where plates are spreading the fastest.

A second study by Argus, Gordon and other colleagues, which was also years in the making and which appears in this month’s issue of GJI, offers additional information that can help refine scientists’ estimates of how Earth’s surface is evolving. In that study, the group used new data to refine best estimates for the exact position of Earth’s center. In examining the movement of tectonic plates based upon data from Global Positioning System satellites, satellite laser ranging and similar methods, scientists must consider how the planet is rotating and where its center of mass lies.

“Don came up with a bunch of criteria to try to find out what the center of Earth is doing, and this paper resulted from that,” Gordon said. “The kinds of differences we’re talking about are corrections of about 2 millimeters a year on how the center of Earth moves with time. It may not sound like much, but at the level of accuracy that we’re operating, that 2 millimeters matters,” Gordon said.

Southern Ocean winds open window to the deep sea

Deploying an Argo ocean profiler in the Southern Ocean.
Deploying an Argo ocean profiler in the Southern Ocean.

Australian and US scientists have discovered how changes in winds blowing on the Southern Ocean drive variations in the depth of the surface layer of sea water responsible for regulating exchanges of heat and carbon dioxide between the ocean and the atmosphere.

The researchers’ findings – published on-line today in Nature Geoscience – provide new insights into natural processes which have a major influence on the rate of climate change.

The surface-mixed layer is a crucial pathway between the atmosphere and the deeper layers of the ocean. Changes in the depth of the mixed layer can affect air-sea exchange, carbon and heat storage in the ocean, and the rate at which water sinks from the surface ocean into the deep ocean.

Changes in the mixed layer also affect biological productivity, by altering how much light and nutrients are available to support growth of plankton at the base of the food chain.

The paper’s lead author, CSIRO Wealth from Oceans Flagship oceanographer Dr Jean-Baptiste Sallée, said the winds over the Southern Ocean had increased in strength and shifted closer to Antarctica in recent decades.

“The shift in winds is one of the strongest trends in southern hemisphere climate over the last 30 years,” Dr Sallée said. “The key question is; ‘How does the wind change affect the ocean?’

“Our knowledge of how the Southern Ocean changes in time is poor because of the lack of ship-based observations in this remote region. But we now have seven years of year-round observations from a fleet of profiling floats known as Argo, which allow us to see for the first time how the Southern Ocean changes with the seasons and from year-to-year.”

The researchers, including Dr Steve Rintoul from the Antarctic Climate and Ecosystems CRC and CSIRO and Professor Kevin Speer from Florida State University, examined the relationship between changes in wind and changes in the surface-mixed layer.

“We found that the depth of the mixed layer was more sensitive than we expected to a wind pattern known as the Southern Annular Mode, the major mode of variability of the southern hemisphere atmosphere,” Dr Sallée said. “Even more surprising was the fact that the response is very different in different regions.”

When the winds strengthen and contract closer to Antarctica, the surface-mixed layer deepens in the eastern Indian and central Pacific oceans, and shallows in the western part of these basins. The reverse is seen when the winds weaken and migrate north.

The asymmetry can be explained by small deviations in the generally west-to-east winds and their effect on the heat exchange between ocean and atmosphere: when cold winds blow from the south, this causes heat loss from the ocean and deeper mixed layers.

“These changes in mixed layer depth affect how much light is available to support the growth of phytoplankton. We found that changes in the mixed layer depth driven by the winds are associated with changes in the amount of phytoplankton biomass,” Dr Sallée said.

Earthquake observatory in Northern Chile to monitor the last seismic gap




Contruction of a geodynamic Station of the Plate-Boundary Observatory Chile
Contruction of a geodynamic Station of the Plate-Boundary Observatory Chile

The high-magnitude earthquake of 27.2.2010 in southern Central Chile closed one of the two remaining seismic gaps at the South American plate boundary. After the quake of Concepción, the remaining gap in the north of Chile now holds potential for a comparable strong quake and is, thus, moving more and more into the focus of attention. The GFZ German Research Centre for Geosciences, has been monitoring this gap with the Integrated Plate Boundary Observatory (IPOC) in Chile since 2006. In a festive ceremony on March 15, the Chairman of the Board of the GFZ, Professor Reinhard Huettl, is handing over this Observatory to the Universidad de Chile with the seismological service of Chile and to the Universidad Catolica del Norte.

“Together with our Chilean colleagues and other partners we have developed and operated the IPOC. The transfer to the Chilean Earthquake Service will further strengthen this cooperation” explained Reinhard Huettl in Santiago de Chile. “The observatory will continue to be jointly operated, GFZ will finance the German share. The location for this observatory has obviously been very well selected, as the quake of 27 February shows. This last non-ruptured segment of the Earth’s crust off the Chilean west coast is highly interesting for geosciences in the whole world”. It is, however, not simply a question of earthquakes. The aim is to continuously measure all processes in connection with the dynamics of this plate boundary.

Approximately one-third of the world-wide seismic energy has discharged during the last century in earthquakes with magnitudes of over M = 8 along the South American-Pacific plate boundary. The repeat-time between two large earthquakes is shorter here than almost anywhere else on our planet.

The IPOC project investigates the area around Iquique on the South American Nazca Plate Boundary. One expects that within the next years a strong to devastating earthquake will occur in this area. Within the framework of investigations, deformation, seismicity, and magnetotelluric fields in the subduction zone will be monitored, i.e. in the periods before, between and possibly also during a quake.

The equipping of the observatory began in close collaboration with the Universidad de Chile (Santiago), the Universidad Católica del Norte (Antofagasta), the IPGP (Paris) and the GFZ (Potsdam). Professor Onno Oncken, Director of the Department “Geodynamics and Geomaterials” at the GFZ (Helmholtz Association) is coordinator of the IPOC activities and explains the construction of the observatory: “Currently the monitoring network consists of 20 seismological stations, equipped with broadband seismometers and acceleration sensors”. In order to do justice to the requirements for dissolution and efficiency of the sensors and data capture, special care was given to choosing the exact location. Thus, at each station a lug of approx. 5 m deep was blown into the rock bed, in order to ensure stable site conditions for the monitoring instruments. All seismic installations are equipped with the new-generation GPS-instruments. Seven measuring points were furthermore equipped beyond that with magnetotelluric measuring instruments and serve for the measurement of electric current in the Earth’s crust.

Professor Oncken has been leading research on geodynamics in the Andes since 1994. These investigations are not only of geoscientific interest. “Due to the numerous expeditions and measuring campaigns over the years in this subduction zone, the GFZ now holds the densest data set world-wide for such an area” says Onno Oncken. “When we monitor the conditions before, during and after a large quake this serves to help develop a hazard model for this and similar regions.

A strong quake in this region can have consequences for the global economy: the earthquakes here develop through the subduction of the Pacific-floor under South America. The same process also leads to the formation of ore deposits in the Earth’s crust. Thus, the largest copper deposit of the world is to be found on the western boundary of the Central Andes. A strong quake could interrupt or even endanger the global supply of copper and lithium.

Texas earthquake study cites ‘plausible cause’

Brian Stump, Chris Hayward and student Ashley Howe install seismic equipment near DFW Airport.
Brian Stump, Chris Hayward and student Ashley Howe install seismic equipment near DFW Airport.

A study of seismic activity near Dallas/Fort Worth International Airport by researchers from Southern Methodist University and the University of Texas at Austin reveals that the operation of a saltwater injection disposal well in the area was a “plausible cause” for the series of small earthquakes that occurred in the area between Oct. 30, 2008, and May 16, 2009.

The incidents under study occurred in an area of North Texas where the vast Barnett Shale geological formation traps natural gas deposits in subsurface rock. Production in the Barnett Shale relies on the injection of pressurized water into the ground to crack open the gas-bearing rock, a process known as “hydraulic fracturing.” Some of the injected water is recovered with the produced gas in the form of waste fluids that require disposal.

The earthquakes do not appear to be directly connected to the drilling, hydraulic fracturing or gas production in the Barnett Shale, the study concludes. However, re-injection of waste fluids into a zone below the Barnett Shale at the nearby saltwater disposal well began in September 2008, seven weeks before the first DFW earthquakes occurred and none were recorded in the area after the injection well stopped operating in August 2009.

The largest of the DFW-area earthquakes was a 3.3 magnitude event reported by the USGS National Earthquake Information Center.

A state tectonic map prepared by the Texas Bureau of Economic Geology shows a northeast-trending fault intersects the Dallas-Tarrant County line approximately at the location where the DFW quakes occurred. The study concludes, “It is plausible that the fluid injection in the southwest saltwater disposal well could have affected the in-situ tectonic stress regime on the fault, reactivating it and generating the DFW earthquakes.”

An SMU team led by seismologists Brian Stump and Chris Hayward placed portable, broadband seismic monitoring equipment in the area after the earthquakes began. The seismographs recorded 11 earthquakes between Nov. 9, 2008 and Jan. 2, 2009 that were too small to be felt by area residents. Cliff Frohlich and Eric Potter of UT-Austin joined the SMU team in studying the DFW-area sequence of “felt” earthquakes as well as the 11 “non-felt” earthquakes. Their study appears in the March issue of The Leading Edge, a publication of the Society of Exploration Geophysicists.

The SMU team also installed temporary monitors in and around Cleburne, Texas where another series of small earthquake began June 2, 2009 – but results from that study are not yet available.

Stump and Hayward caution that the DFW study raises more questions than it answers.

“What we have is a correlation between seismicity, and the time and location of saltwater injection,” Stump said. “What we don’t have is complete information about the subsurface structure in the area – things like the porosity and permeability of the rock, the fluid path and how that might induce an earthquake.”

“More than 200 saltwater disposal wells are active in the area of Barnett production,” the study notes. “If the DFW earthquakes were caused by saltwater injection or other activities associated with producing gas, it is puzzling why there are only one or two areas of felt seismicity.”

Further compounding the problem, Hayward said, is that there is not a good system in place to measure the naturally occurring seismicity in Texas: “We don’t have a baseline for study.”

Enhanced geothermal projects also rely on methods of rock fracturing and fluid circulation. Geological carbon sequestration, an approach being researched to combat climate change, calls for pumping large volumes of carbon dioxide into subsurface rock formations. “It’s important we understand why and under what circumstances fluid injection sometimes causes small, felt earthquakes so that we can minimize their effects,” Frohlich said.

The study notes that fault ruptures for typical induced earthquakes generally are too small to cause much damage.

“There needs to be collaboration between universities, the state of Texas, local government, the energy industry and possibly the federal government for study of this complicated question of induced seismicity,” Stump said. “Everyone wants quick answers. What I can tell you is the direction these questions are leading us.”

World crude oil production may peak a decade earlier than some predict

The world's crude oil production, which comes from sources like this oil field, may peak a decade earlier than some scientists had predicted. -  iStock
The world’s crude oil production, which comes from sources like this oil field, may peak a decade earlier than some scientists had predicted. – iStock

In a finding that may speed efforts to conserve oil and intensify the search for alternative fuel sources, scientists in Kuwait predict that world conventional crude oil production will peak in 2014 – almost a decade earlier than some other predictions. Their study is in ACS’ Energy & Fuels, a bi-monthly journal.

Ibrahim Nashawi and colleagues point out that rapid growth in global oil consumption has sparked a growing interest in predicting “peak oil” – the point where oil production reaches a maximum and then declines. Scientists have developed several models to forecast this point, and some put the date at 2020 or later. One of the most famous forecast models, called the Hubbert model, accurately predicted that oil production would peak in the United States in 1970. The model has since gained in popularity and has been used to forecast oil production worldwide. However, recent studies show that the model is insufficient to account for more complex oil production cycles of some countries. Those cycles can be heavily influenced by technology changes, politics, and other factors, the scientists say.

The new study describe development of a new version of the Hubbert model that accounts for these individual production trends to provide a more realistic and accurate oil production forecast. Using the new model, the scientists evaluated the oil production trends of 47 major oil-producing countries, which supply most of the world’s conventional crude oil. They estimated that worldwide conventional crude oil production will peak in 2014, years earlier than anticipated. The scientists also showed that the world’s oil reserves are being depleted at a rate of 2.1 percent a year. The new model could help inform energy-related decisions and public policy debate, they suggest.