Sand drift explained

Researchers in countries such as Denmark, the Netherlands and Poland study sand drift, but most of them are focusing on sand dunes along the coastline, not on the plains further inland.

“Sand dunes are dynamic. For all we know, they may have been formed last year. But sand plaines are much older and in periods more stable. Thin organic layers present in sands are interesting, when trying to understand sand drift in pre-historic times,” says botanist Lisbeth Prøsch-Danielsen at the University of Stavanger’s Museum of Archaeology.

Together with her colleague, geologist Lotte Selsing, she studies the transportation of sand to the plains behind the sand dunes on the beaches along the coast of Jæren in the south-western part of Norway: Why and when it first occurred, and in which areas it is most prevalent.

Pre-historic sand drift

Aeolian sand consists of particles, usually quartz, which has been transported by the wind.

“As a result of having collided with each other and thereby acquired a rounded shape, sand particles which have been shifted around by the wind over a long period of time, have a characteristically faint surface. Keeping the sand grains moving requires a certain wind force – around 12-15 metres per second. Such wind forces may occur at any time of the year in Jæren since deglaciation,” Selsing says.

Several archaeological excavations have shown aeolian activities. They date back as far as 9000 calendar years. In some places, layers of aeolian sand are quite thick.

“When Stavanger Airport was extended during the 1980-ies, a large area was surveyed archeologically. The site was covered by as much as two metres of sand, which had simply levelled out the entire landscape,” says Selsing.

Changing landscapes

The coastal landscape in Jæren was fundamentally altered by sand drift, and the original topography obscured. Finding pre-historic settlements in areas covered by aeolian sand is thus very difficult. But this new research has enabled us to point out the location of cultural monuments more accurately, Prøsch-Danielsen and Selsing explain.

Their findings indicate that the common occurrence of sand drift in Jæren may be attributed to sea-level changes, and human activities which have influenced the local environment and climate.

“Between 7500 and 5500 years ago, the coast line was one kilometre farther inland from today. The big, shallow fiords and estuaries were filled with sand, deposited during sea-level changes. This sand, dating back to the Glacial and late Glacial times, is the origin of today’s beaches along Jæren. When the sea-level eventually, large areas of sand were exposed, and the wind could play around with the sediments again,” says Prøsch-Danielsen.

For sand drift to occur, a number of factors have to be present, she adds. Sandy material has to be available, together with a lack of vegetation cover and a good measure of wind to transport the sand.

Near the Salthelleren prehistoric site in Ogna, there are traces of sand drift dating back approximately 7000 years – prior to any agricultural activities.

Human activities tore away the vegetation cover, exposing soil to the wind and thereby reinforcing sand drift.

Vanishing forests

“Although it may be difficult to envisage today, Jæren was covered by pine and forest during the Early Stone Age,” says Lisbeth Prøsch-Danielsen.

But early settlers began logging and burning the trees to provide pasture for animal husbandry – resulting in large moors, tended by grazing and slash-and-burn agriculture. In a span of 1500 years, the Jæren forests were completely gone. The coastal heaths were predominant until the Second World War, when modern agriculture finally gathered ground.

This man-made transition from forests to coastal heath land changed the local climate significantly, especially along the coast. There were no trees left to protect the soil from the strong winds coming in from the sea, and because of the wind’s cooling effect, temperatures felt lower, Selsing explains.

Agriculture a contributing factor

When agriculture was introduced in Rogaland 6000 years ago, the aeolian activity increased even further. Human settlements enforced environmental degradation by exposing the coastal landscape to erosion and desertification.

As the first farmers ploughed their fields to sow barley and wheat, they tore up the soil and exposed the sand underneath, thereby sparking off sand drift.

The scientists have uncovered plough marks in layers dating back to the Iron Age. There are also signs of farmers having been forced to move their pastoral fields as a result of sand destruction.

“Sand drift affected the landscape as well as the family units, and the society as a whole,” says Prøsch-Danielsen and Selsing.

Environmental degradation

The Stavanger Airport excavation uncovered alternating strata of soil and sand, indicating stable and unstable cycles during early agricultural times in Jæren.

“Among pre-historic farmers, the desire to reap short-term benefits seems to have overruled the need to preserve land for securing the long-term basis of existence,” says Prøsch-Danielsen.

The impact of deforestation on the local climate and environment was severe. It is comparable to the situation we are facing today, the two scientists observe. But unlike pre-historic man-made environmental changes, modern interventions are more far-reaching and difficult to rectify.

Sand drift and profound environmental changes to the Jæren landscape continued during the Middle Ages until today. There are local pockets of desertification, matched by few sites in Norway. One is Kvitsanden near Rørøs, which is the country’s only inland desert – and the result of logging to fire the former copper mining industry, Prøsch-Danielsen explains.

Earth’s oldest records of sea-floor spreading

Geologists have long-debated about when plate tectonics started on the planet. One of the key indicators has been whether or not fragments of oceanic crust, generated at sea-floor spreading centers, are preserved in the planet’s oldest crust. New research integrating what has been learned about the variations in modern sea floor spreading environments with the geological record of the oldest preserved crust on Earth shows that many belts in these ancient terrains have striking similarities to the different tectonic settings that oceanic crust is generated within the modern plate tectonic framework.

The new study shows that there is at least as much variation between ancient Precambrian (>greater than 2.5 billion years) and modern oceanic spreading processes as there is in the modern oceans. The paper by T. Kusky and colleagues from China, USA, and Canada synthesizes what is known about the variation in modern oceanic crust generated by plate tectonic processes, and compares this with similar features of Precambrian possible oceanic crust, and finds striking similarities to the newly recognized variation between tectonic environments for their origin. The record of oceanic crust generation, according to the new study, extends back until at least 3.8 billion years ago, the age of the most ancient rocks preserved on the plane.

This work has important implications for understanding how the early Earth lost heat, which tectonic settings were dominant, and for the locations for the origin of life on Earth.

Tourism does not harm all caves

Despite the high number of tourists, the large size of the cave means the thermal signal disperses very quickly and gently. -  David Domínguez Villar et al.
Despite the high number of tourists, the large size of the cave means the thermal signal disperses very quickly and gently. – David Domínguez Villar et al.

Unlike the situation in other caves, damage caused by tourists at the Águila cave in Ávila, Spain is “imperceptible”, despite it receiving tens of thousands of visitors each year. This is the main conclusion of an international research study headed by the University of Alcalá (UAH), which measured heat variations in the cave.

“Despite the tens of thousands of visitors that the Águila Cave receives each year, the temperature variations in it are related to the weather outside, while the long-term impact of tourism is virtually non-existent”, David Domínguez Villar, researcher at the Department of Geology of the UAH and lead author of the study published in the journal Acta Carsologica, tells SINC

The research was carried out using data gathered by temperature sensors, which have been fitted in the cave since 2008. These devices make it possible to observe heat variations in the cave, and are very sensitive to the impact of visitors.

“We took data from the cave every 10 minutes and used a filter. The impact of visitor arrivals on temperature increase could be observed immediately. For this reason, we chose the maximum and minimum levels, and we filtered certain periods with or without visitors so that we could differentiate between the natural dynamics of the cave and the impact of the visitors”, says Domínguez.

Despite the high number of tourists, the large size of the cave means the thermal signal disperses very quickly and gently. “This is the opposite of what happens in other caves, such as Altamira, which have a gallery shape, meaning that just a few people have an immense impact”, the expert explains.

The average temperature of the cave was 15.6ºC in 2009, and tourist visits caused thermal anomalies of less than 0.15ºC, with the temperature generally returning to normal overnight.

On days with higher numbers of visitors, the effects of the thermal anomalies lasted “from one day to the next”, and caused temperature increases in the cave for longer periods of time. However, this manmade effect disappeared shortly after the number of tourists fell. In most cases the effect lasted for less than a week.

According to the scientists, the biggest problem in caves with wall paintings is corrosion caused by condensation. “The walls of the Águila cave are also corroded, although it does not have paintings. However, this degradation is due to natural effects. In addition, no condensation-related corrosion can be seen on the stalagmites that are currently growing”, Domínguez adds.

Studying a region’s climate on the basis of a cave

The researchers also intend to study the past climate by using the stalagmites in the cave. “We want to look at how the external and internal temperature is recorded, and see the temperature trends and changes inside the cave”, the researcher adds.

Currently, a certain degree of seasonal change can be seen in the cave, but heat dispersion via rock is much slower than in the air. In fact, the experts say that the thermal signal from outside takes around seven years to reach the inside.

“The temperature records of the cave could be related to the climate of the region, and could be used to reconstruct the temperature of this area, aside from the impact of visitors”, he concludes.

New research suggests strong Indian crust thrust beneath the Tibetan Plateau

Earthquake mechanisms and the style of faulting in the Himalaya-Tibet region show that the Himalayan range is under north-south compression, southern Tibet is in east-west extension, and northern Tibet is in both east-west extension and north-south compression. The study shows that this pattern can be explained if the strong Indian crust thrust under southern Tibet is transmitting the north-south push of India to northern Tibet. -  Caltech's Tectonics Observatory
Earthquake mechanisms and the style of faulting in the Himalaya-Tibet region show that the Himalayan range is under north-south compression, southern Tibet is in east-west extension, and northern Tibet is in both east-west extension and north-south compression. The study shows that this pattern can be explained if the strong Indian crust thrust under southern Tibet is transmitting the north-south push of India to northern Tibet. – Caltech’s Tectonics Observatory

For many years, most scientists studying Tibet have thought that a very hot and very weak lower and middle crust underlies its plateau, flowing like a fluid. Now, a team of researchers at the California Institute of Technology (Caltech) is questioning this long-held belief and proposing that an entirely different mechanism is at play.

“The idea that Tibet is more or less floating on a layer of partially molten crust is accepted in the research community. Our research proposes the opposite view: that there is actually a really strong lower crust that originates in India,” says Jean-Philippe Avouac, professor of geology and director of Caltech’s Tectonics Observatory.

These insights lead to a better understanding of the processes that have shaped the Himalaya Mountains and Tibet-the most tectonically active continental area in the world.

Alex Copley, a former postdoctoral scholar with Caltech’s Tectonics Observatory, along with Avouac and Brian Wernicke, the Chandler Family Professor of Geology, describe their work in a paper published in the April 7 issue of the journal Nature.

Tibet and the surrounding Himalaya Mountains are among the most dynamic regions on the planet. Avouac points out that underground plate collisions, which cause earthquakes and drive up the Himalaya and Tibet, are common geological processes that have happened repeatedly over the course of Earth’s history, but are presently happening with a vigor and energy only found in that area.

Even though the elevation is uniform across the Tibetan Plateau, the type of stress seen within the plateau appears to change along a line that stretches east-west across the plateau-dividing the region into two distinct areas (southern and northern Tibet, for the purposes of this research.)

The researchers propose that a contrast in tectonic style-primarily east-west extension due to normal faulting in southern Tibet and a combination of north-south compression and east-west extension due to strike-slip faulting in northern Tibet-is the result of the Indian crust thrusting strongly underneath the southern portion of the Tibetan Plateau and locking into the upper crust. Strike-slip fault surfaces are usually vertical, and the rocks slide horizontally past each other due to pressure build-up, whereas normal faulting occurs where the crust is being pulled apart. They believe that the locked Indian crust alters the state of stress in the southern Tibetan crust, which can explain the contrast in the type of faulting seen between southern Tibet and northern Tibet.

To test their theory, the team performed a series of numerical experiments, assigning different material properties to the Indian crust. The simulations revealed evidence for a strong Indian lower crust that couples, or locks in, with the upper crust. This suggests that the “channel flow” model proposed by many geophysicists and geologists-in which a low-viscosity magma oozes through weak zones in the middle crust-¬is not correct.

“We have been able to create a model that addresses two long-standing debates,” says Copley, who is now a research fellow at the University of Cambridge. “We have constrained the mechanical strength of the Indian crust as it plunges beneath the Tibetan Plateau, and by doing so have explained the variations in the types of earthquakes within the plateau. This is interesting because it gives us new insights into what controls the behavior of large mountain ranges, and the earthquakes that occur within them.”

According to Wernicke, the results have motivated the team to think of ways to test further the “weak crust” hypothesis, at least as it might apply to the active tectonic system. “One way we might be able to image an extensive interface at depth is through geodetic studies of southern Tibet, which are ongoing in our research group,” he says.

Icy meltwater pooling in Arctic Ocean: A wild card in climate change scenarios

A massive, growing pool of icy meltwater in the Arctic Ocean is a wild card in future climate scenarios, European researchers said today.

Estimated in 2009 at more than 7,500 cubic km – twice the volume of Africa’s Lake Victoria – and growing, the water could flush quickly into the Atlantic with unpredictable effect when prevailing atmospheric patterns shift, as occurred most recently in the 1960s and 1990s.

The situation is one of many disquieting findings captured by project CLAMER, a collaboration of 17 institutes in 10 European countries to inventory and synthesize the research of almost 300 EU-funded projects over 13 years related to climate change and Europe’s oceans and near-shore waters, and the Baltic and Black Seas.

The full inventory and synthesis will be presented at an international conference at the Royal Flemish Academy of Belgium, Brussels, Sept. 14-15. This news release, highlighting research on climate-related physical ocean changes, will be followed in months to come by descriptions of impacts on marine life, and impacts on the economies and people of Europe.

Oceanographer Laura de Steur of the Royal Netherlands Institute for Sea Research says a mostly clockwise wind pattern for the past 12 years in the Arctic has contained – largely in an area known as the Beaufort Gyre (also called the Canada Basin) – a pool of relatively fresh water from unusually high river discharge and melting sea ice.

When the general atmospheric circulation pattern does shift, the fresh, cold water is expected to enter the North Atlantic, with unpredictable impact on an ocean current system important to both European weather and marine food chain. Signs of such an atmospheric shift appeared in 2009 but the episode was too short to cause a major flush.

Says Dr. de Steur: “The volume of water discharged into the Arctic Ocean, largely from Canadian and Siberian rivers, is higher than usual due to warmer temperatures in the north causing ice to melt. Sea ice is also melting quickly – another new record low for ocean area covered was documented this past January by the National Snow and Ice Data Center (http://nsidc.org/arcticseaicenews) – adding even more freshwater to the relatively calm Arctic Ocean.”

“In addition, sea ice that is thinner is more mobile and could exit the Arctic faster. In the worst case, these Arctic outflow surges can significantly change the densities of marine surface waters in the extreme North Atlantic. What happens then is hard to predict.”

The scenario echoes the premise of a controversial 2004 disaster film, “The Day After Tomorrow,” which depicted catastrophic cooling in Europe, dismissed by Dr. de Steur as Hollywood absurdity.

“Ice ages occur on geological time scales of tens of thousands of years,” she says. “However, large regional changes could be in store if the ocean circulation changes.”

Many scientists are concerned about the future of the ocean circulation system that carries heat north to moderate the European climate.

Essentially, as warm water flows from the tropics to the North Atlantic, it cools and increases in salinity, making it heavier. At the north end of the current, near southern Greenland, these currents are cooled strongly by the atmosphere. This cold, dense oxygenated water sinks and cascades like poured cream south along the sea floor. Further south, it warms and rises, lifting nutrients essential to the marine food chain in the process, then flows north again.

It amounts to a giant “conveyor” known as the Atlantic Thermohaline Circulation, or THC.

The hypothesis is that additional ice melting throughout the Arctic region would dilute northern saltwater and alter its density, causing the conveyor to slow.

According to Detlef Quadfasel of the Hamburg University’s climate centre, changes in the THC could be abrupt, occurring over a decade or two, but more gradual change is expected.

Direct observations of ocean currents over the past two decades and numerical model simulations have revealed a remarkable stability of the North Atlantic overturning strength.

However, most climate models predict a 20 per cent weakening of the current by the end of this century.

Scientists note that rising atmospheric temperature related to the build-up of greenhouse gases might at least temporarily counteract the cooling effect on Europe if North Atlantic underwater currents slow. However, the western edge of Europe, particularly the United Kingdom and Scandinavia, could cool substantially nonetheless.

Some 20 institutes from nine European countries, coordinated by the Institution of Oceanography at the University of Hamburg, are now cooperating in extensive studies of the THC through project THOR, for “ThermoHaline Overturning – at Risk?”

Another pair of projects, RAPID and RAPID-WATCH, involves researchers from the UK, Norway, the Netherlands and the United States in the collection of annual readings from 19 monitoring devices across the Atlantic at 26.5 degrees North. Statistically relevant data will be available after a decade of readings in 2014.

Large-scale salinity changes might also be in store for the Baltic Sea, one of the largest brackish-water ecosystems in the world, says Thomas Neumann, at Germany’s Leibnitz-Institute for Baltic Sea Research. Its salinity is controlled by the amount of freshwater flowing off the surrounding land, as well as how much water is exchanged with the North Sea.

The circulation pattern where the two seas meet prevents mixing of the Baltic’s surface and deep water, creating conditions of low or even no oxygen in the lower layer. Life in this zone has become highly adapted to the resulting extremes in salinity and oxygen conditions.

Within the next century, warming and other shifts caused by climate change could lead to lower salinity. “Given the extreme conditions for marine life in the Baltic Sea,” such changes could “dramatically impact species distributions” at all depths, Dr. Neumann says.

“The changes in these physical parameters may totally alter the habitat conditions and distribution patterns of many species,” agrees researcher Muyin Wang, of the University of Washington in Seattle.

Other physical ocean changes in store

The prospect of an altered ocean circulation pattern ranks among the most worrisome physical ocean changes among many predicted by the community of several hundred scientists connected by the European Union-sponsored project CLAMER.

Among other physical ocean changes either underway or foreseen by European researchers:

  • Rising seas around Europe will become warmer and more acidic;
  • The seasonal mixing of deep and shallow waters, essential to the marine food chain will be disrupted; and
  • More powerful and more frequent storms brewed offshore will batter coasts.

Public survey to complement research inventory

“There is a gap between what is known through research and what policy makers and the public know and understand about the impacts of climate change on the oceans,” says Carlo Heip, General Director of the Royal Netherlands Institute for Sea Research, which coordinates project CLAMER.

“This gap must be filled to spur public acceptance of measures essential to reducing and adapting to the impacts in store.”

Project CLAMER will also release in September a pan-European survey revealing public awareness of marine issues, top concerns, most trusted information sources and measures Europeans support to avoid or adapt to serious ocean changes.

While the precise consequences of climate change aren’t fully understood, the research results – a combination of observations and sophisticated computer modeling, point to significant alteration of the oceans, consequent upheavals within and among species that live in them and, as a result, the potential for major economic and social impacts on Europe.

The researchers note that climate change impacts are inter-related and some might amplify each other or cancel each other out.

“We know there is potential for substantial change, with wide-ranging impacts,” says Jan Mees, Director of the Flanders Marine Institute (Vlaams Instituut voor de Zee, VLIZ)

“We must both learn more and disseminate the knowledge in hand. Greater awareness is our best hope for motivating attempts to slow climate change and prepare for what it will bring.”

There is already evidence that physical changes in the oceans will have devastating ecological, biological and economic impacts.

Among other recent research results:

New patterns of seawater mixing on which marine animals depend

The mixing of deeper and shallower ocean waters determines whether and when nutrients, oxygen and heat are distributed. It usually occurs in a seasonal pattern, depending on sea depths, winds, changes in temperature and salinity, and flows of freshwater from rivers and melting. Most often, waters remain in stable layers throughout the summer and this stratification breaks down from fall to spring. Marine species are adapted to these cycles, so changes could impact their reproduction and survival.

Modeling by Britain’s Hadley Centre for Climate Prediction and Research shows the strength of seasonal stratification will increase by 20 per cent on Europe’s sea shelf areas, mainly because of temperature changes, and by 20 to 50 per cent in the open-ocean, largely because of the forecast declines in salinity. In shelf seas not affected by river discharges, stratification is projected to start five days earlier and break down five to 10 days later each year, extending the period when the waters don’t mix by 10 to 15 days.

Warming seawater

Warming is the feature most commonly associated with climate change and, in fact, sea surface temperatures are rising around Europe and throughout the world. The average global increase is 0.004 degrees Celsius per year. The annual rate is 0.002 for the North Atlantic Ocean; for the Black Sea it’s 0.003 degrees; for the North and Mediterranean Seas, 0.004 degrees; and for the Baltic, 0.006.

While there has been significant variability over the past century, major warming has occurred since the 1980s, says Jun She of the Danish Meteorological Institute, with computer models forecasting a rise of 2C or more by 2100.

Britain’s Hadley Centre modeling indicates that Europe’s northwest coastal shelf regions off Greenland will warm substantially more than the open-ocean – by between 1.5C and 4C, depending on location.

Smaller-scale modeling suggests an annual warming of 2C to 4C on the Baltic Sea surface, 1.7C in the North Sea and up to 5C for the Bay of Biscay.

Souring seas

Some of the most dramatic findings to date involve acidification of the oceans as they absorb more of the atmosphere’s growing load of carbon dioxide.

“Ocean acidification is detectable and underway,” says Marion Gehlen, of the Laboratoire des Sciences du Climat et de l’Environnment, near Paris.

Acidification undermines the ability of certain plankton species to grow shells. These tiny creatures support the entire ocean food web and help consume and sink much of the oceans’ carbon dioxide content. Harmful plankton species will replace beneficial varieties in some areas.

A lower pH means higher acidity. The measuring scale is logarithmic, which means even a small numerical difference represents a major change in pH.

The average pH of ocean surface waters is already 0.1 units (30%) lower than in pre-industrial times and a decrease by 0.4 (120%) units is projected by 2100 if greenhouse gas emissions from human activity continue to rise in a ‘business-as-usual’ fashion.

The likely result: “profound changes” in the structure and functioning of marine ecosystems, say Gehlen and Paul Tréguer, of l’Institut Universitaire Européen de la Mers, in Brest, France.

Some of the most important drops in pH have been reported in the Iceland Sea, an important source of North Atlantic deep water. Here, the winter surface water reading decreased by 0.0024 units per year between 1985 and 2008 – a rate 50 per cent faster than at two subtropical monitoring stations.

The depth at which the water contains too little aragonite to support life is now at 1,710 metres, and is increasing by about 4 metres per year. This rate of change, combined with the topography of the ocean floor in the region means that each year another 800 square kilometres of sea floor becomes exposed to this “dead” water.

Plankton surveys invariably reveal harmful impacts of these changes, especially at shallower depths, which are home to more of the organisms that rely on aragonite and calcium carbonate, the report states. Still, “there is an urgent need to clarify the effects.”

Shoreline erosion on the rise

If, as expected, climate change leads to higher sea levels and more frequent and fierce storms, erosion along Europe’s coast will accelerate. Precise predictions are difficult, because the impacts will depend on detailed local conditions, says Andrew Cooper, professor of coastal studies at the University of Ulster, in Ireland.

One general pattern, however, is that in Northern Europe, the land is still rebounding from the weight of Ice Age glaciers and as it rises, sea level, in effect, falls. In Southern Europe, however, with the land static or, in come cases subsiding, the sea is rising relative to the height of the shoreline.

As climate change raises sea level it will likely increase the rate and extent that shorelines migrate inland, while Northern Europe, “may find that sea-level rise now exceeds the rate of land uplift, leading to relative sea level rise for the first time in millennia,” Cooper says. “This would increase the extent of coastline subject to erosion.”

Record depletion of Arctic ozone layer caused increased UV radiation in Scandinavia

Over the past few days ozone-depleted air masses extended from the north pole to southern Scandinavia leading to higher than normal levels of ultraviolet (UV) radiation during sunny days in southern Finland. These air masses will move east over the next few days, covering parts of Russia and perhaps extend as far south as the Chinese/Russian border. Such excursions of ozone-depleted air may also occur over Central Europe and could reach as far south as the Mediterranean. On an international press conference by the World Meteorological Organisation (WMO) in Vienna today, atmospheric researcher Dr. Markus Rex from Germany´s Alfred Wegener Institute for Polar and Marine Research in the Helmholtz Association (AWI) pointed out that the current situation in the Arctic ozone layer is unparalleled.

“Such massive ozone loss has so far never occurred in the northern hemisphere, which is densely populated even at high latitudes,” AWI researcher Markus Rex describes the situation. The ozone layer protects life on Earth’s surface from harmful solar ultraviolet radiation. Because of the low inclination angle of the sun, exposure to ultraviolet radiation is not normally a public health concern at high northern latitudes. However, if ozone-depleted air masses drift further south over Central Europe, south Canada, the US, or over Central Asiatic Russia, for example, the surface intensity of UV radiation could lead to sunburn within minutes for sensitive persons, even in April.

Whether and when this may occur can be forecasted reliably only in the short term. People should thus follow the UV forecasts of regional weather services. “If elevated levels of surface UV occur, they will last a few days and sun protection will be necessary on those days, especially for children”, Rex recommends.

The expected UV intensity during these short episodes will, however, remain in the range of typical exposure at the height of summer and below the values that occur during holiday trips to the tropics. Extreme caution is therefore unnecessary. “The concern is that people don’t expect to get sunburn so rapidly early in the year and consequently don’t take sun protection as seriously as in the middle of summer or while on vacation,” states Rex. Any sunburn increases the risk of developing skin cancer later in life and this adverse effect is particularly pronounced in children.

“But provided that UV-protection is used it is safe and even healthy to exercise normal outdoor activities even during low ozone episodes. Particularly in countries high up in the north people tend to suffer from vitamin D deficit after the dark winter and Sun is a natural source of it”, adds Dr. Esko Kyrö from Arctic Research Center at Finnish Meteorological Institute.

The air masses with very low ozone concentrations will eventually disperse, as the sun warms the stratosphere and the winds change, as happens every year in spring. This will lead to somewhat lower ozone in spring and early summer this year, as the low ozone from the Arctic mixes with other stratospheric air throughout the northern hemisphere. This effect will be small, due to the large dilution of the ozone depleted air masses in background air.

As noted some weeks ago (AWI press release on 14 March 2011), the Arctic stratosphere has been unusually cold this winter, resulting in a transformation of chlorine supplied by industrial compounds into other forms that aggressively remove ozone. Since then the ozone removal process gained additional momentum by the return of sunlight to the Arctic, which is needed for the chemical processes to occur. The current amount of ozone depletion above the Arctic is far beyond that recorded for any other spring, over the time when ozone has been measured by modern instrumentation. These findings are based on an international network of 30 ozone sounding stations in the Arctic and Subarctic that is coordinated by the Alfred Wegener Institute.

BACKGROUND:

This year’s Arctic ozone depletion is caused by industrial CFCs and related compounds. Production of these chemicals was banned by the Montreal Protocol. Ozone loss was particularly large this winter due to unusually low temperature, which results in the presence of clouds in the polar stratosphere. Reactions on the surface of these clouds transform chlorine containing breakdown products of CFCs into compounds that aggressively remove ozone. Even though the Montreal Protocol has successfully banned the production of CFCs and related compounds, chlorine levels in the Arctic stratosphere are only about 5% below the prior peak level, due to the long atmospheric lifetime of CFCs (removal takes 50 to 100 years). The Arctic ozone layer will remain vulnerable to depletion for the next several decades, particularly following unusually cold winters. In contrast, temperatures within the Antarctic stratosphere are cold enough, each winter, to lead to widespread occurrence of stratospheric clouds that are part of the chain of events that causes the Antarctic ozone hole that occurs each spring.

The stratosphere has been observed to cool, following the rise of greenhouse gases (GHGs), because heat that would otherwise reach the stratosphere is trapped below, warming the surface. The situation for the Polar Stratosphere is more complicated because of dynamical heating by waves generated in frontal systems. For several years, however, scientists have noted that the coldest winters in the Arctic stratosphere are getting colder, a development that enhances the ozone-destroying efficiency of the remaining CFCs and could be linked to rising levels of GHGs. “The current winter is a striking continuation of this tendency. Hence, we are not surprised by the fact that such massive ozone depletion has now occurred above the Arctic”, says Rex. “Determining the role that GHG driven climate change might play for Arctic ozone loss is a great challenge and the subject of on-going research throughout the international atmospheric sciences community” states Ross Salawitch of the University of Maryland. The European Union contributes to financing this research in the RECONCILE project, a 3.5 million euro research programme in which 16 research institutions from eight European countries are working towards improved understanding of the Arctic ozone layer.

“On the basis of international agreements on protection of the ozone layer, the specifically the Montreal Protocol and its amendments, we expect, however, that ozone depletion due to CFCs will finally become passé towards the end of the century. This is an impressive success of international environmental policy under the umbrella of the United Nations. This success is only temporarily clouded by the record ozone loss above the Arctic this year”, says Rex. For several decades, however, the fate of the Arctic ozone layer each spring will be closely linked to the evolution of temperatures in the polar stratosphere.

World’s seismologists gather in Memphis to discuss latest earthquake science research

This tip sheet highlights presentations at the upcoming international meeting of SSA, which is an international scientific society devoted to the advancement of seismology and its applications in understanding and mitigating earthquake hazards and in imaging the structure of the Earth.

These summaries reflect submitted abstracts and the actual presentations will include additional data and analysis. We are available to assist you should need to contact speakers at the annual meeting, located at the Marriott Downtown Memphis.

Please cite the Seismological Society of America as the source of this information.

All abstracts can be found at http://www.bit.ly/seismologyabstracts

WEDNESDAY, APRIL 13, 2011


New Madrid Seismic Zone: Our Understanding on the 200th Anniversary of the New Madrid Earthquake Sequence



Ballroom C, 8:30 a.m. – Noon

On the Bicentennial of the New Madrid Seismic Zone (NMSZ) earthquakes, experts examine the state of knowledge about one of the most enigmatic regions of earthquake hazard in the world. The New Madrid region, which stretches some 150 miles from near Memphis to Paducah, Kentucky, is an active seismic zone with 15 earthquakes between M4.0 and M5.0 in the last 36 years. The region has experienced multiple sequences of large M7-M8 earthquakes three times in the last 1,200 years. Most scientists believe the region is vulnerable to future strong earthquake ground shaking generated from M7-M8 earthquakes, but there is debate about how big future earthquakes might be and whether they would repeat in the same region as the 1811-12 sequence. This session reports the latest research on these topics:

  • What do 19th century historical accounts and reporting of the 1811-12 sequence tell us about the history and people of the time?
    [C. Bolton Valencius, Harvard University, cvalenc@fas.harvard.edu]

  • Spectacular ground failure in 1811-12 resulted in liquefaction, sand blows, landslides, riverbank collapse and disappearing islands. How does this information and other pre-historic evidence help seismologist determine the size and recurrence of large earthquake sequences? (E. Schweig, U.S. Geological Survey (USGS), schweig@usgs.gov]

  • Were the three main 1811-12 earthquakes as large as the 2010 M7.0 Haiti quake or were they much larger and closer to the size of the M7.9 1906 San Francisco earthquake? [Several speakers weigh in on the debate: Susan Hough, U.S. Geological Survey, hough@usgs.gov; Chris Cramer, University of Memphis, ccramer@memphis.edu; Tom Holzer, U.S. Geological Survey, tholzer@usgs.gov; and Kent Moran, University of Memphis, nkmoran@memphis.edu]

  • Hot spots or Ice Age crustal loading/unloading and episodes of fluvial erosion have led to theories on causes of central and eastern U.S. earthquakes and the seismic potential of the area. [Several speakers share their latest findings and observations: Roy Van Arsdale, University of Memphis, rvanrsdl@memhis.edu; Eric Calais, Purdue University, ecalais@purdue.edu; Walter Mooney, U.S. Geological Survey, mooney@usgs.gov; and Tom Pratt, U.S. Geological Survey, tpratt@ocean.washington.edu]

  • It’s not just the New Madrid faults — other nearby faults show evidence of earthquakes in the past 50,000 years. Long-term deformation caused by earthquakes encompasses a wider region than previously considered, and the interaction among faults, rather than by the activity along one isolated fault, might play a key role in intracontinental deformation. [M. B. Magnani, University of Memphis, mmagnani@memphis.edu]

  • Computer simulations of earthquake ground motion have been extensively used to understand and anticipate earthquakes along the San Andreas Fault in California. Now L. Ramirez-Guzman and colleagues will report the results of computer simulations of earthquake ground motion in the NMSZ, exploring the variability of ground motion patterns, amplitude and duration of 1811-12 shaking. [L. Ramirez-Guzman, U.S. Geological Survey, lramirezguzman@usgs.gov]

  • What kind of economic losses can we expect from future New Madrid region earthquakes? Analysis by Mary Lou Zoback and colleagues at Risk Management Solutions demonstrates high-expected losses for future moderate earthquakes throughout the region. For example, magnitude 6.4-6.9 earthquakes near Memphis could generate total economic losses to private property and businesses between $80-130B, while a M6.5 earthquake in the Wabash Valley could cause between $20-65B in losses, depending on the proximity of the event to major population centers. In contrast, researchers estimate in excess of $250B in private property and business coverage losses for a M7.7 earthquake on the New Madrid seismic zone (considered an upper bound magnitude by some). Their analyses also indicate that a significant fraction of earthquake losses in the greater New Madrid region (65-80 percent) will be covered by earthquake insurance, exceeding the experience in Hurricane Katrina in 2005, in which only 55 percent of the $125B loss was covered by insurance. [Mary Lou Zoback, Risk Management Solutions, Marylou.zoback@rms.com]

Seismotectonics and Hazards of Active Margins in the Circum-Caribbean Sea and Eastern Pacific Ocean




Ballroom D, 8:30 a.m. – Noon

Seismic Hazard in the Northeast Caribbean

Historical earthquake data, seafloor mapping and GPS data are combined to examine the full suite of seismic hazards in the northern Caribbean. The researchers’ analysis points to places where future tsunamis and earthquakes are likely, shows where strain has accumulated or been relieved as the North American tectonic plate slides under the Caribbean plate, and suggests that the 2010 Haiti earthquake may mark the start of a series of quakes on the main fault in the area. [Uri Ten Brink, U.S. Geological Survey, utenbrink@usgs.gov]

Broadband Ground-Motion Time Series Generation




Ballroom E, 8:30 a.m. – Noon

Seismologists have made significant progress in both observation and theoretical modeling of earthquake strong-ground motion.

Very near-fault ground motion simulation (poster)

Very near-fault ground motions –distances of less than 100 meters– are of interest to engineers who work on designing or retrofitting bridges, freeways, railways and other structures that span faults or lie closely to one side of the fault. But there are few useful direct observations of ground shaking at these near-fault distances. The researchers build models to assess the hazards of very-near-fault shaking. [D. S. Dreger, UC Berkeley, dreger@seismo.berkeley.edu]

Earthquake Triggering and Induced Seismicity




Ballroom D, 2 – 3:45 p.m.

Earthquake by injection in Central Arkansas?



Seismologists have noticed an increase in the rate of earthquakes greater than magnitude 2.5 in central Arkansas (near the towns of Greenbrier and Guy) since April 2009 when waste water from natural gas drilling was injected into seven saltwater disposal wells in the area. But are the two events connected? Stephen Horton and Scott Ausbrooks say the evidence for the water injections triggering earthquakes is “circumstantial” at this time, but suggest the area around the wells is seismically active and needs close monitoring. The waste water comes from a drilling technique called hydraulic fracturing or “fracking,” where fluids are injected under pressure into rock layers, breaking them open and allowing for easier recovery of natural gas or petroleum inside the rock. Horton and colleagues began monitoring the area around two wastewater wells installed in July and August 2010; intense earthquake activity (hundreds of earthquakes) within several kilometers of the wells began in September 2010. The earthquakes helped reveal a previously undetected 13 kilometer-long vertical fault in the area, which may be capable of producing a potentially damaging earthquake if the entire fault ruptured at once. The Arkansas Oil and Gas Commission (AOGC) ordered an emergency shutdown of these wells on March 4, 2011. The shutdown is scheduled to be reconsidered at the AOGC April meeting. [S. Horton, CERI, University of Memphis, shorton@memphis.edu]

Seismic Sources and Parameters




Ballroom E, 2:15 – 5:45 p.m.

Surface icequakes from the Gornergletscher in Switzerland

This study looked at more than 14,000 surface icequakes (driven by surface crack openings) on Gornergletscher, Switzerland’s second-largest glacier. The research shows that the icequakes occur in distinct time clusters, but vary spatially over the glacier. The icequake activity is stronger during the day when there is more melt water and glacier flow is more rapid. Individual crevasses or ruptures often show a preferred “time of day” for rupture. The regions of “daytime” rupture tend to be spatially separated from those of “nighttime” rupture. [D. Kilb, Scripps Institute of Oceanography, dkilb@ucsd.edu]

Seismic Imaging: Recent Advancement and Future Direction




Ballroom D, 4:15 – 5:45 p.m.

Seismic imaging is a powerful tool for geophysicists to probe the Earth’s interior. This session includes presentations on seismic imaging in various scales and application arenas, with special emphasis on recent advances and future directions.

Towards a 3D reflectivity model of Erebus Volcano, Antarctica (poster)



Researchers want to use scattered seismic wave readings to gain a better understanding of the structure and changes inside Antarctica’s Mount Erebus, the world’s southernmost active volcano. Their models aren’t complete, but early results put scientists closer to a 3D picture of the shallow magma chamber inside the volcano and showing how magma system changes during low-level eruptions. [J.A. Chaput, New Mexico Institute of Mining and Technology, Socorro, N.M., jchaput@ees.nmt.edu]

Seismic structure of the crust and uppermost mantle of South America and the surrounding ocean basins (Poster)

The researchers present new maps of the seismic structure of the crust and uppermost mantle under South America and the surrounding ocean floor. Highlights of the maps include: a crust apparently slightly thinner than the global average underneath South America; thicker sediments on the Atlantic than on the Pacific seafloor; crustal parameter signatures of the subducted Nazca plate “flat slab” under the continent; and thinning of the crust along the western edge of the Amazon basin, possibly because of crustal stretching. [G. S. Chulick, Pennsylvania State University and U.S. Geological Survey, gsc13@psu.edu]

THURSDAY, APRIL 14, 2011


Integrating Geodynamic, Structure and Deformation Studies of the Seismogenic and Transition Zones in Subduction Zones and Other Margins




Ballroom D, 8:30 a.m. – Noon

Subduction zones have produced the largest earthquakes in the historic record. Despite the significant hazard posed by subduction zones, the processes that control where they occur remains largely unknown. The growth of observational networks and computational capabilities provides new insights.

Outer-rise earthquakes in the Mariana Subduction Zone

The researchers look at extensional faults at the Mariana subduction zone to see the kinds of stresses occurring between the Philippines and Pacific tectonic plates. They will present data on the plate materials there and whether they are dragging in seawater, possibly affecting stresses on the plate boundaries. [E. L. Emry, Washington University in St. Louis, ericae@seismo.wustl.edu]

Long-term Behavior of Faults and Earthquake Hazards in Intraplate Continental Regions




Ballroom C, 8:30 a.m. – Noon

Large intraplate earthquakes — those occurring far from a tectonic plate boundary – are poorly understood and not accounted for in the current plate tectonic theory. Scientists seek to understand the long-term behavior of intraplate faults in order to assess seismic hazard risk.

Active Fault Zones in the Nation’s Capital

In 1828, President John Quincy Adams recorded in his diary impressions of an earthquake he experienced at the White House. Although earthquakes are a rare event in the nation’s capital, the mid-Atlantic region does have its share of seismic hazards. At least 90 earthquakes have been recorded in the region over the past 20 years,
including the July 2010 magnitude 3.4 earthquake that struck near Germantown, Maryland shaking Washington, DC, last summer. In light of the Germantown earthquake, Lisa Walsh and colleagues have revisited the seismic potential in the nation’s capital. They detail a series of faults in the area, most notably the DC Fault Zone, which runs from the National Zoo to the East Wing of the White House. The Germantown quake may have ruptured on an extension of this fault zone, a new unmapped fault zone, or reactivated an old fault zone. Some maps of stress change induced by the Germantown earthquake suggest a very slight increase in the risk of future seismicity near Washington, DC, the researchers say. [L. S. Walsh, University of Maryland, lsschlei@umd.edu]

New Look at the Jones, Oklahoma Earthquake Swarm (poster)

The Jones, Oklahoma earthquake swarm began in late 2008, with two earthquakes felt by the community. Another 35 earthquakes were felt in the area in 2009 — a surprise, given that the Oklahoma Geological Survey had reported only seven earthquakes in the county prior to 2008. Austin Holland and colleagues now present a detailed look at the unusual swarm, based on data from a local network of seismic detectors installed in the area in 2010. The network located more than 660 earthquakes in Oklahoma County ranging in magnitude from 0.1 to 4.0. Local residents felt more than 64 of these earthquakes. Most of the earthquakes were strike-slip quakes, occurring at depths ranging from 3 to 6 kilometers below the ground surface. [A. A. Holland, Oklahoma Geological Survey, austin.holland@ou.edu]

Vienna (Austria) Basin: its paleoseismological history, producing the largest earthquake north of the Alps

In an effort to determine which faults should be considered when assessing hazard risk to the area, scientists documented the seismic history of the Vienna Basin in Central Europe between the Alps and the Carpathians, identifying five major surface-breaking earthquakes during the last 104,000 years along one single fault that seems seismically inactive during historical times. Evaluation of displacements caused by single events suggests magnitude estimates between magnitude 6.3 and 7.0, the latter being the largest magnitude documented in any paleoseismological investigation in Central Europe north of the Alps. This research results indicate that very slow faults in the Vienna Basin cannot be excluded from seismic hazard assessment. [E. Hintersberger, University of Vienna, Austria, esther.hintersberger@univie.ac.at] A related talk by Kurt Decker of the University of Vienna explores the maximum credible magnitude for the region. His data suggest a maximum magnitude of 6.3 to

Damage to cave formations may help identify timing of past earthquakes in New Madrid Seismic Zone

Scientists examined 15 caves in the Ozarks of southeast Missouri, discovering seven caves that appeared to show repeated episodic breakage of delicate cave formations. While mining and vandalism posed challenges to the identification of good samples, potential earthquake-related breakage was observed from 75 to 105 miles from New Madrid, Missouri. The dated samples coincided with the timing of seismically-induced liquefaction in the Mississippi Valley and the initiation of new mineral deposit growth, suggesting cave formations offer potential to identifying past major seismic events in the central United States. [J. C. Tinsley, U.S. Geological Survey, jtinsley@usgs.gov]

Regional Seismic Hazard Evaluation: Updates, Policy and the Public




Ballroom E, 1:30 – 5 p.m.

Seismic Assessment for U.S. Eastern Nuclear Facilities

Proposed nuclear power facilities must take into account local and regional seismic hazards. But data can be difficult to obtain in areas with relatively few seismic events, such as the region east of the Rocky Mountains. Stephen McDuffie and colleagues now outline a model for regional seismic activity near proposed nuclear sites in the region, sponsored by the commercial nuclear industry, the U.S. Department of Energy and the Nuclear Regulatory Commission. The project, called CEUS SSC (Central and Eastern United States Seismic Source Characterization), will include a comprehensive catalog of historical and instrument-measured seismic events, along with an assessment of the size and recurrence of repeated large-magnitude earthquake sources in the area. The project’s final report and models will be available in late 2011. [S. M. McDuffie, U.S. Department of Energy, Stephen.mcduffie@rl.doe.gov]

Seismic Source Zones in the Central and Eastern U.S.

The CEUS Seismic Source Zone is a regional-scale seismic source characterization for use in hazard analyses that should guide the placement and construction of proposed nuclear power sites in the central and eastern United States. Geologists, seismologists, geophysicists and engineers have worked together to describe the region’s seismicity and its underlying geology. As Ross Hartleb and colleagues discuss, the CEUS project team’s approach resulted in three types of seismic zones for the area: magnitude max zones, which divide the region by expected maximum magnitude earthquakes in the area; seismotectonic zones, which are defined by expected differences in earthquake characteristics (e.g., style of earthquake fault, rupture orientation); and repeated large magnitude earthquake zones, based on the prehistoric and historic occurrence of repeated large earthquakes. Since seismic activity is rare in the region compared to the more active western United States, the scientists also discuss the challenges of developing seismic source characterizations based on data from paleo-earthquakes. [R. Hartleb, Fugro William Lettis & Assoc., r.hartleb@fugro.com]

How Do Eastern Seismic Events Measure Up?

One of the key components of the Central and Eastern United States (CEUS) Seismic Source Characterization (SSC) for Nuclear Facilities project is an earthquake catalog for the region in which all earthquakes can be compared using the same size scale. This uniform size catalog will be useful in defining the conditions that could help predict future seismic hazards in the central and eastern United States, say Robert Youngs and colleagues. The CEUS catalog, which will use the modern moment magnitude scale, was compiled from national seismic hazard mapping catalogs developed by the U.S. Geological Survey and the Geological Survey of Canada. Researchers also used regional catalogs and special studies of historical quake records to create a more complete record. When the catalog is released at the end of 2011, its extensive database will also list non-tectonic (seismic activity unrelated to geological motion) and false seismic signals that have been identified in the past. [R. R. Youngs, Amec Geomatrix, bob.youngs@amec.com] (Other Questions regarding the CEUS SSC Project may be addressed to Larry Salomone, CEUS SSC Project Manager, lawrence.salomone@srs.gov)

Updates to the Eastern Seismic Hazard Maps

The U.S. Geological Survey National Seismic Hazard Maps are updated about every six years by incorporating the latest science on earthquakes and ground motions. The 2008 maps for the central and eastern U.S. were recently updated using new models of the New Madrid and Charleston seismic zones — two of the most historically active seismic zones in the region. The 2008 updates have already been incorporated into national and international building standards, and Mark Petersen and colleagues say the next update will be presented to standards commissions in 2013. The next set of maps will consider new models of repeating seismic activity in the New Madrid region, new earthquake sources considered by models used by nuclear industry planners, new ground motion models for the region, and an updated catalog of the area’s earthquakes. [M. D. Petersen, U.S. Geological Survey, mpetersen@usgs.gov]

What We Don’t Know About Los Angeles Faults

Most seismic hazard studies focus on estimating the average earthquake hazard for a particular region. Researchers are less likely to explore the uncertainty surrounding these estimates. Now, Nilesh Shome and colleagues estimate the uncertainty in the earthquake hazard for “B faults” in the Los Angeles area. B faults are the faults for which the detailed information of occurrence history is not available and the rate of slip parameter required for hazard calculations is only approximate. (B faults can potentially cause earthquakes in the range of magnitude 6.5 to 7.0, with varying occurence rates) B faults, however, contribute significantly to seismic hazard in the Los Angeles area, the researchers note, so it is important to understand how much uncertainty is involved in calculating these hazards. [N. Shome, Risk Management Solutions, Inc., nilesh@stanfordalumni.org and David M. Perkins, United States Geological Survey, perkins@usgs.gov]

Shaking Sites Add Up in California

Seismic hazard models estimate the probabilities of intense ground shaking at individual locations — but they don’t usually provide a complete picture of the total number of locations that are experiencing the same (or higher) intensity shaking. But as Praveen Malhotra points out, the effect of damaging ground shaking at a single location is very different from the effect of damaging shaking at many locations occupied by 1 million or more people. Malhotra discusses the importance of creating an aggregate ground shaking measure that can capture the full effect of shaking and its potential damage, and provides some preliminary aggregate measures for regions of California. [P.K. Malhotra, StrongMotions Inc., Praveen.Malhotra@StrongMotions.com]

Seismic Hazard Maps for Haiti

In the wake of Haiti’s devastating 2010 earthquake, Arthur Frankel and colleagues from the USGS and Purdue University have produced seismic hazard maps that can be used as the scientific basis for new building codes for the country. The maps include data from the major faults in the region, subduction zones where tectonic plates collide, and background earthquakes. They used fault slip rates constrained by GPS data to estimate recurrence rates of earthquakes on the Enriquillo-Plantain Garden, Septentrional, and Matheux Neiba faults, as well as the subduction zones. The researchers say there is substantial seismic hazard throughout Haiti, with the highest hazards along the Enriquillo-Plantain Garden and Septentrional faults and the western end of the Muertos Trough. [A. Frankel, U.S. Geological Survey, afrankel@usgs.gov]

Seismic Hazard Map for Peninsular Malaysia

A new seismic hazard map created by Azlan Adnan and colleagues for Peninsular Malaysia shows a slight increase in seismic hazard for Kuala Lumpur — Malaysia’s capital and largest city — over a 500-year period. The map includes newly available data on historical earthquakes in the region, including more than 700 earthquakes recorded from 1900 to 2009. Using the latest methods for estimating seismic hazard, the researchers developed several maps of possible ground motion hazards for Malaysia’s east and west coasts. [A. Adnan, University of Technology Malaysia, azelan_fka_utm@yahoo.com]

Earthquake Model of the Middle East

The Earthquake Model of the Middle East (EMME) Project, offers a unique and dynamic look at the past, present and future of seismic activity in the Middle East. The project includes data from Turkey, Georgia, Armenia, Azerbaijan, Syria, Lebanon, Jordan, Iran, Pakistan and Afghanistan, and its databases and analyses will be continually updated and refined as new seismic data is acquired, according to Levent Gulen and colleagues. EMME’s users will find a map of the Middle East’s active faults, including information about their physical characteristics and rates of movement. The database will also detail the characteristics of faults that appear to be capable of generating earthquakes of magnitude 5.5 and larger. So far, 6,991 fault sections (about 83,402 kilometers) have been analyzed in detail for the Middle East region. EMME will also feature a database that includes information on the timing and ground displacement for the region’s ancient earthquakes. [L. Gulen, Sakarya University (Turkey), lgulen@sakarya.edu.tr]

Seismic Site Response at the Regional Scale

Site response is the amplification of ground motions at a specific site determined by the soils beneath the site. It’s an important measure in predicting seismic hazard for an area, since more intense shaking can mean more damage, but it’s also a measure that’s hard to determine accurately over a large area. Eric Thompson and colleagues now compare several methods of creating regional-scale site response maps, using the densely spaced, strong motions recorded for the Parkfield, California, area, and propose a new mapping technique that takes advantage of the advantages of the different mapping methods. [E. M. Thompson, Tufts University, eric.thompson@tufts.edu]

Watch for Falling Rocks

Precariously balanced rocks and such fragile geological features as natural rock bridges may be casualties — or agents of destruction — in seismically active regions. But they can also help researchers refine seismic hazard models for a particular area. A fault previously considered active may be downgraded, for instance, if fragile geological features in the area remain unchanged. John Anderson and colleagues report findings from the Workshop on the Application of Precarious Rocks and Related Fragile Geological Features, with the goal of developing recommendations that the U.S. Geological Survey can use in their preparation of U.S. National Hazard Maps. The workshop also suggested specific research that could help fragile geological features become more useful hazard guides in the future, along with guidelines for archiving the data collected from these features. [J.G. Anderson, Nevada Seismological Laboratory, jga@unr.edu]

Recent Advances in Understanding Scaling Characteristics: How Similar are Small and Large Earthquakes?




Room 204/205, 1:30 – 3 p.m.

Why stress drops and apparent stresses do not depend on seismic moment


Does the magnitude of an earthquake depend on the apparent stresses in the quake area? The researchers looked at several quakes, varying in magnitude from 2 to 7.9, to better understand this connection. They conclude that apparent stresses are independent of seismic magnitude because they are controlled by the strength of the fault, which is itself independent of earthquake magnitude. [A. McGarr, U.S. Geological Survey, mcgarr@usgs.gov]

A multi-frequency back-projection analysis of recent large earthquakes


Are the physics different in small and large earthquakes? Studying data from large earthquakes around the world that occurred in the last decade, the researchers suggest the answer is yes. There are differences in high-frequency radiation of seismic waves, thermal processes and fault lubrication that appear to lead to different mechanics in large (greater than 5.5 magnitude) and small quakes. [E. Kiser, Harvard University, kiser@fas.harvard.edu]

FRIDAY, APRIL 15, 2011

Archeoseismology: Learning About Ancient Earthquakes from the Archaeological Record

Ballroom D, 8:30 – 10 a.m.

Evidence of large earthquakes before the advent of modern seismometers is derived from historical, geological and archaeological records:

Late-Holocene fault rupture characteristics of the North Anatolian Fault, Turkey

The Hersek Peninsula is archaeologically rich with information from Roman, Byzantine and Ottoman Empire sites, and encompasses a key area of the ancient Spice Road — it’s also seismically active. The Peninsula was the western endpoint of the major 1999 Izmit earthquake. Excavations in the area turned up a 6th century Byzantine aqueduct that was offset in an earthquake. Data from the aqueduct’s break can help characterize the fault’s activity during the past 1,500 years. [O. Kozaci, Fugro William Lettis & Associates, o.kozaci@fugro.com]

New excavations at early Islamic Ayla on the Gulf Coast of Aqaba along the Southern Dead Sea Transform, Jordan

The early Islamic city of Ayla (near present day Aqaba, Jordan) is situated at the northern end of the Gulf of Aqaba. The city was damaged by earthquakes in 749 and 757 A.D., rebuilt, and then devastated in a 1068 A.D. quake that destroyed the city. Analyses of pottery shards from the ancient city walls trace how the walls were shored up after seismic events, and show a long quiet period since the last major quake, which could mean the area is due for another big event. [A.J. Allison, University of Missouri, ajad36@mail.umkc.edu]

Earthquake versus rockfall, testing two damaging scenarios for a Roman mausoleum

A Roman mausoleum located in the ancient city of Pinara in southwest Turkey shows signs of damage (large blocks fallen off its walls), but is mostly intact. The relatively intact structure of the city makes it a good place to test 3D models that determine whether archaeological damage of this type was caused by earthquake shaking or from rock falls from a nearby cliff. The researchers’ 3D models are consistent with earthquake shaking. [K.G. Hinzen, Cologne University, hinzen@uni-koeln.de]

Seismic surveillance of Cologne Cathedral

Five seismic stations operate within Cologne Cathedral, one of the largest Gothic cathedrals in the world and a World Heritage Site since 1996. This study shows how wind, rain and the ringing of the bells within the cathedral affect movement of the tower. [K.G. Hinzen, Cologne University, hinzen@uni-koeln.de]

Guide to Sustainable Seismographic Networks




Ballroom C, 8:30 a.m. – Noon

Volcano Monitoring: Keep it Simple-Less can be more during

Sugar-grain sized meteorites rocked the climates of early Earth and Mars, according to new study

Bombardments of ‘micro-meteorites’ on Earth and Mars four billion years ago may have caused the planets’ climates to cool dramatically, hampering their ability to support life, according to research published today in the journal Geochimica et Cosmochimica Acta.

Scientists from Imperial College London studied the effects of the Late Heavy Bombardment (LHB), a period of time in the early Solar System when meteorite showers lasting around 100 million years barraged Earth and Mars. This bombardment discharged sulphur dioxide into the upper atmospheres of both planets and the researchers’ analysis suggests that this may have had a catastrophic impact on their environments.

Micro-meteorites come from the rocky asteroid belt between Mars and Jupiter. These space rocks, which are the size of sugar grains, get dragged by gravity towards Earth and Mars. As they enter the planets’ upper atmospheres, they heat up to temperatures of approximately 1000 degrees Celsius, releasing gases including sulphur dioxide. Sulphur dioxide in the atmosphere forms aerosols, consisting of solid and liquid particles, which deflect sunlight away from the surface, making planets cooler.

The authors of the new study have calculated that showers of micro-meteorites delivered approximately 20 million tonnes of sulphur dioxide each year into the upper atmosphere of Earth during the LHB. The team deduced that on Mars, these micro-meteorites delivered up to half a million tonnes of sulphur dioxide each year for the same period of time.

Professor Mark Sephton, an author of the study from the Department of Earth Science and Engineering at Imperial College London, says:

“Far less of the Sun’s energy was reaching Earth 4 billion years ago, which would have made it hard for early life to emerge. Recently denied of its protective magnetic field and constantly subjected to large meteorite impacts, Mars was also starting to lose its greenhouse gases at this time, causing global cooling. The influx of sulphur dioxide into the Mars’s atmosphere would have dealt a further blow to a planet already on the ropes, making conditions for life even more of a challenge.”

The team say that such a large influx of sulphur dioxide into early Earth’s atmosphere had the same cooling effect on the climate as if there was an eruption of the size of the 1991 Mount Pinatubo eruption every year for 100 million years. The 1991 Mount Pinatubo eruption released 17 million tonnes of gases, including sulphur dioxide, into the atmosphere, preventing 10 percent of sunlight from reaching Earth and cooling the planet by half a degree Celsius.

On Mars during the LHB, the scientists predict that the cooling effects of sulphur dioxide on the red planet’s atmosphere would have been the equivalent of an eruption 1/34th the size of Mount Pinatubo occurring every year for 100 million years.

The scientists say that the environmental consequences of sulphur dioxide in Earth’s atmosphere could have been disastrous. At this time, the Sun’s energy was 30 percent weaker than it is today, meaning less energy was reaching the surface. The team believe that a weaker Sun, combined with increasing levels of sulphur dioxide from micro-meteorites, could have plunged Earth into an Arctic winter, lasting millions of years and making conditions for primitive microbial life extremely difficult.

On Mars, being further away from the Sun, the scientists suggest the environmental consequences would have been even more dramatic. High levels of sulphur dioxide would cause temperatures to plunge and water on the surface, in the form of lakes and rivers, to disappear, turning a warm wet world into a cold arid one.

Dr Richard Court, who is lead author of the study from the Department of Earth Science and Engineering at Imperial College London, adds:

“These sugar-grain sized meteorites are left over material from the construction of our early Solar System, helping to build rocky planets such as Earth and Mars. Our study is helping us to see how these tiny space rocks could also bring environmental devastation on a global scale to early Earth and Mars.”

The researchers came to their conclusions by simulating what happens to micro-meteorites as they entered the atmosphere, using a technique called flash pyrolysis to heat rock fragments that were identical to micro-meteorites to 1000 degrees Celsius. They then used infrared spectroscopy to measure the amount of sulphur dioxide released from these rocks. The team then used their results and calculations of meteorite in-fall rates during the LHB to determine how much sulphur dioxide was delivered to Earth and Mars from micro-meteorites.

This study is a continuation of earlier work by the team who have discovered that meteorites are not the source of the present-day methane in the atmosphere of Mars, raising hopes that the methane is being generated by life on the red planet. Their work has also shown that meteorites delivered other important gases to Earth during its early history that would have made it more habitable. In the future, the team will assess the contributions gases from meteorites on planets outside of the Solar System.

New geological field guide ranges from eastern Ohio through Pennsylvania to the Central Appalachian Valley and Ridge, USA

This new book from The Geological Society of America (GSA) features detailed descriptions of eight geological field trips offered during the March 2011 Joint Meeting of GSA’s Northeastern and North-Central Sections in Pittsburgh, Pennsylvania. From glaciers to gristmills, shales to slides, these timely and topical trips highlight the region’s geology from eastern Ohio to the Central Appalachian Valley and Ridge and show how it has shaped the region — topographically, structurally, historically, industrially, and evolutionarily.

Field guide editors Richard M. Ruffolo of GAI Consultants in Homestead, Pennsylvania, and Charles N. Ciampaglio of Wright State University’s Lake Campus in Celina, Ohio, bring together a fascinating group of field trips, with detailed mileage and GPS coordinates. Readers interested in following in the footsteps of the Section Meeting field trip trekkers need only pick up this volume and be transported to an area of field locales.

Trips cover the paleontology and paleoecology of Red Hill and other fossil sites in north-central Pennsylvania; the structures and stratigraphy of the Central Appalachian Valley and Ridge; landslides near Pittsburgh, Pennsylvania; the history and geology of the Allegheny Portage Railroad; early gristmills and iron furnaces in western Pennsylvania and eastern Ohio; oil history in western Pennsylvania; and more.

Warm water causes extra-cold winters in northeastern North America and northeastern Asia

This map shows sea‑surface temperatures averaged over eight days in September 2001, as measured by NASA's Terra satellite. Dark red represents warm water (32 degrees Celsius) and purple is cold (‑2 degrees Celsius). The Gulf Stream can be seen as the orange strip extending from the eastern U.S. toward the Atlantic. -  Ronald Vogel, SAIC for NASA GSFC
This map shows sea‑surface temperatures averaged over eight days in September 2001, as measured by NASA’s Terra satellite. Dark red represents warm water (32 degrees Celsius) and purple is cold (‑2 degrees Celsius). The Gulf Stream can be seen as the orange strip extending from the eastern U.S. toward the Atlantic. – Ronald Vogel, SAIC for NASA GSFC

If you’re sitting on a bench in New York City’s Central Park in winter, you’re probably freezing. After all, the average temperature in January is 32 degrees Fahrenheit. But if you were just across the pond in Porto, Portugal, which shares New York’s latitude, you’d be much warmer-the average temperature is a balmy 48 degrees Fahrenheit.

Throughout northern Europe, average winter temperatures are at least 10 degrees Fahrenheit warmer than similar latitudes on the northeastern coast of the United States and the eastern coast of Canada. The same phenomenon happens over the Pacific, where winters on the northeastern coast of Asia are colder than in the Pacific Northwest.

Researchers at the California Institute of Technology (Caltech) have now found a mechanism that helps explain these chillier winters-and the culprit is warm water off the eastern coasts of these continents.

“These warm ocean waters off the eastern coast actually make it cold in winter-it’s counterintuitive,” says Tapio Schneider, the Frank J. Gilloon Professor of Environmental Science and Engineering.

Schneider and Yohai Kaspi, a postdoctoral fellow at Caltech, describe their work in a paper published in the March 31 issue of the journal Nature.

Using computer simulations of the atmosphere, the researchers found that the warm water off an eastern coast will heat the air above it and lead to the formation of atmospheric waves, drawing cold air from the northern polar region. The cold air forms a plume just to the west of the warm water. In the case of the Atlantic Ocean, this means the frigid air ends up right over the northeastern United States and eastern Canada.

For decades, the conventional explanation for the cross-oceanic temperature difference was that the Gulf Stream delivers warm water from the Gulf of Mexico to northern Europe. But in 2002, research showed that ocean currents aren’t capable of transporting that much heat, instead contributing only up to 10 percent of the warming.

Kaspi’s and Schneider’s work reveals a mechanism that helps create a temperature contrast not by warming Europe, but by cooling the eastern United States. Surprisingly, it’s the Gulf Stream that causes this cooling.

In the northern hemisphere, the subtropical ocean currents circulate in a clockwise direction, bringing an influx of warm water from low latitudes into the western part of the ocean. These warm waters heat the air above it.

“It’s not that the warm Gulf Stream waters substantially heat up Europe,” Kaspi says. “But the existence of the Gulf Stream near the U.S. coast is causing the cooling of the northeastern United States.”

The researchers’ computer model simulates a simplified, ocean-covered Earth with a warm region to mimic the coastal reservoir of warm water in the Gulf Stream. The simulations show that such a warm spot produces so-called Rossby waves.

Generally speaking, Rossby waves are large atmospheric waves-with wavelengths that stretch for more than 1,000 miles. They form when the path of moving air is deflected due to Earth’s rotation, a phenomenon known as the Coriolis effect. In a way similar to how gravity is the force that produces water waves on the surface of a pond, the Coriolis force is responsible for Rossby waves.

In the simulations, the warm water produces stationary Rossby waves, in which the peaks and valleys of the waves don’t move, but the waves still transfer energy. In the northern hemisphere, the stationary Rossby waves cause air to circulate in a clockwise direction just to the west of the warm region. To the east of the warm region, the air swirls in the counterclockwise direction. These motions draw in cold air from the north, balancing the heating over the warm ocean waters.

To gain insight into the mechanisms that control the atmospheric dynamics, the researchers speed up Earth’s rotation in the simulations. In those cases, the plume of cold air gets bigger-which is consistent with it being a stationary Rossby-wave plume. Most other atmospheric features would get smaller if the planet were to spin faster.

Although it’s long been known that a heat source could produce Rossby waves, which can then form plumes, this is the first time anyone has shown how the mechanism causes cooling that extends west of the heat source. According to the researchers, the cooling effect could account for 30 to 50 percent of the temperature difference across oceans.

This process also explains why the cold region is just as big for both North America and Asia, despite the continents being so different in topography and size. The Rossby-wave induced cooling depends on heating air over warm ocean water. Since the warm currents along western ocean boundaries in both the Pacific and Atlantic are similar, the resulting cold region to their west would be similar as well.

The next step, Schneider says, is to build simulations that more realistically reflect what happens on Earth. Future simulations would incorporate more complex features like continents and cloud feedbacks.