Deep-sea Rocks Point To Early Oxygen On Earth

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ScienceDaily (Mar. 25, 2009) — Red jasper cored from layers 3.46 billion years old suggests that not only did the oceans contain abundant oxygen then, but that the atmosphere was as oxygen rich as it is today, according to geologists.

This jasper or hematite-rich chert formed in ways similar to the way this rock forms around hydrothermal vents in the deep oceans today.
"Many people have assumed that the hematite in ancient rocks formed by the oxidation of siderite in the modern atmosphere," said Hiroshi Ohmoto, professor of geochemistry, Penn State. "That is why we wanted to drill deeper, below the water table and recover unweathered rocks."
The researchers drilled diagonally into the base of a hill in the Pilbara Craton in northwest Western Australia to obtain samples of jasper that could not have been exposed to the atmosphere or water. These jaspers could be dated to 3.46 billion years ago.
"Everyone agrees that this jasper is 3.46 billion years old," said Ohmoto. "If hematite were formed by the oxidation of siderite at any time, the hematite would be found on the outside of the siderite, but it is found inside," he reported in a recent issue of Nature Geoscience.
The next step was to determine if the hematite formed near the water's surface or in the depths. Iron compounds exposed to ultra violet light can form ferric hydroxide, which can sink to the bottom as tiny particles and then be converted to hematite at temperatures of at least 140 degrees Fahrenheit.
"There are a number of cases around the world where hematite is formed in this way," says Ohmoto. "So just because there is hematite, there is not necessarily oxygen in the water or the atmosphere."
The key to determining if ultra violet light or oxygen formed the hematite is the crystalline structure of the hematite itself. If the precursors of hematite were formed at the surface, the crystalline structure of the rock would have formed from small particles aggregating producing large crystals with lots of empty spaces between. Using transmission electron microscopy, the researchers did not find that crystalline structure.
"We found that the hematite from this core was made of a single crystal and therefore was not hematite made by ultra violet radiation," said Ohmoto.
This could only happen if the deep ocean contained oxygen and the iron rich fluids came into contact at high temperatures. Ohmoto and his team believe that this specific layer of hematite formed when a plume of heated water, like those found today at hydrothermal vents, converted the iron compounds into hematite using oxygen dissolved in the deep ocean water.
"This explains why this hematite is only found in areas with active submarine volcanism," said Ohmoto. "It also means that there was oxygen in the atmosphere 3.46 billion years ago, because the only mechanism for oxygen to exist in the deep oceans is for there to be oxygen in the atmosphere."
In fact, the researchers suggest that to have sufficient oxygen at depth, there had to be as much oxygen in the atmosphere 3.46 billion years ago as there is in today's atmosphere. To have this amount of oxygen, the Earth must have had oxygen producing organisms like cyanobacteria actively producing it, placing these organisms much earlier in Earth's history than previously thought.
"Usually, we look at the remnant of what we think is biological activity to understand the Earth's biology," said Ohmoto. "Our approach is unique because we look at the mineral ferric oxide to decipher biological activity."
Ohmoto suggests that this approach eliminates the problems trying to decide if carbon residues found in sediments were biologically created or simply chemical artifacts.
Other researchers on the study included Masamichi Hoashi, graduate student at Kagoshima University, Japan; Arthur H. Hickman, geologist with the Geological Survey of Western Australia; Satoshi Utsunomiya, Kyushu University, Japan, and David C. Bevacqua and Tsubasa Otake, former Penn State master's and doctoral students, Penn State; and Yumiko Watanabe, research associate, Penn State.
The NASA Astrobiology Institute supported this work.
Adapted from materials provided by Penn State.

Climate Warming Affects Antarctic Ice Sheet Stability

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ScienceDaily (Mar. 22, 2009) — A five-nation scientific team has published new evidence that even a slight rise in atmospheric concentrations of carbon dioxide, one of the gases that drives global warming, affects the stability of the West Antarctic Ice Sheet (WAIS). The massive WAIS covers the continent on the Pacific side of the Transantarctic Mountains. Any substantial melting of the ice sheet would cause a rise in global sea levels.

The research, which was published in the March 19 issue of the journal Nature, is based on investigations by a 56-member team of scientists conducted on a 1,280-meter (4,100-foot)-long sedimentary rock core taken from beneath the sea floor under Antarctica's Ross Ice Shelf during the first project of the ANDRILL (ANtarctic geological DRILLing) research program--the McMurdo Ice Shelf (MIS) Project.
"The sedimentary record from the ANDRILL project provides scientists with an important analogue that can be used to help predict how ice shelves and the massive WAIS will respond to future global warming over the next few centuries," said Ross Powell, a professor of geology at Northern Illinois University.
"The sedimentary record indicates that under global warming conditions that were similar to those projected to occur over the next century, protective ice shelves could shrink or even disappear and the WAIS would become vulnerable to melting," Powell said. "If the current warm period persists, the ice sheet could diminish substantially or even disappear over time. This would result in a potentially significant rise in sea levels."
ANDRILL--which involves scientists from the United States, New Zealand, Italy and Germany--refines previous findings about the relationship between atmospheric carbon dioxide concentration, atmospheric and oceanic temperatures, sea level rise and natural cycles in Earth's orbit around the Sun, through the study of sediment and rock cores that are a geological archive of past climate.
The dynamics of ice sheets, including WAIS, are not well understood, and improving scientists' comprehension of the mechanisms that control the growth, melting and movements of ice sheets was one of NSF's research priorities during the International Polar Year (IPY). The IPY field campaign, which officially ended March 2009, has been an intense scientific campaign to explore new frontiers in polar science, improve our understanding of the critical role of the polar regions in global processes, and educate students, teachers, and the public about the polar regions and their importance to the global system. NSF was the lead agency for U.S. IPY efforts.
The cores retrieved by ANDRILL researchers have allowed them to peer back in time to the Pliocene era, roughly 2 million to 5 million years ago. During that era, the Antarctic was in a natural climate state that was warmer than today and atmospheric carbon dioxide levels were higher. Data from the cores indicate the WAIS advanced and retreated numerous times in response to forcing driven by these climate cycles.
Powell and Tim Naish, director of Victoria University of Wellington's Antarctic Research Centre, served as co-chief scientists of the 2006-2007 ANDRILL project that retrieved the data and are lead authors in one of two companion studies published in Nature.
Naish said the new information gleaned from the core shows that changes in the tilt of Earth's rotational axis has played a major role in ocean warming that has driven repeated cycles of growth and retreat of the WAIS for the period in Earth's history between 3 million and 5 million years ago.
"It also appears that when atmospheric carbon dioxide concentrations reached 400 parts per million around four million years ago, the associated global warming amplified the effect of the Earth's axial tilt on the stability of the ice sheet," he said.
"Carbon dioxide concentration in the atmosphere is again approaching 400 parts per million," Naish said. "Geological archives, such as the ANDRILL core, highlight the risk that a significant body of permanent Antarctic ice could be lost within the next century as Earth's climate continues to warm. Based on ANDRILL data combined with computer models of ice sheet behavior, collapse of the entire WAIS is likely to occur on the order of 1,000 years, but recent studies show that melting has already begun."
The second ANDRILL study in Nature--led by David Pollard of Pennsylvania State University and Rob DeConto from University of Massachusetts--reports results from a computer model of the ice sheets. The model shows that each time the WAIS collapsed, some of the margins of the East Antarctic Ice Sheet also melted, and the combined effect was a global sea level rise of 7 meters above present-day levels.
Whether the beginnings of such a collapse could start 100 years from now or within the next millennium is hard to predict and depends on future atmospheric CO2 levels, the researchers said. However, the new information from ANDRILL contributes a missing piece of the puzzle as scientists try to refine their predictions of the effects of global warming.
The most recent report of the Intergovernmental Panel on Climate Change (IPCC) noted that because so little is understood about ice sheet behavior it is difficult to predict how ice sheets will contribute to sea level rise in a warming world. The behavior of ice sheets, the IPCC report said, is one of the major uncertainties in predicting exactly how the warming of the globe will affect human populations.
"From these combined data modeling studies, we can say that past warming events caused West Antarctic ice shelves and ice grounded below sea level to melt and disappear. The modeling suggests these collapses took one to a few thousand years," Pollard said.
Pollard and DeConto also underscored the role of ocean temperatures in melting of the ice.
"It's clear from our combined research using geological data and modeling that ocean temperatures play a key role," DeConto said. "The most substantial melting of protective ice shelves comes from beneath the ice, where it is in contact with seawater. We now need more data to determine what is happening to the underside of contemporary ice shelves."
The National Science Foundation (NSF), which manages the U.S. Antarctic Program (USAP), provided about $20 million in support of the ANDRILL program. The other ANDRILL national partners contributed an additional $10 million in science and logistics support.
The ANDRILL Science Management Office, located at the University of Nebraska-Lincoln, supports science planning and the activities of the international ANDRILL Science Committee (ASC). Antarctica New Zealand is the ANDRILL project operator and has developed the drilling system in collaboration with Alex Pyne at Victoria University of Wellington and Webster Drilling and Exploration.
The U.S. Antarctic Program and Raytheon Polar Services Corporation (RPSC) supported the science team at McMurdo Station and in the Crary Science and Engineering Laboratory, while Antarctica New Zealand supported the drilling team at Scott Base.
ANDRILL scientific studies are jointly supported by: the U.S. National Science Foundation, the New Zealand Foundation for Research, the Italian Antarctic Research Program, the German Science Foundation and the Alfred Wegener Institute.
Adapted from materials provided by National Science Foundation.

Earth Science: Lithosphere Deformed And Fractured Under Indian Ocean Much Earlier Than Previously Thought

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ScienceDaily (Mar. 20, 2009) — The discovery by Indian and British scientists that the Earth’s strong outer shell – the ‘lithosphere’ – within the central Indian Ocean began to deform and fracture 15.4–13.9 million years ago, much earlier than previously thought, impacts our understanding of the birth of the Himalayas and the strengthening of the Indian-Asian monsoon.

India and Asia collided around 50 million years ago as a result of plate tectonics – the large-scale movements of the lithosphere, which continue to this day. The new study, published in the scientific journal Geology, focuses on the tectonics-related deformation of the lithosphere below the central Indian Ocean.
“Compression of the lithosphere has caused large-scale buckling and cracking,” says team member Professor Jon Bull of the University of Southampton’s School of Ocean and Earth Science based at the National Oceanography Centre; “The ocean floor has been systematically transformed into folds 100-300 kilometres long and 2,000-3,000 metres high, and there are also regularly spaced faults or fractures that are evident from seismic surveys and ocean drilling.”
The onset of this deformation marks the start of major geological uplift of the Himalayas and the Tibetan Plateau, some 4,000 km further to the north, due to stresses within the wider India-Asia area. Some studies indicate that it began around 8.0–7.5 million years ago, while others have indicated that it started before 8.0 million years ago, and perhaps much earlier.
This controversy has now been addressed by Professor Bull and his colleagues Dr Kolluru Krishna of the National Institute of Oceanography in India, and Dr Roger Scrutton of Edinburgh University. They have analysed seismic profiles of 293 faults in the accumulated sediments of the Bengal Fan. This is the world’s largest submarine fan, a delta-shaped accumulation of land-derived sediments covering the floor of the Bay of Bengal.
They demonstrate that deformation of the lithosphere within the central Indian Ocean started around 15.4–13.9 million years ago, much earlier than most previous estimates. This implies considerable Himalayan uplift before 8.0 million years ago, which is when many geologists believe that the strong seasonal winds of the India-Asia monsoon first started.
“However,” says Professor Bull, “the realisation that the onset of lithospheric deformation within the central Indian Ocean occurred much earlier fits in well with more recent evidence that the strengthening of the monsoon was linked to the early geological uplift of the Himalayas and Tibetan plateau up to 15-20 million years ago.”
Intensive deep-sea drilling within the Bengal Fan should provide better age estimates for the onset of deformation of the lithosphere in the central Indian Ocean and help settle the controversy.
The research was funded by India’s Council of Scientific and Industrial Research (CSIR), and the United Kingdom’s Royal Society and Natural Environment Research Council (NERC).
Adapted from materials provided by National Oceanography Centre, Southampton.

Ozone: New Simulation Shows Consequences Of A World Without Earth's Natural Sunscreen

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ScienceDaily (Mar. 19, 2009) — The year is 2065. Nearly two-thirds of Earth's ozone is gone -- not just over the poles, but everywhere. The infamous ozone hole over Antarctica, first discovered in the 1980s, is a year-round fixture, with a twin over the North Pole. The ultraviolet (UV) radiation falling on mid-latitude cities like Washington, D.C., is strong enough to cause sunburn in just five minutes. DNA-mutating UV radiation is up 650 percent, with likely harmful effects on plants, animals and human skin cancer rates.

Such is the world we would have inherited if 193 nations had not agreed to ban ozone-depleting substances, according to atmospheric chemists at NASA's Goddard Space Flight Center, Greenbelt, Md., Johns Hopkins University, Baltimore, and the Netherlands Environmental Assessment Agency, Bilthoven.
Led by Goddard scientist Paul Newman, the team simulated "what might have been" if chlorofluorocarbons (CFCs) and similar chemicals were not banned through the treaty known as the Montreal Protocol. The simulation used a comprehensive model that included atmospheric chemical effects, wind changes, and radiation changes. The analysis has been published online in the journal Atmospheric Chemistry and Physics.
"Ozone science and monitoring has improved over the past two decades, and we have moved to a phase where we need to be accountable," said Newman, who is co-chair of the United Nations Environment Programme's Scientific Assessment Panel to review the state of the ozone layer and the environmental impact of ozone regulation. "We are at the point where we have to ask: Were we right about ozone? Did the Montreal Protocol work? What kind of world was avoided by phasing out ozone-depleting substances?"
Ozone is Earth's natural sunscreen, absorbing and blocking most of the incoming UV radiation from the sun and protecting life from DNA-damaging radiation. The gas is naturally created and replenished by a photochemical reaction in the upper atmosphere where UV rays break oxygen molecules (O2) into individual atoms that then recombine into three-part molecules (O3). As it is moved around the globe by upper level winds, ozone is slowly depleted by naturally occurring atmospheric gases. It is a system in natural balance.
But chlorofluorocarbons -- invented in 1928 as refrigerants and as inert carriers for chemical sprays -- upset that balance. Researchers discovered in the 1970s and 1980s that while CFCs are inert at Earth's surface, they are quite reactive in the stratosphere (10 to 50 kilometers altitude, or 6 to 31 miles), where roughly 90 percent of the planet's ozone accumulates. UV radiation causes CFCs and similar bromine compounds in the stratosphere to break up into elemental chlorine and bromine that readily destroy ozone molecules. Worst of all, such ozone depleting substances can reside for several decades in the stratosphere before breaking down.
In the 1980s, ozone-depleting substances opened a wintertime "hole" over Antarctica and opened the eyes of the world to the effects of human activity on the atmosphere. By 1987, the World Meteorological Organization and United Nations Environment Program had brought together scientists, diplomats, environmental advocates, governments, industry representatives, and non-governmental organizations to forge an agreement to phase out the chemicals. In January 1989, the Montreal Protocol went into force, the first-ever international agreement on regulation of chemical pollutants.
“The regulation of ozone depleting substances was based upon the evidence gathered by the science community and the consent of industry and government leaders," Newman noted. "The regulation pre-supposed that a lack of action would lead to severe ozone depletion, with consequent severe increases of solar UV radiation levels at the Earth’s surface."
In the new analysis, Newman and colleagues "set out to predict ozone losses as if nothing had been done to stop them." Their "world avoided" simulation took months of computer time to process.
The team started with the Goddard Earth Observing System Chemistry-Climate Model (GEOS-CCM), an earth system model of atmospheric circulation that accounts for variations in solar energy, atmospheric chemical reactions, temperature variations and winds, and other elements of global climate change. For instance, the new model accounts for how changes in the stratosphere influence changes in the troposphere (the air masses near Earth's surface). Ozone losses change the temperature in different parts of the atmosphere, and those changes promote or suppress chemical reactions.
The researchers then increased the emission of CFCs and similar compounds by 3 percent per year, a rate about half the growth rate for the early 1970s. Then they let the simulated world evolve from 1975 to 2065.
By the simulated year 2020, 17 percent of all ozone is depleted globally, as assessed by a drop in Dobson Units (DU), the unit of measurement used to quantify a given concentration of ozone. An ozone hole starts to form each year over the Arctic, which was once a place of prodigious ozone levels.
By 2040, global ozone concentrations fall below 220 DU, the same levels that currently comprise the "hole" over Antarctica. (In 1974, globally averaged ozone was 315 DU.) The UV index in mid-latitude cities reaches 15 around noon on a clear summer day (a UV index of 10 is considered extreme today.), giving a perceptible sunburn in about 10 minutes. Over Antarctica, the ozone hole becomes a year-round fixture.
In the 2050s, something strange happens in the modeled world: Ozone levels in the stratosphere over the tropics collapse to near zero in a process similar to the one that creates the Antarctic ozone hole.
By the end of the model run in 2065, global ozone drops to 110 DU, a 67 percent drop from the 1970s. Year-round polar values hover between 50 and 100 DU (down from 300-500 in 1960). The intensity of UV radiation at Earth's surface doubles; at certain shorter wavelengths, intensity rises by as much as 10,000 times. Skin cancer-causing radiation soars.
"Our world avoided calculation goes a little beyond what I thought would happen," said Goddard scientist and study co-author Richard Stolarski, who was among the pioneers of atmospheric ozone chemistry in the 1970s. "The quantities may not be absolutely correct, but the basic results clearly indicate what could have happened to the atmosphere. And models sometimes show you something you weren't expecting, like the precipitous drop in the tropics."
"We simulated a world avoided," said Newman, "and it's a world we should be glad we avoided."
The real world of CFC regulation has been somewhat kinder. Production of ozone-depleting substances was mostly halted about 15 years ago, though their abundance is only beginning to decline because the chemicals can reside in the atmosphere for 50 to 100 years. The peak abundance of CFCs in the atmosphere occurred around 2000, and has decreased by roughly 4 percent to date.
Stratospheric ozone has been depleted by 5 to 6 percent at middle latitudes, but has somewhat rebounded in recent years. The largest recorded Antarctic ozone hole was recorded in 2006.
"I didn't think that the Montreal Protocol would work as well as it has, but I was pretty naive about the politics," Stolarski added. "The Montreal Protocol is a remarkable international agreement that should be studied by those involved with global warming and the attempts to reach international agreement on that topic."
Adapted from materials provided by NASA/Goddard Space Flight Center.

Drought, Urbanization Were Ingredients For Atlanta's Perfect Storm

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ScienceDaily (Mar. 18, 2009) — On March 14, 2008, a tornado swept through downtown Atlanta, its 130 mile-per-hour winds ripping holes in the roof of the Georgia Dome, blowing out office windows, and trashing parts of Centennial Olympic Park. It was an event so rare in an urban landscape that researchers immediately began to examine NASA satellite data and historical archives to see what weather and climatological ingredients may have combined to brew such a storm.

Though hundreds of tornadoes form each year across the United States, records of "downtown tornadic events" are quite rare. The 2008 Atlanta tornado—the first in the city's recorded history—was also unique because it developed during extreme drought conditions.
In a NASA-funded study, researchers from Purdue University in West Lafayette, Ind., and the University of Georgia (UGA) in Athens found that intermittent rain in the days before the storms—though providing temporary drought relief—may have moistened some areas enough to create favorable conditions for severe storms to form and intensify. Additionally, the sprawling urban landscape may have given the storms the extra, turbulent energy needed to spin up a tornado. The researchers reported their findings in January at the annual meeting of the American Meteorological Society.
"The Atlanta tornado, though forecasted well, caught us by surprise because it evolved rapidly under very peculiar conditions during a drought and over a downtown area," said Dev Niyogi, an assistant professor of regional climatology at Purdue and lead author of the modeling study. "We wanted to know why it hit Atlanta during one of the longest, harshest droughts the southeast has experienced. Was it a manifestation of the drought? Does urban development have an effect on such a storm?"
Such questions are becoming more relevant as the Intergovernmental Panel on Climate Change, NASA, and other institutions investigate the relationships between extreme water cycle events (such as drought), land cover change, weather, and climate change.
In the southeastern U.S., tornadoes are quite common in the spring when upper level wind patterns, surface moisture, and surface weather features promote severe weather. But moisture was scarce in the weeks leading up to the March 2008 Atlanta tornado, and likely should have suppressed a storm, according to atmospheric scientist Marshall Shepherd of UGA. Shepherd, Niyogi and colleagues recently completed a 50-year climatological assessment that finds tornadic activity is often suppressed during droughts in the Southeast.
To get to the bottom of how such a storm could have developed despite the drought, Purdue researchers Niyogi, Ming Lei, and Anil Kumar—along with Shepherd—investigated reports of isolated rain showers that had swept through parts of Alabama and northwest Georgia in the 48 hours prior to the tornado. They suspected that these "wet pockets" might have triggered—but more likely enhanced—the initial thunderstorms.
The scattered rainfall fell between areas that received no rain, setting up pockets of high humidity between areas of warm, dry air. The wet and dry areas may have acted as weak atmospheric fronts or may have promoted air circulation and evaporation that could have intensified the storms. A similar phenomenon promotes severe thunderstorms in Florida, where moist sea breezes interact with dry interior air masses.
Niyogi and Shepherd also found evidence that storm intensity was amplified by the heat-retaining effects of Atlanta's buildings and streets. The "heat island" effect leads to warmer air temperatures in urban areas because impervious surfaces like glass, metal, concrete and asphalt absorb, reflect, and store heat differently than tree or grass-covered land. Urban environments heat the air and cause moisture to rise quickly, creating a "thunderstorm pump" that can fuel or intensify storms. In March 2008, the differences in soil moisture and Atlanta's sprawling land cover may have provided the perfect blend for storms to intensify.
"A thunderstorm, energized by moist pockets within a drought region, grew into a tornado-causing severe thunderstorm because of weather instabilities it encountered at the rural-urban boundary," Niyogi explained.
"Drought and urbanization do not cause the thunderstorms or tornado, but ultimately they added fuel to the fire of an already energized storm," he added. "The variable rain bands created patches of land that were wet and dry, green and not green. The combination created surface boundaries that can destabilize the weather system and energize an approaching storm, providing the one-two punch."
Niyogi, Shepherd, and colleagues used the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA's Aqua satellite to assess the state of ground vegetation immediately before and after the storm, as well the long-term differences before and during the drought. The researchers also examined rainfall estimates captured by NASA's Tropical Rainfall Measurement Mission satellite to identify the unusual bands of rainfall two days before the tornado.
Finally, they examined soil moisture data from the Japanese Advanced Microwave Scanning Radiometer - Earth Observing System (AMSR-E) instrument on NASA's Aqua satellite to evaluate the intensity of the drought at the time of the tornado. When these real drought and urban land cover conditions were included in the team's atmosphere-land surface computer models, the simulations produced a more intense storm that mirrored reality.
"Our findings highlight the difficulty in detangling the influences of the atmosphere and of Earth's surface within the weather-hydroclimate system," said Shepherd. "Soil moisture and urban land cover are not well-represented in weather models, but a new look at satellite data offers a fresh opportunity to improve forecasts."
"With many studies suggesting more potential for urbanization and droughts in our future," Niyogi added, "it will be important to see if this kind of intense storm development could happen more frequently in future climates."
Adapted from materials provided by NASA/Goddard Space Flight Center.

Lessons From Hurricane Rita Not Practiced During Hurricane Ike

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ScienceDaily (Mar. 19, 2009) — A new Rice University report released yesterday, exactly six months after Hurricane Ike slammed the Texas Gulf Coast, suggests that people did not practice the lessons learned from Hurricane Rita.

According to the study, 75 percent of Harris County residents say they would evacuate if a Category 4 hurricane threatened Houston. This is a significant potential increase over the 24 percent of residents who left during the Category 2 Hurricane Ike. It's also a significant increase over the 52 percent of Harris County residents who evacuated in 2005 during the Category 4 Hurricane Rita but found themselves stuck in miles-long traffic jams on highways or stranded as the storm approached.
"Essentially, this study shows that people didn't learn from Hurricane Rita," said the report's co-author Robert Stein, the Lena Gohlman Fox Professor of Political Science at Rice. "Had Hurricane Ike been a severe storm -- a Category 3 or 4 -- more people would have evacuated, and we would have experienced roadway gridlock."
The reports shows that significantly fewer people evacuated during Hurricane Ike than during Hurricane Rita, but a large portion of the population left areas that were not under an evacuation order.
"The timing of evacuations showed no improvement over the experience during Hurricane Rita, when roadways experienced paralyzing gridlock," Stein said. "People evacuating from hurricane Ike all left too late, potentially creating the same conditions that existed during Hurricane Rita had a larger population evacuated."
The report details the results of surveys that assessed people's experience before, during and after each hurricane's landfall. The surveys were conducted in the weeks immediately after each storm -- Sept. 29-Oct. 3 for the Hurricane Rita survey, and Sept. 23-Oct. 24 for the Hurricane Ike survey.
The report is intended to enable policymakers and leaders to be more effective in getting their constituents to comply with evacuation orders.
The report also found:
Local television weather reporters were the most-relied-upon source of information for both hurricanes. During Hurricane Ike, the Weather Channel was the second most-relied-upon source.
In non-evacuation zones during Hurricane Rita, 40 percent of residents evacuated. These "shadow evacuees" were largely responsible for the road congestion. During Hurricane Ike, that number fell to 21 percent.
Evacuees during Hurricane Ike responded correctly by taking fewer vehicles and slightly more people per vehicle. This was particularly true for people from areas under an evacuation order.
The release of this report coincides with a free public forum at Rice University March 12 featuring Houston Mayor Bill White and Harris County Judge Ed Emmett discussing the leadership challenges they had to overcome to guide Houston through the disaster. "Leadership in Crisis: Guiding Houston through the Storm" will be held from 6 to 7 p.m. in Sewall Hall, Room 301, on the Rice campus, 6100 Main St. Stein and report co-authors Leonardo Dueñas-Osorio, assistant professor in civil and environmental engineering, and Devika Subramanian, professor of computer science and in electrical and computer engineering, will be available to take questions before and after the event.
The full report is available at http://www.media.rice.edu/images/media/0312_CCE_HurricaneIke_report.pdf

Earth's Crust Melts Easier Than Previously Thought

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ScienceDaily (Mar. 19, 2009) — A University of Missouri study just published in Nature has found that the Earth's crust melts easier than previously thought. In the study, researchers measured how well rocks conduct heat at different temperatures and found that as rocks get hotter in the Earth's crust, they become better insulators and poorer conductors.

This finding provides insight into how magmas are formed and will lead to better models of continental collision and the formation of mountain belts.
"In the presence of external heat sources, rocks will heat up more efficiently than previously thought," said Alan Whittington, professor of geological sciences in the MU College of Arts and Science. "We applied our findings to computer models that predict what happens to rocks when they get buried and heat up in mountain belts, such as the Himalayas today or the Black Hills in South Dakota in the geologic past. We found that strain heating, caused by tectonic movements during mountain belt formation, quite easily triggers crustal melting."
In the study, researchers used a laser-based technique to determine how long it took heat to conduct through different rock samples. In all of the samples, thermal diffusivity, or how well a material conducts heat, decreased rapidly with increasing temperatures. Researchers found the thermal diffusivity of hot rocks and magmas to be half that of what had been previously assumed.
"Most crustal melting on the Earth comes from intrusions of hot basaltic magma from the Earth's mantle," said Peter Nabelek, professor of geological sciences in the MU College of Arts and Science. "The problem is that during continental collisions, we don't see intrusions of basaltic magma into continental crust. These experiments suggest that because of low thermal diffusivity, strain heating is much faster and more efficient, and once rocks get heated, they stay hotter for much longer. Of course, these processes take millions of years to occur and we can only simulate them on a computer. This new data will allow us to create computer models that more accurately represent processes that occur during continental collisions."
The study was co-authored by Whittington, Nabelek and Anne Hofmeister, a professor at Washington University. The National Science Foundation funded this research.
Journal reference:
. Temperature-dependent thermal diffusivity of the Earth's crust and implications for magmatism. Nature, March 19, 2009
Adapted from materials provided by University of Missouri-Columbia, via EurekAlert!, a service of AAAS.