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Archive for the ‘Geophysics’ Category

Will there be another major Haiti earthquake?

Posted by feww on February 24, 2010

For Fire-Earth Haiti-Jamaica Earthquake forecast See: Another Strong Quake Strikes Haiti as Expected

The following is a Public Release by University of Texas at Austin

Rapid response science missions assess potential for another major Haiti earthquake

To help assess the potential threat of more large earthquakes in Haiti and nearby areas, scientists at The University of Texas at Austin’s Institute for Geophysics are co-leading three expeditions to the country with colleagues from Purdue University, Lamont-Doherty Earth Observatory, the U.S. Geological Survey and five other institutions.


Source: The University of the West Indies at Mona

Rapid response missions can be critical for assessing future risks because a fault can continue to displace the ground for weeks and months after a large earthquake. At the same time, natural weathering processes and human activities can erase valuable geologic evidence.

The goal of the Haiti missions, researchers say, is to understand which segments of the earthquake fault ruptured during the Jan. 12 quake and how much fault movement and uplift of coastal features occurred in locations along or near the fault.

  • Expedition 1: Eric Calais of Purdue University led the first expedition, which has ended, collecting Global Positioning System (GPS) data to determine how land moved as a result of the earthquake. A second team participating in the expedition, led by Paul Mann of the Institute for Geophysics and Rich Koehler of the Alaska Division of Geological & Geophysical Surveys, used a helicopter and fieldwork to search for signs of ruptures-cracks at the surface along the main trace of the suspected earthquake fault. They found no signs of surface rupture but evidence for lateral spreading and liquefaction-a phenomenon in which soils behave like a liquid instead of a solid. Earthquakes most likely caused by the same fault and resulting in the same kind of lateral spreading and liquefaction destroyed the Jamaican capital of Kingston in 1692 and 1907. Funding was provided by the Rapid Response Research Program of the National Science Foundation (NSF).
  • Expedition 2: The second expedition, beginning Feb. 24, will for the first time use a scientific research vessel to examine the underwater effects of the quake. Chief scientist for the expedition is Cecilia McHugh at the City University of New York and Lamont-Doherty Earth Observatory with co-chief scientists Sean Gulick of the Institute for Geophysics and Milene Cormier of the University of Missouri. For two weeks, a team onboard the RV Endeavor will use sonar to map shifted sediments on the seafloor and seismic sensors to examine faults beneath the seafloor. The scientists hope to solve a mystery about how the earthquake unleashed a tsunami that killed seven people and to explain why corals along the coast have now been uplifted above sea level. The 185-foot Endeavor is owned by the NSF and operated by the University of Rhode Island. Funding is provided by the NSF and The University of Texas at Austin’s Jackson School of Geosciences.
  • Expedition 3: The third expedition, led by Fred Taylor of the Institute for Geophysics, will focus on large coral heads exposed by coastal uplift during the earthquake. Taylor will use a specialized chainsaw to collect the now dead coral for study of its tree ring-like structure to reveal clues on recent uplift and previous uplifts extending back hundreds of years. He will be assisted by Mann along with Rich Briggs and Carol Prentice of the U.S. Geological Survey (USGS). The Jackson School of Geosciences and USGS are jointly funding the coral study.

The Jackson School places a special emphasis on mounting rapid response missions to the scenes of geo-hazards, supporting previous missions after the earthquake and tsunami in the Solomon Islands (2007) and Hurricane Ike along the Texas Gulf Coast (2008). Few academic organizations have the infrastructure, equipment and expertise to mount a large field expedition on a few weeks’ notice, yet they can yield valuable insights to prepare communities for future hazards.

“We expect a whole raft of studies about the Haiti earthquake coming out based on remote sensing data from satellites and airplanes,” said Sean Gulick of the Institute for Geophysics. “But there’s no substitute for getting on the ground and in the water to look directly at its immediate effects.”

While collecting information that can save lives in the near future is a top priority of the expeditions, the scientists are also working to help cultivate local earthquake expertise. Two Haitian scientists have been invited to participate-Nicole Dieudonne, a representative of the Haitian Bureau of Mines and Energy, and Steeven Smyithe, a student from the State University of Haiti.

“We’re trying to engage the Haitian science community,” said Mann, who will return to Haiti for the second expedition. “They can help us communicate better with Haitian policy makers and people about the geology behind this devastating earthquake and about the risks going forward.”

In 2008, Mann, Calais and colleagues presented a paper at the Caribbean Conference forecasting a 7.2 magnitude earthquake in the area of Haiti, Jamaica and the Dominican Republic. The forecast was based on an integration of geologic information on the Enriquillo-Plantain Garden fault zone with GPS data collected in the region. David Manaker, Calais and colleagues published an article on the same topic in Geophysical Journal International.

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For more information from the source responsible for the above see:

Contact: Marc Airhart
mairhart@jsg.utexas.edu
University of Texas at Austin

The biggest hurdle for the ‘Rapid Response Expedition Teams’ could prove to be a political one. They may have to find creative ways of preventing USGS Earthquake People from altering the results of their research. See various notes and comments on Fire-Earth about USGS/EHP downgrading the magnitude of earthquakes for political reasons.

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Global temps could rise higher than expected

Posted by feww on December 21, 2009

Global temperatures could rise more than expected, new study shows

The kinds of increases in atmospheric carbon dioxide taking place today could have a significantly larger effect on global temperatures than previously thought, according to a new study led by Yale University geologists. Their findings appear December 20 in the advanced online edition of Nature Geoscience.

The team demonstrated that only a relatively small rise in atmospheric carbon dioxide (CO2) was associated with a period of substantial warming in the mid- and early-Pliocene era, between three to five million years ago, when temperatures were approximately 3 to 4 degrees Celsius warmer than they are today.

Climate sensitivity—the mean global temperature response to a doubling of the concentration of atmospheric CO2—is estimated to be 1.5 to 4.5 degrees Celsius, using current models.

“These models take into account only relatively fast feedbacks, such as changes in atmospheric water vapor and the distribution of sea ice, clouds and aerosols,” said Mark Pagani, associate professor of geology and geophysics at Yale and lead author of the paper. “We wanted to look at Earth-system climate sensitivity, which includes the effects of long-term feedbacks such as change in continental ice-sheets, terrestrial ecosystems and greenhouse gases other than CO2.”

To do this, the team focused on the most recent episode of sustained global warmth with geography similar to today’s. Their reconstructed CO2 concentrations for the past five million years was used to estimate Earth-system climate sensitivity for a fully equilibrated state of the planet, and found that a relatively small rise in CO2 levels was associated with substantial global warming 4.5 million years ago. They also found that the global temperature was 2 to 3 degrees Celsius higher than today while CO2 levels were only between about 365 and 415 parts per million (ppm)—similar to today’s concentration of about 386 ppm.

“This work and other ancient climate reconstructions reveal that Earth’s climate is more sensitive to atmospheric carbon dioxide than is discussed in policy circles,” Pagani said. “Since there is no indication that the future will behave differently than the past, we should expect a couple of degrees of continued warming even if we held CO2 concentrations at the current level.”

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Other authors of the paper include Zhonghui Liu (Yale University and The University of Hong Kong), and Jonathan LaRiviere and Ana Christina Ravelo (University of California, Santa Cruz).

This study used samples provided by the Integrated Ocean Drilling Program and was funded by the National Science Foundation and the Yale Climate and Energy Institute.

Contact: Suzanne Taylor Muzzin
suzanne.taylormuzzin@yale.edu
Yale University

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Global warming likely to be amplified by slow changes to Earth systems

Researchers studying a period of high carbon dioxide levels and warm climate several million years ago have concluded that slow changes such as melting ice sheets amplified the initial warming caused by greenhouse gases.

The study, published in the journal Nature Geoscience, found that a relatively small rise in atmospheric carbon dioxide levels was associated with substantial global warming about 4.5 million years ago during the early Pliocene.

Coauthor Christina Ravelo, professor of ocean sciences at the University of California, Santa Cruz, said the study indicates that the sensitivity of Earth’s temperature to increases in carbon dioxide in the atmosphere is greater than has been expected on the basis of climate models that only include rapid responses.

Carbon dioxide and other greenhouse gases trap heat in the atmosphere, leading to increased atmospheric and sea-surface temperatures. Relatively rapid feedbacks include changes in atmospheric water vapor, clouds, and sea ice. These short-term changes probably set in motion long-term changes in other factors–such as the extent of continental ice sheets, vegetation cover on land, and deep ocean circulation–that lead to additional global warming, Ravelo said.

“The implication is that these slow components of the Earth system, once they have time to change and equilibrate, may amplify the effects of small changes in the greenhouse gas composition of the atmosphere,” she said.

The researchers used sediment cores drilled from the seafloor at six different locations around the world to reconstruct carbon dioxide levels over the past five million years. They found that during the early and middle Pliocene (3 to 5 million years ago), when average global temperatures were at least 2 to 3 degrees Celsius warmer than today, the concentration of carbon dioxide in the atmosphere was similar to today’s levels, about 30 percent higher than preindustrial levels.

“Since there is no indication that the future will behave differently than the past, we should expect a couple of degrees of continued warming even if we held carbon dioxide concentrations at the current level,” said lead author Mark Pagani, an associate professor of geology and geophysics at Yale University.

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Contact: Tim Stephens
stephens@ucsc.edu
831-459-2495
University of California – Santa Cruz

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Posted in Climate Change, CO2, Geophysics, greenhouse gasses, Warming | Tagged: , , , , , | 2 Comments »

Vanishing Lakes

Posted by feww on April 18, 2008

Source: Media Relations

Researchers from the Woods Hole Oceanographic Institution (WHOI) and the University of Washington (UW) have for the first time documented the sudden and complete drainage of a lake of meltwater from the top of the Greenland ice sheet to its base.

From those observations, scientists have uncovered a plumbing system for the ice sheet, where meltwater can penetrate thick, cold ice and accelerate some of the large-scale summer movements of the ice sheet.

According to research by glaciologists Sarah Das of WHOI and Ian Joughin of UW, the lubricating effect of the meltwater can accelerate ice flow 50- to 100 percent in some of the broad, slow-moving areas of the ice sheet.


WHOI glaciologist Sarah Das stands in front of a block of ice that was raised up 6 meters by the sudden drainage of a meltwater lake in Greenland. (Photo by Ian Joughin, UW Polar Science Center)” Image may be copyrighted. See FEWW Fair Use Notice!

“We found clear evidence that supraglacial lakes—the pools of meltwater that form on the surface in summer—can actually drive a crack through the ice sheet in a process called hydrofracture,” said Das, an assistant scientist in the WHOI Department of Geology and Geophysics. “If there is a crack or defect in the surface that is large enough, and a sufficient reservoir of water to keep that crack filled, it can create a conduit all the way down to the bed of the ice sheet.”

But the results from Das and Joughin also show that while surface melt plays a significant role in overall ice sheet dynamics, it has a more subdued influence on the fast-moving outlet glaciers (which discharge ice to the ocean) than has frequently been hypothesized. (To learn more about this result, read the corresponding news release from UW.)

The research by Das and Joughin was compiled into two complementary papers and published on April 17 in the online journal Science Express. The papers will be printed in Science magazine on May 9. Full press release Copyright ©2007 Woods Hole Oceanographic Institution, All Rights Reserved.

Posted in geology, Geophysics, glaciers, hydrofracture, Oceanography | Tagged: , , , , , , , , | 1 Comment »