Climate Change, Earthquakes, Volcanic Eruptions
Posted by msrb on January 1, 2009
Climate Change IS Increasing the Frequencies of Major Geological Events
There will be more earthquakes, volcanic eruptions and landslides both on the land and sea floor
In a study first published on the web in 2004, NASA and United States Geological Survey (USGS) scientists found that retreating glaciers in southern Alaska may lead to more earthquakes in future.
“The study examined the likelihood of increased earthquake activity in southern Alaska as a result of rapidly melting glaciers. As glaciers melt they lighten the load on the Earth’s crust. Tectonic plates, that are mobile pieces of the Earth’s crust, can then move more freely.” [The study appeared in the July 2004 issue of the Journal of Global and Planetary Change.
Jeanne Sauber of NASA's Goddard Space Flight Center and Bruce Molnia, a research geologist at USGS used NASA satellite and global positioning instruments, together with computer models, to analyze tectonic plates movements in relation to melting glaciers in Alaska.
"Historically, when big ice masses started to retreat, the number of earthquakes increased," Sauber said. "More than 10,000 years ago, at the end of the great ice age, big earthquakes occurred in Scandinavia as the large glaciers began to melt. In Canada, many more moderate earthquakes occurred as ice sheets melted there," she added.
"Southern Alaskan glaciers are very sensitive to climate change, Sauber added. Many glaciers have shrunk or disappeared over the last 100 years. The trend, which appears to be accelerating, seems to be caused by higher temperatures and changes in precipitation." the report said.
They discovered that a tectonic plate under the Pacific Ocean in southern Alaska was pushing toward the coast, creating very steep mountains. "The high mountains and heavy precipitation are critical for glacier formation. The colliding plates create a great deal of pressure that builds up, and eventually is relieved by earthquakes."
The sheer weight of massive glaciers that rest atop active seismic areas help minimize plate tectonic movements. "But, as the glaciers melt and their load on the plate lessens, there is a greater likelihood of an earthquake happening to relieve the large strain underneath."
Major earthquakes occur as a result of plate tectonic movements.
The researchers believe that a 1979 earthquake in southern Alaska, dubbed the St. Elias earthquake, which measured 7.2 on the Richter scale, occurred because the local glaciers melted.
"Along the fault zone, in the region of the St. Elias earthquake, pressure from the Pacific plate sliding under the continental plate had built up since 1899 when previous earthquakes occurred. Between 1899 and 1979, many glaciers near the fault zone thinned by hundreds of meters and some completely disappeared. Photographs of these glaciers, many taken by Molnia during the last 30 years, were used to identify details within areas of greatest ice loss."
"Field measurements were also used to determine how much the glacier's ice thickness changed since the late 19th century. The researchers estimated the volume of ice that melted and then calculated how much instability the loss of ice may have caused. They found the loss of ice would have been enough to stimulate the 1979 earthquake.
The two scientists, Sauber and Molnia used data from global positioning system and NASA satellites as well as Shuttle Radar Topography Mission (SRTM) to document the glacier extent and topography.
"In the future, in areas like Alaska where earthquakes occur and glaciers are changing, their relationship must be considered to better assess earthquake hazard, and our satellite assets are allowing us to do this by tracking the changes in extent and volume of the ice, and movement of the Earth," Sauber said. Source
"Climate change: Tearing the Earth apart?"
Bill McGuire, professor of Geophysical Hazards at University College, in an article in New Scientist, titled "Climate change: Tearing the Earth apart?" wrote:
"In the early 1970s John Chappell of the Australian National University in Canberra was the first to make the link between glacial advances and retreats and the rate of global volcanism. We now know that the warming that heralded the start of the current interglacial period around 10,000 years ago brought forth a burst of volcanic activity in Iceland, as melting ice caps reduced pressures on the magma chambers below. Allen Glazner of the University of North Carolina at Chapel Hill identified a similar pattern in eastern California over the past 800,000 years. Increased levels of volcanic activity are also recorded at mid-latitude ice-covered volcanoes in the Cascades Range of the US and in the Andes."
"[I]t shouldn’t come as a surprise that the loading and unloading of the Earth’s crust by ice or water can trigger seismic and volcanic activity and even landslides. Dumping the weight of a kilometre-thick ice sheet onto a continent or removing a deep column of water from the ocean floor will inevitably affect the stresses and strains on the underlying rock.” McGuire said.
“Not every volcanic eruption and earthquake in the years to come will have a climate-change link… Yet as the century progresses we should not be surprised by more geological disasters as a direct and indirect result of dramatic changes to our environment. The only saving grace is that a significant increase in volcanic activity would pump large volumes of sulphate gases into the stratosphere, which would cool the Earth’s surface and slow global warming, at least for a time. It’s a hell of a price to pay, though, for ignoring a phenomenon that could be far more easily sorted if we lived more considered and sustainable lives.” He said.