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Retrospections Fury of the Earth
 
Fury of the Earth
Based on a 'Hot Zone' blog entry for astrobio.net by Alison Hawkes
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Climate
Posted:   02/22/10

Summary: Astrobiology Magazine's climate blog, The Hot Zone, discusses the interconnection of Earth's natural systems and how vulnerable this makes us to the forces of nature. From violent earthquakes to thinning glaciers, we are only beginning to understand how our biosphere, climate and planet interact.


NASA’s Earth Observing-1 satellite with the Advanced Land Imager (ALI) instrument aboard took an image centered on Port-au-Prince, Haiti on Friday, January 15, 2010, three days after the earthquake. The picture on the left is the entire ALI image. The lower right image is a zoom-in of Port-au-Prince, while the upper right image is the same view taken in September 2008, one week after Hurricane Ike.
Credit: Stuart Frye / SGT Inc. and Dr. Lawrence Ong / SSAI at NASA/GSFC
When the 7.0 magnitude earthquake ripped apart Haiti, I was reminded of how vulnerable we are to the Earth’s natural systems. Despite our ability to drastically change the climate, in the end we are subject to the forces of nature, whether they have been unleashed as a result of human actions or not.

The images below were taken by the EO-1 spacecraft managed by NASA’s Goddard Space Flight Center. They show the fault line south of Port-au-Prince that slipped and the resulting disaster.

The fault line is called the Enriquillo-Plantain Garden Fault, part of several fault lines that make up a complicated tectonic region in which the Caribbean plate is slipping onto the North American plate. Here’s a nice image from the University of Miami Geodesy Lab.

As Earth systems are connected, I wondered whether earthquakes might be another symptom of climate change. Indeed, research is showing that just as the occurrence of hurricanes shoots up during climate change, so does violent geological activity in the Earth’s crust.

The physics behind this has to do with change in pressure. University of Alberta geologist Patrick Wu has compared it to pressing in on a soccer ball. The ice sheets are heavy enough to indent the crust, and when they’re removed, the crust springs back into shape in what’s called “isostatic rebound.” Volcanoes bubble up as the magma conduit is opened, while plates slip as a result of destabilization from the pressure change.

Jeanne Sauber of NASA’s Goddard Space Flight Center called them “promoted” earthquakes, and points to a real world example. The 7.2 magnitude St. Elias earthquake in southern Alaska in 1979 was preceded by nearly a century of thinning, or “wasted,” glaciers along the fault zone.

Volcano in Alaska. Alaska is a very geologically active area of the Earth.
Credit: NASA
“Earthquakes in southern Alaska, my study region, are more likely to occur sooner because of the large decrease in ice mass loss over the last 100 years,” Sauber wrote in an email. “The glaciers have changed right above the earthquake subduction zone.”

Evidence also suggests that in previous times of heavy glacial melt, like the end of the last Ice Age 100,000 years ago, big earthquakes occurred in Scandinavia, and to a lesser extent Canada.

But the impact of climate change is very regionally based. Haiti, of course, never had any glaciers.

“There is no physical reason to expect the Haiti earthquake is related to climate change,” wrote Sauber.

The take home message: Haiti’s earthquake would have occurred despite all the climate upheaval. But the severity it caused is a reminder of what could begin happening in glacial areas of the world where melt is unleashing the hidden fury of the Earth’s crust.


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