Tuesday, November 16, 2010

Solid Ground?

Two seismologists, Meredith Nettles and Göran Ekström of Columbia University, discovered a few years ago that unusual earthquakes were emanating from the Greenland glaciers as they dumped the extra ice into the sea. “It’s remarkable that an iceberg can do this, but when that loss of ice occurs, it does generate a signal that sets up a vibration that you can record all across the globe,” Dr. Nettles said in an interview in Greenland.

Analyzing past records, they discovered that these quakes had increased severalfold from the level of the early 1990s, a sign of how fast the ice is changing.

As Glaciers Melt, Science Seeks Data on Rising Seas, NY Times, Nov 13

We like to think we are standing on solid ground. The glacial pace of plate tectonics (pun intended!) makes it a bit too remote to affect our daily experience. On the other hand, when I reflect on forebulging, the lifting up of the earth's crust around continental icesheets of the ice age caused by the weight of the icesheet pushing down on the crust under it. It is like sitting on a couch and noting the "ripple" of cushion around your rear end.

Now I read here that losing just a bit of ice from a glacier is enough to trigger a shifting in the earth's surface, heard via seismograph. It kinda makes me feel humble in the face of forces and movements far beyond my ken.

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