A Planet Frozen in Place

08-01-2008 // Roger Di Silvestro

UH OH. Global warming may release the Earth from the chains of an icy bondage that has helped prevent earthquakes for centuries in the chillier parts of the globe.

The planet is restless, its landmasses erupting occasionally into the outbursts of movement we call earthquakes. But the frequency of earthquakes is not evenly distributed around the world. The Earth flexes its terrestrial muscles most rarely in places covered by ice caps hundreds of yards thick, because the weight of the ice restrains the shifting landmasses. But when the ice melts, the forces that have built up along fault lines--the seams between landmasses--burst free, yielding stronger and more frequent earthquakes than would have occurred had the ice not inhibited the Earth's uneasy skin in previous millennia.

Proof of this arrangement was discovered recently when researchers at Germany's Ruhr University looked at Scandinavia's geological record to investigate the effect of ice caps on earthquakes. Today the study area is covered with ice, and quakes rarely arise. Not so 9,000 years ago, when the melting of the ice sheet that had covered the region during the last ice age triggered a surge in earthquakes.

The message to take home: As ice sheets disappear in the wake of global warming, says Andrea Hampel, one of the researchers, Greenland and Antarctica may become prime sites for more and stronger quakes.

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