How Melting Glaciers Alter Earth's Surface, Spur Quakes, Volcanoes

June 9, 2006; Page A11

Imagine the surface of Earth as a giant trampoline that accumulated a slab of ice over the winter, and you can get a sense of what a growing number of scientists say is in store for the planet as glaciers keep melting.

Once the trampoline's ice turns to water that drips over the edges in the warm days of spring, the concave elastic slowly rebounds to its original flat shape. That's how Earth responds as glaciers retreat, and the consequences promise to be ... interesting.

The reason is that one cubic meter of ice weighs just over a ton, and glaciers can be hundreds of meters thick. When they melt and the water runs off, it is literally a weight off Earth's crust. The crust and mantle therefore bounce back, immediately as well as over thousands of years. That "isostatic rebound," according to studies of prehistoric and recent earthquakes and volcanoes, can make the planet's seismic plates slip catastrophically, and cause magma chambers that feed volcanoes to act like bottles of shaken seltzer. >>>>cont

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