June 11th, 2006
The Wall Street Journal reports that melting of glaciers will increase earthquake and seismic activity. [How Melting Glaciers Alter Earth's Surface, Spur Quakes, Volcanoes] The idea is that melting glaciers changes the weight distribution on the earth’s surface and that the earth rebounds:
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.
The main evidence is from prior geologic history:
That link has reared its ugly head in the past, especially during periods of rapid climate change such as the end of ice ages. When ice sheets retreated 10,000 years ago, for instance, Iceland experienced a surge in volcanic eruptions. Volcanoes in the Mediterranean, Antarctica and eastern California also seem to have been awakened by retreating ice.
When he analyzed 800,000 years of activity from about 50 volcanoes in eastern California (the age of rocks formed from volcanic ash can be determined by radioactive dating), Prof. Glazner found that “the peaks of volcanic activity occurred when ice was retreating globally. At first I thought it was crazy, but other scientists also found evidence that climate affects volcanism.” The likely mechanism: glacial retreat lifts pressure that had kept the magma conduit closed.