I used to think global warming would cause drought, storms, and rising sea levels. This June, scientists realized that global warming is also going to increase global earthquake activity. How? The answer has to do with glacier movement.
Glaciers are huge rivers of ice, progressing in a stately fashion from an ice sheet into the sea at a relatively constant rate. That rate might be increased by global warming, but only slowly. At least, that's what we used to think. Recent research suggests that some ice sheets move in a 'stick-slip' pattern. That is, they become stuck to the ice next to them and pressure accumulates along their edges, until they slip forward a few inches at a time. These massive lurches forward produce earthquakes of up to 7 magnitude on the Richter scale- nearly the magnitude of the recent Sichuan earthquake in China. How often does the Whillans Ice Stream-- the first glacier observed with this behavior-- lurch forward? Twice a day. Each slip produces tremors that can be felt 4,000 miles away in Australia. What does this have to do with Global Warming? As the glaciers melt, they move faster, so we can expect more and more earthquakes from the Whillans Ice Stream. This increase has been observed in recent years, as glacial earthquakes increased. The increase in glacial earthquakes is bad news for the Greenland ice sheet, whose glaciers are thunderously pounding into the sea. Glaciers are often on, or connected to massive ice sheets like the Greenland sheet.
As ice sheets slip away, earthquake frequency is likely to increase. Scientists have observed this in Alaska, and models support the idea that melting ice sheets leads to earthquakes. It seems large, stable ice sheets hold tectonic plates in place, preventing their movement and the associated earthquakes. As ice sheets melt at an ever faster rate, we can expect to see global increases in earthquake activity. Further Reading: