Quake vs. Volcano: Which One’s Worse?

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Both earthquakes and volcanoes result from ruptures in the Earth's crust, and both can cause widespread human and ecological devastation. But picking a winner in a destruction derby could be a tough call.

What causes earthquakes, and will we ever be able to tell when a big one's going to hit?
DCI

Despite Sunday’s big 6.0 temblor in Napa Valley, Calif., a 6.9 quake in southern Peru, and rumblings on an Icelandic volcano, these geologic events aren’t trying to outdo one another, according to Steve Sparks, professor of earth sciences at the Bristol University (UK).

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“There are connections, but it’s a very loose connection,” Sparks said. “The places where you tend to get lots of earthquakes, you also get lots of volcanoes. Those are the boundaries of tectonic plates.”

Napa Valley (and much of California) sits near the boundary of the North American and Pacific plates, which rub against each other about two inches a year. Over time, deformations or strains build up, and the pressure is too much -- the plates slip. Then comes the earthquake.

Peru and Chile are also along a tectonic border zone, while Iceland straddles the boundary between the North American and Eurasian plates, which are slowly moving apart. Iceland has 30 active volcanoes, 13 of which have erupted since it was settled by European seafarers in the 800s. Many sit underneath a massive glacier called Vatnajokull.

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In fact, as Vatnajokull and other glaciers retreat due to climate change, many scientists believe we may be entering a time of greater seismic and volcanic activity. Imagine the 1,300-foot glacier acting as crushing deep-freeze for hot lava coming from the Earth’s core. Less ice, more magma. “If we have global warming and the ice does melt away,” Sparks said, “there may be a small effect.”

Luckily, the volcanoes lying below ice sheets in Iceland, neighboring Greenland, and Alaska -- regions experiencing melting glaciers -- are nowhere near as big as those that have exploded in recent times, such as Indonesia’s Tamboura in April 1815. That powerful blast released an ash cloud that covered much of the planet, led to summertime frosts, crop failures, and famines, and forced migrations of North American farmers.

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