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Wednesday, July 3, 2013

Earthquakes Cause Volcanoes To Shrink

At least that's what they think....

The biggest earthquakes also move mountains - down.

The evidence gathered to prove a still unproved link between earthquakes and volcanoes involves data from the 9.0 Magnitude Japan earthquake of 2011 and the 8.8 M quake that smashed Chile in 2010.

What's the evidence? Apparently after the quakes, several large volcanoes in each area actually sank into the ground by up to six inches (15 centimeters), according to a pair (2) of studies.

Back on April 4, 2011, less than a month after the big Japan quake (and tsunami), I wondered if there was a link between volcanoes and earthquakes... was the March 13, 2011 eruption of the Shinmoedake volcano hundreds of miles away linked to the Sendai quake of March 11, 2011?

You can read that article of mine: HERE. I'm not taking credit for the theory, mind you, but I have always wondered about a possible link since I was a kid. Really. I'm weird that way, and I curse myself for not cracking the books more (at all, actually... I never studied - ever, right through university... just bloody coasted!). Even Charles Darwin noticed that volcanoes often erupt after earthquakes...

So... even though the mountains in Chile and the mountains in Japan are on the opposite sides of the Pacific Ocean, both experienced a drop.

According to data published on June 30m 2013 in the magazine Nature Geoscience: "It's amazing, the parallels between them," says Matthew Pritchard, a geophysicist at Cornell University in the United Sates, and lead author of one of the studies looking at Chile. "I think it makes a really strong case that this is a ubiquitous process."

The thought is that the huge earthquakes can trigger small tremors at volcanoes thousands of miles away, but no one has yet been able to prove - or disprove - that theory.

The two research groups independent of each other set out to track signs of coming eruptions. But instead of finding bulging volcanoes — a hint that magma is rising underground — the teams only discovered sagging mountains, or no changes at all. No signs of eruptions appeared in the scores of volcanoes in the two countries.

What each group found was that volcanoes - areas as large as nine by 18 miles (15 by 30 kilometers) — dropped by two to six (five to 15 centimeters).

Each area was shaped like a long oval, lined up parallel to the offshore earthquake fault that was located between 200 to 300 km (about 125 to 185 miles) away.

Now, lest you think the researchers climbed the volcanoes with a measuring tape, let me tell you that instead they utilized satellites to spot the diminishing mountains.

"Even without visible eruptions, large earthquakes affect volcanoes," says Takada Youichiro (surname first), a geophysicist at Kyoto University in Japan and lead author of the other study.

Pritchard says that he thinks the earthquakes shook uncorked fissures and fractures that released pent-up hydrothermal fluids at the volcanoes-like when your Coke bottle explodes after shaking - and as the fluids escaped, the ground settled and sank.

Takada, however, thinks magma chambers under the volcanoes sank more than the surrounding region because the hot volcanic rock becomes weaker and the then gives way after the crustal changes caused by a big quake.

According to Takada, their evidence shows the volcanoes dropped as soon as the earthquake struck.

So... who is right?

Now the plan is for both these research teams to look through past satellite data to see if there is other evidence of volcano shrinkage after earthquakes of varying sizes, and, of course to observe volcanic activity after any future earthquakes and then check for any dips in size.

Andrew Joseph

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