Volcanic explosions expected in Chile quake's wake

[n2doc]

15:38 01 March 2010 by Kate Ravilious

Besides aftershocks, Chile's magnitude 8.8 earthquake on 27 February may also leave a legacy of volcanic explosions. "We expect to see an upsurge in volcanic activity over the next 12 months," says David Pyle, a volcanologist at the University of Oxford.

Charles Darwin was among the first people to suggest a link between large earthquakes and increased volcanic activity. In his records, he notes that a large earthquake off Chile's coastline in February 1835 appeared to resurrect previously inactive volcanoes, and cause active ones to increase their eruption rates.

Last year, Pyle and his colleagues confirmed that this was a real effect in Chile, showing that increases in volcanic activity have occurred following other large earthquakes along its coastline.

In particular, they found that after a magnitude 8.3 in 1906 and a magnitude 9.5 earthquake in 1960, there were three or four more volcanic eruptions within about 500 kilometres of the epicentre in the following year than would normally be expected.

more

http://www.newscientist.com/article/dn18587-volcanic-explosions-expected-in-chile-quakes-wake.html

[MineralMan]

1. It's not surprising. Since the Chilean earthquake occurred at a

subduction zone, and since subduction zones create volcanic activity inland from them, I'd expect a major movement to generate some volcanic activity.

[eppur_se_muova]

2. Magnitude 9.5 ?!? Please tell me that's a typo!

I thought anything over 9.0 would leave pieces of the planet flung off into space.

[Codeine]

3. Why would you think that?

I think the Anchorage quake was about a 9. And the Valdivia quake in Chile in 1960 (I think I got the name right) was definitely a 9.5 -- largest quake ever recorded.

[eppur_se_muova]

4. Just something I read long ago -- 9.0 was supposedly an upper limit of the Richter scale.

Actually, the Richter scale is open-ended, but I read that anything much over a 9 would involve so much energy release it would break up the Earth -- so you could still assign a number to it, even if no one survived.

Apparently, the Richter scale has its problems, but that's not one of them. It can't measure quakes above magnitude 7. Maybe I read a garbled version of that, or garbled it myself. Or maybe it's just an old "fact" that was superceded by better understanding. According to http://en.wikipedia.org/wiki/Richter_magnitude_scale there has never been an earthquake recorded above magnitude 10.0, but they have certainly occurred, without breaking up the Earth. The Chicxulub impact is estimated to have been a mag. 11.3 seismic event. Hard even to imagine.

I had never heard about the Valdivia quake before, although I did know about the Lisbon one (not that it was a 9.0, though). I guess that's a case of it being too recent to be history, but already too old to be news, when I was growing up. The great Alaska quake happened when I was ~8 years old, and I can remember that being big news.