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Researchers Find Some Volcanoes 'Scream' At Increasing Pitches Until They Blow
vinces99 writes "Swarms of small earthquakes often precede a volcanic eruption. They can reach such rapid succession that they create a "harmonic tremor" that resembles sound made by some musical instruments. A new analysis of an eruption sequence at Alaska's Redoubt Volcano in March 2009 shows the harmonic tremor glided to substantially higher frequencies and then stopped abruptly just before six of the eruptions. Scientists at the U.S. Geological Survey's Alaska Volcano Observatory have dubbed the highest-frequency harmonic tremor at Redoubt Volcano 'the screams' because the episodes reach such high pitch compared with a 1-to-5 hertz starting point. Alicia Hotovec-Ellis, a University of Washington doctoral student in Earth and space sciences and an author of two papers examining the phenomenon, has created a 10-second recording and a one-minute recording that provides a 60-times faster representation of harmonic tremor and small earthquakes."
So, it's like a teapot when it gets boiling?
I bet the volcano's still have better pitch control than Justin Beiber.
sudo make me a sandwich
some volcanoes will erect before they blow.
after a night at Taco Bell
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Could this be a possible explanation to how animals sometimes perceive an impending disaster? What decibel would this be at from, say, five miles?
At their peak, just before they blow, these "screams" get to a high enough frequency that humans could hear them. Of course, to us it would sound like a low frequency rumble.
In other words, if you are standing on a volcano, and start to hear it grumble, get away. Fast.
About 12 years ago there were swarms of tremors around the Long Valley, near Mammoth Mountain, California. 600-800 earthquakes per day from sub 1.0 to 3.0+ and elevation changes around the caldera indicated pressure was building. Then suddenly nothing happened and they subsides. Still a few here and there, but some activity took place and then ended. Massive false alarm or very long range warning? You scare a lot of people with eruption talk, which doesn't materialize, and you'll have most of them home when it suddenly goes BOOM without warning.
A feeling of having made the same mistake before: Deja Foobar
If you RTFA you would see this:
She documented the rising tremor frequency, starting at about 1 hertz (or cycle per second) and gliding upward to about 30 hertz. In humans, the audible frequency range starts at about 20 hertz, but a person lying on the ground directly above the magma conduit might be able to hear the harmonic tremor when it reaches its highest point (it is not an activity she would advise, since the tremor is closely followed by an explosion).
However this is slashdot so no need to RTFA, just carry on with redundant questions veiled in the shape of a seemingly innocuous post.
... if they're fracking it?
So what I'd like to know is: do Elephants (who's auditory range of 16-12,000 hertz covers much more of the tremors) always know when a nearby volcano is going to erupt?