The linkage between earthquakes and apparent resultant volcanic
activity has always been inferred and generally accepted. However,
today we have a smoking gun to make thing completely certain. The
quake and the actual vertical drop in the volcanic chain turn out to
be effectively simultaneous.
Thus we can be certain that Earthquakes do trigger the pent up
subsidence of volcanic buildups as a matter of course and can be
predicted.
In fact volcano prediction modeling for most can be predicated to
triggering quake likelihood. Actual stand alone events are what we
know and anticipate but adjacent active faults can trigger a far more
extensive era of volcanism and may explain certain anomalies in the
geological record.
Massive Earthquakes
Make Volcanoes Sink
By Becky Oskin
Mon, 1 Jul, 2013
The biggest
earthquakes also move mountains.
The massive
earthquakes that struck Japan and Chile in 2011 and 2010,
respectively, sank several big volcanoes by up to 6 inches (15
centimeters), two new studies report.
This is the first time
scientists have seen a string of volcanoes drop after an earthquake.
Even though the mountains are on opposite sides of the Pacific Ocean,
their descents look remarkably similar. The two teams have different
explanations for why the volcanoes sank, according to the studies,
published today (June 30) in the journal Nature Geoscience. However,
both groups agree it's likely scientists will discover more examples
of drooping volcanoes after big earthquakes, and find a single
mechanism that controls the process.
"It's amazing,
the parallels between them," said Matthew Pritchard, a
geophysicist at Cornell University in Ithaca, N.Y., and lead author
of one of the studies. "I think it makes a really strong case
that this is a ubiquitous process."
Into the deep
Researchers as far
back as Charles Darwin have noticed that volcanoes sometimes blow
their top after earthquakes. And colossal earthquakes, such as
the magnitude-9.0 2011 Japan earthquake and the
magnitude-8.8 2010 Chile temblor, can trigger small tremors at
volcanoes thousands of miles away. But pinning down a direct link
between earthquakes and eruptions has eluded scientists.
After the Chile and
Japan quakes, the research teams behind the two new studies (each
group working independently), set out to track signs of coming
eruptions. But instead of finding bulgingvolcanoes — 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.
Instead, volcanoes and
massive caldera complexes similar to those at Yellowstone National
Park — areas as large as 9 by 18 miles (15 by 30 kilometers) —
dropped by 2 to 6 inches (5 to 15 cm). 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.
Satellite data revealed the changes to both teams.
"Even without
visible eruptions, large earthquakes affect volcanoes,"
Youichiro Takada, a geophysicist at Kyoto University in Japan and
lead author of one of the studies, said in an email interview.
Competing causes
Pritchard and his
colleagues, who studied the Chilean earthquake, think the seismic
shaking uncorked fissures and fractures that released pent-up
hydrothermal fluids at the volcanoes, akin to shaking a soda bottle
and then opening the top. As the fluids escaped, the ground settled
and sank.
But Takada's group,
who studied the Japan quake, thinks magma chambers under the
volcanoes sank more than the surrounding region. The hot rock is
weaker and deforms more in response to the crustal changes caused by
the massive quake.
Their data, which is
more precisely timed than the Chile group's thanks to Japan's dense
GPS monitoring network, also shows the volcanoes dropped as
soon as the earthquake struck.
Further work will tell
which model is right, or even if they're both wrong, said Sigurjon
Jonsson, a geophysicist at the King Abdullah University of Science
and Technology in Saudi Arabia who was not involved in the study.
"The observations
in Japan and Chile are so similar that I'm certain that they are
caused by the same mechanism (and maybe more than one), instead of
two different ones in the two different countries," Jonsson said
in an email interview.
Both teams plan to
comb through the satellite record for evidence of past sinking after
earthquakes of varying sizes, and watch volcanoes during future
quakes and catch any changes.
The studies also offer
further evidence of why some earthquakes trigger eruptions and
some don't, Pritchard said.
"Basically, the
volcanic system has to be primed and ready to go for the earthquake
to tip it over the edge," Pritchard said. "If, by chance,
no volcanoes are close to that point, no volcanic eruptions are
triggered [after an earthquake]," he said.
This is cool!
ReplyDelete