The good news is that we will get centuries of actual warning as the
lava pool fills up. In fact, what has been learned during the past
thirty years is that a lava injection is the actual cause of volcanic
activity expressed on the surface and that we can hear and see it
through sensors. Linking all that with previous history, it is now
possible to formulate policy as the situation develops. We saw that
happen very successfully with Mount Pinatubo in particular. If there
is a fault, it is the sheer unwillingness of the living to respond
quickly to the dangers.
Once a caldera forms, the risk of an explosion or a hot ash flow is
real and constantly present. We have experienced vulcanologists out
gambling and finally losing. It is no particular trick to map out no
go zones and refugia from which to handle observations. I think that
it needs to be codified and made mandatory. There is no data out
there that is worth getting killed over and generally this has been
about egos.
Our technology is good enough to establish hundreds of listening
posts in duplicate and this allows the development of a detailed 3d
map of what is happening internally until it starts to get rough.
That is essentially the only data we truly need. The rest is
chemical and can be generally acquired anytime.
Today we know that volcanoes erupt on their own time scales as we
always did, but we now recognize both the warning signs and the scale
of the risks involved and are steadily improving our ability to
forecast the scale of a present eruptive event.
Thus we can expect to have ample time to vacate even half a continent
if it comes to that. We will never tame the beast, but we can live
with it.
Supervolcanoes 'can
grow in just hundreds of years'
30 May 2012 Last
updated at 18:00 ET
Long Valley is the
site of one of the world's "supervolcanoes"
These "supervolcanoes"
were thought to exist for as much as 200,000 years before releasing
their vast underground pools of molten rock.
Researchers reporting
in Plos One have sampled the rock at the supervolcano site of Long
Valley in California.
Their findings suggest
that the magma pool beneath it erupted within as little as hundreds
of years of forming.
That eruption is
estimated to have happened about 760,000 years ago, and would have
covered half of North America in its ash.
Such super-eruptions
can release thousands of cubic kilometres of debris - hundreds of
times larger than any eruption seen in the history of humanity.
Eruptions on this
scale could release enough ash to influence the global weather for
years, and one theory holds that the Lake Toba eruption in Indonesia
about 70,000 years ago had long-term effects that nearly wiped out
humans altogether.
What little is known
about the formation of these supervolcanoes is largely based on the
study of crystals of a material called zircon, which contains small
amounts of radioactive elements whose age can be estimated using the
same techniques used to date archaeological artefacts and dinosaur
bones.
Zircon studies to date
have suggested that the time between the formation of the enormous
magma pools and the eventual super-eruptions can be measured in the
hundreds of thousands of years.
Now, Guilherme Gualda
of Vanderbilt University and his colleagues present several lines of
evidence from the Bishop Tuff deposit at Long Valley, suggesting that
the pools are "ephemeral" - lasting as little as 500 years
before eruption.
Enormous eruptions
such as that at Yellowstone result in "calderas", which can
become huge lakes
Initially, the magma
pools are nearly purely liquid rock, with few bubbles or
re-crystallised minerals.
Over time, crystals
develop, but the process stops at the point of the eruption. As a
result, the characteristic development time of these crystals can
also give an estimate of how long a magma pool existed before
erupting.
Rather than zircon,
the team's target was crystals of the common mineral quartz.
Because the processes
and timescales of quartz formation in the extraordinary underground
conditions of a magma pool are well-known, the team was able to
determine how long the crystals were forming within Long Valley's
supervolcano before being spewed out in the eruption.
Their estimates
suggest the quartz formed over a range of time between 500 and 3,000
years.
"Our study
suggests that when these exceptionally large magma pools form they
are ephemeral and cannot exist very long without erupting," said
Dr Gualda.
"The fact that
the process of magma body formation occurs in historical time,
instead of geological time, completely changes the nature of the
problem."
At present, geologists
do not believe that any of Earth's known giant magma pools are in
imminent danger of eruption, but the results suggest future work to
better understand how the pools develop, and aim ultimately to
predict devastating super-eruptions.
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