July 2016 – SUPERVOLCANO– A
new study has determined that super-eruptions -volcanic events so large
they spew out hundreds of cubic kilometers of magma and ash -typically
give only one year’s warning before they erupt, a prospect which would
leave humanity little time to prepare for the worldwide devastation
produced by such an eruption.The 2010 eruption of the Eyjafjallajökull
volcano in Iceland disrupted air traffic and coated much of Northern
Europe with volcanic ash, while the eruption of Mount St. Helens in
Washington State in May of 1980, which was the deadliest and most
economically costly volcano blast in U.S. history, covering 11 states
with ash and killing approximately 57 people.
But neither of these disasters comes
close to the power and devastation of what geologists refer to as
super-eruptions volcanic explosions that register highest on the
Volcanic Explosivity Index and send up between 100 and 1000 cubic
kilometers of ejecta into the atmosphere.
Scientists have long tried to pinpoint
when and where the next supervolcano will erupt. Now, researchers at
Vanderbilt University and the University of Chicago have used
microscopic analysis of quartz crystals to conclude that the
decompression process which releases gas bubbles prior to an eruption
begins less than a year before the actual event.
“Super-eruptions have been described as
the ultimate geologic hazard,” say the study’s authors, whose research
is published in the scientific journal Plos One. “And in many ways,
understanding the potential hazards associated with super-eruptions is
the ultimate geologic exercise, in which we are pressed to learn as much
as possible from the geologic record of past super-eruptions.”
Researchers looked at quartz collected
from the Bishop Tuff rock formation in eastern California, created by a
super-eruption 760,000 years ago, and found that the telltale rims which
form on quartz crystals in the lead-up to an eruption had developed in
just the days and months before the explosive event. “More than 70 per
cent of rim growth times are less than 1 year,” say the study’s authors.
The closest thing to a such an event in
recent history was the Mount Tambora eruption in Indonesia in 1815,
which ejected approximately 180 cubic kilometres of material in just a
few days and precipitated what was called the “Year without a summer” in
1816 – a volcanic winter that plummeted global temperatures and caused
massive famine and civil unrest for the decade to follow. The last true
super-eruption occurred 26,000 years ago in the Taupo Volcanic Zone in
New Zealand, preceded by the Toba super-eruption in Sumatra some 75,000
years ago.
Historically, North America has seen
super-eruptions at the Yellowstone Caldera in the state of Wyoming and
in Canada at what’s known as the Blake River Megacaldera on the border
between Ontario and Quebec. Why is a super-eruption so devastating?
Volcanic ash is the main problem, as billions of tonnes of particulate
travel through the air, making breathing difficult, blocking out the Sun
and covering everything in sight for thousands of kilometres around.
The ash from a super-eruption would contaminate lakes and rivers and
make much of the region close to the volcanic site uninhabitable, while
sulfur compounds in the ash which reflect sunlight would bring about a
volcanic winter and threaten agricultural production worldwide.
The chances of a super-eruption
occurring in the near future are slim, however, as geologists have not
seen the telltale signs of significant magma buildup underneath any of
the known supervolcano sites around the world. “As far as we can
determine, none of these places currently house the type of melt-rich,
giant magma body needed to produce a super-eruption,” says Guilherme
Gualda, professor of earth and environment sciences at Vanderbilt
University and co-author of the new study. “However, they are places
where super-eruptions have happened in the past so are more likely to
happen in the future.” –Cantech Letters
Supervolcanoes ALERT: One Year Warning may precede Giant Volcanic Eruptions
