We'll only have
one year's warning before a planet-devastating super-eruption
Enough
time to build a space ark?
PETER DOCKRILL 22 JUL 2016
Scientists in the US have discovered
that rare volcanic eruptions – so catastrophically powerful that they could
potentially devastate the entire planet – might only give up to a year's
warning before they unleash fiery hell.
Super-eruptions,
which can eject thousands of cubic kilometres of magma to the planet's surface,
build up over a massive time frame – but volcanic samples suggest the final
stage of decompression before magma release happens much more quickly.
"The
evolution of a giant, super-eruption-feeding magma body is characterised by
events taking place at a variety of time scales," says geochemist Guilherme Gualda from Vanderbilt University.
"Now
we have shown that the onset of the process of decompression, which releases
the gas bubbles that power the eruption, starts less than a year before
eruption."
To investigate the duration of the
final stage before a super-eruption, Gualda and fellow researcher Stephen
Sutton from the University of Chicago examined quartz crystal deposits from Bishop Tuff – a rocky outcrop that formed from the
super-eruption that created the Long Valley Caldera in central California some
760,000 years ago.
Scientists previously thought that this
quartz crystal – which covers the surface rims at super-eruption sites –
Using a new method to measure rim
growth times based on the concentration of titanium in the crystal, the
scientists think that the eleventh hour before a super-eruption can occur very
quickly, capping a volcanic buildup that might have slowly developed over tens
of thousands of years.
"Maximum
rim growth times span from approximately 1 minute to 35 years, with a median of
approximately 4 days,"
the researchers write in PLOS ONE. "More than 70 percent of rim growth times are less than 1 year,
showing that quartz rims have mostly grown in the days to months prior to
eruption."
According to the researchers, this rim
growth heralds the onset of a transition from "pre-eruptive to
syn-eruptive conditions", during which volcanic magma would begin to decompress and
expand underground – a geological phenomenon that the researchers suggest would
likely have noticeable effects on the Earth's surface in the final months
before a cataclysmic super-eruption.
Why would a super-eruption be so
dangerous? Not necessarily because of the ejection of magma and massive
geological movements on a local scale – meaning you really wouldn't want to be
close-by for
The 1815 Eruption of Mount Tambora is the largest super-eruption in recent
(recorded) history, and the subsequent ash cloud lowered temperatures around
the globe – creating in 1816 what became known as the "Year Without a Summer",
the "Poverty Year", the "Summer that Never Was", and any
number of other dramatic nicknames.
The good news is that the researchers
think that Earth's supervolcanos that could give rise to subsequent
super-eruptions in the future – like Yellowstone Caldera in the US and Lake Toba in Indonesia – won't do so any time
soon – although
In any case, it's likely that the world
hasn't seen its last year without a summer – but hopefully it won't be
something that happens in the near future.
"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," said Gualda.
"However,
they are places where super-eruptions have happened in the past so are more
likely to happen in the future."
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