It's hard to believe, but
this wind swept patch of desert was once the site of
not only Utah's but perhaps the world's largest volcanic eruption.
About six thousand cubic kilometers magma erupted in a catastrophic event
30 million years ago. Then it turns out it's one of the largest
super eruptions that we are aware of in the world.
any age, anywhere. Right now
We're sitting in the middle of this caldera that's right here on the
Nevada-Utah border. From north to south, that's about
30 miles. The largest eruptions on earth have been called super volcanoes
and in order to be a supervolcano,
it has to be over a thousand cubic kilometers in mass. Take, for comparison,
the eruption of Mount Saint Helens that occurred in 1980,
omitted one cubic kilometer of volcanic material.
The eruption we're looking at here errupted six thousand times
that amount of material.
Most people, when they think of a volcano, they think of a
conical edifice with a single vent.
Super volcanoes, they don't stand as high combed. Instead,
they for large holes in the ground. At the heart of the supervolcano
is a large collapse. As a super volcano forms, a
massive pool of magma builds up and domes
the surface. Eventually, the roof breaks, starting a huge eruption and emptying
the magma chamber
to form a bowl-shaped impression a few miles deep. The hot magma rips violently
as clouds of ash and ground-hugging pyroclastic flows rapidly spread
hundreds of miles across the landscape
and fill the newly formed caldera.
The ash would have cut out the sun and it would've been total darkness.
This would have been a catastrophic event.
It took many many years for us to fully realize
that we have a super volcano here in western Utah and it took so long
because remnants of this caldera were found in
five mountain ranges. For years, we've been looking for the source of this
very widespread pyroclastic deposit.
It's so old that it's been completely eroded, completely obliterated
so the only way that we know that it's here is by looking at the rocks.
In these 250
drawers, there are thousands of rock samples
that were collected over about a 30 year period
with the help of hundreds of students. The basis of all our work, of course,
is in the field. A lot of the time is actually spent in the lab.
Many hours are spent at a microscope trying to
find out the details of the minerals. Many other hours are spent with
analytical instruments to find out
the composition of the grains of the rocks. As we accumulated the data
and verified the arial extent of the Wal Wal Springs, we found that indeed
it was a super eruption from a supervolcano.
In the news, you may have heard of other super volcanoes. Some of them
are still active and still churning away. The Yellowstone Caldera
is a super volcano and it's still an active system.
If this is one of Earth's largest super volcanoes, do the people in western Utah
need to worry about an eruption here as well?
The answer is no. The tectonic setting is different. The
caldera has been ripped apart. This volcano erupted
30 million years ago and there's no threat of that style, the large super
eruption here in western Utah,
today. One of the things that geologists are always trying to piece together
is the history of the Earth. The history of the Earth has been punctuated by
catastrophic events, and identifying one of those
that occurred here in western Utah will help us piece together
the long chain of events that are part of Earth's history.