I posted on the bulging at Yellowstone last year and we now have this item from the
National Geographic. One finds that the
process is largely benign and likely to remain so. Certainly there is no mountain building going
on.
The sheer of the super volcano is
staggering and well worth celebrating.
Of course, I would love to see it all tapped for geothermal energy, even
if that meant burying the facilities.
The yield would be high and the capacity would be huge. However the designation of national park sharply
curtails such efforts although it actually should not.
Our problem is that there is a
belief that all development requires an unlimited surface right which is not
true and also bone stupid. The oil
industry today comes, extracts and cleans up and leaves a land that is swiftly
reclaimed by nature.
Geothermal works on a closed
circuit basis and placing the surface component underground or part of a
general park facility is not difficult.
Everything else (particularly power lines) can be buried and should be
anyway.
Some places saw the ground rise by ten inches, experts report.
Main Content
Steam rises from Castle Geyser in Yellowstone National Park
Photograph by Mark Thiessen, National Geographic
Brian Handwerk
Published January 19, 2011
Yellowstone National Park's supervolcano
just took a deep "breath," causing miles of ground to rise
dramatically, scientists report.
The simmering volcano has produced major eruptions—each a thousand
times more powerful than Mount St. Helens 's
1980 eruption—three times in the past 2.1 million years. Yellowstone's caldera,
which covers a 25- by 37-mile (40- by 60-kilometer) swath of Wyoming, is an ancient crater formed after the last big
blast, some 640,000 years ago.
(See "When Yellowstone
Explodes" in National Geographic magazine.)
Since then, about 30 smaller eruptions—including one as recent as
70,000 years ago—have filled the caldera with lava and ash, producing the relatively
flat landscape we see today.
But beginning in 2004, scientists saw the ground above the caldera rise
upward at rates as high as 2.8 inches (7 centimeters) a year. (Related: "Yellowstone
Is Rising on Swollen 'Supervolcano.'")
The rate slowed between 2007 and 2010 to a centimeter a year or less.
Still, since the start of the swelling, ground levels over the volcano have
been raised by as much as 10 inches (25 centimeters) in places.
"It's an extraordinary uplift, because it covers such a large area
and the rates are so high," said the University
of Utah 's Bob Smith, a longtime expert in Yellowstone 's
volcanism.
Scientists think a swelling magma reservoir four to six miles (seven to
ten kilometers) below the surface is driving the uplift. Fortunately, the surge
doesn't seem to herald an imminent catastrophe, Smith said. (Related: "Under
Yellowstone, Magma Pocket 20 Percent Larger Than Thought.")
"At the beginning we were concerned it could be leading up to an
eruption," said Smith, who co-authored a paper on the surge published in
the December 3, 2010, edition of Geophysical Research Letters.
"But once we saw [the magma] was at a depth of ten kilometers, we
weren't so concerned. If it had been at depths of two or three kilometers [one
or two miles], we'd have been a lot more concerned."
Studies of the surge, he added, may offer valuable clues about what's
going on in the volcano's subterranean plumbing, which may eventually help
scientists predict when Yellowstone 's next
volcanic "burp" will break out.
Smith and colleagues at the U.S.
Geological Survey (USGS) Yellowstone Volcano Observatory have been
mapping the caldera's rise and fall using tools such as global positioning
systems (GPS) and interferometric synthetic aperture radar (InSAR), which gives
ground-deformation measurements.
Ground deformation can suggest that magma is moving toward the surface
before an eruption: The flanks of Mount St. Helens ,
for example, swelled dramatically in the months before its 1980 explosion.
(See pictures of
Mount St. Helens before and after the blast.)
But there are also many examples, including the Yellowstone
supervolcano, where it appears the ground has risen and fallen for thousands of
years without an eruption.
According to current theory, Yellowstone 's
magma reservoir is fed by a plume of hot rock surging upward from Earth's
mantle. (Related: "New
Magma Layer Found Deep in Earth's Mantle?")
When the amount of magma flowing into the chamber increases, the
reservoir swells like a lung and the surface above expands upward. Models
suggest that during the recent uplift, the reservoir was filling with 0.02
cubic miles (0.1 cubic kilometer) of magma a year.
When the rate of increase slows, the theory goes, the magma likely
moves off horizontally to solidify and cool, allowing the surface to settle
back down.
Based on geologic evidence, Yellowstone has probably seen a continuous
cycle of inflation and deflation over the past 15,000 years, and the cycle will
likely continue, Smith said.
Surveys show, for example, that the caldera rose some 7 inches (18
centimeters) between 1976 and 1984 before dropping back about 5.5 inches (14
centimeters) over the next decade.
"These calderas tend to go up and down, up and down," he
said. "But every once in a while they burp, creating hydrothermal
explosions, earthquakes, or—ultimately—they can produce volcanic
eruptions."
Predicting when an eruption might occur is extremely difficult, in part
because the fine details of what's going on under Yellowstone
are still undetermined. What's more, continuous records of Yellowstone 's
activity have been made only since the 1970s—a tiny slice of geologic
time—making it hard to draw conclusions.
"Clearly some deep source of magma feeds Yellowstone, and since
Yellowstone has erupted in the recent geological past, we know that there is
magma at shallower depths too," said Dan Dzurisin, a Yellowstone expert
with the USGS Cascades Volcano Observatory in
Washington State
"There has to be magma in the crust, or we wouldn't have all the
hydrothermal activity that we have," Dzurisin added. "There is so
much heat coming out of Yellowstone right now that if it wasn't being reheated
by magma, the whole system would have gone stone cold since the time of the
last eruption 70,000 years ago."
The large hydrothermal system just below Yellowstone's surface, which
produces many of the park's top tourist attractions, may also play a role in
ground swelling, Dzurisin said, though no one is sure to what extent.
"Could it be that some uplift is caused not by new magma coming in
but by the hydrothermal system sealing itself up and pressurizing?" he
asked. "And then it subsides when it springs a leak and depressurizes?
These details are difficult."
And it's not a matter of simply watching the ground rise and fall.
Different areas may move in different directions and be interconnected in
unknown ways, reflecting the as yet unmapped network of volcanic and
hydrothermal plumbing.
The roughly 3,000 earthquakes in Yellowstone
each year may offer even more clues about the relationship between ground
uplift and the magma chamber.
For example, between December 26, 2008, and January 8, 2009, some 900 earthquakes
occurred in the area around Yellowstone
Lake
This earthquake "swarm" may have helped to release pressure
on the magma reservoir by allowing fluids to escape, and this may have slowed
the rate of uplift, the University
of Utah
"Big quakes [can have] a relationship to uplift and deformations
caused by the intrusion of magma," he said. "How those intrusions
stress the adjacent faults, or how the faults might transmit stress to the
magma system, is a really important new area of study."
Overall, USGS's Dzurisin added, "the story of Yellowstone
deformation has gotten more complex as we've had better and better technologies
to study it."
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