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The real stoy from Yellowstone today! Enjoy!!!!!!!
Yellowstone "Super Volcano" has 3.9 Quake
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Yellowstone National Park was shaken by a host of small earthquakes for a third straight day Monday, and scientists are watching closely to see
whether the more than 250 tremors were a sign of something bigger to come.
Clusters of small earthquakes happen frequently in Yellowstone, but it's very unusual for so many earthquakes to happen over several days, said
Robert Smith, a professor of geophysics at the University of Utah.
"They're certainly not normal," Smith said. "We haven't had earthquakes in this energy or extent in many years."
Smith directs the Yellowstone Seismic Network, which operates seismic stations around the park. He said the quakes have ranged in strength from barely
detectable to one of magnitude 3.9 that happened Saturday. A magnitude 4 quake is capable of producing moderate damage.
"This is an active volcanic and tectonic area, and these are the kinds of things we have to pay attention to," Smith said. "We might be seeing
something precursory.
"Could it develop into a bigger fault or something related to hydrothermal activity? We don't know. That's what we're there to do, to monitor it
for public safety."
The strongest of dozens of tremors Monday was a magnitude 3.3 quake shortly after noon. All the quakes were centered beneath the northwest end of
Yellowstone Lake.
A park ranger based at the north end of the lake reported feeling nine quakes over a 24-hour period over the weekend, according to park spokeswoman
Stacy Vallie. No damage was reported.
"There doesn't seem to be anything to be alarmed about," Vallie said.
Smith said it's difficult to say what might be causing the tremors. He pointed out that Yellowstone is the caldera of a volcano that last erupted
70,000 years ago.
He said Yellowstone remains very geologically active — and its famous geysers and hot springs are a reminder that a pool of magma still exists five
to 10 miles underground.
"That's just the surface manifestation of the enormous amount of heat that's being released through the system," he said.
Yellowstone has had significant earthquakes as well as minor ones in recent decades. In 1959, a magnitude 7.5 quake near Hebgen Lake just west of the
park triggered a landslide that killed 28 people.
Yellowstone is an active volcanic and tectonic area, and small earthquakes happen frequently. But scientists say the spate of small quakes that shook
up the area on Monday were unusual.
Recent History - ScienceDaily -- The Yellowstone "super volcano" rose at a record rate since mid-2004, likely because a Los Angeles-sized,
pancake-shaped blob of molten rock was injected 6 miles beneath the slumbering giant, University of Utah scientists report in the journal Science.
There is no evidence of an imminent volcanic eruption or hydrothermal explosion. That's the bottom line," says seismologist Robert B. Smith, lead
author of the study and professor of geophysics at the University of Utah. "A lot of calderas [giant volcanic craters] worldwide go up and down over
decades without erupting."
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The upward movement of the Yellowstone caldera floor -- almost 3 inches (7 centimeters) per year for the past three years -- is more than three times
greater than ever observed since such measurements began in 1923, says the study in the Nov. 9 issue of Science by Smith, geophysics postdoctoral
associate Wu-Lung Chang and colleagues.
"Our best evidence is that the crustal magma chamber is filling with molten rock," Smith says. "But we have no idea how long this process goes on
before there either is an eruption or the inflow of molten rock stops and the caldera deflates again," he adds.
The magma chamber beneath Yellowstone National Park is a not a chamber of molten rock, but a sponge-like body with molten rock between areas of hot,
solid rock.
Chang, the study's first author, says: "To say if there will be a magma [molten rock] eruption or hydrothermal [hot water] eruption, we need more
independent data."
Calderas such as Yellowstone, California's Long Valley (site of the Mammoth Lakes ski area) and Italy's Campi Flegrei (near Naples) huff upward and
puff downward repeatedly for decades to tens of thousands of years without catastrophic eruptions.
Smith and Chang conducted the study with University of Utah geophysics doctoral students Jamie M. Farrell and Christine Puskas, and with geophysicist
Charles Wicks, of the U.S. Geological Survey in Menlo Park, Calif.
Measuring a Volcano Getting Pumped Up
The orange shapes in this image represent the magma chamber -- a chamber of molten and partly molten rock -- beneath the giant volcanic crater known
as the Yellowstone caldera, which is represented by the rusty-colored outline at the top. The red rectangular slab-like feature is a
computer-generated representation of molten rock injected into the magma chamber since mid-2004, causing the caldera to rise at an unprecedented rate
of almost 3 inches a year, according to a new University of Utah study. In reality, the injected magma probably is shaped more like a pancake than a
slab. The two rusty circles within the caldera outline represent the resurgent volcanic domes above the magma chamber.
In the new study, the scientists measured uplift of the Yellowstone caldera from July 2004 through the end of 2006 with two techniques:
Twelve Global Positioning System (GPS) ground stations that receive timed signals from satellites, making it possible to measure ground uplift
precisely.
The European Space Agency's Envisat satellite, which bounces radar waves off the Yellowstone caldera's floor, another way to measure elevation
change.
The measurements showed that from mid-2004 through 2006, the Yellowstone caldera floor rose as fast as 2.8 inches (7 centimeters) per year -- and by a
total of 7 inches (18 centimeters) during the 30-month period, Chang says.
"The uplift is still going on today but at a little slower rate," says Smith, adding there is no way to know when it will stop.
Smith says the fastest rate of uplift previously observed at Yellowstone was about 0.8 inch (2 centimeters) per year between 1976 and 1985.
He says that Yellowstone's recent upward motion may seem small, but is twice as fast as the average rate of horizontal movement along California's
San Andreas fault.
The current uplift is faster than ever observed at Yellowstone, but may not be the fastest ever, since humans weren't around for its three
supervolcano eruptions.
Chang, Smith and colleagues conducted computer simulations to determine what changes in shape of the underground magma chamber best explained the
recent uplift.
The simulations or "modeling" suggested the molten rock injected since mid-2004 is a nearly horizontal slab -- known to geologists as a sill -- that
rests about 6 miles (10 kilometers) beneath Yellowstone National Park. The slab sits within and near the top of the pre-existing magma chamber, which
resembles two anvil-shaped blobs expanding upward from a common base.
Smith describes the slab's computer-simulated shape as "kind of like a mattress" about 38 miles long and 12 miles wide, but only tens or hundreds
of yards thick.
In reality, he believes the slab resembles a large, spongy pancake formed as molten rock injected from below spread out near the top of the magma
chamber.
The pancake of molten rock has an area of about 463 square miles, compared with 469 square miles of land for the City of Los Angeles.
Smith and colleagues believe steam and hot water contribute to uplift of the Yellowstone caldera, particularly during some previous episodes, but
evidence indicates molten rock is responsible for most of the current uplift.
Chang says that when rising molten rock reaches the top of the magma chamber, it starts to crystallize and solidify, releasing hot water and gases,
pressuring the magma chamber. But gases and steam compress more easily than molten rock, so much greater volumes would be required to explain the
volcano's inflation, the researchers say.
Also, large volumes of steam and hot water usually are no deeper than 2 miles, so they are unlikely to be inflating the magma chamber 6 miles
underground, Smith adds.
Ups and Downs at Yellowstone
Conventional surveying of Yellowstone began in 1923. Measurements showed the caldera floor rose 40 inches during 1923-1984, and then fell 8 inches
during 1985-1995.
GPS data showed the Yellowstone caldera floor sank 4.4 inches during 1987-1995. From 1995 to 2000, the caldera rose again, but the uplift was greatest
-- 3 inches -- at Norris Geyser Basin, just outside the caldera's northwest rim.
During 2000-2003, the northwest area rose another 1.4 inches, but the caldera floor itself sank about 1.1 inches. The trend continued during the first
half of 2004. Then, in July 2004, the caldera floor began its rapid rate of uplift, followed three months later by sinking of the Norris area that
continued until mid-2006.
Smith believes that uplift of the middle of the caldera decreased pressure within rocks along the edges of the giant crater, "so it allowed fluids to
flow into the area of increased porosity." That, in turn, triggered small earthquakes along the edge of the "pancake" of magma. The amount of hot
water flowing out of the deflated Norris area is much smaller than the volume of magma injected beneath the caldera, Smith says.
The research was funded by the National Science Foundation, the U.S. Geological Survey and the Brinson Foundation.