This activity could have a whole range
of consequences. In a study released last year, the
United States Geological Survey (USGS) said possible hazards could
include hydrothermal explosions, when steam breaks through the surface
and forms a crater. That has happened 26 times in the park's 127 years
of record-keeping. The USGS discounted chances for cataclysmic eruption
of the caldera, noting that the hot, active magma chamber
below Yellowstone has turned into "largely crystallized mush."
But the same study also said: "Depending on the nature and magnitude
of a particular hazardous event and the particular time and season
when it might occur, 70,000 to more than 100,000 persons could be
affected; the most violent events could affect a broader region or
even continent-wide areas." Jake Lowenstern, Ph.D.,
YVO's chief scientist, who also is part of the USGS
Volcano Hazards Team, told TIME that a supervolcano event does not
appear to be imminent. "We don't think the amount of magma exists
that would create one of these large eruptions of the past," he said.
"It is still possible to have a volcanic eruption comparable to
other volcanoes. But we would expect to see more and larger quakes,
deformation and precursory explosions out of the lake.
We don't believe that anything strange is happening right now."
Last summer YVO installed new instrumentation in boreholes 500 to
600 ft. deep to better detect ground deformation.?Says Lowenstern:
"We have a lot more ability to look at all the data now." (See an
interactive graphic depicting how scientists monitor
volcanoes.)
The Yellowstone Caldera — formed by the massive upheaval 642,000 years
ago that spread airborne debris all the way to the Gulf of Mexico
— is nowhere close to being extinct. Areas of the park's topography
inflate like a bellows because of magma infusing
into volcanic chambers about 6 miles below the surface.
About 1,000 to 2,000 tremors a year (mostly small) have been recorded
since 2004, when interpretation of satellite imagery with GPS readings
indicated the caldera had been rising as much as 3 in. a year. The
past week's number of tremors — about 400 — is considered unusual.
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