Sara S
09-11-2009, 05:58 AM
from delancyplace.com:
In today's encore excerpt - tidbits for your next
Yellowstone National Park vacation:
"In the 1960s, while studying the volcanic history of
Yellowstone National Park, Bob Christiansen of the
United States Geological Survey became puzzled
about something: ... he couldn't find the park's
volcano. ...
"By coincidence just at this time NASA decided to test
some new high-altitude cameras by taking
photographs of Yellowstone, copies of which some
thoughtful official passed on to the park authorities on
the assumption that they might make a nice blow-up
for one of the visitors' centers. As soon as
Christiansen saw the photos he realized why he had
failed to spot the [volcano]: virtually the whole
park - 2.2 million acres - was [a volcano]. The
explosion had left a crater more than forty miles
across - much too huge to be perceived from
anywhere at ground level. At some time in the past
Yellowstone must have blown up with a violence far
beyond the scale of anything known to
humans.
"Yellowstone, it turns out, is a supervolcano. It sits on
top of an enormous hot spot, a reservoir of molten
rock that rises from at least 125 miles down in the
Earth. The heat from the hot spot is what powers all of
Yellowstone's vents, geysers, hot springs, and
popping mud pots. ... Imagine a pile of TNT about the
size of Rhode Island and reaching eight miles into the
sky, to about the height of the highest cirrus clouds,
and you have some idea of what visitors to
Yellowstone are shuffling around on top of. ...
"Since its first known eruption 16.5 million years ago,
[the Yellowstone volcano] has blown up about a
hundred times, but the most recent three eruptions
are the ones that get written about. The last eruption
was a thousand times greater than that of Mount St.
Helens; the one before that was 280 times bigger,
and the one before was ... at least twenty-five hundred
times greater than St. Helens. ...
"The Yellowstone eruption of two million years ago put
out enough ash to bury New York State to a depth of
sixty-seven feet or California to a depth of twenty. ... All
of this was hypothetically interesting until 1973,
when ... geologists did a survey and discovered that a
large area of the park had developed an ominous
bulge. ... The geologists realized that only one thing
could cause this - a restless magma chamber.
Yellowstone wasn't the site of an ancient
supervolcano; it was the site of an active one. It was
also at about this time that they were able to work out
that the cycle of Yellowstone's eruptions averaged one
massive blow every 600,000 years. The last one,
interestingly enough, was 630,000 years ago.
Yellowstone, it appears, is due."
Bill Bryson, A Short History of Nearly Everything,
Broadway, Copyright 2003 by Bill Bryson, pp. 224-228.
In today's encore excerpt - tidbits for your next
Yellowstone National Park vacation:
"In the 1960s, while studying the volcanic history of
Yellowstone National Park, Bob Christiansen of the
United States Geological Survey became puzzled
about something: ... he couldn't find the park's
volcano. ...
"By coincidence just at this time NASA decided to test
some new high-altitude cameras by taking
photographs of Yellowstone, copies of which some
thoughtful official passed on to the park authorities on
the assumption that they might make a nice blow-up
for one of the visitors' centers. As soon as
Christiansen saw the photos he realized why he had
failed to spot the [volcano]: virtually the whole
park - 2.2 million acres - was [a volcano]. The
explosion had left a crater more than forty miles
across - much too huge to be perceived from
anywhere at ground level. At some time in the past
Yellowstone must have blown up with a violence far
beyond the scale of anything known to
humans.
"Yellowstone, it turns out, is a supervolcano. It sits on
top of an enormous hot spot, a reservoir of molten
rock that rises from at least 125 miles down in the
Earth. The heat from the hot spot is what powers all of
Yellowstone's vents, geysers, hot springs, and
popping mud pots. ... Imagine a pile of TNT about the
size of Rhode Island and reaching eight miles into the
sky, to about the height of the highest cirrus clouds,
and you have some idea of what visitors to
Yellowstone are shuffling around on top of. ...
"Since its first known eruption 16.5 million years ago,
[the Yellowstone volcano] has blown up about a
hundred times, but the most recent three eruptions
are the ones that get written about. The last eruption
was a thousand times greater than that of Mount St.
Helens; the one before that was 280 times bigger,
and the one before was ... at least twenty-five hundred
times greater than St. Helens. ...
"The Yellowstone eruption of two million years ago put
out enough ash to bury New York State to a depth of
sixty-seven feet or California to a depth of twenty. ... All
of this was hypothetically interesting until 1973,
when ... geologists did a survey and discovered that a
large area of the park had developed an ominous
bulge. ... The geologists realized that only one thing
could cause this - a restless magma chamber.
Yellowstone wasn't the site of an ancient
supervolcano; it was the site of an active one. It was
also at about this time that they were able to work out
that the cycle of Yellowstone's eruptions averaged one
massive blow every 600,000 years. The last one,
interestingly enough, was 630,000 years ago.
Yellowstone, it appears, is due."
Bill Bryson, A Short History of Nearly Everything,
Broadway, Copyright 2003 by Bill Bryson, pp. 224-228.