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June
15, 2001 marks the tenth anniversary of the eruption of Mt.
Pinatubo, one of the most destructive volcanic eruptions of
the last century. Found on the Bataan Peninsula on the island
of Luzon in the Philippines, the volcano had been dormant for
500 years when clouds of sulfur dioxide and tons of ash spewed
from the crater. Ultimately over 600 lives were lost in the
explosion and its aftermath.
In addition to the devastation
on the ground, however, the eruption had far reaching effects
on our global atmosphere. Spreading sulfur dioxide and dust
into the stratosphere affected both global temperature and
Earth’s protective layer of ozone.
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Landsat Looks
at Mt. Pinatubo
This recent false color
Landsat-7 image, from January 2001, shows Mt. Pinatubo as it
stands today. The caldera is seen in the middle of the image,
underneath clouds. Ten years after the blast, vegetation is
re-growing on the slopes of the mountain (in green.) Streams
of mud, called lahars, (resulting from ash from the eruption
mixing with water- seen as the lighter sediment) continue to
flow down the sides of the mountains, as well as channels of
water (darker streams). However, as vegetation grows back, the
ash becomes more stabilized and less likely to form the
destructive lahars.
Image Courtesy: NASA/USGS/University
of Hawaii
Sulfur
Dioxide After the Eruption
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here for an animation of the sulfur cloud and for print res
images
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The eruption of Mt. Pinatubo
blasted a huge cloud of sulfur dioxide, shown in red, into the
stratosphere. This data taken from NASA's Total Ozone Mapping
Spectrometer (TOMS) instrument shows that initial burst of
sulfur dioxide and its international path in the days
following the eruption, from June 16th to June 30th. The
sulfur gas cloud dissipates as the gas turns into droplets of
sulfuric acid. Both the gas and subsequent acid were
contributors to the overall dust cloud that cooled the global
climate.
Image Courtesy: NASA
Decrease in
the Ozone Levels
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for an animation of the equatorial ozone hole and for print
res images
During the year and a half
after the eruption, global stratospheric ozone levels
decreased as a result of chemical reactions with the ozone and
the sulfur dioxide gases released by the volcano. However, the
initial effect of the injection of sulfur dioxide into the
atmosphere was so strong, that a small hole was created in the
ozone layer, (from June 15th, 1991 through June 30, 1991) as
seen here, in blue, using TOMS data. This visualization shows
global ozone levels before and after the eruption. After the
hole dissipates, continued low levels of ozone, in very light
blue, can be seen around the tropics.
Image Courtesy: NASA
Shuttle
Images of the Atmosphere
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here for print res image top left
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These images highlight the
difference in the atmosphere before and after the Mt. Pinatubo
eruption. Showing the earth’s limb at sunset, first in
September 1984, the atmosphere is relatively clear. The second
image, taken in August of 1991, a little more than a month
after the eruption, shows distinct layers of aerosols in the
upper reaches of the atmosphere. These aerosols eventually
made their way around the globe, contributing to a temporary
worldwide cooling.
Images Courtesy: NASA/
JSC
Shuttle
Images of Mt. Pinatubo
This sequence of images taken
from various Space Shuttle missions highlight the evolution of
Mt. Pinatubo over time.
Hi-res
March of 1982, STS 003: The
mountain as it appeared before the eruption and after 500
years of dormancy. At the time of the eruption, many people
lived around the volcano.
Hi-res
July of 1992, STS 050: One year
after the eruption, the summit has been blasted away.
Hi-res
STS-046, August 1992: The mudflows
are clearly seen trailing down the mountainside. The lahars
filled the existing river beds on Mt. Pinatubo
Hi-res
STS 080, Nov-Dec. 1996
Images Courtesy: NASA/JSC
Spacebourne Radar
Looks at Pinatubo
One of the most devastating impacts of
the eruption was the subsequent mud flows, called lahars, that
streamed down the side of the mountain. The tons of ash, seen
here in great quantity on the western slope, mixed with heavy
rainfall to create destructive streams of mud, capable of
moving at speeds up to 20 miles per hour. This false color
image was taken from the Spacebourne Imaging Radar-C (SIR-C)
instrument onboard the Space Shuttle in April of 1994 and
highlights the ash in purple.
Image Courtesy: NASA/DARA/ASI/University
of Hawaii
SIR-C Images
Hi-res
Hi-res
These false color images, also taken
from the Spacebourne Imaging Radar-C (SIR-C) instrument
onboard the Space Shuttle, highlight the difference in a lahar
before (April 1994) and after (October 1994) the rainy season.
After the monsoons, the lahar has widened considerably.
Image Courtesy:
NASA/DARA/ASI/University of Hawaii
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