Previously dormant volcanoes in two widely separated areas of the Pacific “ring of
fire” are showing signs of life, as documented by new images taken by the Advanced
Spaceborne Thermal Emission and Reflection Radiometer (Aster) on NASA’s Terra

The images are available at: .

Geologists had previously considered Chiliques, a simple 5,778-meter (18,957-foot)
stratovolcano with a 500-meter (1,640-foot)-diameter circular summit crater in northern
Chile, to be dormant. However, a January 6, 2002 nighttime thermal infrared image from
Aster found a hot spot in the summit crater, as well as several others along the upper flanks
of the volcano’s edifice, indicating new volcanic activity. Examination of an earlier
nighttime thermal infrared image from May 24, 2000 showed no such hot spots.

Stratovolcanoes such as Chiliques account for approximately 60 percent of Earth’s
volcanoes. They are marked by eruptions of cooler, stickier lavas such as andesite, dacite
and rhyolite. Because these lavas tend to plug up volcanic plumbing, gas pressures can
more easily build up to high levels, often resulting in explosive eruptions. They are
typically made up of about half lava and half loose or fragmented rock ejected from the
volcano, and are therefore also commonly known as composite volcanoes. Mount Saint
Helens in Washington and Mount Pinatubo in the Philippines are examples of

The daytime image of Chiliques was acquired on November 19, 2000 and was
created by displaying Aster bands 1, 2 and 3 in blue, green and red. The nighttime image is
a color-coded display of a single thermal infrared band. The hottest areas are white, and
colder areas are darker shades of red. Both images cover an area of 7.5 by 7.5 kilometers
(4.7 by 4.7 miles), and are centered at 23.6 degrees south latitude, 67.6 degrees west

Meanwhile, a couple of thousand miles to the northwest, a 10-by-20-kilometer (6.2-
by-12.4-mile) section of ground near one of the long-dormant Three Sisters volcanoes in
the Cascade Mountains of west-central Oregon has risen approximately 10 centimeters
(3.94 inches) since 1996. According to the U.S. Geological Survey, this indicates the slow
flow of magma or underground lava into the area. A simulated natural color image from
Aster has been draped over digital topography from the U.S. Geological Survey National
Elevation Dataset to create this new perspective view of Three Sisters.

The Three Sisters area — which contains five volcanoes — is only about 273.6
kilometers (170 miles) from Mount St. Helens, which erupted in 1980. Both are part of the
Cascades Range, a line of 27 volcanoes stretching from British Columbia in Canada to
northern California.

With its 14 spectral bands from the visible to the thermal infrared wavelength
region, and its high spatial resolution of 15 to 90 meters (about 50 to 300 feet), Aster will
image Earth for the next six years to map and monitor the changing surface of our planet.

Aster is one of five Earth-observing instruments on Terra, and is its only high-
resolution imaging sensor. Japan’s Ministry of Economy, Trade and Industry built the
instrument. JPL is responsible for the American side of the joint U.S.-Japan science team
that is validating and calibrating the instrument and data products.

Aster’s broad spectral coverage and high spectral resolution will provide scientists
in numerous disciplines with critical information for surface mapping, and monitoring
dynamic conditions and temporal change. Example applications are: monitoring glacial
advances and retreats; monitoring potentially active volcanoes; identifying crop stress;
determining cloud morphology and physical properties; evaluating wetlands; monitoring
thermal pollution; monitoring coral reef degradation; mapping soil and geology surface
temperatures; and measuring surface heat balance.

More information on Aster is available at: .

NASA’s Earth Science Enterprise is a long-term research and technology program
designed to examine Earth’s land, oceans, atmosphere, ice and life as a total integrated

JPL is a division of the California Institute of Technology in Pasadena.