Mount Saint Helens is a prime example of how Earth's topographic form can
greatly change even within our lifetimes. The mountain is one of several
prominent volcanoes of the Cascade Range that stretches from British
Columbia, Canada, southward through Washington, Oregon, and into northern
California. Mount Adams (left background) and Mount Hood (right
background) are also seen in this view, which was created entirely from
elevation data produced by the Shuttle Radar Topography Mission.
Prior to 1980, Mount Saint Helens had a shape roughly similar to other
Cascade peaks, a tall, bold, irregular conic form that rose to 2950 meters
(9677 feet). However, the explosive eruption of May 18, 1980, caused the
upper 400 meters (1300 feet) of the mountain to collapse, slide, and
spread northward, covering much of the adjacent terrain (lower left),
leaving a crater atop the greatly shortened mountain. Subsequent eruptions
built a volcanic dome within the crater, and the high rainfall of this
area lead to substantial erosion of the poorly consolidated landslide
material.
Eruptions at Mount Saint Helens subsided in 1986, but renewed volcanic
activity here and at other Cascade volcanoes is inevitable. Predicting
such eruptions still presents challenges, but migration of magma within
these volcanoes often produces distinctive seismic activity and minor but
measurable topographic changes that can give warning of a potential
eruption.
Three visualization methods were combined to produce this image: shading
of topographic slopes, color coding of topographic height, and then
projection into a perspective view. The shade image was derived by
computing topographic slope in the northeast-southwest (left to right)
direction, so that northeast slopes appear bright and southwest slopes
appear dark. Color coding is directly related to topographic height, with
green at the lower elevations, rising through yellow and tan, to white at
the highest elevations. The perspective view simulates the geometry of the
surface as it would be viewed on a clear day.
Elevation data used in this image were acquired by the Shuttle Radar
Topography Mission aboard the Space Shuttle Endeavour, launched on Feb.
11, 2000. SRTM used the same radar instrument that comprised the
Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR)
that flew twice on the Space Shuttle Endeavour in 1994. SRTM was designed
to collect 3-D measurements of the Earth's surface. To collect the 3-D
data, engineers added a 60-meter (approximately 200-foot) mast, installed
additional C-band and X-band antennas, and improved tracking and
navigation devices. The mission is a cooperative project between NASA,
the National Geospatial-Intelligence Agency (NGA) of the U.S. Department
of Defense and the German and Italian space agencies. It is managed by
NASA's Jet Propulsion Laboratory, Pasadena, Calif., for NASA's NASA's
Science Mission Directorate, Washington, D.C.
Size: View distance about 150 km (about 100 miles)
Location: 46.2 degrees North latitude, 122.2 degrees West longitude
Orientation: View Southeast
Image Data: Shaded and colored SRTM elevation model
Date Acquired: February 2000
