Unified Interior Regions

An east-west fault across middle of summit area and an uplift or bulge on upper north flank of the volcano are also visible in this photo.

View from the north of Mount St. Helens' eruption and first crater.

Although seismic activity began under Mount St. Helens on March 20, this overflight showed no unusual features except numerous tracks of earthquake-triggered snow avalanches. No evidence of fracturing of summit area was detected during careful visual observations on the afternoon of March 24, 1980. On March 25, the first cracks were noted by Bud Kimball, Tacoma, Washington

Studebaker Ridge formed during the Tertiary geologic time period (65 million to 2.6 million years ago). The pyroclastic surge from the May 18, 1980 eruption destroyed the trees on the ridge.

Before the eruption of May 18, 1980, Mount St. Helens' elevation was 2,950 m (9,677 ft). View from the west, Mount Adams in distance. S. Fork Toutle River is valley in center of photo.

Mount Adams elevation is 3,745 m (12, 286 ft). Mount St. Helens was the smallest of five major volcanic peaks in Washington State.

Summit region (Kalama age–1479 to 1720 C.E.) of Mount St. Helens looking northeast. Spirit Lake and Mount Adams in background. September 28, 1979.

Worm Complex on the southeast flank of Mount St. Helens—Middle Kalama lava flows in center of image. Photo from September 28, 1979. Click to view larger image.

Researcher measuring sturgeon length. Bottom trawl for young-of-year (YOY) indexing. Columbia River.

Tiltmeters allowed 24-hour monitoring as the information was telemetered back to CVO. Other instruments such as displacement meters for measuring cracks, seismometers for measuring earthquakes, gas sensors for measuring gas concentrations, and magnetometers for measuring the magnetic field, were also used for 24-hour monitoring. Spirit Lake is visible in the background in