Eos, Transactions American Geophysical Union

Geophysical events

Authors

  • Anonymous


Abstract

Mount St. Helens Volcano, Cascade Range, southern Washington, USA (46.20°N, 122.18°W). All times are local (GMT-8 h). Mount St. Helens remained quiet as of March 10, as it has since the end of the lava extrusion episode of February 5–7. The February lava approximately doubled the volume of the composite dome in the crater, adding about 5×106 m3 of new material to the 1.5×106 m3 extruded October 18–19 and the 3.57×106 m3 extruded December 27—January 4. All of the preexisting dome, except for a portion of the December–January southeast lobe, was covered by the February lava. Between February 8 and 21, the February lobe spread 12 m while sagging 3 m, resulting in dimensions for the new lava of 281 m in EW direction and 119 m in maximum height above the crater floor.

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