| The dacite dome at Mount St. Helens grew episodically between October 18, 1980, and October 22, 1986, chiefly by extrusion of thick flows but also by endogenous growth resulting from intrusion into its molten core. Typical growth episodes lasted several days and produced volumes of 1.2-4.5x10^6 cubic meters, but growth was continuous from February 1983 to February 1984. By the end of October 1986, the volume of the dome and its talus apron was about 74.1x10^6 cubic meters, and the volume of all erupted material (including tephra and debris removed from the dome by explosions and rockfalls) was about 77.1x10^6 cubic meters. -- Swanson and Holcomb, 1989 |
