Global Volcanism Program

Volcanoes of the World

Rainier

Volcanic Activity Reports

Mount Rainier, at 4392 m the highest peak in the Cascade Range, forms a dramatic backdrop to the Puget Sound region. Large Holocene mudflows from this massive, heavily glaciated volcano have reached as far as the Puget Sound lowlands. The present summit was constructed within a large crater breached to the north during the a mid-Holocene eruption as a result of the collapse of a once-higher edifice. Several postglacial tephras have been erupted from Mount Rainier; tree-ring dating places the last recognizable tephra deposit during the 19th century. Extensive hydrothermal alteration of the upper portion of the volcano has contributed to its structural weakness; an active thermal system has caused periodic melting on flank glaciers and produced an elaborate system of steam caves in the summit icecap.

Index of Volcanic Activity Reports

Reports are organized chronologically and indexed below by Month/Year (Publication Volume:Number), and include a one-line summary. Click on the index link or scroll down to read the reports.

06/69 (CSLP 53-69) Increased seismicity since September 1968

Complete Contents of Volcanic Activity Reports

All information contained in these reports is preliminary and subject to change.

06/69 (CSLP 53-69) Increased seismicity since September 1968

"Local activity has been increasing each month for the last three months. We have been averaging about 1-3 'Mt. Ranier Events' per 5-day period with an increase to about five per 5-day period last September 1968. This April, the events increased to approximately five per 5-day period. In May, it increased to about six per 5-day period and as of 15 June the increase is to approximately 12 per 5-day period."

Information Contact: N. Rasmussen, Seismology Station, University of Washington.

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