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Preliminary Mineralogic and Stable Isotope Studies of Altered Summit and Flank Rocks and Osceola Mudflow Deposits on Mount Rainier, Washington

By Robert O. Rye1, George N. Breit1, and David R. Zimbelman2


1U.S. Geological Survey, Box 25046, MS 973, Denver, CO 80225
2G.O.Logic, PO Box 1878, White Salmon, WA 98672

U.S. Geological Survey Open-File Report 03-464

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Version 1.0


About 5600 years ago part of Mount Rainier’s edifice collapsed with the resultant Osceola Mudflow traveling more than 120 km and covering an area of at least 505 km2. Mineralogic and stable isotope studies were conducted on altered rocks from outcrops near the summit and east flank of the volcano and samples of clasts and matrix from the Osceola Mudflow. Results of these analyses are used to constrain processes responsible for pre-collapse alteration and provide insight into the role of alteration in edifice instability prior to the Osceola collapse event.

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