A Recent volcanic mudflow of exceptional dimensions from Mount Rainier, Washington

Pumice and other pyroclastic deposits in Mount Rainier National Park, Washington

“…Such an origin was proposed for the clayey component of the Osceola Mudflow, a large clay-rich Holocene mudflow that originated on the northeast flank of Mount Rainier (Crandell and Waldron, 1956). The "airlaid facies" of the Osceola described by Crandell and Waldron is the clay-rich layer F northeast of the summit.…”

“…Crandell and Waldron (1956) and Crandell (1963a;1963b;1971) inferred that the montmorillonitic clay minerals in the mudflow came from altered rock within Mount Rainier, and that the mudflow probably was caused in some way by an eruption. Crandell (1963b, p. B139) suggested that a phreatic explosion had caused a large part of a former summit to avalanche and form the mudflow.…”

“…Carithers (1946) studied pumice deposits erupted at Mount St. Helens and noted that some of them extended into Mount Rainier National Park. Crandell and Waldron (1956) described thesequence of tephra deposits in the park relative to the Osceola Mudflow.…”

Volcanic hazards at Mount Rainier, Washington

“…Thus, layer Cis approximately between 2,000 and 2,350 years old. Crandell and Waldron (1956) described the layer in a measured section on the northeast side of Mount Rainier as brown and light-gray pumiceo us cinders, and others (Hopson and others, 1962;Fiske and others, 1963) have described it as coarse-grained tawnybrown to light-gray pumice that crunches underfoot.…”

“…The largest postglacial mudflow, which is estimated to have had a volume of nearly half a cubic mile, is the 5,000-year-old Osceola Mudflow (Crandell and Waldron, 1956). This clayrich mudfiow probably originated from the avalanching of rock, previously altered partly to clay by steam, from the summit and upper slopes of the volcano (Crandell, 1963a, b).…”