Geology (Unit 2) - Wall Mountain Tuff

Following the uplift of the ancestral Rocky Mountains during the late Paleozoic, most sediments deposited before that time were eroded. This formed deep valleys by the Late Eocene.

Into these deep valleys the Wall Mountain Tuff was deposited. The Wall Mountain Tuff formed from the cooling of an enormous pyroclastic flow originating from a caldera near Mount Princeton, 50 miles west of Florissant. The landscape of the Florissant area would have been devastated following the eruption that created the Wall Mountain Tuff about 37 million years ago.

Pyroclastic Flow
A pyroclastic flow from the August 7, 1980 eruption stretches from Mount St. Helens' crater to the valley floor below.

USGS Photograph by Peter W. Lipman.

Pyroclastic Toe
A USGS scientist examines pumice blocks at the toe of a pyroclastic flow at Mount St. Helens.

SGS Photograph taken on October 17, 1980, by Terry Leighley, Sandia Labs.

Wall Mountain Tuff
View of Wall Mtn Tuff - Barksdale Picnic Area
Wall Mountain Tuff
Park Paleontologist Herb Meyer lecturing in front of the Wall Mountain Tuff at the Barksdale Picnic Area

Last updated: February 24, 2015

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