Cascade Range Volcanoes Three Sisters Mount JeffersonMt. HoodMt.Adams Mt.Saint Helens Mt Rainier

Types of Volcanoes

California Volcanoes

Mount Lassen Helen Lake Elevation 10,457ft Most recent activity occurred in

Lassen Erupts May 22, 1915

Mount Shasta Shastina Elevation 14,162ft Mt. Shasta debris avalanche covers an area of 450 square miles. 10 times the volume of the 1980 Mt. Saint Helens Eruption 2nd Tallest Peak in the Cascades

Mount Shasta and Haley’s Comet

Oregon Volcanoes

Crater Lake Wizard Island. A small cinder cone volcano. Mt. Mazama’s massive eruption created a caldera, forming Crater Lake Hillman Peak 8,126ft Highest point on the rim of the caldera Mt. Mazama was 10, ,000ft prior to collapse

Mount Hood 11,239ft Most recent eruptive activity ( A.D.) occurred just prior to Lewis & Clark’s visit in 1805.

Mount Hood from Portland Mt. Hood is located 75km Southeast of Portland, Oregon

Washington Volcanoes

Mount Adams 12,276ft Second in eruptive volume only to Mt. Shasta Third Tallest Peak in the Cascades

Mount Rainier 14,410ft Highest Peak in the Cascades Erupted as recently as the 1840’s Last large eruptions occured 1000 and 2300 years ago. Tacoma / Puget Sound

Mount Saint Helens Emerged from dormancy in May 1980 with a devastating eruption. Recently became active again in September 2004

The Bulge

USGS geologist: Dave Johnston

9,677ft

Highest point of crater rim: 8,364ft (1,313ft lower)

Pyroclastic Flows Super-heated gases mixed with fine ash, cinders and volcanic bombs rush down the slopes of Mt. Saint Helens in the days following the large eruption.

David Johnston’s last know location

Before and After

May 18, 1980: Ashfall in downtown Yakima, WA

Smith Creek

Logging Mill on the Banks of the North Fork Toutle River

Pumice Plain Tributaries to NF of Toutle Creek *Note evidence of erosion taking place on the pumice plain

Mudd River Creeks needed to downcut through the ash and pumice.

Mt. ShastaMt. Saint Helens

Cubic Kilometers of Ejecta from Historic Eruptions