Cascade Range Volcanoes

Three Sisters

Mount JeffersonMt. HoodMt.AdamsMt.Saint Helens Mt Rainier

Types of Volcanoes

California Volcanoes

Mount Lassen

Helen Lake

• Elevation 10,457ft

Most recent activity occurred in 1914-1917.

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 10,800-12,000ft prior to collapse

Mount Hood

• 11,239ft

Most recent eruptive activity (1760-1810 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

• 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 PlainTributaries to NF of Toutle Creek

1980

2004

*Note evidence of erosion taking place on the pumice plain

Mudd River

Creeks needed to downcut through the ash and pumice.

Mt. Shasta Mt. Saint Helens

Cubic Kilometers of Ejecta from Historic Eruptions