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