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PLASTER & PAINT PHASE -

12. High Cascade Volcanoes: land of fire and ice

Exotic Terranes

The crest of the Cascade Range of Oregon has been built by the continuing eruptions of hundreds of volcanoes ranging in age from a few million years old to just a few hundred years old. Most of the eruptions have occurred at small cinder cones and produce lava flows that cover a few hundred acres to a few square miles. A few larger volcanoes including Mount Hood, the Three Sisters, and Mount McLoughlin, alternate between lava flows and explosive eruptions of ash, pumice, and broken lava. Even rarer are huge eruptions like the Mazamasee Unit 19 explosion that created Crater Lake and blanketed surrounding states with ash. Some of these young volcanoes extend beyond the Cascade Range. Portland is one of the few cities in the world where young volcanoes lie within the urban area. Most of the largest peaks in the Cascade Range are still considered active volcanoes.

OGDC units: Pliocene to Quaternary volcanic, and volcaniclastic vent rocks of the late High Cascade volcanics and early High Cascade volcanics, predominantly basalt and basaltic andesite with minor andesite

Age Range: 6 million to 220 years ago
Rock Types: basalt, andesite, scoria, tuff
Did You Know? The most recent volcanic eruption in Oregon occurred in the 1790s on Mount Hood.
square bullet Go See It!
Mt. Hood
Dee Wright Observatory on McKenzie Pass
Mount Tabor Park in Portland

 

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