Knowledge you can walk. Read the idea below, then step up to the general, across to peers or down to the specific.
Physical
Lower Columbia Mountains and Volcanoes
A guide to the Lower Columbia's volcanic peaks: Mount Hood, Mount St. Helens, Beacon Rock and Silver Star Mountain.
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The idea
The peaks in this guide were all shaped by volcanoes, but in different ways. Mount Hood and Mount St. Helens are active stratovolcanoes in the Cascade Range, part of the Cascade Volcanic Arc. A stratovolcano is a tall, steep cone built up from layers of lava and ash. Mount Hood was formed by a subduction zone along the Pacific Coast, where one plate of Earth's crust slides beneath another.
At 11,249 feet, Mount Hood is the highest mountain in Oregon, about 50 miles east-southeast of Portland. It holds 12 named glaciers and snowfields, and since 1950 the volcano has experienced several earthquake swarms annually. Mount St. Helens, 52 miles northeast of Portland in Washington, erupted on May 18, 1980. The eruption killed 57 people and lowered the summit from 9,677 to 8,363 feet, leaving a horseshoe-shaped crater.
Beacon Rock is an 848-foot basalt volcanic plug on the north shore of the Columbia River, 32 miles east of Vancouver. A volcanic plug is hard rock that filled a volcano's vent and was left standing after softer rock wore away. Silver Star Mountain, in the Gifford Pinchot National Forest, is not an extinct volcano as local legend says, but an uplifted ridge made of the debris and roots of very old volcanic vents.
Check yourself
Question 1 of 2
Which of these peaks stands on the north shore of the Columbia River, 32 miles east of Vancouver?
Composition
what it's made of
- Mount Hood — Oregon's highest mountain, an active stratovolcano with a summit at 11,249 feet.
- Mount St. Helens — An active stratovolcano in Washington, known for its May 18, 1980, eruption.
- Beacon Rock — An 848-foot basalt volcanic plug on the north shore of the Columbia River.
- Silver Star Mountain — An uplifted ridge of old volcanic rock in the Gifford Pinchot National Forest.
- Cascade Volcanic Arc — The chain of volcanoes, part of the Pacific Ring of Fire, that includes Mount Hood and Mount St. Helens.
Connection
how it relates
Under Lower Columbia Region
Change
how and why it evolves
- Past
- On October 31, 1805, the Lewis and Clark Expedition reached Beacon Rock and first measured tides on the river, a sign they were nearing the ocean.
- Now
- Mount St. Helens built a new lava dome from 2004 until 2008, and today it is a popular hike that is climbed year-round. Since 2020, three monitoring stations on Mount Hood have helped warn of volcanic activity, after a dispute over placing them in a protected wilderness.
- Next
- Geologists predict that future eruptions at Mount St. Helens will be more destructive, and scientists will likely keep watching Mount Hood for warning signs.