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PLASTER & PAINT PHASE -

19. Unstable Oregon: land of 10,000 landslides

Exotic Terranes

Landslides are common in Oregon, and geologists have mapped thousands of them, ranging from a few acres to a truly gigantic offshore landslide covering over 2,000 square miles. The slide off the southern Oregon coast is one of the largest known in the world and probably produced a massive tsunami when it occurred tens of thousands of years ago. Over thousands of years the combination of steep terrain, heavy rainfall, and periodic great earthquakes has produced landslides in all parts of the state.
Most are inactive . . . for now.

OGDC units: landslide deposits

Age Range: 500,000 years ago to now
Rock Types: broken rock, soil
Did You Know? In 850 AD, a mountainside on the Washington side of the Columbia River Gorge collapsed in a massive landslide near modern-day Cascade Locks. The slide temporarily dammed the Columbia River and may be the source of the Native American "Bridge of the Gods" legend.
square bullet Go See It!
Bridge of the Gods in the Columbia River Gorge
Hole in the Wall near the Powder River

 

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