Science Fair Project Encyclopedia
Bonneville Slide
The Bonneville Slide was a large landslide that took place in the Pacific Northwest of the United States, blocking the Columbia River.
Approximately five hundred years ago a mountain underwent a large landslide, spliting in two and forming Table Mountain and Greenleaf Peak . The southern halves of them slid down the mountain and blocked the Columbia Gorge close to modern-day Cascade Locks, Oregon forming a land bridge approximately 200 feet high. The river eventually removed it, but this event is remembered in local legends of the Native Americans as the Bridge of the Gods.
The Pacific Northwest is still geologically active; there was the large earthquake of the Juan de Fuca Plate in 1700, and Mount Hood erupted in 1781-82. More recently, Mount St. Helens erupted on May 18, 1980 (see 1980 Mount St. Helens eruption), and February 28, 2001 had a 6.8 magnitude earthquake in Seattle. The slide occurred sometime in the eighteenth century and may be tied to the Cascadia Earthquake, though evidence does not seem solid as yet.
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