–Northwest Discovery Water Trail-5b-Natural World-Geology

Geology

The Northwest Discovery Water Trail flows through the Columbia River Plateau, an area shaped by a series of ancient lava flows and sculpted by ice age floods. Over 17 million years ago, molten lava began oozing out of immense cracks in the earth’s crust, eventually covering an area of 63,000 square miles in northeast Oregon, southwest Washington and western Idaho, with layers of lava reaching more than 6,000 feet deep.

During the last Ice Age, a vast glacier moving across northwest Montana damned rivers and created several large lakes. One of the largest lakes, known as Glacial Lake Missoula, eventually broke its ice dam, allowing a tremendous volume of ice and water to rush across northern Idaho and into eastern Washington and Oregon, eroding the basalt landscape and creating large deposits of flood sediment. The peak rate of flow was ten times the combined flow of all the rivers of the world! This process was repeated many times across the region until the glacier began to retreat at the end of the Ice Age. The result of these Ice Age Floods is a landscape of canyons, buttes, boulder fields, and gravel bars.

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