![]() ![]() ![]() Salmonid fish generally are believed to have been present in the Columbia River Basin for about 50 million years.ġ5,000-12,800 B.P.: More than 40 tremendous floods of almost inconceivable force and dimension swept across large parts of the Columbia River drainage, beginning in present-day northwestern Montana and coursing to the sea, laying down the modern channel of the Columbia through Washington and the Cascade mountains to the ocean. 6 million-16 million B.P.: The greatest outpouring of lava in the history of North America, 90,000 cubic miles, oozes to the surface of the ancient Northwest in repeated flows, forming the Columbia Plateau of present-day central Washington and Oregon and, over time, redirecting the course of the ancient Columbia River.ĥ million B.P.: Salmon known today are believed to have evolved in the Columbia River Basin at about this time. ![]()
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