|
A Brief Geologic History of Columbia Basin The history of the Columbia is as long and powerful as the river is today. It includes two amazing true reality shows about two incredulous floods: one of molten rock and one of water. The timeline starts 13 million years ago with the birth of the Columbia River basin. About that time, there was an outpouring of molten lava from north south fissures along the present day border of Washington and Oregon. These basalt floods came in wave after wave for about four million years, and continued until they had covered most of what is now eastern Washington and northeastern Oregon with a blanket of rock up to five thousand feet thick. This rise in the Columbia Plateau diverted the ancient Columbia River forcing it to make a massive detour, called Big Bend, as it flowed into what is now Canada. The river was forced west, then south, then east to meet the Snake river before it finally turned west again for its final run to the Pacific. Between five million and two million years ago, as the Columbia continued to bend around and eat away at the basalt, the Cascades Mountain began to arch up. The river, did not give ground and the mighty Columbia cut a deep V-shaped canyon for itself.
During the last ice age, two million to 12,000 years ago, erosion and stiff winds during spread sand and silt across the Columbia Plateau, in some areas stacking up 150 feet. Then about 14,000 to 12,000 years ago, the catastrophic floods began. Advancing ice sheets from Canada got stuck in a canyon in what is now northwest Montana. The ice formed a giant dam that stood 2,500 feet high (nearly five times as high as the Grand Coulee dam). Behind the dam a lake formed that contained five hundred cubic miles of water, about half the volume of Lake Michigan. And then, suddenly in geologic time, the ice dam let go and the lake exploded into a flood that rampaged across eastern Washington with 10 times the combined flow of all the rivers of the world. It traveled at 50 miles per hour and released energy 225 times greater than the Hiroshima bomb, 33 times greater than the largest recorded earthquake. The floods occurred at least 40 times, ripping away silt, blasting through rock, creating a tormented landscape of coulees, dry falls, and barren channels. The great floods found their way to the Pacific by reaming out the Cascade canyon that the Columbia River had been slowly cutting for several million years. They changed the V-shaped canyon into a magnificent U-shaped gorge. Landslides that dropped as many as fifty square miles of earth continuing to shape the north side.
Two hundred years ago, “bad rapid” “verry bad rapid’, Clark would write in his journals over and over as the Corps of Discovery made its way to the Ocean. He further noted, “I was determined to pass through this place notwithstanding the horrid appearance of this agitated gut swelling, boiling and whorling in every direction.” Also around 200 years ago, Native American populations had reached several hundred thousand. Only 100 years ago, there were about 100,000 non-Indian people settled in the Portland metro area and we had 50% more wetlands in the lower river than we have today. Just 50 years ago (in 1950), you could stand at Celilo Falls and catch as much as 1000 pounds of salmon a day. The history of the Columbia is a long one; it took nature millions of years to create what we have today. The next chapter is ours to write. Humans have the ability to change geologic history is a short timeframe. What will the story be 50 years from now? 100 years from now? For more information on Columbia River geologic history, take a look at the excellent book:
|
|||||||||
 |
|
|
|
|
||||||
