FINAL STAGES OF THE FLOOD
FINAL STAGES OF THE FLOOD |
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The torrent widened and deepened the Columbia River Gorge, baring the majestic cliffs seen today.
Floodwaters followed and deepened the Columbia River channel on their way to the ocean. Not far from the present day site of Portland, the river makes two 90 degree turns. It was here that ice and debris formed a temporary dam causing the floodwaters to spill into the Willamette Valley as far south as present day Eugene. Piles of rocks left behind near Eugene were brought by icebergs broken off the original ice dam formed by the Purcell lobe of the Cordilleran Ice Sheet. As waters receded the icebergs were left behind, and when they melted they deposited their contents.
Each time Lake Missoula emptied, the Purcell lobe, continuing its southerly progression, would form a new dam which would cause the lake to refill, resulting in a new flood. This happened on an average of every 55 years or so for 2,000 years!
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