Saturday, April 21, 2012

Field of Erratics

Glacial erratics and moraines Columbia River valley

The east side of the Cascades can be very green depending on the time of year. In the spring after the cold weather ends and before the soil dries out one could even think it looks like my tribal home land.

I took the above picture while driving up the east side of the Columbia River valley north of Wenatchee on the way up to the northern Waterville Plateau. The route crossed over a series of terminal moraines from the tongue of ice that had extended down this stretch of the Columbia River valley from the continental Okanogan glacial ice lobe. The moraines are rubble left around the outer edge of the glacial ice.

It appears the vast majority of these erratics are Columbia River Basalt Group likely plucked off the uplands to the north and northeast and then left behind by the melting ice. The underlying bedrock in this portion of the valley is much older gneiss.
Several ice margin terraces along the valley sides with multiple erratic boulders

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