Geologic Overview of the Clackamas Basin Peter Wampler OSU.
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Transcript of Geologic Overview of the Clackamas Basin Peter Wampler OSU.
High Cascades
• Young volcanic chain
• Composite volcanoes erupting ash and pumice
• Young basalt flows and cinder cones cover large areas
• Glacial deposits are present near peaks
Western Cascades• Produced 6 times the
volcanism of the high cascades
• Collision during formation was “head on” and at a steeper angle
• Comprised of deeply eroded and weathered volcanic rocks
• Prone to mass wasting• Columbia River Basalts
occur with the same geographic area but are more similar to High Cascades in terms of erosion potential
The Willamette Valley Province
• Valley Sediments (filling the bowl)– Recent Alluvium (<1,000 years old)– Holocene (<10,000 years old) Terraces– Pleistocene (>10,000 years old)– Sand River Mudstone– Springwater Formation– Missoula Flood Silts
•Clackamas River is very dynamic
• Cut down from Estacada Surface approximately 140 ft since Missoula Floods