Two geologists present opposing hypotheses regarding the formation of the Channeled Scablands, a region of deeply eroded channels in eastern Washington.
Geologist 1
The Channeled Scablands were carved rapidly by a sudden, catastrophic deluge. A massive glacial ice dam holding back Lake Missoula failed, releasing approximately of water in a few days. This high-velocity flood eroded basaltic bedrock into deep coulees and left behind giant current ripples—gravel bars up to high. The erratic boulders found throughout the region were transported rapidly by this fast-moving water.
Geologist 2
The Channeled Scablands were formed gradually over millions of years. Meltwater streams flowing along ice sheet margins during multiple glacial cycles slowly eroded the basalt bedrock. No catastrophic flood occurred. The giant gravel formations are actually ancient sand dunes deposited and shaped by wind over long periods, and the erratic boulders were deposited directly by moving glaciers.
Match each scientific claim regarding the features of the Channeled Scablands to the geologist whose hypothesis it supports.
- Bedrock channels were carved rapidly by a sudden, massive release of water.Geologist 1's claim on channel carving
- Bedrock channels were carved gradually by meltwater streams over multiple glacial cycles.Geologist 2's claim on channel carving
- Giant gravel structures are water-deposited current ripples from a flood.Geologist 1's claim on gravel structures
- Giant gravel structures are wind-deposited sand dunes formed over a long period.Geologist 2's claim on gravel structures