Which mechanism most directly enhances stream downcutting into bedrock in humid temperate climates?

💡 Explanation

When streams transport sediment, abrasion occurs as the sediment particles grind against each other and the bedrock channel, physically eroding it. Therefore, abrasion by sediment and bedrock is the dominant downcutting mechanism rather than frost wedging, dissolution, or root penetration, which are less directly related to stream flow.

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