Which risk increases when rapid alluvial fan deposition blocks a mountain valley outlet?

💡 Explanation

When rapid alluvial fan deposits block the valley outlet, impoundment occurs because the flowing water is obstructed. This creates a lake upstream. Therefore formation of a proglacial lake is the result, rather than debris flow, ephemeral stream, or weathering increase which involve different processes.

• Which phenomenon causes offset stream channels along transform plate boundaries?
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• Which risk increases following rapid glacial isostatic rebound?
• Which risk increases near transform plate margins during locked phases?
• Which mechanism causes liquefaction of soil during an earthquake in a saturated sandy deposit?
• Which geologic hazard increases when a dam reservoir fills near a transform fault?