Which outcome results when base level falls sharply during alluvial fan formation?

💡 Explanation

Fan entrenchment occurs because knickpoint migration causes channels to cut downwards, rather than deposit sediment; this triggers channel incision up-fan, which decreases deposition and changes drainage patterns on the fan's surface; therefore A, rather than alternatives that suggest stability or increased deposition.

• Which geographic effect on regional climate results when a mountain range obstructs prevailing winds?
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• Which outcome occurs when rapid snowmelt increases river discharge past the original design height of levees?