Which primary mechanism causes cyclical avulsions on the apex of an alluvial fan?

💡 Explanation

When an alluvial fan’s channel bed aggrades due to over-sedimentation, flow path instability results because reduced flow capacity causes frequent overbank floods promoting sediment deposition. Therefore, channel avulsion occurs leading to new depositional lobes, rather than changes caused by base level, tectonics, or stabilization.

• Which consequence results when overgrazing reduces bioturbation rates?
• Which process exacerbates debris flow risk on an alluvial fan originating from glacial valleys?
• Which mechanism increases the frequency of oxbow lake formation in fluvial floodplains with easily eroded cohesive soils?
• Which mechanism triggers a tsunami when a subduction zone fault ruptures offshore?
• Which change occurs in global precipitation patterns when Hadley cells widen due to polar warming?
• Which outcome occurs when repeated freeze-thaw cycles saturate high-latitude silty soils on a moderate slope?