Which process primarily creates the conical structure observed in alluvial fans?

💡 Explanation

Alluvial fans form at mountain bases because stream gradients abruptly decrease. This reduction causes rapid sediment deposition via decreased flow competence of the river; therefore, coarser materials are deposited first towards the apex, creating the characteristic fan shape, rather than other processes.

• Which mechanism significantly increases flood risk in an alluvial river system after deforestation in the upstream drainage basin?
• Which ecosystem change results when sequential pyroclastic flows deposit stratified materials atop one another?
• Which cave formation process stops completely during droughts?
• Increased stratification hinders vertical mixing within gyres causing what?
• Which morphological change dominates when high-viscosity rhyolitic lava cools?
• Which process leads to gradual sediment transport breakdown of barrier islands?