Why do some fresh earthquake fault scarps become rounded faster than others?
Show answer & explanation
Answer: Their loose sediment moves downhill easily
Their loose sediment moves downhill easily ✓ — A scarp rounds when loose surface material is moved off the steep face and into lower spots. Gravity, rain, soil creep, and small slides all help redistribute that debris, so easier sediment transport means faster smoothing. The useful mental model is a pile slowly spreading downhill, not a cliff being polished from the outside.
They started out much taller — A taller scarp has more relief to lose, so height is a tempting clue. But height alone cannot explain why similar scarps age at different speeds in different climates or surface materials. The shape changes fastest when loose material is actually carried away from the steep part.
Their bedrock is simply denser — Denser bedrock can matter for many geologic questions, but the visible rounding mostly happens in the loose cover on the surface. If that cover barely moves, the scarp can stay sharp even over dense rock. Surface transport controls the rounding more directly than rock density.
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