to wear away by the action of water, wind, or glacial ice.
wear away, in this case by water and rocks constantly rubbing
become ground down or deteriorate; "Her confidence eroded"
remove soil or rock; "Rain eroded the terraces"
To wear away by wind, water or other forms of abrasion.
To wear (something) away by or as if by abrasion, for example, waves eroded the shore; to make or form by wearing away, for example, the river eroded a deep valley.
To wear away gradually. To cause to deteriorate.
to wear away gradually by erosion. [AHDOS