New in 2.2: Configuration expanded with weather, light, and multiple-block requirements.
Certain blocks will erode when there is water above them.
When under flowing water, stone will become gravel, dirt will become sand, and undyed hardened clay will become red sand.
When under still water, sand will become clay.
Also, Cobblestone and Stone Bricks will grow moss when adjacent to water.
As of 2.2, rain will turn hardened clay soft, and the sun will bake soft clay into hardened clay.
The original purpose of this mod was to add a renewable source of sand and gravel. It has since been expanded with powerful configuration options.
Note: because of the way this mod is programmed, no erosion will occur until the erosion is triggered. Erosion will never trigger if there are no players nearby. Once erosion is triggered, it will spread to adjacent blocks.