sand win transition contracting in sand & soil erosion means soil loss through wind / water / animals ->  soil erosion caused by water will cause grooves in soil  soil erosion caused by water will cause grooves in soil & squirrels is a mean of land -> rainwater can cause grooves in soil rainwater can cause grooves in soil  attacks can effect values in sand & a riverbank is made of soil -> rainwater can cause grooves in a riverbank