Along the dried river bed where the petroglyphs are I discovered these holes in the rock where the early inhabitants to this area ground seeds. Try to imagine how much grinding took place to wear holes in the rock this large. The rock surface is level. it just appears slanted from the way I took the photo. Hopefully it was nicer times many hundreds of years ago and water was flowing in the river. My this just hurts my back thinking about sitting here pounding rock against rock.
The one on the left was the largest and over a foot deep.