Hannah is comparing a rock from a riverbed and a rock from deep underground. One is very smooth, and the other has very rough edges. Explain why each rock was probably found in that location.
The rock found in the riverbed that is smooth is from the result of weathering of water in the river and erosion. The rock deep underground was most likely a product of erosion. The dirt and ground above it were eroded and displaced there to cover the rock.
