The diagram above shows clearly the formation of the triangular faced scarps seen on very young faults. Stream erosion fed by snow melt and drainage from higher elevations cutting through the uplifted block forms V shaped erosion channels carrying the water down to the level of the dropped block. The remaining face of the block is still well defined because the longer term forces of rain and wind erosion have not yet significantly altered the exposed rock.
The presence of these well defined triangular faces of scarps, as seen in a photograph of the Teton fault scarp, is a certain sign of a young fault.
