High-velocity impact can deliver force at the tip of a point which is exceptionally high relative to the point’s small size.  Sometimes this can initiate flakes which propagate down one or both faces of the point.  The impact fractures are usually initiated by bending or wedging, although conchoidal initiations can also occur.  Due to the disproportionate force relative to point’s mass, the crack path is often unstable, creating closely-spaced or ‘stacked’ undulations on the impact scar.