by earlier geological activity. Extensional faults form parallel to the axis of the rift.An extensional fault may be seen as a crack in the crust that extends down at an angle to the vertical. As the two sides pull apart, the hanging wall ("hanging over" the sloping fault) will move downward relative to the footwall.A rift basin is created as the crust thins and sinks. In the rift basin, warm mantle material wells up, melting the crust and frequently triggering the eruption of volcanoes.

Extensional