Impact craters generally have a rim with ejecta around them; in contrast volcanic craters usually do not have a rim or ejecta deposits.
 As craters get larger (greater than 10 km in diameter), they usually have a central peak.
The peak is caused by a rebound of the crater floor following the impact.
 Sometimes craters will display layers in their walls.
 Since the collision that produces a crater is like a powerful explosion, rocks from deep underground are tossed unto the surface.
 Hence, craters are useful for showing us what lies deep under the surface.
Impact craters generally have a rim with ejecta around them; in contrast volcanic craters usually do not have a rim or ejecta deposits.  As craters get larger (greater than 10 km in diameter), they usually have a central peak. The peak is caused by a rebound of the crater floor following the impact.  Sometimes craters will display layers in their walls.  Since the collision that produces a crater is like a powerful explosion, rocks from deep underground are tossed unto the surface.  Hence, craters are useful for showing us what lies deep under the surface.
Ismenius Lacus quadrangle