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.
 Since the collision that produces a crater is like a powerful explosion, rocks from deep underground are tossed onto the surface.
 Hence, craters can show 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.  Since the collision that produces a crater is like a powerful explosion, rocks from deep underground are tossed onto the surface.  Hence, craters can show us what lies deep under the surface.
Aeolis quadrangle