An impact crater is caused by the high-velocity collision of a smaller projectile with the larger body of a planet or a planetary object. Because impact craters are usually caused by meteorites, they are often called “meteorite craters.” Impact craters generally have a roughly circular outline and a raised rim. The size of an impact crater can range anywhere from a small, simple, shallow depression in the ground to an extremely large, multi-ringed basin.
The impact craters on Earth are not usually easy to recognize due to many years of erosion and weathering. Famous impact craters include Meteor Crater in Arizona and Chicxulub on the Yucatan coast in Mexico. Most scientists believe the meteor that hit Chicxulub is the one that led to the extinction of the dinosaurs at the end of the Cretaceous period. It is interesting to note that the Chicxulub crater is far below the surface of the earth and cannot be seen by the naked eye.
A volcanic crater is a circular depression in the ground caused by volcanic activity. It is typically a basin, circular in form within which occurs a vent (or vents) from which magma erupts as gases, lava, and ejecta. A crater can be of large dimensions, and sometimes of great depth. During certain types of climactic eruptions, the volcano’s magma chamber may empty enough for an area above it to subside, forming what may appear to be a crater but is actually known as a caldera.