crater

A crater is a roughly circular indentation on a planetary surface, typically formed by an impact, volcanic activity, or collapse of material. The term applies to both impact craters and volcanic craters; larger depressions created by collapse are often called calderas, though the terms are related rather than identical.

Impact craters range from simple bowl-shaped pits to complex structures with terraced rims, flat floors, and sometimes a central peak. Simple craters are generally smaller; larger ones develop central peaks and multi-ring basins as the crust rebounds after excavation. Volcanic craters form at vents where magma erupts and can be filled by lava or collapse into basins.

Formation of an impact crater begins when a meteoroid strikes the surface, releasing energy, excavating material, and ejecting debris. Volcanic craters form during eruptions or by volcanic collapse. On Earth, weathering and sedimentation often erase craters. On the Moon, Mars, and other bodies with thin atmospheres, many craters are well preserved for billions of years.

Notable craters include Meteor Crater in Arizona, Chicxulub in the Yucatán, and the Vredefort impact structure in South Africa. On the Moon, prominent examples are Tycho and Copernicus. Craters are found on all solid bodies in the solar system and are used to study surface age and planetary history.

Studying craters informs planetary geology, impact physics, and hazard assessment, providing clues to the history of a body’s surface and the frequency of energetic impacts in the solar system.