Explosive eruptions and meteorite impacts both leave bowl-shaped scars. A crater is a roughly circular depression formed by either volcanic activity or the collision of an extraterrestrial body. Volcanic craters sit at the summits of many cones; impact craters can appear anywhere.

Volcanic craters form when magma is blasted out or when the ground collapses into an emptied chamber. Impact craters excavate and eject target rock, often producing raised rims and central peaks in larger examples. Erosion eventually softens their profiles.

Fresh craters expose deep rock layers and provide natural laboratories for studying shock metamorphism or volcanic processes. On other planets and moons, crater counts help estimate surface ages. On Earth, most ancient impact structures are recognized by shocked minerals and distinctive circular geophysical anomalies.

• Bowl-shaped depression from eruption or impact
• Volcanic craters occur at vent sites
• Impact craters excavate and eject rock
• Useful for dating planetary surfaces