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Facts about Craters for Kids

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.

  • 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.
  • In the majority of typical volcanoes, the crater is situated at the top of a mountain formed from the erupted volcanic deposits such as lava flows and tephra.
  • Volcanoes that terminate in such a summit crater are usually of a conical form.
  • Other volcanic craters may be found on the flanks of volcanoes, and these are commonly referred to as flank craters.
  • Some volcanic craters may fill either fully or partially with rain and/or melted snow, forming a crater lake.
  • A crater may be breached during an eruption, either by explosions or by lava, or through later erosion.
  • Some volcanoes, such as maars, consist of a crater alone, with scarcely any mountain at all.
  • These volcanic explosion craters are formed when magma rises through water-saturated rocks and causes a phreatic eruption.
  • Volcanic craters from phreatic eruptions often occur on plains away from other obvious volcanoes.

Impact Crater

  • An impact crater is an approximately circular depression in the surface of a planet, moon, or other solid body in the Solar Systemor elsewhere, formed by the hypervelocity impact of a smaller body with the surface.
  • In contrast to volcanic craters, which result from explosion or internal collapse, impact craters typically have raised rims and floors that are lower in elevation than the surrounding terrain.
  • Meteor Crater is perhaps the best-known example of a small impact crater on Earth.
  • Impact craters are the dominant geographic features on many solid Solar System objects including the Moon, Mercury, Callisto, Ganymede and most small moons and asteroids.
  • In early literature, before the significance of impact cratering was widely recognised, the terms cryptoexplosion or cryptovolcanic structure were often used to describe what are now recognised as impact-related features on Earth.
  • The cratering records of very old surfaces, such as Mercury, the Moon, and the southern highlands of Mars, record a period of intense early bombardment in the inner Solar System around 3.9 billion years ago.
  • Although Earth’s active surface processes quickly destroy the impact record, about 170 terrestrial impact craters have been identified.
  • Few undersea craters have been discovered because of the difficulty of surveying the sea floor, the rapid rate of change of the ocean bottom, and the subduction of the ocean floor into Earth’s interior by processes of plate tectonics.
  • Daniel Barringer (1860–1929) was one of the first to identify an impact crater, Meteor Crater in Arizona; to crater specialists the site is referred to as Barringer Crater in his honor.
  • On Earth, ignoring the slowing effects of travel through the atmosphere, the lowest impact velocity with an object from space is equal to the gravitational escape velocity of about 11 km/s.
  • Impacts at these high speeds produce shock waves in solid materials, and both impactor and the material impacted are rapidly compressed to high density.
  • It is convenient to divide the impact process conceptually into three distinct stages: (1) initial contact and compression, (2) excavation, (3) modification and collapse.
  • The cavity continues to grow, eventually producing a paraboloid (bowl-shaped) crater in which the centre has been pushed down, a significant volume of material has been ejected, and a topographically elevated crater rim has been pushed up.
  • Some of this impact melt rock may be ejected, but most of it remains within the transient crater, initially forming a layer of impact melt coating the interior of the transient cavity.
  • At the largest sizes, one or more exterior or interior rings may appear, and the structure may be labeled an impact basin rather than an impact crater.
  • Complex-crater morphology on rocky planets appears to follow a regular sequence with increasing size: small complex craters with a central topographic peak are called central peak craters, for example Tycho; intermediate-sized craters, in which the central peak is replaced by a ring of peaks, are called peak-ring craters, for example Schrödinger; and the largest craters contain multiple concentric topographic rings, and are called multi-ringed basins, for example Orientale.
  • The distinctive mark of an impact crater is the presence of rock that has undergone shock-metamorphic effects, such as shatter cones, melted rocks, and crystal deformations.