#volcanic_crater__crater  a bowl-shaped opening at the top of a volcano
  supertype:  scissure__crack__cleft__crevice__fissure  a long narrow opening
  part of:  volcano
  subtype:  caldera  a large crater caused by the violent explosion of a volcano that collapses into a depression
  subtype:  maar  a flat-bottomed volcanic crater that was formed by an explosion; often filled with water

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