DAVID HARDY / SCIENCE PHOTO LIBRARY DAVID HARDY / SCIENCE PHOTO LIBRARY
Diagram illustrating the formation processes of the main types of volcanic crater. At the top is the hornito. This is a small and narrow type of crater which is formed by small explosions of lava, so the lava is still molten when it lands. In the middle is the maars type. These are typically very wide (up to 1 kilometre) but low- lying. They are formed by explosive events when ground water comes into contact with magma. At the bottom is the familiar cinder cone. These form when bubbles of gas in the magma burst, throwing lava high into the air. The lava solidifies in flight, and falls to the ground making a conical pile of loose, cinder-like dry material.
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