A vent is a single opening through which magma escapes to the earth's surface as lava.
A crater is a bowl-shaped depression or hollow at the top of the volcano. It may contain a lake called a crater lake.
A central passageway called a pipe joins the crater to the vent.
A magma chamber below the volcano contains the magma.
A violent eruption may blast off the top of the cone so that the crater becomes enlarged. This enlarged crater is called a caldera.
Viscous acid lava that solidifies in the central pipe of a volcano formed a spine or a volcanic plug. The volcanic plug in an extinct volcano is exposed when the volcanic cone is eroded. An example is the Devil's Tower in Wyoming, the USA.
A solfatara is a vent through which vapour and sulphur-enriched gases are emitted.
A fumarole is a vent through which mainly steam from superheated water is released.
A geyser is a violent ejection of hot water and steam through a vent. Most of the geysers in the world are found in Iceland, North Island of New Zealand and Yellowstone National Park in the USA.
A hot spring is formed when heated water with dissolved minerals flows back to the earth's surface quietly and continuously.
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