A volcano is an opening in a planet or moon'south crust through which molten rock, hot gases, and other materials erupt. Volcanoes often form a hill or mountain every bit layers of stone and ash build upward from repeated eruptions.

Volcanoes are classified every bit active, dormant, or extinct. Active volcanoes have a recent history of eruptions; they are likely to erupt again. Dormant volcanoes have non erupted for a very long fourth dimension just may erupt at a future time. Extinct volcanoes are not expected to erupt in the time to come.

Within an active volcano is a chamber in which molten rock, called magma, collects. Pressure builds upwardly within the magma sleeping accommodation, causing the magma to move through channels in the rock and escape onto the planet'due south surface. Once it flows onto the surface the magma is known as lava.

Some volcanic eruptions are explosive, while others occur as a dull lava menses. Eruptions tin can occur through a main opening at the top of the volcano or through vents that form on the sides. The rate and intensity of eruptions, too as the composition of the magma, determine the shape of the volcano.

Volcanoes are institute on both land and the sea floor. When volcanoes erupt on the ocean floor, they often create underwater mountains and mountain ranges every bit the released lava cools and hardens. Volcanoes on the bounding main floor become islands when the mountains get so large they ascent to a higher place the surface of the ocean.

Volcanoes

Volcanic eruptions can create colorful and dramatic displays, such as this eruption of this volcano in the Virunga Moutains of the Congo-kinshasa.

active volcano

Noun

volcano that has had a recorded eruption since the final glacial flow, about 10,000 years ago.

dormant volcano

Noun

volcano that has erupted in the past but is unlikely to erupt soon.

erupt

Verb

to explode or suddenly squirt fabric.

lava

Noun

molten rock, or magma, that erupts from volcanoes or fissures in the Earth'south surface.

Noun

molten, or partially melted, stone beneath the Globe's surface.

molten

Describing word

solid material turned to liquid by heat.

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    Director

    Tyson Brownish, National Geographic Guild

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    National Geographic Society

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    Sarah Appleton, National Geographic Society
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    Last Updated

    April 5, 2019

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