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Parts of a Volcano

Structure of a volcano. Image credit: NASA

Structure of a volcano. Image credit: NASA

The diagram with this article shows all the different parts of a volcano. Here’s more information about each part of a volcano.

  • Magma Chamber – A magma chamber is a large underground pool of molten rock sitting underneath the Earth’s crust. This magma is less dense than the surrounding mantle and so it seeps up to the surface through cracks and flaws in the crust. When it reaches the surface, it results in a volcanic eruption.
  • Lava – Lava is the rock expelled from a volcano during an eruption. When it first comes out, the lava can have a temperature higher than 700 degrees C. It then flows downhill from the eruption point until it cools and hardens.
  • Main Vent – A volcano’s main vent is the point in the Earth’s crust where hot magma has reached the surface. The familiar cone-shaped volcano builds up as ash, rock and lava ejected during eruptions fall back to Earth around the vent.
  • Crater – A volcanic crater is a circular depression in the ground caused by volcanic activity. A volcano’s vents are located at the bottom of the crater.
  • Pyroclastic Flow – Pyroclastic flows are fast moving currents of hot gas and rock with travel down hill from a volcano, reaching speeds of 700 km/hour. The gas can reach temperatures of more than 1,000 degrees C, and is one of the greatest dangers from volcanic eruptions.
  • Ash Cloud – Volcanic ash consists of small pieces of pulverized rock and glass created during volcanic eruptions. These fragments are so small, and heated to such a temperature that they can be carried in the air for many kilometers.
  • Volcanic Bombs – Volcanic bombs are chunks of lava blasted into the air which solidify before they reach the ground. Some bombs can be extremely large, measuring 5-6 meters in diameter and landing more than 500 meters from the volcanic vent.
  • Secondary Vent – On large volcanoes, magma will reach the surface through several different vents, and not just the main vent. This can form cones, eject lava, and cause destruction.
  • Secondary Cone – Secondary cones build up around secondary vents on larger volcanoes.

We have written many articles all about volcanoes for Universe Today. Here’s an article about different types of volcanoes, and here’s an article about composite volcanoes.

Want more resources on the Earth? Here’s a link to NASA’s Human Spaceflight page, and here’s NASA’s Visible Earth.

We have also recorded an episode of Astronomy Cast about Earth, as part of our tour through the Solar System – Episode 51: Earth.



Fraser Cain is the publisher of Universe Today. He's also the co-host of Astronomy Cast with Dr. Pamela Gay.

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