When a volcano erupts, it’s spewing forth lava, ash and hot rock. But where does this material come from, and how does it get to the surface? A volcano conduit is the pipe or vent at the heart of a volcano where material wells up from beneath the surface.
The surface of the Earth is relatively cool, but things get hotter as you descend beneath the ground. When you get about 30 km down (beneath the continents), you reach the Earth’s mantle. This is region of the Earth where rocks can be heated to more than 1,000 degrees C. Because of this high heat and pressure, liquid rock squeezes out of the mantle and collects in magma chambers beneath the Earth’s crust. The magma is “lighter” than the surrounding rock, so it floats to the surface, finding its way though cracks and faults in the crust. Eventually it reaches the surface and erupts as a volcano.
The volcano conduit is the pipe that carries this magma from the magma chamber, up through the crust and through the volcano itself until it reaches the surface. Stratovolcanoes, the largest kind of volcano, can have entire networks of volcano conduits inside them, and they can have eruptions from the central crater at the top, or from volcanic vents on the side.
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After an eruption, the lava can cool and harden in the volcano conduit forming a hard plug. In some cases the plug causes the volcano to build up additional pressure and have an explosive eruption. In other cases, the volcano goes extinct, and the hard plug is all that remains when the rest of the volcano erodes away. Some of the most beautiful natural structures are these volcanic necks perching up above the surroundings.
We have written many articles about volcanoes for Universe Today. Here’s an article about dormant volcanoes, and here’s an article about extinct volcanoes.
We have also recorded an episode of Astronomy Cast about Earth, as part of our tour through the Solar System – Episode 51: Earth.