What's the source of magma at the bottom of the vent called?

The source of magma at the bottom of the vent is called magma chamber. This where all the vents are fed with magma and transport it to the surface. The magma chambers are like a big underground pool of liquefied rock (magma), and under the immense pressure the magma is released on the surface through the vents.

Answer barren with few trees, in the northern hemisphere;

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