What makes a volcano erupt? How does the lava get so hot? What would be the biggest volcano eruption that you have heard of?

Ruth-Anne

Hi Ruth-Anne,

1. A volcano erupts when the pressure within the molten magma below the surface becomes stronger than the strength of the rocks on the surface. The magma then finds the path of least resistance to the surface and erupts. The magma pressure comes from the expansion of gas bubbles that are within the magma.

2. The heat source for all erupted materials comes from natural radioactive decay within the Earth. The concentration of radioactive elements in the Earth is not really very high, but the volume of the Earth is great enough so that there is enough of a contribution of heat from the decay to produce melting. The material that melts (magma) has a lower density and it migrates to the surface to erupt.

3. There probably isn't a very good idea of which eruption was the biggest. The main problem is that as we go back in time the ability to tell the details of eruptions (or any geologic event) get harder and harder to determine. Certainly some of the biggest eruptions have been those from Yellowstone and Long Valley, in the western United States. Fortunately, these were a very long time ago and we haven't had to deal with anything nearly as big as them during human history.

Sincerely,

Scott Rowland

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