Q&A: How Hot Can Lava Get?


Q. Is all volcanic magma the same temperature?

A. The temperature of magma inside a volcano — and of lava as it emerges — is highly variable and depends in part on the chemical composition of the molten rock.

The heat has been described as ranging from that inside a pizza oven to that in Dante’s Inferno. One type of magma, called felsic or rhyolitic, is about 65 percent to 75 percent silicon dioxide; its temperature is roughly 1,112 to 1,472 degrees Fahrenheit.

An intermediate type of magma, at about 55 to 65 percent silicon dioxide, ranges from 1,472 to 1,832 degrees Fahrenheit. The mafic or basaltic magma, which is only about 45 to 55 percent silicon dioxide, can be a very hot 1,832 to 2,192 degrees Fahrenheit.

Molten rock that glows red is probably in the felsic temperature range. Orange is hotter, in the intermediate range, and yellow is hotter still, in the mafic range.

Kilauea releases mafic magma, and the temperature at eruption is about 2,140 degrees Fahrenheit. By comparison, Mount St. Helens spewed cooler lava, about 1,472 degrees Fahrenheit.

The lava surface cools off very quickly as it contacts the air, dropping hundreds of degrees a second. Water flowing into a hot crater can get heated and trapped, and then escape explosively, carrying aloft large chunks of rock.


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