Volcano Power

“The violent eruption of Mount St. Helens [in Washington State] on May 18 of last year was one of the most closely monitored, most intensively photographed and most fully documented volcanic eruptions in history,” says Scientific American magazine. The article observes that the power of such eruptions is often described in terms of the energy of a nuclear explosion​—in this case, the equivalent of a 400-megaton bomb, or “eight times more powerful than that of the largest nuclear device ever detonated.” But this method of comparison is said to be somewhat misleading because nuclear explosions occur in an instant, while the Mount St. Helens eruption was spread over nine hours. A more accurate comparison, the article suggests, would be the “serial detonation of some 27,000 Hiroshima-size bombs: nearly one a second for nine hours.” The magazine also notes that “the eruptions of the past century are probably only small samples of the volcanic energy still at the earth’s command.”​—March 1981, page 68.