Fired Up

So there we were watching, for lack of anything better to do (a shameful admission, I know), a show on the Discovery Channel called "Krakatoa: Volcano of Destruction". (As opposed to all those other non-destructive volcanoes of creation, I suppose.) Naturally, the term "pyroclastic flow" was used, and I began to wonder where the word came from. "Pyro-" is obvious enough; it's found in "pyrotechnics" and "pyre" and is from the Greek for "fire". But "-clastic"?

I wondered aloud what other words might use some variation of "-clastic"; I was, as usual, shortening it, changing the vowels, adding bits onto it, all in my head, all in an attempt to unpick it, and then Jim said, "Well, it's the same as in 'iconoclastic'." So it is! Smart as a whip, that one. I think I'll keep him.

An iconoclast is literally an icon-smasher; "-clastic", as it turns out, is from the Greek for "to break". A pyroclastic flow, which results from the collapse of a volcano's output, is composed of chunks of volcanic rock: "pyroclastic" means not "a breaker of fire" but "broken (up) by fire", which describes the rock content of the cloud of hot gas and solids.

By the way, "icon"--don't tell me you weren't wondering about this, too--is from the Greek "eikon", "image", which is from another Greek word meaning "to resemble".