No-plumes debate reaches the boil

It started a decade ago and gained visibility early in 1991: a split among the experts over mantle "hotspots." This summer the debate has spread and heated up.

The dissidents say that hotspots (1) aren't hot, (2) aren't spots and (3) don't arise as plumes of hot matter from the bottom of the mantle to form volcano chains like the Hawaiian Islands. They gathered at a special conference in Iceland last month to share ideas (and their papers, at www.mantleplumes.org, make fascinating reading). And since April the Geological Society Web site has been collecting a lively set of letters on the subject. The Web makes this kind of serious scientific conflict open to all kinds of spectators.