Grove Karl Gilbert - Meteor Crater

Meteor Crater

In 1891 in one of the most controversial moves of his career, he proclaimed that Meteor Crater in Arizona (then referred to as Coon Butte) was the result of a volcanic steam explosion rather than an impact of a meteorite. Gilbert had based his conclusions on a belief that for an impact crater, the volume of the crater including the meteorite should be more than the ejected material on the rim and also a belief that if it was a meteorite then iron should create magnetic anomalies. Gilbert's calculations showed that the volume of the crater and the debris on the rim were roughly equal. Further there were no magnetic anomalies. Gilbert argued that the meteorite fragments found on the rim were just "coincidence." Gilbert would publicize these conclusions in a series of lectures in 1895. Subsequent investigations would reveal that it was in fact a meteor crater. Ironically, Gilbert would be among the first to say that the moon's craters were caused by impact events rather than volcanos.