1797-1876

English geologist who first realized that volcanoes build up in time as rock and ash are ejected from a volcanic vent, not by catastrophic uplifts. Based on his observations of volcanic rocks in Auvergne, France, he became an advocate of the enormity of geologic time. He also recognized that earthquakes precede volcanic activity, that water and heat in lava result in fluidity, and that volatiles are an important component in lava.