1870-1949

American geologist who analyzed igneous rocks. Educated at Columbia University, Fenner briefly worked as an assayer and surveyor for mining companies. He accepted a position with the Carnegie Institution's geophysical laboratory in Washington, D.C. Fenner studied how minerals form and crystallize, especially volcanic rocks in South and North America. He also examined radioactive rocks and how they represent geological age. Fenner assessed geological composition and steam pressure in core samples from Yellowstone National Park's geyser.