Preston Cloud

Preston Ercelle Cloud Jr., known as Preston Cloud, was an American earth scientist, biogeologist, cosmologist and paleontologist who lived from 1912 to 1991 and spent his career at Harvard University and the University of California, Santa Barbara. He was the first scientist to systematically recognize the importance of the rich Cambrian fossil record in evolutionary terms, coining the term eruptive evolution in 1948 to describe how adaptive radiation in a favorable ecological setting could drive diversification from an original population. His work through the 1960s and 1970s on mineralogical differences in sedimentary rocks and on banded iron formations led him to propose the Great Oxidation Event, the pivotal turning point when the oceans and atmosphere of the Earth first became enriched in molecular oxygen. He also named the Hadean eon and authored more than two hundred scientific publications for both academic and general audiences. He received the Penrose Medal in 1976.