Adolph Knopf

Adolph Knopf was an American geologist born December 2, 1882, in San Francisco, California, who died November 23, 1966, in Palo Alto, California, and who worked primarily as a petrologist and mineralogist, contributing later in his career to geochronology; he conducted extensive fieldwork in Alaska, Montana and California investigating mineral deposits and igneous rock formations, discovered the minerals hulsite and paigeite in Alaska, studied tin deposits on the Seward Peninsula as the basis of his doctoral dissertation, and proposed geochronological lower-bound estimates for the age of the Earth, first around two billion years and later around four and a half billion years. He worked for the United States Geological Survey from 1906 to 1920, held successive positions at Yale University from 1920 to 1951 including the Silliman professorship and the Sterling professorship of geology, and held a visiting appointment at Stanford University from 1951 to 1966. He was elected to the National Academy of Sciences in 1931, served as president of the Geological Society of America in 1944, was a fellow of the American Academy of Arts and Sciences, and received the Penrose Medal in 1959.