had done; this helped mitigate the agency's brain drain following the departures. Knopf began at Yale as an associate professor but was promoted to full professor in 1923. He was named the Silliman Professor of Geology in 1937 and a Sterling Professor in 1938. He was director of graduate studies from 1933 until his retirement from Yale in 1951. Upon retiring he returned to his native Woodside, California, settling not far from his family's old ranch. There he accepted a visiting appointment at the Stanford University School of Earth Sciences, where he remained until his death in 1966. Knopf's field work continued through his Yale and Stanford appointments, again with a focus on western states. He continued his work in the Boulder Batholith and investigated intrusive igneous rock bodies in the Spanish Peaks in Colorado. He also contributed to the emerging field of geochronology, putting lower bounds of 2 billion years and later 4.5 billion years on the age of the Earth. Knopf was elected to the National Academy of Sciences in 1931. He was also a Fellow of the American Academy of Arts and Sciences and of the Geological Society of America. He was president of the Geological Society of America in 1944, and he received the Penrose Medal in 1959. In 1937 he was vice president of the Society of Economic Geologists. Personal life In 1908 Knopf married Agnes Burchard Dillon. They had three daughters and one son, though one of the daughters died in infancy. Agnes died in 1918 in that year's flu pandemic. In June 1920, Knopf married fellow USGS geologist Eleanora Frances Bliss, who as Eleanora Knopf became a frequent collaborator and travel companion. When Adolph moved to Yale, which did not then hire women, Eleanora worked out of Adolph's office, teaching private classes and still accepting USGS assignments. When they moved to California, Stanford hired her as a research associate. Legacy Knopf died November 23, 1966, in Palo Alto, California. In his will he endowed a chaired professorship at Yale. The sitting Adolph Knopf Professor of Petrology is Shun-ichiro Karato. Adolph and Eleanora Knopf also endowed a graduate fellowship in petrology at Stanford. Mount Adolph Knopf in Juneau Borough, Alaska is named after him. References External links Hulsite mineral data Paigeite mineral data 1882 births 1966 deaths People from Woodside, California American people of German descent University of California, Berkeley alumni United States Geological