U.S. geologist and petrologist, noted for his work concerning crustal evolution and the petrology of igneous rocks (igneous rock).

Poldervaart was a lecturer at the University of Cape Town from 1946 until 1949, when he joined the Bechuanaland Protectorate (now Botswana) Geological Survey; he became a member of the faculty of Columbia University in 1951. His work includes investigations of the petrogenesis (composition, occurrence, and origin) of igneous and metamorphic rocks and Precambrian (older than 570,000,000 years) geology. He specialized in applying petrologic techniques to problems of Earth history. He edited Crust of the Earth (1955) and wrote Basalts (The Poldervaart Treatise on Rocks of Basaltic Composition) (1967).