Seymour O. Schlanger, the William Deering Professor of Geology at Northwestern University, Evanston, Ill., died June 30, 1990. Sy's work profoundly affected many areas of Earth science, including globally distributed Cretaceous black shales and their implications for paleoceanography, the subsidence history of oceanic volcanos as revealed by the diagenesis of carbonates drilled and dredged on Pacific atolls and guyots, reef facies as semiquantitative indicators of paleolatitude, the timing of (Cretaceous) Pacific oceanic volcanism, and tests of and alternatives to the fixed-hotspot hypothesis. Sy was also well known to fellow AGU members for his organizational and intellectual contributions to the Deep Sea Drilling project and its successors. Sy participated in or led four legs and was founding chairman of the Joint Oceanographic Institutions/U.S. Science Advisory Committee (USSAC).