NATIONAL ACADEMY OF SCIENCES AARON CLEMENT WATERS 1905–1991 A Biographical Memoir by CLIFFORD A. HOPSON Any opinions expressed in this memoir are those of the author and do not necessarily reflect the views of the National Academy of Sciences. Biographical Memoirs COPYRIGHT 2006 NATIONAL ACADEMY OF SCIENCES WASHINGTON, D.C. Department of Earth Sciences, University of Claifornia, Santa Barbara AARON CLEMENT WATERS May 6, 1905–May 18, 1991 BY CLIFFORD A. HOPSON ARON C. WATERS, ONE OF the leading volcanologists of the A twentieth century, passed away on May 18, 1991, at age 86 in Tacoma, Washington. Professor Waters, best known for his pioneering work on the Columbia River Basalt, led the way also in other studies of basaltic volcanism in the Pacific Northwest, the mechanics of basaltic lava flows, the development of lava-tube cave systems, and violently explo- sive basaltic volcanism recorded by maar-type volcanoes. This expertise led directly to his participation in studies of lunar geology as the U.S. space program got underway, including composition and origin of the lunar surface, the assessment of Apollo landing sites, and geologic training of the Apollo astronauts. But it was the breadth of Aaron Waters’s geo- logic accomplishments, rather than specialization, that marks his distinguished career. He made important contributions to our understanding of calc-alkaline volcanism, to grani- toid batholiths and their hypabyssal intrusive complexes, to deep-seated metamorphism, and to the geomorphic evolu- tion of landscapes as well as facets of structural and eco- nomic geology. The Pacific Northwest region was the focus of his diversified studies, and he was regarded for many years as the leading geologic authority on that region. Yet, his studies extended also to other parts of the United States, 4 BIOGRAPHICAL MEMOIRS the world, and the Moon. Professor Waters was known, too, as an outstanding mentor of graduate students, the coau- thor of a leading textbook on the principles of geology, the builder of distinguished geology departments in leading universities, and, late in his career, a valued geologic con- sultant to federal research organizations. BEGINNINGS AND EARLY DIRECTIONS Aaron Waters was born in Waterville, Washington, on May 6, 1905, the son of pioneer parents and the youngest of seven children. His early years were spent on the family homestead and wheat ranch near Waterville, on the west- ern edge of the Columbia River Plateau in the shadow of the Cascade Mountains. He worked on the ranch during his youth and helped to run it at age 12 and 13 during the last years of World War I, when his older brothers went off to war. Following graduation from high school, Aaron en- tered the University of Washington, supporting himself by work in a gas station and other jobs. He began prelaw stud- ies but later changed to geology, partly from his love of the out-of-doors but influenced especially by his college friend Richard E. Fuller, who later became both a distinguished geologist and a long-time director of the Seattle Museum of Art. Waters earned a B.Sc. in geology (cum laude) in 1927 and an M.Sc. in 1928, both from the University of Washing- ton. Waters continued his studies at Yale University, known for its program in geology and development of leaders in that field. He earned his Ph.D. in 1930 under the mentorship of Professor Adolph Knopf. His dissertation, “Geology of the Southern Half of the Chelan [30'] Quadrangle, Wash- ington,” provided the basis for several outstanding papers, and had a lasting influence on the direction of his career. The eastern part of his map area overlapped the Columbia AARON C. WATERS 5 River Plateau, one of the world’s great outpourings of tholei- itic plateau basalt. His doctoral study of those lavas was a first step toward later preeminence in the study of plateau basalts and leadership in establishing the stratigraphy of the Columbia River Basalt Group. The western part of the Ph.D. map area exposed the pre-Tertiary crystalline base- ment of the North Cascades. Here his work encompassed both the bedrock geology and the geomorphology, also lead- ing to important publications. THE STANFORD YEARS: PART 1, 1930-1941 The first taste of university teaching came during his doctoral studies at Yale, where Waters served as instructor in the Geology Department (1928-1930). Teaching proved congenial and complimentary to his research interests, and it was here that his ability to stimulate and motivate stu- dents first blossomed. Here, too, the choice of a career was determined and with his scholarly reputation growing, Wa- ters accepted appointment as assistant professor of geology at Stanford University. He soon rose to professor and re- mained at Stanford for 21 years (1930-1951). Waters’s early research was not yet focused on volcanic rocks but reflected broad interests in Pacific Northwest re- gional geology, interests that spanned igneous and meta- morphic petrology, geomorphology, and tectonics. His stat- ure and reputation grew as the excellence of his published research during the prewar period (1930-1941) became widely recognized and appreciated. Two influential papers soon emerged from continued work on the bedrock geology of his Washington field area: “A Petrologic and Structural Study of the Swakane Gneiss” (1932) and “Petrology of the Con- tact Breccias of the Chelan Batholith” (1938). The latter was the first of several perceptive studies of granitoid plu- ton emplacement and crystallization. 6 BIOGRAPHICAL MEMOIRS Aaron’s interest in geomorphology vied with that in petrology during his early years at Stanford. He deciphered the complex record of Pleistocene glaciation, where the continental ice sheet—advancing across and retreating from the Columbia River Plateau—had dueled with the alpine glaciers flowing down from the Cascade Mountains. Their interaction is brilliantly documented in “Terraces and Cou- lees along the Columbia River near Lake Chelan, Washing- ton” (1933). His “Resurrected Erosion Surface in Central Washington” (1939) was followed later by other papers (e.g., 1955) that describe the geomorphic evidence for Neogene deformation of the southwestern margin of the Columbia River Plateau and uplift of the Cascade Mountains. These and other aspects of Aaron’s early studies in north-central Washington and his coeval projects in Oregon (e.g., 1927, 1929, 1935), along with his exceptional breadth spanning volcanism, plutonism, metamorphism, geomorphology, and tectonics contributed to Aaron’s growing reputation as an expert on regional geology of the Pacific Northwest. Aaron Waters’s arrival at Stanford also ignited a new interest (cataclasites and mylonites) launched by his discov- ery of those distinctive rock types along the San Andreas Fault zone near Crystal Springs Lake. The San Andreas was an enigma back then: It was thought to be a “big” fault from the contrasting rocks on each side, but its huge strike- slip displacement was not yet recognized. Mylonites had first been described along faults in Scotland, so their occur- rence here within the San Andreas Fault zone seemed con- sistent with a fault-related origin. With doctoral student Charles Campbell he studied the rocks petrographically, reviewed the occurrence of similar rocks elsewhere, and devised a descriptive and genetic classification for mylonitic rocks (1934) that remained authoritative for many years. AARON C. WATERS 7 His papers led to a Guggenheim Fellowship for studies in Scotland and Scandinavia in 1938-1939, where other mylonites reinforced his awareness of the role of penetra- tive mechanical deformation in developing fine-grained, banded crystalline rocks. It was therefore no accident that his next major field study, with doctoral student and later distinguished professor Konrad Krauskopf, addressed the unique banded granodioritic rocks that bordered the east- ern side of Washington’s Okanogan Valley. Their resulting paper, “The Protoclastic Border of the Colville Batholith, Washington” (1941), attracted wide interest. Known now as the Okanogan gneiss dome and recognized as one of a semicontinuous belt of metamorphic core complexes that extend from southern Arizona to British Columbia, it records the penetrative deformation of midcrustal crystalline rocks and hypersolidus mushes, later brought to the surface dur- ing crustal extension. But the fundamental role of protoclastic deformation—the penetrative crushing, granulation, and neo- recrystallization of rock in the presence of an interstitial melt phase—first established by Waters and Krauskopf, re- mains valid today. Another aspect of Professor Waters’s Guggenheim studies in Scotland, however, had greater influence on the direc- tion of his future work. His examination of the Tertiary volcanic centers and ring-dike complexes on the Inner Hebrides islands of Mull, Ardnamurchan, and Skye returned his attention to basaltic volcanism and its shallow plutonic connections, This became a focus of his research. THE WAR YEARS (1942-1945) AND AFTERMATH World War II intervened, and Waters took leave from Stanford to join the U.S. Geological Survey’s expanded ex- ploration program for strategic minerals, deemed vital to the war effort. Mercury was among those essential metals 8 BIOGRAPHICAL MEMOIRS whose known reserves were limited, and Waters teamed with other volcanologists—mercury ores being associated with volcanic and subvolcanic rocks—to improve the inventory. His introduction to mercury (quicksilver) deposits had be- gun in the prewar years in southwestern Oregon (1935), and these were now the focus of his war-related fieldwork in Arkansas, Oregon, and elsewhere in the western United States. Resulting U.S. Geological Survey (USGS) publica- tions appeared in 1951. Beyond the primary purpose of strategic mineral assessment, this work extended Waters’s grasp of regional volcanism in Oregon, and the volcanogenic processes that concentrated trace elements. A brief return to ore deposits research came with Waters’s participation in the USGS’s uranium exploration program on the Colorado Plateau (1951-1952), where volcanogenic processes once again proved important (1953).