David Varnes was born on 5 April 1919 and had a distinguished career in geology spanning more than 60 years. Following graduation from the California Institute of Technology with Honors (1940) and a year of graduate study at Northwestern University, he began a lifelong association with the US Geological Survey in 1941. By 1945, Dave was supervising studies of mineral deposits in the San Juan Mountains. His classic USGS Professional Paper on this work, in which he was able to relate the mineralisation to structure by directly comparing the theoretical discontinuity pattern with that mapped, admirably demonstrated Dave's ability to integrate geological observations with theoretical analyses.
In 1948 Dave joined the newly formed USGS Engineering Geology Branch, under Ed Eckel, where he was able to pursue his strong interest in the application of geology to engineering problems, particularly with regard to landslides. An outstanding example of this was his study of the ground conditions for the new Air Force Academy at Colorado Springs. The subsequent paper, with Glen Scott, won the Geological Society of America's Burwell Award in 1970. In parallel, Dave began a 40-year study of landslide classification, for which he is probably best known internationally. His paper in the Highway Research Board book on Landslides and Engineering Practice (1958) together with its revisions (1978 and, with David Cruden, 1996) established a worldwide standard for such classification.
After serving as Chief of the USGS Engineering Geology Branch (1961-64) Dave was involved in engineering geological mapping and assessment of slope stability around Anchorage, following the 1964 earthquake. A perceptive 1974 paper on the logic of engineering geological maps applied in practice brought him an unprecedented second Burwell Award. His work on engineering geological mapping and landslide hazard zonation was stimulated by a commission from the International Association of Engineering Geology (IAEG), which resulted in a seminal UNESCO publication in 1984. This work was recognised by the French government in 1985, when Dave was made Chevalier de L'Ordre des Palmes Academiques. His involvement with the IAEG led Dave to set up and chair an American IAEG Regional Group. Subsequently, the IAEG honoured David with their highest award, the Hans Cloos Medal.
From about 1970, his other interests included creep to failure and, sagging features in the Rocky Mountains (with Dorothy Radbruch-Hall). This creep work absorbed him increasingly, as he attempted, through careful analysis of case records and theoretical work, to predict volcanic eruptions, large landslides and earthquakes. The earthquake-related work, exemplified by his 1996 paper with Chuck Bufe, may well be his most enduring contribution.
David married Helen Dowling of the USGS in 1943, and it was through Helen's work on landslides that he developed his career-long interest in that field. After Helen's death (1964) he married Katherine Buck, also a USGS geologist, who survives him.
David Varnes was an incisive geologist, a true scholar and a gentleman.
John Hutchinson