Published by the American Geophysical Union as part of the Field Trip Guidebooks Series, Volume 186. The Nevada Test Site (NTS) was established on December 18, 1950, to provide an area for continental testing of nuclear devices. In January of 1951, testing began with an airdrop into Frenchman Flat in conjunction with Operation Ranger. In addition to airdrops, above ground testing included surface detonations, tower shots, and balloon suspensions. Underground testing began in 1957, and since 1963, all events have been buried in large-diameter drill holes or tunnels. Geologists from the U.S. Geological Survey (USGS) mapped much of the NTS region between 1960 and 1965. These maps formed the basis for subsequent studies by Lawrence Livermore National Laboratory, Los Alamos National Laboratory, Sandia National Laboratories, and the USGS. A good understanding of the stratigraphy, structure, geochemistry, and physical properties of the rocks is essential for containment of underground nuclear tests. Many of the recent geologic studies at NTS, particularly in Yucca Flat, Pahute Mesa, and Mid Valley, are aimed at understanding subsurface geology to help ensure complete containment. The potential nuclear waste site at Yucca Mountain is located approximately 100 miles (160 km) by road northwest of Las Vegas, Nevada, and situated on land controlled by three Federal |