During the 1984 field season, two research holes were cored into the Inyo chain of young rhyolite domes, which cuts across the northwest margin of Long Valley Caldera, Calif. (Figure 1). One hole slanted under the vent of Obsidian Dome and completely penetrated the conduit of the volcano. It was spudded on August 16 and reached its final depth on September 9. The second hole was sited along Glass Creek between Obsidian Dome and the next dome to the south; it intersected the rhyolite dike which underlies the chain. It was spudded on September 18 and reached final depth on October 28.