The Valles-Toledo caldera complex is famous as the site of early research on caldera formation and for its caldera-hosted, high-temperature geothermal system. Scientific drilling in the west half of the complex, sponsored by the Office of Basic Energy Services of the Department of Energy (DOE), is part of a long-term program to answer basic questions about caldera formation processes, silicic volcanism, high-temperature hydrothermal systems, and volcanogenic ore bodies.
A DOE workshop to evaluate the drilling was held October 18–20, 1989, in Los Alamos, N. Mex.; about 50 scientists came. The purpose was to review the progress of research and to consider the scientific merit of continuing corehole drilling as proposed in the original scientific management plan [Goff and Nielson, 1986]. At the end of the first day, a long discussion was held to determine if results so far justified the expense of continuing the program. The answer was unequivocal: Yes. The next question was, Where should the next corehole be located?