Don Thomas grew up in Maryland, and attended Dickinson Collge, earning a BS in Physics and Chemistry. He received a Master's in Chemistry in Oregon (Graduate Institute of Science and Engineering). He was then recruited by the University of Hawaii at Manoa to study volcanoes, and received a Ph.D. in Chemistry.
DT spent the next four decades working at UH as a research scientist. His areas of interest include geothermal energy, water resources, and gas emissions from volcanoes. Early on, he became interested in core drilling, in which rock samples are extracted from the ground in sequential cores, providing a rich geologic history of the area. The many drilling projects that were funded under DT's leadership allowed for models of groundwater storage to be refined, and provided new discoveries about the history of the formation of the Big Island.
In 1995, Don Thomas was appointed Director of the Center for the Study of Active Volcanoes, and immediately set about writing grant proposals to expand the program. Funding from FEMA supported the CSAV Outreach program, allowing continuation of public seminars and expansion to teacher training workshops and school visits to educate the public about natural hazards and mitigation.
As Director of CSAV, DT received generous funding from the USGS Volcano Disaster Assistance Program to support the International Training Program held in Hawaii each summer. By 2020, over 260 participants to this course have come from 30 countries, returning home with knowledge and techniques to better monitor dangerous volcanoes in their countries, and with a brotherhood of cooperation between the participants, formed by working with one another in field and class.
In 1998, DT was appointed PI for the newly established Cooperative Agreement between UH Hilo and the USGS Hawaiian Volcano Observatory. This collaborative partnership resulted in research projects between the two organizations, including hiring of students, post-docs and full-time assistants, as well as providing equipment needed by researchers.