Remembering David Blackwell

David Blackwell, founder of the SMU Geothermal Laboratory and Professor Emeritus, passed away on July 16. Blackwell was the third holder of the William B. Hamilton Chair in Earth Sciences in Dedman College and was renowned for his studies of the thermal structure of the continental crust.

Blackwell was a major proponent of the commercialization of geothermal energy – a renewable resource derived from the heat that originates from the Earth’s interior. A founding member of the Geothermal Resources Council (now Geothermal Rising), Blackwell also played an important role with the creation of the International Geothermal Association. His leadership in developing the U.S. Department of Energy's National Geothermal Data System continues to impact the development of geothermal energy to this day.

Geothermal industry expert Walter “Dick” Benoit notes that Blackwell’s research helped develop a detailed understanding of complex temperature profiles in geothermal systems and introduced the concept of how the temperature profiles change with time in dynamic geothermal systems. Blackwell’s legacy, he said, is carried by his students, the attendees of workshops that he hosted over the life of his career, and through the SMU Geothermal Database, the primary geophysical data set that the geothermal industry first looks to acquire in assessing geothermal prospects in the United States.

Blackwell’s legacy includes two maps representing major contributions to the earth sciences: the Geological Society of America’s Decade of North American Geology (1992) Geothermal Map of North America and the American Association of Petroleum Geologist’s Geothermal Map of North America (2004). In 2004, the detail of the original map was dramatically increased by including data from oil exploration of sedimentary basins and again in 2011 for the continental USA. These maps and the related databases stored at SMU still provide the foundation future work on the thermal structure and the economic potential of the crustal heat. 

Blackwell earned a B.S. in geology and mathematics at SMU in 1963, followed by M.S and Ph.D. degrees in geophysics at Harvard University by 1967. He completed his dissertation work under the direction of geophysicist Francis Birch, a seminal figure in the history of solid Earth geophysics. A member of the SMU faculty since 1968, he served as chair of the Department of Geological Sciences (now Earth Sciences) from 1982-1986.

Blackwell is renowned for his studies of the thermal structure of the continental crust. In his Ph.D. dissertation, he measured temperature/depth profiles in mining bore holes in the western United States along with thermal conductivities of rocks from the same drill holes. His Harvard graduate student colleagues, Robert Roy and Edward Decker, pooled their data from similar research projects to join him along with their advisor Francis Birch on an influential 1968 paper presenting 138 new heat flow measurements for the United States, a major achievement for its time providing the road map for all future continental heat flow determinations.

Starting in 1968, the Harvard group (Birch, Blackwell, Decker and Roy) in different combinations recognized the relationship between surface heat flow and radioactive heat production. Blackwell’s early work showed that the heat flow out of the continental crust was mixture of deeply-sourced heat (the whole Earth) and shallowly-sourced heat in equal or greater proportions from in situ shallow crustal radioactivity.

Blackwell’s dissertation work on heat flow in continental crustal rocks was taking place in parallel with the plate tectonic revolution and exploration of Earth’s ocean basins. Geophysical data collected from the seafloor indicated that the oceanic crust operated much differently than the continental crust; heat flow data for the oceans became one of the fundamental pieces of evidence for plate tectonics. His work on the thermal structure of sedimentary basins, the Pacific Northwest basalt flows, Cascades and the Basin and Range province of the western USA is important for understanding the origin of oil and gas and geothermal systems, a renewable source of future clean energy.

From 2006 to 2018, Blackwell and his colleague, Maria Richards, began a series of nine conferences hosted by the SMU Geothermal Laboratory that promoted the potential of geothermal energy covering topics on the science, the technology, public policy, the law, and finance.

Blackwell was a fellow of the Geological Society of America. He supervised two dozen graduate student dissertations with students going on to have careers in industry, government laboratories, and academia as well as numerous undergraduate students.

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