Yellowstone Caldera Chronicles is a weekly column written by scientists and collaborators of the Yellowstone Volcano Observatory. This week's contribution is from Shaul Hurwitz, research hydrologist with the U.S. Geological Survey, and Patrick Muffler, emeritus research geologist with the U.S. Geological Survey.

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Yellowstone's diverse hydrothermal features have attracted numerous scientists ever since Ferdinand V. Hayden led the geological survey of northwestern Wyoming in 1871 and Yellowstone National Park was established in 1872. One of the most distinguished researchers and staunchest supporters of Yellowstone was the late Don White (1914-2002) of the U.S. Geological Survey (USGS). Don had a significant impact on hydrothermal research in Yellowstone, and his testimony before Congress, together with former park superintendent John Townsley, is what gave Yellowstone its protection under the Geothermal Steam Act's amendments in 1970.

Don's career was devoted almost entirely to the study of hydrothermal processes in the Earth's crust, focusing on both active geothermal systems and extinct hydrothermal systems now represented by mineral deposits. His papers on the thermal waters of volcanic origin and on magmatic, connate, and metamorphic waters provided much of the framework for interpreting the unique chemical compositions of thermal waters in volcanic systems such as Yellowstone, and they are still widely cited more than six decades after they were published.

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Don had a passionate interest in understanding how geysers work. His innovative studies and meticulous field observations at Steamboat Springs and Beowawe in Nevada utilized many types of scientific investigation methods that included drilling into the hydrothermal system. His research led to a classic journal paper on geyser activity published in 1967. Based on what Don had learned about geysers in Nevada, he was the first to warn the National Park Service of the sensitivity of geysers and hot springs to even minimal human-induced exploitation. Don worked closely with park naturalist George Marler documenting the response of Yellowstone's geysers to the 1959 magnitude 7.2 Hebgen Lake earthquake. This earthquake, which occurred about 30 miles (48 kilometers) northwest of the Upper Geyser Basin, profoundly affected hot springs and geysers in Yellowstone. White and Marler reported that, by the day after the earthquake, at least 289 springs in the geyser basins had erupted as geysers; of these, 160 were springs with no previous record of eruption. Based on their work, White and Marler concluded that "Geysers are exceedingly complex hot springs, no two of which are alike".

In the 1960s Don White led a large USGS multidisciplinary research effort at Yellowstone that included research drilling. The study produced a unique set of data and an improved understanding of the three-dimensional distribution of water temperature, pressure, chemistry, and mineralogy in the hydrothermal system. Results of this effort allowed for objective science to be brought to bear on the issue of preserving natural geyser activity in those places where geothermal development might occur. The lessons learned from this effort were major contributions to understanding of not only Yellowstone's hydrothermal system, but hydrothermal systems worldwide.

Don was also the leader of an extensive research project on the geology and remarkable thermal activity of Norris Geyser Basin adjacent to the north rim of the Yellowstone Caldera. The study generated a detailed geologic map of the basin and characterized the wide range of thermal water chemical compositions and inferred their origins. The study also provided detailed descriptions of alteration minerals in core from depths of up to almost 1100 feet (335 meters), where the measured temperature was 460 degrees Fahrenheit (238 degrees Celsius). These unique alteration minerals form when thermal waters react with the volcanic rocks in the basin's subsurface.

Under Don's leadership, two seminal journal papers that were published in 1971 are still gold standards. The first paper describes areas where most of the heat and water are discharged at the ground surface as steam ("vapor dominated zones"). The second paper describes the deposits from large hydrothermal explosions in Yellowstone's Lower Geyser Basin and analyzes the processes that drive these eruptions.

Don received many prestigious awards from professional societies in recognition of his significant achievements and his impact on the scientific community, including being elected as a member of the U.S. National Academy of Sciences. Don was an inspiration to hundreds, even thousands, of scientists at the USGS, the National Park Service, and from around the world.