Bill Evans, PhD
My research focused on volcanic volatiles and water-rock interaction in geothermal systems.
Gases are an important factor in volcanic hazards because of their role in driving explosive eruptions and their intrinsic toxicity. Part of the answer to, “What could happen?” at a restless volcano comes from gas studies. The mechanism of gas generation at depth and gas migration up through boiling hydrothermal systems, cold groundwaters, and the unsaturated zone are all complex processes that are only partly understood. The goal of my research is to use gas flux, composition, and isotope values to refine our general understanding of these processes and to apply this information to studies that focus on the behavior and hazards of individual volcanoes. The research involved identifying the areas of highest interest, planning the field investigations, determining the most appropriate sampling protocol, analyzing for the bulk composition and isotopic characteristics of the gas, and interpreting and publishing the results.
Science and Products
Dissolved gases in hydrothermal (phreatic) and geyser eruptions at Yellowstone National Park, USA
The Lassen hydrothermal system
Hydrothermal response to a volcano-tectonic earthquake swarm, Lassen, California
Monitoring ground-surface heating during expansion of the Casa Diablo production well field at Mammoth Lakes, California
Origins of geothermal gases at Yellowstone
Developing a new, passive diffusion sampling array to detect helium anomalies associated with volcanic unrest
Magmatic gas emissions at Holocene volcanic features near Mono Lake, California, and their relation to regional magmatism
Hydrothermal monitoring in a quiescent volcanic arc: Cascade Range, northwestern United States
Crustal migration of CO2-rich magmatic fluids recorded by tree-ring radiocarbon and seismicity at Mammoth Mountain, CA, USA
Prodigious degassing of a billion years of accumulated radiogenic helium at Yellowstone
Geochemical investigation of the hydrothermal system on Akutan Island, Alaska, July 2012
Ca, Sr, O and D isotope approach to defining the chemical evolution of hydrothermal fluids: example from Long Valley, CA, USA
Non-USGS Publications**
**Disclaimer: The views expressed in Non-USGS publications are those of the author and do not represent the views of the USGS, Department of the Interior, or the U.S. Government.
Science and Products
Dissolved gases in hydrothermal (phreatic) and geyser eruptions at Yellowstone National Park, USA
The Lassen hydrothermal system
Hydrothermal response to a volcano-tectonic earthquake swarm, Lassen, California
Monitoring ground-surface heating during expansion of the Casa Diablo production well field at Mammoth Lakes, California
Origins of geothermal gases at Yellowstone
Developing a new, passive diffusion sampling array to detect helium anomalies associated with volcanic unrest
Magmatic gas emissions at Holocene volcanic features near Mono Lake, California, and their relation to regional magmatism
Hydrothermal monitoring in a quiescent volcanic arc: Cascade Range, northwestern United States
Crustal migration of CO2-rich magmatic fluids recorded by tree-ring radiocarbon and seismicity at Mammoth Mountain, CA, USA
Prodigious degassing of a billion years of accumulated radiogenic helium at Yellowstone
Geochemical investigation of the hydrothermal system on Akutan Island, Alaska, July 2012
Ca, Sr, O and D isotope approach to defining the chemical evolution of hydrothermal fluids: example from Long Valley, CA, USA
Non-USGS Publications**
**Disclaimer: The views expressed in Non-USGS publications are those of the author and do not represent the views of the USGS, Department of the Interior, or the U.S. Government.