Source: Journal of Geophysical Research: Solid Earth
Geysers are unique, but well recognized, geological features characterized by abrupt transient eruptions of water vapor and other gases. They exist on the Earth, as well as Jupiter’s Europa, Neptune’s Triton, and Saturn’s Enceladus. On Earth they are rare with less than a thousand known and these are concentrated in a few locations with about half of the terrestrial geysers found at Yellowstone National Park in Wyoming.
Despite nearly two centuries of theorizing, laboratory mimicking, probing vents, and passive seismic monitoring, our understanding of the processes driving these transient, and sometimes dependably periodic, eruptions remains elusive. We have not been able to fully understand the active processes largely because, first, we had not really ‘seen’ the 3D structure of a geyser and, second, we had not tracked how the fluids within it may evolve with time.
The recent near surface geophysical investigations of Yellowstone’s Sprouter Geyser by Ciraula et al. [2023a, 2023b] have added considerable new information to address this problem. The authors combined ground penetrating radar (GPR), active source high resolution seismic tomography, and electrical resistivity tomography (ERT) to reconstruct Sprouter Geyser’s 3D structure to at least 15 meters depth.
They found that rocks surrounding the vent are anomalously resistive and have high seismic wave speeds, both of which indicate high levels of stiffening by silica precipitation in the pores and fractures. Unique repeated time-lapse ERT surveys further highlight distinct temporal changes in the resistivity near the top of the hydrothermal system that can only be associated with the buildup of highly resistive water vapor. These results support the ‘bubble trap’ model in which water vapor is temporarily trapped beneath liquid water.
Citations: Ciraula, D. A., Carr, B. J., & Sims, K. W. (2023a). Geophysical imaging of the shallow geyser and hydrothermal reservoir structures of Spouter Geyser, Yellowstone National Park: Geyser Dynamics I. Journal of Geophysical Research: Solid Earth, 128, e2022JB024417. https://doi.org/10.1029/2022JB024417
Ciraula, D. A., Carr, B. J., & Sims, K. W. (2023b). Time-lapse geophysical investigation of geyser dynamics at Spouter Geyser, Yellowstone National Park: Geyser Dynamics II. Journal of Geophysical Research: Solid Earth, 128, e2022JB024426. https://doi.org/10.1029/2022JB024426
—Douglas R. Schmitt, Editor, JGR: Solid Earth