Plugging Away Under Pressure: Silica Sealing and Petrologic Evolution Preceding the 2024 Hydrothermal Explosion at Black Diamond Pool, Yellowstone National Park
Category: Research Poster
Author(s): Sophia Caunt
Presenter(s): Sophia Caunt
Mentors(s): Phillip Kondracki
Hydrothermal explosions occur when pressurized liquid water in the subsurface flashes to steam due to rapid depressurization. On July 23, 2024, Black Diamond Pool in Biscuit Basin of Yellowstone National Park violently exploded, depositing siliceous sinter, obsidian-rich sandstones, gravels, clays, conglomerates, and breccias around the pool and damaging the boardwalk. This investigation aims to characterize the degree of alteration and petrologic textures of obsidian-rich sandstones ejected by this hydrothermal explosion. Additionally, thin sections of hydrofractured breccia and an intensely silica-sealed unit, informally known as “the cork”, will be analyzed using a polarized light microscope to determine mineral assemblages and textural relationships. Furthermore, scanning electron microscopy and electron probe microanalysis (EPMA) will assist in further identifying mineralogy, alteration phases, and quantifying silica deposition. The hypothesized trigger for the 2024 explosion involves priming by progressive silica precipitation within a confining sedimentary unit which reduces porosity and permeability and promotes the buildup of pressurized hydrothermal fluids within the subsurface. Eventually the pressure builds to a point where it overcomes the strength of the confining rock and the system explodes. Thus, mineral alteration and silica deposition along veins and fractures may provide insight into the evolution of system sealing prior to the explosion. By researching the development of geologic units via hydrothermal deposition and alteration, the conditions that cause hydrothermal explosions may be better constrained, assisting development of predictive models and geothermal hazard management for visitors, stewards, and scientists in Yellowstone.