Cordilleran Section - 115th Annual Meeting - 2019

Paper No. 9-12
Presentation Time: 9:00 AM-6:00 PM


HARRISON, Lauren1, KELLER, William E.2 and HUNGERFORD, Jefferson2, (1)Lawrence Livermore National Lab, (2)National Park Service, Yellowstone Center for Resources, Yellowstone National Park, WY 82190

Yellowstone National Park’s Norris Geyser Basin is a dynamic hydrothermal system that is the hottest and one of the most acidic basins in the Park. It has been speculated that ground deformation, earthquake activity, flux of magmatic fluids, Earth tides, and climatic cycles all may have an effect on Yellowstone’s geyser activity. Real-time observations of thermal feature chemistry, behavior, and temperature provides the opportunity to examine the interactions between these factors and explore how rare events may be triggered.

This study collected pH, temperature, specific conductance, and high-precision location data on 916 thermal features in Norris Geyser Basin during the summer of 2018. During the same time period, the World’s largest geyser, Steamboat, erupted a record-setting 32 times (the previous record was 29 eruptions in 1964). Concurrently, tectonic faults ~25 km west of Norris Geyser Basin at Maple Creek experienced a swarm of increased seismic activity. There was also above average snow water equivalent and total precipitation in 2017-2018, as well as discharge of Tantalus Creek during April-June 2018. The inventory of Norris thermal features in 2018 captures a snapshot of the hydrothermal system during this unique period.

The pH of 75% of Norris thermal features were between 2-4 (pH 2-3=28.3%; pH 3-4=46.7%), maintaining Norris’ position as one of the most acidic basins. Specific conductance correlates with the concentration of dissolved geothermal solutes and is highest in the lowest pH features. The median value was ~2000S/cm with 95% of features above 1000S/cm, confirming a strong influx of geothermal water to the majority of Norris features. Comparing 2018 data to a 2007 inventory show that 79% of features decreased in specific conductance, 60% increased in temperature, and there was no change in pH. We speculate that the hotter temperatures in 2018 relative to 2007 may reflect a more direct and voluminous connection between deep magmatic hydrothermal waters and the shallow meteoric system that experienced both greater mass and heat exchange in 2018, possibly augmented by the seismic and deformational unrest. Statistical analysis has the potential to further probe the possible connection between increased precipitation, subsurface unrest, and hydrothermal system changes.