Thumping Cycle Variations of Doublet Pool in Yellowstone National Park, USA.

Doublet Pool is an active hydrothermal feature in Yellowstone National Park, USA. Approximately every half hour, it thumps for about 10 min due to bubbles collapsing at the base of the pool. To understand its thermodynamics and sensitivity to external factors, we performed a recurring multiple‐year passive seismic experiment. By linking recorded hydrothermal tremor with active thumping, we determine the onset and end of thumping, and the duration of silence between each thumping cycle. The silence interval decreased from around 30 min before November 2016 to around 13 min in September 2018. This change followed unusual thermal activity on the surrounding Geyser Hill. On a shorter time scale, wind‐driven evaporative cooling can lengthen the pre‐thumping silence interval. Based on energy conservation, we determine the heating rate and heat needed to initiate thumping to be 3–7 MW and ∼6 GJ, respectively. Plain Language Summary: Doublet Pool is a hot spring in Yellowstone that has thumping cycles in which bubbles collapse underwater, producing vibrations that people can hear and feel. We placed two seismometers next to Doublet Pool to time its thumping cycles and analyze how they change over time. Strong winds lengthen the thumping interval by removing energy through the pool's surface. Over time scales of months to years, the duration of thumping cycles is controlled by changes in heating and pressurization from the hydrothermal system beneath Doublet Pool. Key Points: We observe short and long‐term variations in the thumping cycle recorded by two geophones deployed between 2015 and 2021On hourly to daily time scales, the time to initiate thumping correlates with the wind speedOn monthly to yearly time scales, cycle variations reflect changes in heating rate that vary by a factor of about 2 [ABSTRACT FROM AUTHOR]