Characteristics of a CO2-driven Cold-Water Geyser, Crystal Geyser in Utah: Experimental Observation and Mechanism Analyses

Several cold-water geysers and springs are located adjacent to the Green River in Utah where two major east-west faults, the Little Grand Wash and the Salt Wash Graben faults, trend roughly parallel to each other. Among these springs and geysers is Crystal Geyser, located immediately north of the Little Grand Wash fault and approximately 6 km south of the town of Green River. Anomalously high soil-CO2 fluxes (>700 g/m2day) have been measured along traverses perpendicular to these two fault zones. During August 4-6 and September 1-5, 2010, we performed additional CO2 flux measurements adjacent to Crystal Geyser. The highest CO2 flux recorded was approximately 1600 g/m2day. In this study, the fluid mechanics of the regularly erupting Crystal Geyser was investigated by instrumenting its conduit with pressure, temperature, pH, EC, and dissolved oxygen sensors, measuring every 1 minute during and between eruptions. Results of these measurements suggest that the time-scale of a single-eruption cycle ranges from 30 to 40 hours and is composed of four successive eruption types with two recharge periods. Current eruption patterns exhibit a bimodal distribution although previous measurements and anecdotal evidence suggests that this pattern was different prior to recent seismic activity. The geyser's eruptions are regular and predictable, and reflect pressure, temperature, EC, pH, and dissolved oxygen changes resulting from Joule-Thomson cooling, endothermic CO2 exsolution, and exothermic CO2 dissolution. An additional interesting fact is that the eruption pattern (uni- or bi-modal) and eruption duration of the Crystal Geyser have evolved since the geyser was drilled in 1936. In 1936, the geyser erupted every 15 minutes with a typical height of 25 m and approximately every 9 hours with a typical height of 45 m, showing the bi-modal eruption patterns. All historical observation before 2004 indicated that the eruption duration was less than 20 minutes. However, in 2005, the duration reached more than 2 hours. Furthermore, our dataset collected in 2010 showed that the geyser eruption has a bimodal pattern but its duration is significantly longer (B-type: 1 hour and D-type: 5 to 7 hours). The seismic events presumably have initiated movement of the Little Grand Wash fault system and disturbed the eruption patterns of the Crystal Geyser. For example, between 1960 to 1970, many seismic events with magnitude greater than 2.0 recorded adjacent to the Crystal Geyser. Perhaps, these multiple seismic events could induce the alteration of eruption intervals. Finally, one implication of this critical observation is that the known cold-water eruptive systems are likely very sensitive to tectonic stresses. If so, we suggest that engineered sequestration sites where stored CO2 may leak to the surface could be altered by such tectonic impacts.