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Geysers are unique hydrothermal features, requiring specific geometry, fluid, and vapor input, and heat to produce eruptions. In a geyser eruption, the decompression of superheated hydrothermal fluids results in a conversion of thermal to kinetic energy. Recent studies conclude that a laterally offset cavity structure (bubble trap) plays an integral role in the geyser eruption process. In this second study of Spouter Geyser, Yellowstone National Park (YNP), we build on the geyser structure developed in the first publication and explore how structural components, such as the bubble trap, control eruption dynamics. We utilize time‐lapse electrical resistivity tomography (ERT) and transient electromagnetics (TEM) geophysical methods to track changes in the saturation of conductive hydrothermal fluid and resistive vapor through the eruption cycle. Additionally, we use pressure‐temperature transducer data to measure eruption and recharge durations over the past 23 years at Spouter Geyser, identifying long‐period trends in geyser behavior. The geophysics results support the bubble trap model, capturing an increase in resistivity in the bubble trap structure during the recharge phase interpreted as a vapor saturation increase. The TEM also captures a resistivity increase in the 20–30 m depth interval during the eruption phase, interpreted as a vapor‐dominated "flash eruption zone" where the superheated hydrothermal fluids flash into steam and drive fluid out of this zone during the eruption. From the temperature time‐series detailing 23 years of eruption and recharge durations, we find that eruption durations have remained constant at ∼2 hr while recharge durations have decreased linearly at 6.6 min/year. Plain Language Summary: Current geyser eruption models include a bubble trap structure, a laterally offset, subsurface cavity that pressurizes with hydrothermal fluid and vapor before an eruption. Hydrothermal fluid conducts electrical current more efficiently than hydrothermal vapors, and thus the two phases have different electrical resistivity properties, a measurable geophysical parameter. Here, we pioneer the application of active, time‐lapse electrical and electromagnetic geophysical methods, sensitive to the subsurface electrical resistivity properties, to track hydrothermal fluid and vapor through a geyser system at Spouter Geyser, Yellowstone National Park. Through this, we expand on conclusions of Spouter Geyser's structure (Geyser Dynamics I) by investigating the movement of hydrothermal fluids and vapors to contribute to the understanding of geyser eruption dynamics. We find that electrical resistivity at the top of the geyser hydrothermal reservoir increases while the geyser is not erupting, indicative of vapor buildup in a bubble trap structure. We also find that electrical resistivity increases in a section of the geyser hydrothermal reservoir during the eruption, interpreted as hydrothermal vapors flashing to steam and driving fluids to the surface. Finally, we investigate eruption durations over the past two decades at Spouter Geyser, revealing constant average eruption durations but an increase in eruption frequency. Key Points: Time‐lapse electrical and electromagnetic methods track changes in hydrothermal fluid and vapor saturations in Spouter Geyser's structureTime‐lapse geophysics informs a conceptual model of eruption dynamics at Spouter Geyser that supports the bubble trap geyser modelA 6.6 min/year decrease in Spouter Geyser's average recharge duration over the last 23 years offers insight into long‐duration behavior [ABSTRACT FROM AUTHOR]