Despite more than 200 years of scientific study, the internal dynamics of geyser systems remain poorly characterized. As a consequence, there remain fundamental questions about what processes initiate and terminate eruptions, and where eruptions begin. Over a one-week period in October 2012, we collected down-hole measurements of pressure and temperature in the conduit of an exceptionally regular geyser (132 s/cycle) located in the Chilean desert. We identified four stages in the geyser cycle: (1) recharge of water into the conduit after an eruption, driven by the pressure difference between water in the conduit and in a deeper reservoir; (2) a pre-eruptive stage that follows the recharge and is dominated by addition of steam from below; (3) the eruption, which occurs by rapid boiling of a large mass of water at the top of the water column, and decompression that propagates boiling conditions downward; and (4) a relaxation stage during which pressure and temperature decrease until conditions preceding the recharge stage are restored. Eruptions are triggered by the episodic addition of steam coming from depth, suggesting that the dynamics of the eruptions are dominated by geometrical and thermodynamic complexities in the conduit and reservoir. Further evidence favoring the dominance of internal processes in controlling periodicity is also provided by the absence of responses of the geyser to environmental perturbations (air pressure, temperature and probably also Earth tides).

We compare and contrast data collected in 2012 and 2014 from the El Tatio geyser field, Chile. We identify geyser systems that evolve over time, including changes in the interval between eruptions, development of new thermal features, and interactions between geysers. We study three different cases: (a) an isolated geyser, which is periodic and has nearly identical eruptions every cycle; (b) a geyser and coupled noneruptive pool, where the geyser has nonregular cycles and several preplay eruptions before the main eruption; and (c) two geysers and a mud volcano, which have nonregular cycles and are all interacting. Though geysers erupt with different styles, we recognize some common features: the conduit recharges with liquid during the quiescent period, bubbles enter the conduit before eruptions, and eruptions occur when water boils in the upper part of the conduit. The episodic addition of heat may govern the periodicity, while the depth where heat is added dictates the eruption style: conduits with deeper heat input are more likely to show preplay or minor eruptions. The interactions between thermal features can be explained by pressure transmission in subsurface permeable layers between geyser conduits.

Palisade fabric is a ubiquitous texture of silica sinter found in low temperature (<40°C) regimes of hot spring environments, and it is formed when populations of filamentous microorganisms act as templates for silica polymerization. Although it is known that postdepositional processes such as biological degradation and dewatering can strongly affect preservation of these fabrics, the impact of extreme aridity has so far not been studied in detail. Here, we report a detailed analysis of recently silicified palisade fabrics from a geyser in El Tatio, Chile, tracing the progressive degradation of microorganisms within the silica matrix. This is complemented by heating experiments of natural sinter samples to assess the role of diagenesis. Sheathed cyanobacteria, identified as Leptolyngbya sp., were found to be incorporated into silica sinter by irregular cycles of wetting, evaporation, and mineral precipitation. Transmission electron microscopy analyses revealed that nanometer-sized silica particles are filling the pore space within individual cyanobacterial sheaths, giving rise to their structural rigidity to sustain a palisade fabric framework. Diagenesis experiments further show that the sheaths of the filaments are preferentially preserved relative to the trichomes, and that the amount of water present within the sinter is an important factor for overall preservation during burial. This study confirms that palisade fabrics are efficiently generated in a highly evaporative geothermal field, and that these biosignatures can be most effectively preserved under dry diagenetic conditions.

We performed field measurements at a geyser nicknamed “El Cobreloa,” located in the El Tatio Geyser Field, Northern Andes, Chile. The El Cobreloa geyser has two distinct eruption styles: minor eruptions and more energetic and long‐lived major eruptions. Minor eruptions splash hot water intermittently over an approximately 4 min time period. Major eruptions begin with an eruption style similar to minor eruptions, but then transition to a voluminous liquid water‐dominated eruption, and finally end with energetic steam discharge that continues for approximately 1 h. We calculated eruption intervals by visual observations, acoustic measurements, and ground temperature measurements and found that each eruption style has a regular interval: 4 h and 40 min for major eruptions and ∼14 min for minor eruptions. Eruptions of El Cobreloa and geochemical measurements suggest interaction of three water sources. The geyser reservoir, connected to the surface by a conduit, is recharged by a deep, hot aquifer. More deeply derived magmatic fluids heat the reservoir. Boiling in the reservoir releases steam and hot liquid water to the overlying conduit, causing minor eruptions, and heating the water in the conduit. Eventually the water in the conduit becomes warm enough to boil, leading to a steam‐dominated eruption that empties the conduit. The conduit is then recharged by a shallow, colder aquifer, and the eruption cycle begins anew. We develop a model for minor eruptions which heat the water in the conduit. El Cobreloa provides insight into how small eruptions prepare the geyser system for large eruptions.