Journal of Volcanology and Geothermal Research 323 (2016) 129–147

Contents lists available at ScienceDirect

Journal of Volcanology and Geothermal Research

journal homepage: www.elsevier.com/locate/jvolgeores

Modeling and observations of geyser activity in relation to catastrophic landslides–mudflows (Kronotsky nature reserve, Kamchatka, Russia)

Alexey Kiryukhin

Institute of Volcanology & Seismology FEB RAS, Piip 9, Petropavlovsk-Kamchatsky 683006, Russia Kronotsky Federal Nature Biosphere Reserve, Ryabikova 48, Elizovo 684000, Russia article info abstract

Article history: This study reports and interprets observational data of geyser cycling in the Valley of Geysers and Uzon hydro- Received 15 December 2015 thermal systems between 2007 and 2015. The monitoring of the Velikan and Bolshoy Geysers after the cata- 14 May 2016 strophic landslide on 3.06.2007 (which dammed and created Podprudnoe Lake, drowning some geysers) and Accepted 16 May 2016 before a mudflow on 3.01.2014 (which destroyed the dam and almost completely drained Podprudnoe Lake) Available online 18 May 2016 shows that the interval between eruptions (IBE) of the Bolshoy Geyser decreased from 108 to 63 min and that Keywords: the IBE of the Velikan Geyser slowly declined over three years from 379 min to 335 min. The seasonal hydrolog- Geysers ical cycle of the Velikan Geyser shows an increase in the IBE during winter (average of 41 min). The dilution of the Kamchatka chloride deep components of the Bolshoy (−23%) and Velikan Geysers (−12%) is also observed. A local TOUGH2 Landslide model of the Velikan Geyser is developed. This model is used to describe the transient thermal hydrodynamic and

Modeling CO2 changes in a Velikan Geyser conduit during the entire cycling process by using cyclic, time-dependent TOUGH2 boundary mass flow conditions (major eruption discharge and sub-cyclically assigned CO2 mass flow recharge Velikan into the base of the geyser conduit and water recharge at the mid-height of the geyser conduit) and a constant mass flow of water into the geyser at depth. This model also indicates a seepage element at the conduit's top to allow pre-eruptive discharge and a buffering isothermal reservoir below to compensate for pressure declines from major eruptions at earlier times. A local TOUGH2 model is successfully calibrated against temperature ob- servations at both the mid-height and base of the conduit of the Velikan Geyser, which shows the essential role of the above parameters in describing the functionality of the geyser. A reservoir model of shallow production gey- sers is also developed. This 2D model is used to describe changes in the thermal hydrodynamic state and evolving chloride concentrations in the areas of most prominent discharge, both at steady state and when perturbed by cold water injection from Podprudnoe Lake and other cold water sources (after 3.06.2007). A “well on deliver- ability” option is used to model the geyser discharge features in the model. The modeled increases in geyser dis- charge that is caused by an increase in the reservoir pressure from cold water injection reasonably matches observations of IBE decreases in the Bolshoy (~58%) and Velikan Geysers (~9%). The modeling also shows the possibility of chloride dilution in the Velikan Geyser but no dilution in the Bolshoy Geyser. The latter observation is attributed to the presence of direct cold water inflow into the Bolshoy Geyser conduit. © 2016 Elsevier B.V. All rights reserved.

1. Introduction Averiyev, V. I. Belousov, B. V. Ivanov, V. I. Kononov, V. M. Sugrobov, V. A. Droznin, V. L. Leonov, N. G. Sugrobova, etc.) revealed that the Valley 1.1. Brief history of the exploration of the Valley of Geysers of Geysers' hydrothermal system has the greatest natural discharge of the twelve highest-temperature Kamchatka hydrothermal systems, The Valley of Geysers is located in the Kronotsky State Nature Re- with an approximate discharge rate of 300 kg/s and water temperature serve on the Kamchatka Peninsula. This region was first discovered by of 100 °С. At least 57 geysers have been discovered (Sugrobov et al., T. I. Ustinova on April 14, 1941 (Ustinova, 1955) in the canyon of the 2009), and explorers have conducted systematic observations of the ac- Geysernaya river basin, which is 8 km long and 400 m deep. Geological tivity cycle of 13 geysers (Pervenetz, Troynoy, Konus, Maly, Bolshoy, and hydrogeological studies that were conducted in 1960–1970 (V. V. Schel, Fontan, Velikan, Zhemchuzhny, Gorizontalny, Rozovy Konus, Burlyaschy, and Vosmerka). The Valley of Geysers has significant touris- tic, scientific and educational value because it is the only place in Russia E-mail address: [email protected]. where one can watch the activity of geysers, use these observations to

http://dx.doi.org/10.1016/j.jvolgeores.2016.05.008 0377-0273/© 2016 Elsevier B.V. All rights reserved. 130 A. Kiryukhin / Journal of Volcanology and Geothermal Research 323 (2016) 129–147 understand the conditions of the formation of hydrothermal systems the water temperature in the chamber reaches the boiling point for (discharge conditions, heat sources, reservoir structure, and role of the the hydrostatic pressure that is produced by the water-filled conduit caprock), and explore the potential of geothermal energy. (Steinberg et al., 1981). This model was numerically tested by N.M. The number of visitors to the Valley of Geysers reaches 3000 people Saptadji (1995) with the AUTOUGH2 program. The model geometry annually. Therefore, identifying the mechanisms of geyser formation, was assigned as a vertical 12 m and 0.1 m2 cross-section, highly perme- the parameters of the hydrothermal system, and the factors that control able conduit (8e−8m2) that was connected to a less permeable hydrothermal explosions and landslides is important, as is monitoring (2.5e−10 m2), large-volume “cold water” reservoir (75 °C, 2.1 bars) these parameters to predict possible catastrophic natural phenomena at the bottom. A “hot water” mass source of 1 kg/s and 853 kJ/kg and assess the impact of changes in the discharge/recharge conditions (200 °C) was also specified at the bottom of the conduit (chamber). on the geyser regime, which survived disastrous landslides and mud- The above model successfully demonstrated cycling with an flows in 2007 and 2014. This article describes and discusses recent re- IBE ≈ 15 min and eruption flowrates of 9–16 kg/s. The model also sults (from 2007 to 2014) of hydrogeological regime monitoring for reproduced the characteristics of the known Whakarewarewa geysers the Velikan and Bolshoy Geysers and modeling approaches that explain (Pohutu, Feathers and Waikorohihi) and checked the model's sensitiv- the changes in the geyser activity. ity to the input parameters (cold water reservoir recharge, pressure, temperature, etc.). 1.2. Brief overview of the worldwide experience of geyser observations and The chamber (or bubble-trap) model was recently supported by modeling multiple instrumental (seismometer, tilt meter, and temperature radar) observations of the Lone Star geyser (Yellowstone) (Karlstrom Natural geysers (cyclically erupting springs of boiling water) are et al., 2013; Vandemeulebrouck et al., 2014), which yielded estimates found in a few places around the world, the most famous of which are of various geyser parameters (a 3-hour IBE, a four-phase cycling period located in Iceland (Haukadalur basin), the United States (Yellowstone with a 28-min major eruption duration, and a 20.8 m3 eruption volume Park), New Zealand (Rotorua) and Russia (Kronotsky Reserve) that was discharged) and revealed continuous hydrothermal tremors in (Rinehart, 1980). Geyser observations is a subject that involves numer- the geyser conduit and in an area to the northeast, where the source ous scientific research applications, which began from simply visually reservoir's “bubble trap” was assumed to be located. This trap suggested counting the number of cycles per day (since 1937 in Yellowstone) a compressed vapor store of thermal and mechanical energy that is re- and progressed to continuous logging with temperature sensor records leased during eruptions and relaxation. The bubble trap model in the since 2003 (Hurwitz et al., 2008). The transient data that are used to un- Valley of Geysers was discussed by Belousov et al. (2013). derstand the features of the cycling activity of geysers (geyser eruption Some laboratory experimental studies were designed to test concep- intervals, GEI, or intervals between eruptions, IBE) include the height tual models, including recent studies (Toramaru and Maeda, 2013; and duration of eruptions; the eruption volumes; the chemical compo- Adelstein et al., 2014). In particular, these models (Adelstein et al., sition of the discharged fluid; the local barometric pressure, tempera- 2014) provide insight into the roles of pre-play and the bubble-trap ture and wind; the reservoir water recharge conditions (estimated structure during the geyser eruption process (pure water component based on a local river's discharge); local, regional and global seismic fluid). The transport of vapor up the conduit during pre-play events events; and tidal and tectonic stress deformations (Rojastczer et al., warms the conduit, moving the system closer to the required boiling 2003; Husen et al., 2004; Hurwitz et al., 2008, 2012, 2014). Despite state for eruption. The position of the bubble trap structure allows for the easy access to observations of the characteristics of surface erup- vapor accumulation below the upper conduit and the episodic release tions, the geometry of geyser conduits has rarely been described in de- of the vapor and its enthalpy. tail, with exceptions including the chamber-shaped dormant Te Waro The main outcomes of the long-term geyser monitoring studies at geyser in Whakarewarewa, Rotorua (Rinehart, 1980) and the vertically Yellowstone (Rojastczer et al., 2003; Husen et al., 2004; Hurwitz et al., shaped Old Faithful geyser in Yellowstone (Hutchinson et al., 1987). 2008, 2012, 2014) are the following: (1) the IBE's (interval between The mechanisms of cyclic eruption are conceptually explained and eruptions) sensitivity to seasonal hydrological recharge conditions experimentally verified in terms of three basic models: (1) a chamber (more recharge and higher reservoir pressures shorten the IBE, while (or bubble trap) model (Rinehart, 1980; Vandemeulebrouck et al., windier and colder winter conditions cause heat loss at the top and 2014), (2) a well model (Droznin, 1980; Ingebritsen and Rojstaczer, lengthen the IBE of pool geysers); (2) the IBE's sensitivity to neighbor- 1996; Lu et al., 2005), and (3) a mixing model (Steinberg et al., 1981). ing hydraulically connected geyser eruptions; (3) the IBE's sensitivity The well model (“well” with a possibility of relatively cold recharge to local, regional and global earthquakes (dynamic pressures greater from the top) was numerically tested by Ingebritsen and Rojstaczer than 0.1 MPa), which can significantly affect the permeability of geyser (1996) with the Hydrotherm program. Geyser cycling (cyclic increase conduits (the IBE increases or decreases as earthquake effects accumu- in the flowrate at the top of up to 40 kg/s) was successfully performed late); and (4) the IBE's lower sensitivity to short-period barometric (less in a highly permeable conduit at 200 m depth in a low permeability en- than 5 mbars) and tidal deformations. Recently monitoring of the El Jefe vironment with a 2 MW heat source at the bottom and fixed state (1 bar, geyser in Chile (Munoz-Saez et al., 2015) demonstrated the lack of re- 100 °C) atmospheric conditions at the top. Some outputs of this study sponses to environmental perturbations (air pressure, temperature included the appearance of a steam phase at the bottom to initiate and probably Earth tides). This study also noted the periodic release of high discharge near the top and the sensitivity of the IBE to the conduit's steam bubbles from the reservoir system below, which triggered geyser porosity, permeability contrast, relative permeability (a change from eruptions. Nevertheless, an example of a geyser that was sensitive to the linear to Corey relative permeabilities switched the cycling to a bimodal atmospheric pressure was found in Waiotapu, New Zealand, where the regime), top pressure and temperature, depth and cross-sectional area Wai O Tapu geyser stops/starts cycling when the atmospheric pressure of the conduit. Another type of well model was tested by Lu et al. passes a threshold value of ~1010/1015 hPa (Davidson, 2014). New

(2006), who found that adding a non-condensable gas (CO2) compo- Zealand's experience with geysers and water level monitoring for the nent made 12-min cycling viable in a 70 m-deep and 0.1 m-diameter exploitation of Whakarewarewa-Rotorua shows the possibility to iden- well that was recharged by fluids at a rate of 0.2 kg/s, temperature of tify periodic variations for both anthropogenic and barometric distur-

87 °C, and mass fraction of CO2 = 3000 ppm at the bottom. These au- bance in the range of 2.8–5.2 mm-H2O when the Earth tidal thors found that the IBE was sensitive to the mass fraction of CO2 and amplitudes are less than 1 mm-H2O(Leaver and Unsworth, 2007). the recharge flowrate. The mixing model (conduit with the possibility of two contrasting recharges from the bottom) assumes that an eruption will occur when A. Kiryukhin / Journal of Volcanology and Geothermal Research 323 (2016) 129–147 131

1–2 2. Geological setting & landslides–mudflows on 03.06.2007 & pyroclastics (αQ3 ); 6 — aquifer (αβQ1–2)basaltlavas,7— an aquifer 03.01.2014 of Pliocene tuffs, basalts and sandstones; and 8 — a basement that is composed of Tertiary sedimentary basins (Fig. 2). 2.1. Geological setting (according to Leonov, 2009) 2.3. Initial thermal discharge conditions The age of the Uzon–Geysernaya caldera (Fig. 1) was estimated to be 39,600 ± 1000 years according to the radiocarbon dating of soil samples The geysers' hydrothermal system includes three discharge areas: below the caldera-forming ignimbrites. Uzon–Geysernaya pre-caldera i) the Lower Geysers field (geysers and boiling springs), ii) the Upper deposits comprise dacite–andesite tuffs and lavas that are 40,000– Geysers field (including geysers, boiling springs, and fumarole areas), 1–2 3 3 140,000 years old (αQ3 , αQ3, and Q3 ust). Initially, this caldera was and iii) Death Valley (steam and gas discharge area). The main thermal an isolated hydrological basin, where volcanogenic and sedimentary discharge zone strikes in a WSW-ENE direction and is hosted in pre- 4 lake deposits were formed (Q3). These deposits, which have thicknesses caldera Upper Pleistocene units of lake tuffs and sedimentary deposits 3 up to 400 m near the caldera rim, are represented by layered pumice that are complicated by a dyke complex (Q3ust). This zone is traced by tuffs and minor breccias and conglomerates. Caldera lake deposits are boiling springs and geysers that discharge at a total estimated rate of overlain by 15,000–20,000-year-old rhyolite–dacite lavas, which 260–300 kg/s. Another significant thermal discharge zone is present to formed large domes and adjacent lava flows up to 100–150 m thick the NNW–SSE (parallel to the caldera rim) and is traced by fumaroles 4 4 (ξQ3 and αξQ3). and steaming ground in the Upper Geysers field. These two permeable Approximately 9000 to 12,000 years ago, the southeastern wall of fault zones are the main sources of heat and mass for the Valley of Gey- the caldera was eroded by the Shumnaya and Geysernaya Rivers, initiat- sers' hydrothermal system. The caprock of the hydrothermal reservoir 4 ing the drainage of the hydrological basin. The ultimate lake below the consists of the Geysernya unit (Q3 grn), which formed from caldera Upper Geyserny field was drained because of the Geysernaya River ero- lake deposits and dips at an angle of 8–25° in the NW direction towards sion that occurred approximately 5000 to 6000 years ago. Hence, a 400– the Geyzernaya river basin. When thermal fluid upflow reaches this in- 500 m elevation drop in the discharge area occurred in the Geysernaya clined caprock layer, it laterally shifts in a westerly direction, forming river basin. The absence of recent basaltic volcanism in the upper stream geysers and hot spring discharge along the Geysernaya river valley. of the Geysernaya River may indicate the existence of shallow, partially The geyser and hot spring fluids have neutral pH, low mineralized melted magma bodies there, which trap emerging basaltic dykes. sodium chloride in the Lower Geysers and most of the Upper Geysers (Appendix A,Tables1–5), and are characterized by free discharged

2.2. Hydrogeological stratification gases with a CO2–N2 composition. The upstream hot springs in the Upper Geysers and Death Valley have lower pH and very low chloride The following hydrogeological units were identified in the Uzon– values, which reflect a change from water-dominated reservoir condi- Geyzernaya caldera: 1 — aquifers of alluvial and glacial deposits; 2 — rel- tions to two-phase zone reservoir conditions in the upper part of the 4 atively low permeability units of caldera lake deposits (Q3 grn, pmz, js, Geysernaya river basin. The maximum estimated values of Na–K and and col), including pumice tuffs, sandstones and breccias; 3 — perme- SiO2 geothermometers (Fournier, 1981) that were applied to the gey- 4 able units of rhyolite, dacite and andesite extrusions (αξQ3); 4 — pre- sers and hot springs in the Lower and Upper Geysers areas are caldera upper Pleistocene permeable units of lake tuffs and sedimentary 205 °C–215 °C. These values indicate possible high-temperature 3 deposits, which are complicated by a dyke complex (Q3ust), andesite upflows that recharge the Valley of Geysers' hydrothermal system. 3 3 lavas (αQ3), pumice breccias (ξQ3) and caldera rim dacite and rhyolite The Avery boiling spring (#21) has the highest stable flow rate 3 extrusions (ξQ3); 5 — an aquifer of basalts, andesites, dacite lavas and (12 kg/s) of the surviving boiling springs and geysers in the Lower

Fig. 1. Schematic 3D view of the Uzon–Geysernaya caldera. The geological units are shown by colors: alluvial and glacial deposits (light gray), caldera lake deposits (yellow), rhyolite– dacite extrusions (pink), pre-caldera tuffs and sedimentary deposits (gray), and basalt-andesite lavas (green). Geysers under monitoring: 1 — Velikan, 2 — Bolshoy, and 3 — Shaman (Mutny). Scale: 34 km × 16 km. Y — north, X — east. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.) 132 A. Kiryukhin / Journal of Volcanology and Geothermal Research 323 (2016) 129–147

4 Fig. 2. Schematic map of the Valley of Geysers. Legend: 1 — Alluvial and glacial deposits Q3–4;2— permeable units of rhyolite, dacite and andesite extrusions (αξQ3); 3 — basalt, andesite, 1–2 4 and dacite lavas and pyroclastics (αQ3 ); 4 — relatively low permeability units of caldera lake deposits (Q3 grn, pmz, js, and col), including pumice tuffs, sandstones and breccias, pre- 3 caldera upper Pleistocene permeable units of lake tuffs and sedimentary deposits, which are complicated by a dyke complex (Q3ust); 5 — thermal fluid-conducting faults; 6 — Uzon– Geysernaya caldera boundary; 7 — uplifted area that is associated with the contours of the active magma reservoir; 8 — geysers and hot springs (for numeration, see Table 6 in the Appendix A); 9 — Podprudnoe Lake and Podprudnoe Lake-2 dumb by mudflows; 10 — catastrophic landslide-mudflow on 3.06.2007; 11 — landslide-mudflow on 3.01.2014 (the contours were digitized from an aero photo survey that was performed in Sept. 2014 and processed by A. N. Matveev). Grid scale — 500 m.

Geysers field (Appendix A, Table 6). Velikan (#23) and Bolshoy (#28) boiling springs and geysers (M, 21, 23, 52, 54, N16, and N17) may be at- are the largest regularly cycling geysers in the Valley of Geysers, so tributed to dilution and rock interaction with geothermal water in they were selected for monitoring chemical and thermal hydrodynamic higher-temperature regions of the hydrothermal system. Larger δ18O changes. shifts are associated with higher chloride concentrations. The Lower Geysers hot springs (21, 23, and M) show higher proportions of deeper 2.4. Recharge conditions fluid components (less dilution) compared to the Upper Geysers field (N16, N17, 52, and 54). The low chloride springs (59 and 56) plot The elevation of the recharge areas for meteoric waters was identi- along the meteoric line and seem to be steam-heated meteoric waters. fied based on the isotopic composition of the thermal fluids (δDand These geysers (3-Pervenets and 45-Truby) are significantly diluted δ18O) (Kiryukhin et al., 2012, Kiryukhin et al., 2015). Boiling springs and are located close to the meteoric water line. from the Lower Geysers field were sampled in 1985 and 2010–2014. The convergence of the meteoric water line with data points from geo- 2.5. Heat sources thermal fluids (δD and δ18O) confirms their meteoric origin, while the δD values, which range from −98 to −106‰, correspond to an eleva- The primary heat source of the Valley of Geysers' hydrothermal sys- tion of the recharge area from +700 to +1200 m.a.s.l. (Kiryukhin tem is supposed to be a partially melted magma body below the Upper et al., 2012, Kiryukhin et al., 2015). The most favorable recharge zones Geysers field. Its uplift with an amplitude of up to 15 cm from 1999 to coincide with the outcrops of rhyolite extrusions with deep, highly per- 2003 (around 4 cm per year), which was identified by radar interferom- 4 meable roots (ξQ3) and with the caldera boundary, especially within etry data analysis (Lundgren and Lu, 2006). The horizontal extent of the heated parts, which allow infiltration during all seasons. One such can- suggested magma body, which is shown as the red dotted line in Fig. 2, didate is the Mt. Geysernaya (Fig. 2) rhyolite extrusion, which has an el- corresponds to a deformation of approximately 10 cm along the contour evation from +600 to +1085 m.a.s.l. and a surface area of more than line and coincides with some ground temperature anomalies (steaming 6km2.The~1–2 ‰ decay in δ18O that was observed for some of the ground) that were identified by infra-red (IR) surveys in August 2010 A. Kiryukhin / Journal of Volcanology and Geothermal Research 323 (2016) 129–147 133 and April 2014. Some anomalies appear to be recently emplaced dykes southeastern end of the upflow axis zone on the right bank of the (Fig. 3; Kiryukhin and Rychkova, 2011). The magmatic system supplies Shumnaya River, near its junction with the Geyzernaya River (N1). heat to meteoric waters (Kiryukhin et al., 2012, 2015) and generates This observation also indicates a fluid pressure increase in the hydro- high-temperature fluid upflows with base temperatures of 205- thermal system at the time of the Giant Landslide. New fumaroles and 215 °C. The upflow rate is assumed to correspond to the discharge hot springs arose in the Giant Landslide's cut-off zone, which disap- mass flow rate, which was estimated to be 300 kg/s by the chloride peared in 2008. The total discharge of those springs, which had temper- method in 1989 (Sugrobov et al., 2009) and re-estimated by the same atures from 12 to 26 °C, was estimated to be 30 kg/s. The chemical method to be 260 kg/s in 2008–2014 (Kiryukhin et al., 2012, 2015). composition corresponds to steam-heated meteoric water. During the summer of 2008, significant cold spring discharges were recorded in 2.6. Catastrophic landslide on 3.06.2007 the Giant Landslide's detachment zone. This discharge eroded the de- tachment wall by 150–200 m. The drainage probably indicates the On 3.06.2007, a catastrophic landslide (Giant Landslide) occurred in cold-water recharge boundary, which occurs from rhyolite extrusions 4 the Valley of Geysers, Kamchatka. This event occurred synchronously (αξQ3) along the caldera rim. with a steam explosion and later transformed into a debris mudflow. Two to three days before the Giant Landslide event, unusual gas Steam explosions rose to a height of 250–300 m on the site of a new fu- smells were observed on the Gornoe Plateau and left towards the marole field, which was documented by a video at the time of the Giant Geysernaya basin area according to V. Zlotnikov (then-ranger of the Landslide. Approximately 300 m-high steam clouds were clearly seen Kronotsky State Reserve, pers. comm., 2007). Nevertheless, regional around the Giant Landslide's cut-off point (N7). N7 (Fumarola Podryva seismic catalog data show no seismic events during that time. or “Blasting” fumarole) occurs in a 60°NE-dipping fracture with a length The possible reasons for the catastrophic landslide on 3.06.2007 are of 20 m and a width of 10 cm. The caprock thickness above the N7 cavity (1) the inclination of the bottom of the Geysernaya unit (sliding plane) was estimated to be ~20 m before the landslide, so 2–3 bars of steam towards the Geysernaya river basin; (2) a 2–3 bar pressure increase (see pressure were required to cause a caprock lift up. above) in the fluid-magma system; (3) the over-saturation of the hang- Within a few minutes, 20 × 106 m3 of rocks shifted 2 km down- ing block by water and snow during spring flooding; (4) the hydrother- stream in the Geysernaya River, which created a dam with Podprudnoe mal alteration and weakness of the sliding plane (the matrix of the tuff Lake and buried more than 23 geysers, including 5 famous geysers sliding plane, which originally consisted of glass, was completely altered (Pervenetz, Troinoy, Conus, Maly and Bolshoy). The 20–30 m-deep and contained hydrophilic, highly silicified zeolites, such as mordenite Podprudnoe Lake started to inject cold water into the remaining part and clinoptilolite, and smectites); and (5) steam explosions along the of the Valley of Geysers' hydrothermal system (Fig. 2). sliding plane. Newly formed boiling springs (N9, N11, N12, and N15 - N17) with Shteinberg et al. (2013) expressed some doubts regarding the ability flow rates of 8.3 kg/s were found in the Upper Geysers field. The up- of low-reservoir pressures (less than +2 m above the geyser head) to stream shifting (20–30 m elevation rise) of the newly formed boiling trigger hydrothermal explosions, which “require fluid pressures that ex- chloride springs (N15, N16, and N17) corresponds to a water table rise ceed lithostatic pressure plus the tensile strength of rock”. Nevertheless, of 20–30 m and a corresponding pressure increase of 2–3 bars in the hy- two-phase high temperature reservoirs can transfer high pressures up- drothermal system. A new group of boiling springs emerged at the wards if the vertical profile is defined by a steam density gradient.

Fig. 3. Interval between eruptions (min) of the Bolshoy Geyser (upper graph) and the relative level (cm) of Podprudnoye Lake (lower graph and vertical arrows). The black boxes along the time axis correspond to non-eruption time intervals. The uncertainty in the IBE estimation is 5 min. 134 A. Kiryukhin / Journal of Volcanology and Geothermal Research 323 (2016) 129–147

2.7. Catastrophic landslide-mudflow on 3.01.2014 hydrothermal system: Pervenetz, Bolshoy, Truby, Verkhny, Chloridny, N16, N17 (the last two boiling springs were discovered after the 2007 On 3.01.2014, the edge of the caldera wall's rhyolite–dacite extru- catastrophic landslide), 56 (Kisly Kotel), M (Mladenetz, or Krepost’), 4 sion layer (αξQ3) slid down into the left bank of the Geysernaya River, and N37 (a boiling spring on the nip of the lake, which arose after the triggering a 3 km-long and 50–200 m-wide mudflow, which signifi- landslide near the site of Artifact, 2011, and moved in 2012 to the posi- cantly damaged geysers and hot springs along its track (Fig. 2). The tion of Skalisty). In 2012, the Burlyaschy geyser and springs in the upper total volume of displaced mass was estimated to be 3.2 ∙ 106 m3 (D. Goryarchy and Teply streams, and a spring at the exit point of the 2007 Dobrynin, pers. comm). The relative height of the mudflow outbreaks landslide were also sampled. reached 10–15 m. The site of the 3.01.2014 landslide's cut-off (upstream of the 3.2. Bolshoy Geyser (see photos in Appendix 2) Goryachy and Teply creeks) was assumed to be potentially dangerous long before the slide occurred. A survey and sampling of hot spring dis- Observations from 2008 to 2013 (after the 2007 landslide) showed charges from hydrothermally weakened rocks below a 100–150 m- that the regime of the Bolshoy Geyser was most sensitive to the position thick rhyolite–dacite layer were performed on 23 Aug., 2012. At that of Podprudnoye Lake's level. The eruptions at the Bolshoy Geyser ceased time, the temperature of the springs was 22–24 °C (although T Na–K when the relative level of the lake was above the lower edge of the gey- was 153-155 °C) and the flowrate was 100 kg/s. During a field survey ser pool and cold water from the lake penetrated the geyser pool (June on 3 Sept., 2013 a significant increase in the discharge was observed 2010). When the lake level fell below that of the pool edge (25–30 cm), (up to 300–400 kg/s) and the color of the water in the descending the Bolshoy Geyser started erupting again with intervals between erup- creek was brown. On 19 Sept., 2013, a relatively small precursor- tions (IBE) from 45 to 85 min. In addition, observations from 2011 to mudflow run along Geysernaya River to Podprudnoe Lake induced a 2013 demonstrated the cessation of Bolshoy Geyser eruptions during water level drop of 2.3 m in the lake (the source of this mudflow was spring–summer floods (June 18 –July 9, 2011, June 22–24 and July 2–3, definitely in the upstream Goryachy and Teply creeks). 2012, and June 5–July 10, 2013) and during autumn typhoons and The catastrophic mudflow on 3.01.2014 completely blocked the floods (October 18–20, 2013), although the lake level was below the boiling springs 54, N16, N17, and 56 and significantly damaged the gey- edge of the pool, which probably indicates the incomplete sealing of sers in the Lower Geysers field. The Velikan Geyser's conduit was par- the geyser pool walls as they deteriorated with time. The average IBE tially filled by mudflow debris, and the conduit's depth decreased of the Bolshoy Geyser during the observation period of 2007–2013 from 5.3 m to 1.9 m; the upper pool was reduced to 0.2–0.3 m depth, rose to 63 min, when 19,712 geyser eruptions were registered; the and the pool's surface area decreased from 12 m2 to 4–5m2 (observa- IBEs fit a normal distribution with a standard deviation of 7 min tions on April 2014). (Fig. 3). Usually, the Bolshoy Geyser's eruptions reached a height of 5– 8 m and lasted 2–3 min. Before 2007, according to the measurements 3. Geyser cycling and hydrogeological observations in 2007–2014 from August–October 2003, the average Bolshoy Geyser eruption period was 108 min (V. A. Droznin, 2007). 3.1. Measurement methods A new catastrophic landslide–mudflow (total volume of 3.2 ∙ 106 m3, D. Dobrynin, pers. comm) occurred in January 2014. Thanks to the per- HOBO U12-015 temperature loggers were used to measure the in- manent temperature logger, the Bolshoy Geyser data indicated almost terval between eruptions (IBE) of the Velikan and Bolshoy Geysers the exact time of this event, namely, ~23:00 (local time) on 3.01.2014 starting in July 2007. The loggers, which were installed in the channels (Fig. 4). Afterwards, the Bolshoy cycle decreased stepwise from of water discharge out of geysers, recorded the temperature of the 60 min to 30 min and then slowly increased to 44 min by September water outflow every 5 min. The eruption time of the geysers was esti- 6, 2014. No clear visual decline in the Bolshoy Geyser's eruption mated according to the time of the absolute maximum temperature power (height and discharge rate) occurred. prior to its absolute minimum (in a cycle). A pair of HOBO U20-001-04 loggers with set interval measurements 3.3. Velikan Geyser (see photos in Appendix 2) of 20–30 min was used to log the level of Podprudnoe Lake. One logger recorded the barometric pressure, and the other was installed in the 3.3.1. Velikan Geyser cycling parameters (2007–2014) lake to record the total pressure of the water column and the atmo- Prior to the catastrophic 2007 landslide, the mean interval between spheric pressure. The relative level of the lake was determined by the eruptions (IBE) of Velikan was 375–379 min according to data from difference between the pressure records of the two loggers. Podprudnoe 1991 to 2004 (Droznin, 2007). Earlier discrete observations indicated Lake is recharged by the Geysernaya River, so the lake's level is linked that the IBE had been slowly increasing from 180 min to 400 min during with the river's flowrate. A formula to determine the river's flowrate the past 50 years (Fig. 5). by the level of the lake was calibrated according to the results of hydro- From July 2007 to September 2013, the average IBE of the Velikan metric observations at the river cross-sections “Plotina” and “Schel”.The Geyser was 340 min, when 8216 geyser eruptions were registered; subaqueous discharges of thermal springs were estimated by the chlo- these IBEs fit a normal distribution with a standard deviation of ride method at the observation cross-section “Plotina”. Starting from 52 min (Fig. 6). The decrease in the average IBE shows a tendency of sta- May 2012, a HOBO U24-001 logger (range of 0–10,000 μS/cm with a bilization after its reduction during the first three years after the disas- set recording interval of 20 min) was used to continuously record the trous 2007 landslide: 379 min (2007), 359 min (2008), 323 min solution conductivity at the cross-section “Plotina”, which enabled the (2009), 334 min (2010), 337 min (2011), 337 min (2012), and simultaneous assessment of changes in the chloride ion concentration 334 min (2013). The observation results also show that the recurrence and, thereby, the changing dynamics of a hidden discharge value and of activity at the Velikan Geyser depends on the amount of precipitation the thermal power of the hydrothermal system. We understood that in the vicinity of the geyser pool. In addition, heavy snowfall and ty- the uncertainty of estimating the hidden thermal discharge may reach phoons may delay eruptions, creating longer cycles. The maximum ob- 20–30% according to Fournier (1989). served IBE was 32 h during heavy snowfall on February 29, 2008 (no Velikan and Bolshoy (Fig. 2) are the most powerful and spectacular doubt exists regarding this long IBE because the logger was installed di- geysers in the Valley of Geysers (Kiryukhin and Rychkova, 2011; rectly in the channel of hot water discharge out of the geyser pool). An Table 3), so they were selected to monitor the cycling and analysis of the relationship between the recurrence of Velikan Geyser hydrochemical regime. In addition, the list of monitored sites included eruptions and atmospheric pressure shows that this relationship was large, boiling hot springs and geysers at different sites in the absent. The cloud of points is fairly evenly distributed in an ellipse, A. Kiryukhin / Journal of Volcanology and Geothermal Research 323 (2016) 129–147 135

Fig. 4. Bolshoy Geyser's response to the mudflow on 3.01.2014. Lower graph — temperature records near the discharge channel; upper graph — interval between eruptions. The uncertainty in the IBE estimation is 5 min. Time axis format: D/M/YY hh:mm. covering changes in the atmospheric pressure of 91.5–98.5 kPa (average (Fig. 7) showed that the average IBE during winter was larger by 41 min 95.8 kPa) and changes in the IBE of 150–500 min (Kiryukhin et al., 2015; compared to summer values, as was the IBE variability, which exhibited Fig. 5). extreme values from 200 to 600. During the slow erosion of the dam by the Geysernaya River, the The likely reasons for this seasonality are (1) increased heat loss water level in Podprudnoye Lake systematically lowered (130 cm over from the surface of the Velikan pool during periods of low winter tem- 4 years, or about 33 cm per year). This decrease was superimposed on peratures, snowfalls and strong winds (according to V. M. Stepanenko, the seasonal changes in the lake level (Fig. 6). A comparison of the IBE 2012, the average value of the wind energy potential in winter is 4.4 of Velikan Geyser with a level change in Podprudnoye Lake clearly times higher than that in summer, as detailed by the weather station shows that abnormal IBE increases in the Velikan Geyser occurred at “Semyachik”); (2) a reduction in the overall recharge of the hydrother- discrete Podprudnoye Lake levels of 10–20 cm, −45 cm, −70 cm, and mal system during winter because of the freezing of water supply areas; −120 cm. These levels correspond to all the winter seasons from (3) local aquifer changes, which affected the boundary conditions in the 2007 to 2013. This seasonal change in IBE indicates the geyser's depen- thermal fluid discharge areas and increased the reservoir pressure dur- dence on the hydrological conditions in the surrounding aquifer. ing spring–summer flooding periods. This pressure rise may decrease The changes in the Velikan Geyser's IBE within the hydrological cycle IBE, as noted by the modeling results below (Section 4.1.2). from January to December for the entire 2007–2013 observation period

Fig. 5. Interval between eruptions of the Velikan Geyser. The red circle data are from Sugrobov et al. (2009), the gray circles are from Droznin (2007), and the open circles are data from this paper. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.) 136 A. Kiryukhin / Journal of Volcanology and Geothermal Research 323 (2016) 129–147

Fig. 6. Interval between eruptions (min) of the Velikan Geyser (upper graph) and the relative level (cm) of Podprudnoe Lake (lower graph and vertical arrows). The uncertainty in the IBE estimation is 5 min.

Fig. 7. Interval between eruptions (min) of the Velikan Geyser within the hydrological cycle during 2007–2014. The red thick line is the 2nd order approximation of the data points. The IBE is clipped in the fig. at 800 min. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.) A. Kiryukhin / Journal of Volcanology and Geothermal Research 323 (2016) 129–147 137

The mudflow on 3.01.2014 significantly damaged the Velikan Gey- These estimates have been confirmed by using a tracer method. Ap- ser. Its ground surface was cut off by a mudflow at ~0.5 m; a large shal- proximately 4.8 kg of a tracer (NaCl) was put in the conduit (Fig. 8) dur- low pool with an area of 12.2 m2 shrank to 5.5 m2 (Fig. 8). The geyser ing an eruption cycle from 1300 to 1710, April 18, 2013. Before the conduit was partially filled with mudflow debris, so the depth of the tracer was introduced, the concentration of chloride ions in the conduit 3 conduit decreased to 1.9 m from 5.3 m. The temperature logging/cycling was С1 =0.744kg/m (average of three samples); 20 min after stirring monitoring equipment was swept away by mudflow debris; hence, no and dissolving during intermediate boiling in the geyser conduit, the 3 record of geyser cycling exists from Sept. 2013 until April 2014. On chloride ion concentration in the conduit was С2 =0.904kg/m (aver- April 27 and 28, a restored logging system showed that the Velikan age of three samples). No major eruptions occurred between sampling 1 IBE was 90 min; by September 2014, the IBE had linearly increased to and sampling 2, only intermediate boiling (play), which helped the 130 min. The height of the geyser plume declined to 1–1.5 m in 2014 tracer (NaCl) to dissolve and mix throughout the geyser conduit. compared to 15–20 m in previous years, clearly demonstrating the dra- Hence, the volume of the conduit was determined by the formula 3 matic decline of the Velikan Geyser's eruption power. V = 0.60684 m/(C2–C1) = 18.2 m (where 0.60684 is the weight frac- tion of Cl in NaCl), and the water mass in a full conduit, given its density 958 kg/m3 at boiling temperature (100 °С), was М = 17,400 kg. To es- 3.3.2. Velikan Geyser average flowrate and conduit characteristics timate the average discharge rate, we must add an additional 4210 kg The mass of Velikan eruptions is almost equal to the mass of water in of water that overflowed during 6 intermediate boiling events (plays). its conduit, which is completely emptied during the eruption. A previ- The level decreased by 6 cm in the geyser pool during this intermediate ous estimate of the Velikan conduit's volume was V = 20 m3 according discharge. Given that the pool area was 12.2 m2,0.732m3 or 701 kg of to the volume of water that poured into the conduit after the eruption water flowed out of the geyser at each intermediate boiling. Thus, the (N. G. Sugrobova, 1982). actual average mass discharge rate of the Velikan Geyser during the

Fig. 8. Geometry of the Velikan Geyser's conduit. Upper figure — topography of the Velikan Geyser's conduit fitted to a volume of 18 m3, surface area and section at 40 cm depth as measured in Aug., 2007 and Sept., 2013, with the cross-hatched area marking the upflow zone at the bottom of the conduit; lower figures — cross-sections AB and CD inside the conduit. The scale is in cm. 138 A. Kiryukhin / Journal of Volcanology and Geothermal Research 323 (2016) 129–147 relevant eruption cycle of 4 h and 10 min on April 18, 2013 was esti- (standard deviation of 17 min), although the geyser IBE sometimes mated to be 1.44 kg/s. Nevertheless, the Velikan Geyser's mass dis- reached 1000 min or greater during winter. The average IBE for July charge rate during eruptions (which predominantly involves 2014–May 2015 declined to 129 min. Analyses of this phenomenon, in- emptying the geyser conduit in 30–40 s) was estimated to be 435– cluding its relationship with seismicity, is on-going. 580 kg/s. Fig. 11 summarizes the IBE data of the above geysers.

3.4. Geochemistry transient data 4. TOUGH2-modeling of the Velikan Geyser's cycling activity

The discharge composition of the geysers and hot springs in the Val- We attempted to reproduce the cycling mode by using the TOUGH2 ley of Geysers is subalkalic low-mineralized chloride-sodium waters. model. This model uses hysteretic saturation switching to explain cy- Data on the chemical composition prior to the catastrophic landslide cling well discharge (Kiryukhin and Pruess, 2000). During this study, a on 3.06.2007 and the results of testing in 2010–2014 are provided in numerically induced cycling effect was found when coarse vertical this study (Kiryukhin et al., 2012, 2015) and in the Appendix A grids generated adequate pressure cycling. We also investigated the (Tables A1–A5). Gas sampling from September 2013 showed that the possibility of explicit cycling by using a previously developed TOUGH2 gas component of the hydrothermal reservoir that fed the Velikan Gey- model. We attempted to run the Saptadji model (described in detail in ser was dominated by carbon dioxide (СО2, 61.5%) and nitrogen (N2, Section 6.2, p. 176–194, Saptadji, 1995) and found that cycling disap- 32.1%), along with а significant amount of methane (CH4,5.8%)andhy- peared when a finer numerical grid was used, although this model drogen (Н2,0.45%). showed cycling when using the original set of parameters. Although The transient changes in chloride ion concentration are explicitly we reproduced Ingebritsen and Rojstaczer (1996) model by using manifested for the Bolshoy and Velikan Geysers with a maximum TOUGH2 on a course numerical grid (ΔZ=20m,Fig. 2, Ingebritsen fixed dilution of 23% and 12%, respectively, compared to the data before and Rojstaczer, 1996), we did not observe cycling on a finer numerical 2007 (Fig. 9). The changes in sulfate ions, other chemical components grid (ΔZ = 1 m), which may also be caused by the model's sensitivity and water isotope δD‰ and δ18O‰ for these geysers are insignificant to the numerical grid that is used. Thus, we focused our local geyser or do not exceed the errors in the determination. No significant changes model study on model calibration by using temperature observations in the Na–KandSiO2 geothermometers have been identified so far. in a geyser conduit and estimating the corresponding cyclically chang- Additionally, the average value of deep-fluid component discharge ing external heat and mass flow conditions in the geyser conduit. in the geysers' hydrothermal system was estimated at the exit from Podprudnoe Lake to be 215 kg/s according to the chloride method. 4.1. Local Velikan Geyser model This fluid discharge decreased significantly (30%) during May–June flooding, most probably because of blockage from the rising groundwa- 4.1.1. Model setup ter levels (Kiryukhin et al., 2015). A TOUGH2 model was developed to represent the conditions in the Velikan Geyser before 3.01.2014, when a mudflow buried the lower 3.5. Shaman (Mutny) Geyser, Uzon caldera conduit. The model accommodated both the known geyser conduit and the adjacent reservoir. The aim of this modeling was to understand After the partial loss of geysers in the Valley of Geysers from the cat- the possible mechanism of the Velikan Geyser's cycling under external astrophic landslide in 2007, a new geyser appeared at 652 m.a.s.l. in the cycling source conditions, matching the modeling output and transient Uzon caldera in the autumn of 2008 (Fig. 1). This geyser was named observational temperature data in the geyser conduit. Mutny (Shaman) (G. Karpov, 2012) and arose in place of a former chlo- The conduit geometry of the geyser comprised an upward-open ride sodium hot spring with a temperature of 80 °C. After the switch cone with a total volume of 18.9 m3. The horizontal cross-sectional from a hot spring to a geyser, its chemical composition remained rela- areas were 12.2 m2 at 0.0 m depth, 5.5 m2 at 0.4 m depth, 3.62 m2 at tively stable (Cl: 1223–1454 ppm; Na: 812–941 ppm), while the tem- 2.5 m depth and 1 m2 at 5 m depth. This geometry was constrained by perature increased to 99 °C. The start of geyser migration from the tracer testing and measurements from the surface, as shown in Fig. 8. valley to the caldera may have been associated with a total pressure in- The effective cross-sectional area versus depth was spline- crease in the regional hydrothermal system because of magmatic activ- approximated based on the above four reference points. The geyser ity. The results of monitoring the cycling activity of this new geyser are conduit's geometry is shown in Fig. 12 as a domain of eleven equal rect- shown in Fig. 10. The average IBE for Aug. 2012–May 2014 was 137 min angular elements; the volume of each element was assigned according

Fig. 9. Transient changes in the chloride ion concentration in Velikan Geyser and Bolshoy Geyser. The data before 2007 are from Sugrobov et al. (2009). A. Kiryukhin / Journal of Volcanology and Geothermal Research 323 (2016) 129–147 139

Fig. 10. Interval between eruptions (min) of the Shaman (Mutny) Geyser. The IBE was clipped by axis range. The continuous lines are the running average (81) fits.

to the variable cross-sectional area of the Velikan Geyser (see above) by infinite grain (mineral phase) density was assigned to maintain zero using the following sequence of element volumes: 1 × 10 m3, heat balance in the accumulation term. The domain DISCH (one ele- 4 × 1.45 m3,and6×0.7m3. ment) was used to specify a fixed atmospheric pressure of 0.956 bars A hot water recharge (mass source, 1.2 kg/s, 440 kJ/kg or 105 °C) was for seepage and thermal insulation at the top of the geyser conduit. assigned to a bottom element in the model at −5.5 m depth. This bot- Zero heat conductivity and 1.0 residual steam saturation were assigned tom element was horizontally connected to an adjacent, large-volume, in this domain, and fixed state conditions (steam phase) were specified isothermal 110 °C reservoir (volume 100 m3). The element that capped in this domain element (TOUGH2 insulated seepage boundary the conduit was connected to an inter-eruption discharge element, conditions). where atmospheric seepage conditions are assigned (fixed atmospheric The model was run in the previously described cyclic mode for 10 pressure of 0.956 bars and thermal insulation, meaning zero heat con- eruption cycles that lasted 20,000 s each to ensure that the output ductivity and no return flow). was not sensitive to the initial conditions (hydrostatic, saturation of

The model was run in a cyclic mode with an interval between erup- 0.001, and PCO2 = 0.01 bars). The model output's sensitivity to the tions (IBE) of 20,000 s during 10 eruption cycles of 20,000 s each. The grid spacing was also examined on a model with a vertical resolution major eruption discharge of the Velikan Geyser was approximated by of 55 elements. the time-dependent production from the “well”, which extracted fluid from the bottom element (mass transfer of 25 kg/s during the time inter- 4.1.2. Observational data for model calibration vals [k∙20,000, 600 + k∙20,000 s, k = 0, 1, 2,…9], 15,000 kg in total during The observational data included temperature logging (one record one cycle). Additional time-dependent mass sources in the model in- per minute) at depths of 515 cm and 285 cm (corresponding to absolute cluded the following: 1. a bottom mass source, which represented a con- depths of 465 cm and 257 cm) during a 51-hour time interval (1500 stant upflow of hot water (1.2 kg/s, 440 kJ/kg or 105 °C) and CO2 cycling 21.07.2007–1840 23.07.2007) (Fig. 16). For these purposes, two HOBO upflow (one cycle of 22 min); 2. a bottom cycling mass source of CO2 (in- U12-015 temperature loggers were attached to a 5.3 m-long iron tube jection of 0.024 kg/s during the time intervals [0 + k∙1333.3, that was installed at the bottom of geyser (installation dip angle was 667 + k∙1333.3 s, k = 0, 1, 2…149], which represented observed inter- 80°). At this time, eight cycling events were observed at the Velikan vals of sub-cycles during each of the major eruptions for a 20,000-s geyser Geyser. We used these data to match temperature records with tran- cycle); 3. a return water inflow mass source (active after the geyser con- sient temperatures in corresponding model elements (T1 and T2, duit was re-filled), which was assigned in the model at a depth of 4.25 m Fig. 12) during temperature recovery processes between subsequent (time-dependent injection of 0.3 kg/s, 268 kJ/kg or 64 °C during the time eruptions. intervals [5000 + k∙20,000, 20,000 + k∙20,000 s, k = 0, 1, 2,…9]), al- though this source “was prompted by the model” to fit transient temper- 4.1.3. Model analysis ature differences at the observation points T1 and T2 (for details, see The TOUGH2-EOS2 modeling (scenario S8_CO2+) reasonably Section 4.1.2 below), so some fraction of erupted water returned back matched the observational data (Fig. 14) and replicated the following into the geyser conduit through secondary conduits (such as the hole stages within the Velikan Geyser's cycle: Stage 1 — atemperature thatisshowninPhoto6inAppendix2)fromthesurface.Allthesource drop (vacuum pressure declined under the eruption, the geyser conduit values were the results of model calibration runs. was empty at this time); Stage 2 — a temperature build-up with a The material properties that were used in the model are listed in water-level rise in the geyser conduit until the seepage surface was Table 1. The model domain GEYSR (eleven elements) represented a gey- reached; Stage 3 — some cool-down as the inflow of returning cold ser conduit and thus has large permeability, with porosity close to 1.0. water began; and Stage 4 — another gradual temperature build-up The model domain RESER (one element) represented an adjacent, from hot water recharge at the base and related heat overbalance, large-volume, isothermal 110 °C reservoir (volume of 100 m3), so an with clear geyser pre-play events observed during this stage (see 140 A. Kiryukhin / Journal of Volcanology and Geothermal Research 323 (2016) 129–147

Fig. 12. Conceptual model and TOUGH2 model geometry of the Velikan Geyser. The mass

from the bottom during major eruptions, CO2 recharge (kg/s) and return water inflow are specified in the model in a cyclic mode according to the observed features of the Velikan Geyser. T1 and T2 represent temperature measurement points.

Major eruptions at the Velikan Geyser reached 97–98 °C in the middle of the conduit, as shown by the T2 logger (Figs. 13 and 14), which indi-

cated a lower boiling temperature/pressure because of CO2 partial pressure. A. Belousov (videos, 2012, pers. comm) noted that bubbles can be observed at the base of the Velikan Geyser at ~5 m depth. The saturation temperature is 111.5 °C at a given absolute pressure of 1.5 bars, which is greater than the maximum recorded temperature of 105.5 °C (Fig. 13)

and suggests that the bubbles may be CO2. The slightly underestimated Fig. 11. Histograms of the interval between eruptions (min) of the Velikan, Bolshoy and temperatures (98 °C compared to 98.5 °C, which is required at 95.8 kPa; Shaman (Mutny) Geysers during the observations from 2008 to 2014 (Velikan and Bolshoy) and 2012–2014 (Shaman). Section 3.3.1) of most of the boiling springs (Appendix A, Table 6) also indicates a possible CO2 bubbling partial pressure of 2–3 kPa.

Photo 13 in Appendix 2). A preparation stage that precedes major erup- 4.2. Geysers reservoir model tions is called “pre-play”, which is characterized by pulses of liquid and/ or steam discharge (Kieffer, 1984; Karlstrom et al., 2013; Namiki et al., 4.2.1. Model setup 2014). This sequence lasted until a subsequent eruption initiated. The aim of this model was to better understand the role of heat These transient temperature profiles were obscured by fifteen sub- sources and mass recharge under natural conditions in the Valley of cycles from bottom CO2 injection events, which finally triggered an Geysers (Fig. 15) and to estimate the influence of Podprudnoe Lake, eruption. which formed on 3.06.2007, on the geyser activity. The key model parameters that were used for the model calibration A TOUGH2 two-dimensional model that was based on the geometry included the following: 1. the return water inflow rate, which was re- of the cross-section in Fig. 15 was developed. An EOS1 + tracer fluid sponsible for the recorded temperature difference between the upper module was used to simulate the transient transport of chemical tracers and lower temperature loggers; 2. the cycling bottom CO2 upflow rate, (such as chloride). This model covered the shallow geyser production which was responsible for inter-eruption boiling and the temperature reservoir (consists of pre-caldera upper Pleistocene permeable units of amplitudes during sub-cycles; and 3. the permeability of the buffer res- lake tuffs and sedimentary deposits, which are complicated by the 3 ervoir, which controlled the high rate of the initial temperature build- dyke complex Q3ust) along the line AB (Fig. 15). The geyser production up. reservoir was likely fed by lateral high-temperature inflow from a deep

The major difference in the CO2 modeling scenario compared to the NE-oriented strike fault zone, as shown in Fig. 2. The horizontal model non-CO2 modeling scenarios was that the observed temperature histo- dimensions of the geyser production reservoir were 1000 m × 100 m. ries only applied to single-phase conditions, even though the non-CO2 The bottom of this shallow reservoir was assumed to be located at modeling scenario generally reproduced these histories. These condi- +350 m.a.s.l. (the lowest elevation of the geyser discharge in the tions excluded any boiling, which is essential for geyser eruptions. area; see Table 6 in the Appendix A). The top coincided with the A. Kiryukhin / Journal of Volcanology and Geothermal Research 323 (2016) 129–147 141

Table 1 Rock material properties that were assigned in the local Velikan Geyser model (Fig. 15).

Model parameters Model domains

GEYSR RESER DISCH (fixed state)

Permeability, m2 1e−81e−10 1e−10 Porosity 0.99 0.5 Compressibility, Pa−1 1e−71e−5 Relative permeability Linear Swr = 0.0, Sgr = 0.0 Linear Swr = 0.0, Sgr = 0.0 Linear Swr = 0.0, Sgr = 1.0 Grain (mineral phase) density, kg/m3 2500 1e50 2600 Heat conductivity, W/m °C 2.0 2.0 0.0 Specific heat, J/kg °C 1000 1000 1000

topographic surface. A 2D regular rectangular numerical grid (with the depth that is shown in Fig. 15) with well pressures Pwb that (100×1×60,ΔX=10m,ΔY=100m,andΔZ = 2 m) was used. correspond to hydrostatic pressure at a given bottom depth and produc- The model zonation in Fig. 15 included reservoir and caprock do- tivity indices PI of 1e−7m2. The mass rate q of phase β of the wells on mains with the thermal and petrophysical properties in Table 2. The re- deliverability were defined against a prescribed flowing bottom-hole charge conditions were assigned on the right side of the bottom layer. A pressure, Pwb, with a productivity index PI (Pruess et al., 1999) from a 2 mass flux of 5.2e−3kg/sm , enthalpy of 504 kJ/kg (120 °C) and chlo- grid block with phase pressure Pβ N Pwb: ride mass flux of 4.86e−6kg/sm2 (corresponding to a chloride concen- ÀÁ tration of 900 ppm) were assigned, which correspond to estimated krβ qβ ¼ ρβ∙PI∙ Pβ−Pwb hydrothermal mass flow recharge of 260 kg/s (see Section 2.3). Fixed μβ state atmospheric-meteoric groundwater boundary conditions were assigned (pressure of 1.5 bars, temperature of 10 °C, and Cl mass con- Here, krβ, ρβ,andμβ are the relative permeability, density and viscos- centration of 2e−6) at the top of the model. No-flow and heat bound- ity of phase β, respectively. Thus, each well (23, 21, 20, 65, 28, 29, and ary conditions were assigned on the left and right vertical sides of the 36) that was represented in the model corresponded to a geyser (ac- model. cording to its number in Table 6 in the Appendix A) and all other adja- The geyser and boiling hot spring discharges were modeled in terms cent thermal discharges. The upstream weighted mobility and of “wells” by using the “well on deliverability” option. All the thermal permeability at the interface and the average density at the interface discharge features were represented by seven “wells on deliverability” of adjacent elements were also specified in the model.

Fig. 13. Observational data for model calibration: transient temperature logs in the Velikan Geyser conduit. The red points are the temperature log T1 at an absolute depth of 465 cm, and the blue points are the temperature log T2 at a depth of 257 cm. This figure clearly shows nine subsequent temperature cycling events, which each cycle (numbered in the figure) starting from an absolute minimum temperature after an eruption and terminating at a maximum temperature just before the next eruption. Note 1: The Velikan Geyser's eruptions start when the absolute maximum temperatures are reached in the temperature logger T1 (upper red curve, eight eruptions passed); the eruption lasts 30–40 s. Note 2: The temperature at the midpoint (log T2) of the Velikan Geyser's conduit is less than the boiling temperature at 1 bar; see Section 4.1.3 for further explanation. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.) 142 A. Kiryukhin / Journal of Volcanology and Geothermal Research 323 (2016) 129–147

Fig. 14. TOUGH2 modeling output (modeling scenario # S8_CO2+) and observed data. The observed data from Set 1 were used. The rates in the model are the assigned time-dependent mass flows: geyser discharge flowrate, return water inflow rate and bottom CO2 recharge according to the model specification (see Fig. 12).

4.2.2. Model results and discussion scenario C (with an additional injection upstream of the Geysernaya Natural state (steady state conditions) modeling showed rather uni- River) explained the observed decrease in the IBE of the Velikan Geyser form temperatures and chloride concentrations in the shallow geyser (−9%) during 2011–2013. A seasonal IBE decline in the Velikan Geyser production reservoir (Fig. 16A). Hot water upflow was mostly tapped (−11%, Fig. 7) may also be treated as a result of a seasonal change in the by wells (representing geysers in the model). Cold water injection injection recharge upstream of the Velikan Geyser area. from Podprudnoe Lake (after the catastrophic landslide on 3.06.2007) Both modeling scenarios predicted new thermal discharge features on was implemented in the model as a fixed state condition along the the left bank of the Geysernaya River (Fig. 16) close to geysers 30–31 and flooded geysers conduits 36, 29 and 28 (hydrostatic pressure distribu- 34–37 (Fig. 15). In fact, new high-discharge boiling springs arose in this tions, P = 44.0–0.1·Z, where P is estimated in bars and Z is the absolute location in 2007 (37 N, Artifact-2; see Table 6 in the Appendix A) and elevation in m; see Fig. 15A) with a temperature of 10 °C. The corre- flowed until the catastrophic mudflow on 3.01.2014 breached the dam sponding pressure rise in the reservoir at 370 m.a.s.l. below the lake and Podprudnoe Lake was almost completely drained. was estimated to be 3.5 bars (Conus geyser, #36 in Fig. 15B). The Additionally, Sugrobova (1982) presented data on the 30-min re- model was run for a period of 3 years until the lake's level decreased, duction in the IBE of the Velikan Geyser when the water level of the which allowed the Bolshoy Geyser to resume its cycling activity Geysernaya River increased by 80 cm during flooding in June 1975. (Fig. 16B). Then, the Bolshoy Geyser switched from a cold water injec- This phenomenon was explained by the build-up of reservoir pressure tion sink into a “well on deliverability”, and the model was run for an following the increase in the river level. The modeling results demon- additional 4 years (Fig. 16C). strated that a similar effect was expected to be produced on the geysers The modeling scenario D assumed the possibility of additional cold by the newly formed Podprudnoye Lake or as a result of another cold water penetration during the last 4 years in areas upstream of the water injection source depending on the distance and the hydraulic Velikan Geyser (Fig. 16D). This cold water injection area may have connection between the lake/cold water source and the specificgeyser. been created by recent minor flooding events and mudflows (2011– As mentioned above, both model scenarios (C and D) did not predict 2013) that had eroded the river bottom's silica caprock, allowing cold chloride dilution in the Bolshoy Geyser (#23) when it resurfaced above water to access the production geyser reservoir. the water level in the lake. The significant chloride dilution in the Both modeling scenarios (C and D) showed a significant increase in Bolshoy Geyser (−23%) (Fig. 9) can be attributed to the observed direct the Bolshoy Geyser's discharge (+56%, Table 3) in terms of the “well cold water stream inflow in the geyser conduit through an open hole in on deliverability” flowrate. The modeling scenario D also showed a sig- a cone of the geyser (Appendix 2, Photo 6). The chloride dilution in the nificant increase in the Velikan Geyser's discharge (+7%, Table 3). No Velikan Geyser may be explained by additional injection in the up- significant change in the chloride concentration in the Bolshoy Geyser stream area of the Geysernaya River. was predicted (Fig. 16). Nevertheless, some chloride dilution in the Velikan Geyser was predicted by the model if the assumption of addi- 5. Discussion tional cold water penetration during the last 3 years in areas upstream of the geyser was valid (Fig. 16D). The natural state of hydrothermal systems is assumed to be rather Thus, the above model scenarios (C and D) explained the sharp de- steady, and human-induced exploitation is the most dynamic transient cline in the IBE of the Bolshoy Geyser (−58%) because of its increase change in a hydrothermal system's lifetime. Nevertheless, the Valley of in flowrate if we assumed that the IBE had an inverse relationship Geysers in Kamchatka is an example of natural transient changes, as de- with the average geyser discharge over an entire cycle. Thus, model scribed by Tatiana Ustinova, who discovered a “kingdom of geysers” in A. Kiryukhin / Journal of Volcanology and Geothermal Research 323 (2016) 129–147 143

Fig. 15. A) Local map of the Lower Geysers area, which shows the major distribution of the geysers. The two-digit numbers correspond to the geysers (see Table 6 intheAppendix A). Podprudnoe Lake's extension area in 2007, 2009, 2013 and 2014 is shown in different colors with corresponding year labels. B) Cross-section AB of the Lower Geysers area; the position of the cross-section is shown in Fig. 15A. The cross-section AB represents the 2D model, including the boundaries, zonation, geyser locations (assigned as “wells on deliverability” in the model) and the numerical grid that was used. Legend: 1, 2, 3 — model domains (1 — reservoir (RESR), 2 — caprock (CAPRK), and 3 — upflow zone (UPFLO)); 4 — well-geyser heads (numbers correspond to geysers, see Table 6 in the Appendix A); 5 — well/geyser conduits (assumed), some of which (28, 29, and 36) acted as a cold water injection domain (INJEC) after 3.06.2007.

April, 1941. This “kingdom of geysers” was partially broken in a few mi- Table 2 Rock material properties and type of model element conditions that were assigned in the nutes on 3.06.2007 because of its internal processes and properties, in- geyser production reservoir model (Fig. 15B). The UPFLO and INJEC domains have the cluding a rise in the magma-hydrothermal system's fluid pressure, an same material properties as RESR. unlucky dip of the caprock, hydrothermally weakened reservoir rocks, fl Model parameters Model domains rock saturation from snow melting/ ooding, and phase transitions (steam eruptions). The second strike on this geyser kingdom occurred RESR (Reservoir) CAPRK (Caprock) 6.5 years later on 3.01.2014 after the caldera wall collapsed (driven by hy- − − Horizontal permeability, 1e 12 1e 15 drothermal discharge), which triggered a 3-km mudflow downstream to 1e−15 m2 Vertical permeability, 5e−14 1e−15 the Geysernaya River, where the remaining geysers reside. Between these 1e−15 m2 two events, one geyser “promptly emigrated” to Uzon. Before these Porosity 0.4 0.4 events, the Velikan Geyser (the largest geyser) was not so steady: its pe- − Compressibility, Pa 1 1e−7 riod of cycling increased from 3 h in 1941 to 6.6 h in 1991. Relative permeability Grant Swr = 0.3, Ssr Grant Swr = 0.3, Ssr = We used the TOUGH2 (Pruess et al, 1999) and iTOUGH2 (Finsterle, = 0.05 0.05 1999) simulation codes in this paper to analyze multiphase flow mecha- Grain density, kg/m3 2500 2500 “ ” Heat conductivity, W/m °C 2.0 10.0 nisms. We understand that TOUGH2 natural state modeling of the Val- Specific heat capacity, J/kg °C 1000 1000 ley of Geysers hydrothermal system (that is not truly steady state) — is an Type of model element Enabled Fixed state 1.5 bars, 10 °C, approach we have to use to verify conceptual hydrogeological models of 2 ppm this hydrothermal system formation, with subsequent forecasts of 144 A. Kiryukhin / Journal of Volcanology and Geothermal Research 323 (2016) 129–147

A B

C D

Fig. 16. TOUGH2-EOS1 tracer modeling (chloride, in mass fractions): A — steady state (before cold water injection from Podprudnoe Lake); B — 3 years after cold water injection from Podprudnoe Lake began; C — 7 years after cold water injection from Podprudnoe Lake began; D — the same as C, plus cold water injection upstream of the Geysernaya River (right side of the model). The scale bars range from 2e−6to900e−6.

different “fault” scenarios using natural state as a reference point for fu- the transient temperature history and showed the propagation of ture predictions. In fact, we were troubled by using a whole scale hydro- two-phase conditions throughout the geyser conduit (because of CO2 thermal systems TOUGH2 model with high topographic elevation lowering the boiling pressure). Minor pre-play eruptions are clearly differences (on the order of 1000 m) and layered type grids due to numer- seen in Fig. 13 as a growing sequence of local temperature maximums, ical non-convergence problems (Kiryukhin, 2011, Kiryukhin et al., 2012). which are synchronized with a water level rise of 20–30 cm in the Instead in this paper a shallow geysers production reservoir model (2D, Velikan Geyser pool. The modeling showed that minor pre-play erup-

1000 m × 120 m) was developed and clearly explained the principal fea- tions were driven by CO2 cyclic discharges at the bottom of the geyser. tures and effects of the Podprudnoe Lake cold water injection through Major eruptions began when the CO2 and saturation profiles in a con- conduits of the flooded geysers, and bottom caprock eroded upstream duit reached “explosion levels” at the bottom. areas of the Geysernaya river. Velikan, the largest and most impressive geyser in the Valley of Gey- 6. Conclusions sers, can eject 18 m3 of boiling water up to a height of 15–20 m in less than one minute (30–40 s). The Velikan cycling period included 1.5– (1) The monitoring of the Velikan and Bolshoy Geysers after the cata- 2 h of 18-m3 pool water recharge, followed by 4–5 h of intermediate strophic landslide on 3.06.2007 (which dammed and created boiling and 6–8 small minor 0.7-m3 discharges. Transient temperature Podprudnoe Lake, drowning some geysers) and before the mud- records from the bottom and middle regions of the geyser conduit flow on 3.01.2014 (which destroyed the dam and almost drained were used for model calibration. We found some reasonable TOUGH2- Podprudnoe Lake) showed that the interval between eruptions

EOS2 (water and CO2 components) model solutions that reproduced (IBE) of the Bolshoy Geyser decreased from 108 to 63 min and that the IBE of the Velikan Geyser slowly declined over three years from 379 min to 335 min. The seasonal hydrological cycle of the Velikan Geyser exhibited an increase in the IBE of ~41 min Table 3 during winter. The dilution of chlorides in the geyser conduits Estimates of the relative changes in the “well on deliverability” flowrates, which represent − − geyser discharges in the model: B — 3 years after cold water injection from Podprudnoe was also observed: Bolshoy by 23% and Velikan by 12%. Lake began; C — 7 years after cold water injection from Podprudnoe Lake began; D — the same as C, plus additional cold water injection upstream from the Velikan Geyser, (2) A TOUGH2 model of the Velikan Geyser was developed. This which represents caprock erosion. model was used to describe the transient thermal hydrodynamic

Well on deliverability/geyser Relative change in flowrate, % and CO2 changes in the Velikan Geyser conduit during the entire BC D cycling process by using a cyclic time-dependent boundary mass flow condition. A major eruption discharge and sub-cycle CO2 23, Velikan Geyser 2 1 7 mass flow recharge were assigned at the base of the geyser con- 21 2 2 5 20 5 4 6 duit, a return water recharge to the middle of the conduit, and a 65 6 4 5 constant mass flow to the geyser base. A local TOUGH2 model 28, Bolshoy Geyser 56 56 was successfully calibrated against temperature observations at A. Kiryukhin / Journal of Volcanology and Geothermal Research 323 (2016) 129–147 145

the middle and bottom of the Velikan Geyser conduit, which Table 2 demonstrated the essential role of the key parameters (espe- Chemical composition (in ppm) of hot springs and geysers in 2011. Samples collected by A. V. Kiryukhin, analyzed by L. N. Gartseva, N. A. Solovieva, V. V. Dunin-Barkovskaya in cially CO2 bubbling flux) in regulating the eruption periodicity. Central Chemical Lab Institute of Volcanology and Seismology. Geyser/spring ## corre- sponds to Table 6. (3) A shallow production geyser reservoir model was also developed. This 2D model was used to describe changes in the transient ther- Date ## pH CO3 HCO3 Cl SO4 Na K Ca Mg NH4 H3BO3 SiO2 mal hydrodynamics and chloride concentrations in the area of the 15.10.2011 N17 9.4 18 23 497 134 381 25 18 b0.05 0.1 67 159 most prominent geyser discharge (260 kg/s over an area of 15.10.2011 N16 9.6 11 23 447 154 340 24 14 0.7 0.1 25 184 1000 m × 100 m), either in steady state or when disturbed by 15.10.2011 54 9.4 17 16 600 115 397 35 19 0.2 0.1 30 260 15.10.2011 52 9.6 22 42 454 163 363 22 17 0.2 0.1 50.7 208 cold water injection from Podprudnoe Lake (after 3.06.2007). A 15.10.2011 45 10.4 55 67 128 144 208 9 4 b0.05 0.1 0 214 “well on deliverability” option was used to model the geyser dis- 16.10.2011 21 9.5 20 16 795 154 554 46 22 b0.05 0.1 32 180 charge in the model. Cold water injection was specified as a 16.10.2011 23 8.9 8 38 781 163 545 47 22 0.5 0.1 101 176 fixed-state cold water hydrostatic condition along the flooded 16.10.2011 M 6.7 - 43 682 230 528 30 24 0.5 0.1 37 215 16.10.2011 3 9.1 9 27 462 144 336 25 25 0.7 0.1 26 172 geyser conduits and in some upstream areas, where the caprock 16.10.2011 28 9.1 11 20 667 144 460 29 25 0.5 0.1 12 139 was eroded by minor floods and mudflows (2011–2013). The modeled geyser discharge increased because of the build-up of reservoir pressure from cold water injection, which reasonably matched the observed geyser IBE decreases in both the Bolshoy Geyser (−58%) and the Velikan Geyser (−9%). This modeling also indicated the possibility of chloride dilution in the Velikan Geyser but not in the Bolshoy Geyser. The chloride dilution in the Bolshoy Geyser can be attributed to the observed inflow of a Table 3 cold stream at the surface through an open hole in the cone of Chemical composition (in ppm) of hot springs and geysers in 2012. Samples collected by the geyser. A. V. Kiryukhin (Sept. 2014), analyzed V. V. Dunin-Barkovskaya, O. V. Shulga in Central Chemical Lab Institute of Volcanology and Seismology. Geyser/spring ## corresponds to Table 6. (4) A new disastrous mudflow hit the Valley of Geysers on 3.01.2014, which reduced the Bolshoy Geyser's eruption frequency from Date ## pH CO3 HCO3 Cl SO4 Na K Ca Mg NH4 H3BO3 SiO2 60 min to 30–45 min, reduced the Velikan Geyser's power, and 24.08.2012 N17 8.9 13 24 533 154 390 29 17 b0.05 b0.1 82 401 b b changed the Velikan Geyser's eruption frequency from 340 min 23.08.2012 N16 8.9 17 50 469 154 362 26 15 0.05 0.1 68 377 b – 23.08.2012 54 7.9 76 695 106 470 49 14 6.0 0.1 113 55 to 90 130 min. Modeling studies of these effects and the possibil- 23.08.2012 52 9.1 23 31 479 173 360 28 20 4.0 0.4 32 182 ity of geyser recovery are on-going. 23.08.2012 45 9.7 13 24 533 154 390 29 17 b0.05 b0.1 82 401 24.08.2012 21 8.7 14 33 880 146 598 52 20 b0.05 b0.1 88 242 08.05.2012 23 8.5 11 52 734 192 468 34 22 1.0 b1 108 123 24.08.2012 23 8.5 1 72 780 288 482 49 22 120.0 2 117 229 Acknowledgments 24.08.2012 M 8.5 16 34 660 192 489 33 24 0.0 2.3 91 85 24.08.2012 3 8.8 16 40 461 230 377 44 22 5.0 1.25 70 172 TheauthorisgratefultoV.A.Droznin,V.L.Leonov,V.M.Sugrobov,M. 24.08.2012 28 8.8 16 34 660 192 489 33 24 0.0 2.3 91 85 Yu.Puzankov,A.B.Belousov,S.A.Chirkov,Ye.V.Kartasheva,V.I.Guseva, 26.08.2012 N37 6.5 32 543 96 354 18 23 b0.05 b0.1 68 317 23.08.2012 56 6.8 74 3 65 21 11 30 b0.05 b0.1 b0.6 319 P. A. Kiryukhin, N. A. Soloviev, A. V. Mushinsky, O. O. Miroshnik, P. O. 23.08.2012 46 8.4 12 49 449 269 393 15 25 11.0 b0.1 69 220 Voronin, T. V. Rychkova, A. Y. Polyakov, V. Y. Lavrushin, T. I. Shpilenok, D.M.Panicheva,A.N.Matveev,E.L.Subbotina,D.Dobrynin,A.V.Leonov, V. A. Otkidach, A. Verezhak, V. Gavrikova, and E. Lyakhova for their help in conducting investigations in the Valley of Geysers. The author also appre- ciatesJ.Newson,S.FinsterleandD.Elsworth's editorial help along with J. Vandemeulebrouck, S. Hurwitz and three other unknown reviewers, who provided positive feedback for this paper's improvement. The study was supported by the RFBR (Russian Foundation for Basic Table 4 Research) project 15-05-00676. Chemical composition (in ppm) of hot springs and geysers in 2013. Samples collected by A. V. Kiryukhin, analyzed by O. V. Shulga in Central Chemical Lab Institute of Volcanology Appendix A. Appendix 1 and Seismology. Geyser/spring ## corresponds to Table 6. Date ## pH CO3 HCO3 Cl SO4 Na K Ca Mg NH4 H3BO3 SiO2

Table 1 03.09.2013 N17 8.9 16 32 496 93 342 35 5 0.0 0.9 73 141 Chemical composition (in ppm) of hot springs and geysers in 2010. Samples collected by 03.09.2013 N16 9.2 22 34 411 183 289 33 3 0.1 0.9 96 158 A. V. Kiryukhin directly from geysers conduits, analyzed by L. N. Gartseva in Central Chem- 03.09.2013 54 8.9 15 34 638 83 408 42 7 0.1 1.0 116 152 ical Lab Institute of Volcanology and Seismology (for Na, K, Ca and Mg analysis — spec- 03.09.2013 51 8.8 9 39 418 125 302 17 13 0.0 1.1 38 250 trometer SOLAAR M, for SiO2 and NH4 spectrophotometer UVmini-2140 were used, 04.09.2013 21 8.9 19 35 869 145 571 60 12 0.0 0.6 91 151 “Анион”— HCO3 and CO3 were analyzed using titration, standard pH meter for pH deter- 18.04.2013 23 8.5 9 49 752 269 508 88 43 5.4 2.0 94 161 mination). Geyser/spring ## corresponds to Table 6. 18.04.2013 23 8.0 67 752 192 494 87 18 7.3 2.0 94 184 18.04.2013 23 8.3 10 46 727 192 504 87 19 9.1 2.5 94 152 Date ## pH CO3 HCO3 Cl SO4 Na K Ca Mg NH4 SiO2 04.09.2013 23 8.6 6 52 780 133 531 60 12 0.1 1.6 79 139 12.09.2010 N16 8.3 511 164 393 29 14 0.9 308 04.09.2013 23 8.6 5 52 798 145 540 59 13 0.1 1.6 85 142 12.09.2010 N17 8.8 66 563 110 400 30 19 4 0.9 318 04.09.2013 23 8.6 7 49 798 145 540 60 11 0.1 1.5 89 137 12.09.2010 54 8.7 0.9 27 643 103 441 37 22 0.7 0.9 323 04.09.2013 M 8.5 5 43 674 296 552 45 10 0.1 1.3 93 143 12.09.2010 52 8.9 3 52 494 175 377 23 15 5 0.6 282 05.09.2013 3 8.3 70 468 137 378 37 8 0.2 1.2 64 143 12.09.2010 45 9.3 14 155 158 146 218 10 3 3 0.6 247 19.04.2013 28 8.4 12 40 635 154 449 87 24 4.9 b0.1 87 158 13.09.2010 23 8.3 0.6 45 794 171 554 50 18 7 0.3 303 04.09.2013 28 8.8 11 40 691 135 486 42 11 0.0 1.4 89 148 13.09.2010 21 8.8 2 59 846 135 568 48 17 8 0.1 291 03.09.2013 56 7.0 94 1 84 34 12 18 2.1 1.4 6 224 14.09.2010 M 8.3 0.6 45 692 219 508 29 16 6 1.2 243 03.09.2013 46 8.6 6 50 411 238 319 17 5 0.0 1.1 74 141 15.09.2010 3 8.7 0.9 61 466 142 342 24 21 5 1.6 220 04.09.2013 20 8.7 9 65 716 121 507 53 7 0.1 1.1 74 69 146 A. Kiryukhin / Journal of Volcanology and Geothermal Research 323 (2016) 129–147

Table 5 Chemical composition (in ppm) of hot springs and geysers in 2014. Samples collected by A. V. Kiryukhin, analyzed by A. A. Kuzmina, V. V. Dunin-Barkovskaya, O. V. Shulga, S. V. Sergeeva in Central Chemical Lab Institute of Volcanology and Seismology. Geyser/spring ## corresponds to Table 6.

Data ## pH HCO3 CO3 Cl SO4 NH4 Na K Ca Mg NH4 H3BO3 SiO2 p

04.09.2014 23 8.6 67 2 766 231 1 566 59 14 b0.05 1.6 115 297 04.09.2014 20 8.7 70 7 709 135 0 492 61 19 0 0.4 72 400 04.09.2014 28 8.8 54 9 695 154 1 468 45 24 0 1.3 78 332 04.09.2014 21 8.9 52 20 869 173 0 582 68 25 b0.05 0.1 101 538 06.09.2014 45 9.7 121 59 142 77 0 216 8 2 0 0.2 19 283 06.09.2014 25 8.5 59 8 787 192 1 570 57 16 b0.05 0.7 89 284 06.09.2014 46 8.9 41 12 408 231 1 356 20 20 b0.05 0.6 56 160 06.09.2014 51 4.4 2 301 192 2 207 51 23 4 1.9 55 189 06.09.2014 47 8.9 48 13 567 231 1 460 22 35 3 0.6 79 238 07.09.2014 65 8.0 40 72 67 0 57 5 20 5 0.1 11 54 27.04.2014 20 8.5 55 5 716 110 b0.002 487 47 6 b0.1 b0.002 b0.28 242 28.04.2014 23 8.5 55 4 808 192 b0.002 590 56 7 0 b0.002 106 183 28.04.2014 23 8.9 41 18 787 196 b0.002 590 73 3 0 b0.002 101 149

Table 6 Geysers Valley: most significant geysers, fumaroles and hot springs. ## — denote numbers used in a maps and figures; X, Y, Z — local coordinates, m; T — temperature in °C; Q — discharge, kg/s. Status: G — geysers, CBS — cycling boiling springs, BS — boiling springs, HS — hot springs, F — fumaroles, FL — flooded geysers, D — drowning geysers and hot springs.

## Name Local coordinates T °C Q kg/s Status

X Y Z Before 3.06.2007 Before 3.01.2014 Sept. 2015

3 Pervenets 2671 2658 357 98 2 G CBS G 5 Troinoy 3169 2615 384 98 1.2 G D D 6 Sakharny,Sosed 3180 2628 381 98 2 G D D 8 Drevny 3488 2437 424 96 2 G D D 14 Vanna 4149 2408 450 93 1.2 BS BS BS 15 Kovarny 4175 2403 451 98 1.5 G G G 18 Leshy 4216 2452 424 98 1.2 G FL FL 19 Fontan 4254 2418 446 98 8 G G G 20 Grot 4231 2413 446 98 3 G G G 21 Avery 4304 2432 444 98 12 BS BS BS 23 Velikan 4361 2421 443 98 1.5 G G G,DMG 24 Paryashy 4396 2467 440 98 2.3 G G G 25 Zhemchuzhny 4394 2436 444 98 1 G G G,DMG 26 Horizontalny 4400 2431 442 98 1 G G D 28 Bolshoy 3996 2639 423 98 4 G G G 29 Maly 3972 2674 411 98 7 G FL FL,BS 30 Pesherny 3962 2721 402 98 1 G FL FL 31 Krasny 3964 2744 402 98 1 G FL FL 34 Kamenka 3724 2773 390 98 1 G FL FL 35 Buratino 3796 2803 394 98 1 G FL FL 36 Conus 3686 2725 396 98 0.36 G FL FL 37 Artifact 3667 2730 369 98 0.8 G FL FL N37 Artifact-2 3684 2693 420 98 1 BS BS 38 Scalisty 3651 2706 400 98 3 G FL FL 45 Truby 4982 1852 490 98 4 BS BS BS 46 Burlyashy 5263 1878 500 98 2 G G G 47 Peshera 5412 1780 505 98 0.5 BS BS BS 48 Vosmerka 5586 1807 515 98 0.2 G G G 49 Plachushy 5696 1724 530 98 0.3 G G G 50 5707 1646 550 90 0.5 BS BS BS 51 5650 1666 520 98 0.3 BS BS BS 52 Verkhny 5961 1706 560 98 0.2 BS CBS CBS 54 Chloridny 6147 1662 580 98 0.2 BS BS D 55 Kipyashy Kotel 6847 1965 770 98 0.25 F F F 56 Kisly Kotel 6635 2358 660 70 2 HS HS D 57 Bolshaya Fumarola 6957 2603 690 110 F F F 59 Neozhidanny 8856 2944 900 26 1 HS HS HS 65 Shell 4176 2521 423 98 0.01 G G G N1 t98Q2 2608 2733 464 98 2 BS BS N7 F-Podryva 4118 1162 626 0.1 F, ceased in 2008 F, ceased in 2008 N8 t24Q05 4740 1895 484 24 0.5 HS HS N9 t98Q2 5300 1757 518 98 2 HS HS N10 t98Q02 5529 1834 521 98 0.2 HS HS N11 t98Q01 5738 1644 538 98 0.1 HS D N12 t98Q01 5781 1652 548 98 0.1 HS D N13 t52Q3R 5817 1715 553 52 3 HS HS N14 t60Q4L 5882 1647 576 60 4 HS HS N16 t98Q3R 6208 1862 611 98 3 HS D N17 t98Q3L 6227 1835 611 98 2 HS D N17A 6250 1841 611 98 1 HS D M Mladenets (Krepost) 4257 2558 423 98 0.02 G G G A. Kiryukhin / Journal of Volcanology and Geothermal Research 323 (2016) 129–147 147

Table 7 Kiryukhin, A.V., 2011. Inverse Modeling of the Natural State of the Geysers Valley Hydro- Chemical composition of free gas (vol.%), which is characterized feeding reservoir of thermal System (Kronotsky Nature Reserve, Kamchatka) Preceding of the Giant Velikan Geyser. Sampling was performed by A. V. Kiryukhin in Sept. 2012 from hot Landslide // V53A-2585 AGU Abstract (San Francisco, USA). degassing pool located in 8 m from Velikan Geyser. Sample 1 was analyzed by V. I. Guseva Kiryukhin, A., Pruess, K., 2000. Modeling studies of pressure cycling associated with seis- in IVS FEB RAS, sample 2 was analyzed by V. Y. Lavrushin in GIN RAS. micity in Mutnovsky Geothermal Field, Kamchatka, Russia. Proc. World Geothermal Congress 2000, Japan, pp. 2659–2664.

## Н2 Ar О2 N2 CО2 CO CН4 H2S Sum % Kiryukhin, А.V., Rychkova, T.V., 2011. Environment and conditions of the hydrothermal system of the valley of geysers (Kronotsky Nature Reserve, Kamchatka), geoecology. 1 0.9 6.6 48.9 32.7 0.3 9.2 0.03 98.6 Engineering Geology. Hydrogeology. Geocryology 3, pp. 238–253. 2 0.45 0.02 32.1 61.5 0.003 5.8 99.6 Kiryukhin, A.V., Rychkova, T.V., Dubrovskaya, I.K., 2012. Hydrothermal system in Geysers Valley (Kamchatka) and triggers of the Giant landslide. Appl. Geochem. J. 27, 1753–1766. Appendix B. Supplementary data Kiryukhin, А.V., Rychkova, T.V., Dubinina, E.O., 2015. Analysis of hydrothermal regime of the valley of geysers (Kronotsky nature reserve, Kamchatka) after the disaster of – Supplementary data to this article can be found online at http://dx. 3.06.2007. Volcanol. Seismol. 1, 3 20. Leaver, J.D., Unsworth, C.P., 2007. Fourier analysis of short-period water level variations in doi.org/10.1016/j.jvolgeores.2016.05.008. the Rotorua geothermal field. N. Z. Geothermics 36, 539–557. Leonov, V.L., 2009. Geological Structure and History of Geysers Valley, in: Sugrobov, V.M., References Sugrobova. Lu, X., Watson, A., Gorin, A.V., Deans, J., 2005. Measurements in a low temperature CO2- driven geysering well, viewed in relation to natural geysers. Geothermics 34, Adelstein, E., Tran, A., Muñoz Saez, C., Shteinberg, A., Manga, M., 2014. Geyser preplay and 389–410. eruption in a laboratory model with a bubble trap. J. Volcanol. Geotherm. Res. 285, Lu, X., Watson, A., Gorin, A.V., Deans, J., 2006. Experimental investigation and numerical 129–135. modelling of transient two-phase flow in a geysering geothermal well. Geothermics Belousov, A., Belousova, M., Nechayev, A., 2013. Video observations inside conduits of 35, 409–427. erupting geysers in Kamchatka, Russia, and their geological framework: implications Lundgren, P., Lu, Z., 2006. Inflation model of Uzon caldera, Kamchatka, constrained by sat- for the geyser mechanism. Geology 41 (3), 1–4. http://dx.doi.org/10.1130/G33366.1. ellite radar interferometry observations. Geophys. Res. Lett. 33, L06301. Davidson, H., 2014. Spring temperature analysis in the Taupo Volcanic Zone. A Report Munoz-Saez, C., Manga, M., Hurwitz, S., Rudolph, M., Namiki, A., Wang, C., 2015. Dynamics Under Contract RIG 2013/2014-1052 Between Waikato Regional Council and Massey within geyser conduits, and sensitivity to environmental perturbations: insights from University (24 p). a periodic geyser in the El Tatio geyser field, Atacama Desert, Chile. J. Volcanol. Droznin, V.А., 1980. Physical Model of Volcanic Process. Nauka Publ, Moscow 92 p. (in Geotherm. Res. 292, 41–55. Russian). Namiki, A., Munoz-Saez, C., Manga, M., 2014. El Cobreloa: a geyser with two distinct erup- Droznin, V.А., 2007, (http://www.ch0103.emsd.iks.ru/) tion styles. J. Geophys. Res. 119. http://dx.doi.org/10.1002/2014JB11009. Finsterle, S., 1999. iTOUGH2 User's Guide//Lawrence Berkeley National Laboratory Report Pruess, K., Oldenburg, C., Moridis, G., 1999. TOUGH2 User's Guide, Version 2.0. Rep. LBNL- LBNL-40040 (Berkeley. CA. USA. 130 p.). 43134, Lawrence Berkeley Natl. Lab., Berkeley, California (198 р). Fournier, R.O., 1981. Application of water chemistry to geothermal exploration and reser- Rinehart, J.S., 1980. Geysers and Geothermal Energy. Springer-Verlag, New York (223 pp). voir engineering. In: Rybach, L., Muffler, L.J.P. (Eds.), Geothermal Systems. Principle Rojastczer, S., Galloway, D.L., Ingebritsen, S.E., Rubin, D.M., 2003. Variability in geyser and Case Histories, pp. 109–143. eruptive timing and its causes: Yellowstone National Park. Geophys Res. Lett. 30, 1–4. Fournier, R., 1989. Geochemistry and dynamics of the Yellowstone National Park Hydro- Saptadji, N.M., 1995. Modelling of Geysers Ph.D. thesis Department of Engineering Sci- thermal System. Annu. Rev. Earth Planet. Sci. 17, 13–53. ence, University of Aukland. Hurwitz, S., Kumar, A., Taylor, R., Heasler, H., 2008. Climate-induced variations of geyser Shteinberg, A., Manga, M., Korolev, E., 2013. Measuring pressure in the source region for periodicity in Yellowstone National Park, USA. Geology 451–454. geysers, Geyser Valley, Kamchatka. J. Volcanol. Geotherm. Res. 264, 12–16. Hurwitz, S., Hunt, A.G., Evans, W.C., 2012. Temporal variations of geyser water chemistry Steinberg, G.S., Merzhanov, A.G., Steinberg, A.S., 1981. Geyser process: its theory, model- in the Upper Geyser Basin, Yellowstone National Park, USA. Geochem. Geophys. ing, and field experiment. Mod. Geol. 8, 67–86. Geosyst. 13, Q12005. http://dx.doi.org/10.1029/2012GC004388. Stepanenko, V.M., 2012. Program Performance Report of Research Work on “Complex Hurwitz, S., Sohn, R.A., Luttrell, K., Manga, M., 2014. Triggering and modulation of geyser Meteorological Research in Kronotsky Reserve” in 2012, Moscow State University, eruptions in Yellowstone National Park by earthquakes, earth tides, and weather. 2012 (42 p.). J. Geophys. Res. Solid Earth 119. http://dx.doi.org/10.1002/2013JB010803. Sugrobov, V.M., Sugrobova, N.G., Droznin, V.A., Karpov, G.A., Leonov, V.L., 2009. The Valley Husen, S., Taylor, R., Smith, R.B., Healser, H., 2004. Changes in geyser eruption behavior of Geysers — The Pearl of Kamchatka (Scientific Guide). Kamchatpress, Petropav- and remotely triggered seismicity in Yellowstone National Park produced by the lovsk-Kamchatsky (108 p.). 2002 M 7.9 Denali fault earthquake, Alaska. Geology 537–540. Sugrobova, N.G., 1982. Some Regularities of the Kamchatka Geysers Regime, Volcanology Hutchinson, R.A., Westphal, J.A., Kieffer, S.W., 1987. In situ observations of old faithful gey- and Seismology, #5. ser. Geology 25 (10), 875–878. Toramaru, A., Maeda, K., 2013. Mass and style of eruptions in experimental geysers. Ingebritsen, S.E., Rojstaczer, S.A., 1996. Geyser periodicity and the response of geysers to J. Volcanol. Geotherm. Res. 257, 227–239. deformation. J. Geophys. Res. 101 (B10), 21891–21905. Ustinova, T.I., 1955. Kamchatka Geysers. Geographysdat, Moscow (120 p). Karlstrom, L., Hurwitz, S., Sohn, R., Vandemeulebrouck, J., Murphy, F., Rudolph, M., Vandemeulebrouck, J., Sohn, R., Rudolph, M., Hurwitz, S., Manga, M., Johnston, M., Soule, Johnston, M., Manga, M., McCleskey, R., 2013. Eruptions at lone star geyser, Yellow- A., McPhee, D., Glen, J., Karlstrom, L., Murphy, F., 2014. Eruptions at lone star geyser, stone National Park, USA: 1. Energetics and eruption dynamics. J. Geophys. Res. Yellowstone National Park, USA: 2. Constraints on subsurface dynamics. J. Geophys. Solid Earth 118, 1–15. http://dx.doi.org/10.1002/jgrb.50251. Res. Solid Earth 119. http://dx.doi.org/10.1002/2014JB011526. Karpov, G., 2012. Evolution of regime and physical–chemical characteristics of the new formed Geyser in Caldera Uzon (Kamchatka). Volcanol. Seismolog. 3, 3–14. Kieffer, S.W., 1984. Seismicity at old faithful geyser: an isolated source of geothermal noise and possible analogue of volcanic seismicity. J. Volcanol. Geotherm. Res. 22, 59–95.