Karymsky Volcano Research Articles

SEISMICITY of the VOLCANIC AREAS of KAMCHATKA in 2018–2019

The results of near real-time monitoring of the active Kamchatka volcanoes are described. Continuous monitoring was carried out using three remote methods: 1) seismic monitoring according to automatic telemetric seismic stations; 2) visual and video observation; 3) satellite observation of the thermal anomalies and the ash clouds. Daily information about volcanic activity is published in the Internet (http://www.emsd.ru/ ~ssl/monitoring/main.htm) since February 2000. The results of seismic activity of the Northern (Shiveluch, Kluchevskoy, Bezymianny, Krestovsky and Ushkovsky), Avacha (Avachinsky and Koryaksky), MutnovskyGorely volcano group and Kizimen, Zhupanovsky, Karymsky and Kambalny volcanoes for 2018–2019 are presented. Within two years 29199 earthquakes with KS=1.6–10.1 were located for Northern volcano group, 714 earthquakes with KS=1.6–7.6 – for Avacha volcano group, 247 earthquakes with KS=1.7–7.3 – Mutnovsky-Gorely volcano group, 116 earthquakes with KS=2.6–8.7 for Kizimen volcano, 315 earthquakes with KS=2.2–10.9 for Zhupanovsky volcano, five earthquakes with KS=6.2–8.3 for Kambalny volcano and four earthquakes with KS=5.2–6.7 for Karymsky volcano. Maps of epicenters, quantities of seismic energy and earthquake distribution according to class are given. All periods of activity were fixed and investigated by remote methods in 2018–2019: intensive volcanic activity of Sheveluch volcano associated with new cone, two paroxysmal explosive eruptions of Bezymianny volcano and the summit explosive-effusive eruptions of Kluchevskoy volcano.

СЕЙСМИЧЕСКИЕ ЭФФЕКТЫ, ПРЕДВАРЯВШИЕ ЭКСПЛОЗИИ НА ВУЛКАНЕ КАРЫМСКИЙ (п-ов КАМЧАТКА) В ФЕВРАЛЕ 2019 ГОДА

After a short period of quiescence, in February 2019, Karymsky volcano (Kamchatka Peninsula, Russia) became active. During the month, a large number of moderate explosions were recorded, some of which were preceded with some periodicity by long-period earthquakes with a high degree of similarity of waveforms. The duration of the multiplet events that preceded the explosions ranged from 4 to 70 minutes. The period between earthquakes decreased as the multiplets developed. The amplitude of earthquake records either increased or remained at the same level. The multiplets with higher amplitude of earthquake records preceded the strongest eruptions. The decreasing period between earthquakes is most likely related to the acceleration of magma ascent and an increase in gas pressure in the volcanic channel. If this is true, the absence of long-period earthquakes after the eruption marks a complete release of gas pressure in the volcanic edifice.

Karymsky volcano eruptive plume properties based on MISR multi-angle imagery, and volcanological implications.

Space-based, operational instruments are in unique positions to monitor volcanic activity globally, especially in remote locations or where suborbital observing conditions are hazardous. The Multi-angle Imaging SpectroRadiometer (MISR) provides hyper-stereo imagery, from which the altitude and microphysical properties of suspended atmospheric aerosols can be derived. These capabilities are applied to plumes emitted at Karymsky volcano from 2000 to 2017. Observed plumes from Karymsky were emitted predominantly to an altitude of 2-4 km, with occasional events exceeding 6 km. MISR plume observations were most common when volcanic surface manifestations, such as lava flows, were identified by satellite-based thermal anomaly detection. The analyzed plumes predominantly contained large (1.28 µm effective radius), strongly absorbing particles indicative of ash-rich eruptions. Differences between the retrievals for Karymsky volcano's ash-rich plumes and the sulfur-rich plumes emitted during the 2014-2015 eruption of Holuhraun (Iceland) highlight the ability of MISR to distinguish particle types from such events. Observed plumes ranged from 30 to 220 km in length, and were imaged at a spatial resolution of 1.1 km. Retrieved particle properties display evidence of downwind particle fallout, particle aggregation and chemical evolution. In addition, changes in plume properties retrieved from the remote-sensing observations over time are interpreted in terms of shifts in eruption dynamics within the volcano itself, corroborated to the extent possible with suborbital data. Plumes emitted at Karymsky prior to 2010 display mixed emissions of ash and sulfate particles. After 2010, all plumes contain consistent particle components, indicative of entering an ash-dominated regime. Post-2010 event timing, relative to eruption phase, was found to influence the optical properties of observed plume particles, with light-absorption varying in a consistent sequence as each respective eruption phase progressed.

Leaching of Trace Elements from Rocks under the Action of Organic Acids

Experiments were carried out on the leaching of trace elements (Li, Rb, Cs, Sr, Ba, V, Mn, Fe, Co, Ni, Cu, Tl, Y, La, Ce, Th, and U) from unmodified ashes of Karymsky volcano (the Kamchatka Peninsula) under the interactions with 0.01 M oxalic, salicylic, tartaric, citric, and acetic acids at various proportions of solid and liquid phases. Based on the data we obtained, it was concluded that the trace elements were mainly mobilized owing to the destruction of crystalline structures of rock-forming minerals, as well as to the reduction of Fe(III) and Mn(IV) oxide–hydroxides into soluble Fe(II) and Mn(II) compounds (in the case of oxalic acid). The formation of organic complexes increased the stability of metals in a solution and provided the attainment of higher concentrations of the dissolved forms compared to the case without organic ligands.

Leaching of trace elements from the rocks under action of organic acids

The experiments on studying leaching of trace elements (Li, Rb, Cs, Sr, Ba, V, Mn, Fe, Co, Ni, Cu, Tl, Y, La, Ce, Th, U) from unaltered ash of the Karymsky volcano (Kamchatka) under its interaction with 0.01 M solutions of oxalic, salicylic, tartaric, citric, and acetic acids at the different solid/liquid phases mass ratio were lead. Based on the obtained data it is drawn a conclusion that mobilization of trace elements occurs mainly as a result of demolition of crystal structure of rock-forming minerals, as well as (in case of oxalic acids) at reduction of Fe(III) and Mn(IV) oxyhydroxides to soluble Fe(II) and Mn(II) compounds. Organic complexes formation increases of the metals stability in solution and provides a possibility of achievement of much higher values of the dissolved forms concentration than for the lack of organic ligands.

The CO2 flux from hydrothermal systems of the Karymsky volcanic Centre, Kamchatka

The CO2 flux provided by the hydrothermal activity within the Karymsky Volcanic Centre, Kamchatka, was measured, and the CO2 balance of the Karymsky caldera lake was estimated in the framework of a Deep Carbon Observatory (DCO) project. The Karymsky Volcanic Centre located in the SE of the Kamchatka Peninsula, in the middle of the modern volcanic front, consists of two calderas, hosts a caldera lake and is characterized by hydrothermal activity that is manifested at several thermal fields. Within the Akademii Nauk (AN) caldera which is filled by a caldera lake, the Akademii Nauk springs discharge boiling water into the lake. The lake is drained by the Karymsky River that then crosses the caldera of the Karymsky volcano (Karymsky caldera) and drains the thermal field of CO2-rich Karymsky springs. The lake after the 1996 sublimnic eruption is in a steady-state condition with the total dynamic CO2 budget of about 4t/day, and has a total amount of CO2 stored inside of the lake of around 8000t. The thermal springs of the Karymsky caldera drained by the Karymsky River enrich the river in dissolved carbon species. A total CO2 output of 320t/day from both Karymsky Centre calderas was estimated, carrying around 130t/day carbon species (expressed as CO2) as dissolved species (HCO3 and CO2(aq)), and emitting to the atmosphere around 190t/day of CO2 as the diffusion flux from the soil and bubbling emanations from the springs.

Hydrothermal systems of the Karymsky Volcanic Centre, Kamchatka: Geochemistry, time evolution and solute fluxes

Karymsky Volcanic Centre (KVC) at the middle of the frontal volcanic chain of the Kamchatka arc consists of two joined calderas (Akademii Nauk and Karymsky volcano) and hosts two hydrothermal systems: Akademii Nauk (AN) and Karymsky (K). The AN is a typical boiling system, with Na-Cl waters (TDS~1g/l), low gas content (CO2-N2), with deep calculated temperatures of ~200°C. In contrast, springs of the K system have lower temperatures (up to 42°C), strong gas bubbling, TDS ~2.5g/l, and are enriched in HCO3− and SO42−, with Mg2+ as the main cation. There are two intriguing characteristics of the K field: (i) their CO2-rich gas (>97mol%) has the highest 3He/4He ratios ever measured for hydrothermal systems in Kamchatka of ~8Ra (where Ra=1.4×10−6) and (ii) their thermal waters have an unusual cation composition (Mg>Na>Ca). After the 1996 sublimnic eruption within AN caldera, new hot springs appeared close to the eruption site. In this paper we synthesize all published and new geochemical data sets. The Karymsky Lake and post-1996 new thermal springs demonstrate exponential decreases in their main dissolved species, with a characteristic time of 5 to 8years. The chemistry of AN and K springs did not change after the eruption. However, the concentration of chloride in the lake water approached ~35mg/l, compared with a background of 8–11mg/l revealing a possible new source of hot water within the Karymsky Lake. All thermal fields of the KVC are drained by the Karymsky River with an outflow rate at the source of ~2m3/s (flowing out from Karymsky Lake) and at the exit from the Karymsky caldera of ~4.5m3/s. Using the measured solute fluxes at the source (AN springs) and at the exit (AN+K springs) the natural heat flux from the two systems can be estimated as ~67MW and ~120MW, respectively, and ≥20t/d for the chloride output from both systems.

Frequency based satellite monitoring of small scale explosive activity at remote North Pacific volcanoes

Monitoring of volcanoes in the North Pacific can be an expensive and sometimes dangerous task, specifically for those located in Alaska (USA) and Kamchatka (Russia). An active frequency detection method previously used at Stromboli, Italy, uses the thermal- and mid-infrared wavelength bands from the Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data to detect anomalies at a volcano. This method focuses on small scale explosive activity, often referred to as Strombolian activity which can produce small spatter fields near a volcano's active vent. In the North Pacific, there are a number of volcanoes which exhibit small scale explosive activity and three are the focus of this study: Chuginadak (Mt. Cleveland) and Shishaldin in Alaska, and Karymsky Volcano in Kamchatka. Satellite images from the Advanced Very High Resolution Radiometer (AVHRR) were used to monitor the frequency of thermal features as well as the occurrence of ash plumes at each volcano. This data was then used to produce a time series spanning 2005–2010 for all three volcanoes. During this time period, each volcano underwent a series of eruptive cycles including background levels of activity, heightened frequency of small explosions (identified as precursory activity), and heightened activity typified by ash plume-producing eruptions. Each location has a unique precursory signal, both in timing and magnitude. The use of a previously developed method on a new sample set of volcanoes has proved the validity of this method as a monitoring tool for volcanoes with small scale explosive activity. This method should be applied to a larger set of volcanoes to continue the development and database production for its use as a volcano monitoring tool.

Three-dimensional volcano-acoustic source localization at Karymsky Volcano, Kamchatka, Russia

We test two methods of 3-D acoustic source localization on volcanic explosions and small-scale jetting events at Karymsky Volcano, Kamchatka, Russia. Recent infrasound studies have provided evidence that volcanic jets produce low-frequency aerodynamic sound (jet noise) similar to that from man-made jet engines. For man-made jet noise, noise sources localize along the turbulent jet flow downstream of the nozzle. Discrimination of jet noise sources along the axis of a volcanic jet requires high resolution in the vertical dimension, which is very difficult to achieve with typical volcano-acoustic network geometries. At Karymsky Volcano, an eroded edifice (Dvor Caldera) adjacent to the active cone provided a platform for the deployment of five infrasound sensors in July 2012 with intra-network relief of ~600m. The network was designed to target large-scale jetting, but unfortunately only small-scale jetting and explosions were recorded during the 12-day experiment. A novel 3-D inverse localization method, srcLoc, is tested and compared against a more common grid-search semblance technique. Simulations using synthetic signals show that srcLoc is capable of determining vertical solutions to within ±150m or better (for signal-to-noise ratios ≥1) for this network configuration. However, srcLoc locations for explosions and small-scale jetting at Karymsky Volcano show a persistent overestimation of source elevation and underestimation of sound speed. The semblance method provides more realistic source locations, likely because it uses a fixed, realistic sound speed of ~340m/s. Explosion waveforms exhibit amplitude relationships and waveform distortion strikingly similar to those theorized by modeling studies of wave diffraction around the crater rim. We suggest that the delay of acoustic signals and apparent elevated source locations are due to raypaths altered by topography and/or crater diffraction effects, implying that topography in the vent region must be accounted for when attempting 3-D volcano acoustic source localization. Though the data presented here are insufficient to resolve small-scale jet noise sources, similar techniques may be successfully applied to large volcanic jets in the future.

Characterization and interpretation of volcanic activity at Karymsky Volcano, Kamchatka, Russia, using observations of infrasound, volcanic emissions, and thermal imagery

A multiparameter data set including measurements of infrasound, volcanic emissions, and thermal imagery is used to characterize and interpret diverse volcanic activity observed during field campaigns in August 2011 and July 2012 at Karymsky Volcano, Kamchatka, Russia. Four activity types are visually identified and characterized according to: SO2 emission rate, ash mass, event duration, peak temperature, thermal radiation energy, infrasound onset and frequency, reduced infrasonic pressure, and acoustic energy. These activity types include: (1) ash explosions, (2) pulsatory degassing, (3) gas jetting, and (4) explosive eruption. Unique infrasound signals are associated with all four activity types suggesting that infrasound can be used to help remotely and continuously detect and characterize volcanic activity at Karymsky and other similar volcanoes. Our observations suggest that SO2 is emitted continuously, though in varying abundance, while ash is emitted discontinuously and is only associated with certain types of activity. Our data set supports previous models that attribute variations in surface activity to changes in conduit permeability at Karymsky Volcano. Evidence for a decrease in conduit permeability as a trigger for ash explosions and explosive eruption activity types is supported by weakened but still detectable SO2 emission rates prior to eruption, along with the highly impulsive infrasonic onset and large reduced infrasound pressure indicating high pressure at the vent. We speculate that changes in conduit permeability at Karymsky Volcano result from changes in magma supply from the shallow‐crustal storage region though additional measurements are required to validate this hypothesis.

Composition and evolution of the melts erupted in 1996 at Karymskoe Lake, Eastern Kamchatka: Evidence from inclusions in minerals

The powerful eruption in the Akademii Nauk caldera on January 2, 1996, marked a new activity phase of Karymsky volcano and became a noticeable event in the history of modern volcanism in Kamchatka. The paper reports data obtained by studying more than 200 glassy melt inclusions in phenocrysts of olivine (Fo82–72), plagioclase (An92–73), and clinopyroxene (Mg# 83–70) in basalts of the 1996 eruption. The data were utilized to estimate the composition of the parental melt and the physicochemical parameters of the magma evolution. According to our data, the parental melt corresponded to low magnesian, highly aluminous basalt (SiO2 = 50.2 wt %, MgO = 5.6 wt %, Al2O3 = 17 wt %) of the mildly potassic type (K2O = 0.56 wt %) and contained much dissolved volatile components (H2O = 2.8 wt %, S = 0.17 wt %, and Cl = 0.11 wt %). Melt inclusions in the minerals are similar in chemical composition, a fact testifying that the minerals crystallized simultaneously with one another. Their crystallization started at a pressure of approximately 1.5 kbar, pro ceeded within a narrow temperature range of 1040 ± 20°C, and continued until a nearsurface pressure of approximately 100 bar was reached. The degree of crystallization of the parental melt during its eruption was close to 55%. Massive crystallization was triggered by H2O degassing under a pressure of less than 1 kbar. Magma degassing in an open system resulted in the escape of 82% H2O, 93% S, and 24% Cl (of their initial contents in the parental melt) to the fluid phase. The release of volatile compounds to the atmosphere during the eruption that lasted for 18 h was estimated at 1.7 × 106 t H2O, 1.4 × 105 t S, and 1.5 × 104 t Cl. The concen trations of most incompatible trace elements in the melt inclusions are close to those in the rocks and to the expected fractional differentiation trend. Melt inclusions in the plagioclase were found to be selectively enriched in Li. The Lienriched plagioclase with melt inclusions thought to originate from cumulate layers in the feeding system beneath Karymsky volcano, in which plagioclase interacted with Lirich melts/brines and was subsequently entrapped and entrained by the magma during the 1996 eruption.

Finite-difference time-domain modeling of transient infrasonic wavefields excited by volcanic explosions

[1] Numerical modeling of waveform diffractions along the rim of a volcano vent shows high correlation to observed explosion signals at Karymsky Volcano, Kamchatka, Russia. The finite difference modeling assumed a gaussian source time function and an axisymmetric geometry. A clear demonstration of the significant distortion of infrasonic wavefronts was caused by diffraction at the vent rim edge. Data collected at Karymsky in 1997 and 1998 were compared to synthetic waveforms and variations of vent geometry were determined via grid search. Karymsky exhibited a wide range of variation in infrasonic waveforms, well explained by the diffraction, and modeled as changing vent geometry. Rim diffraction of volcanic infrasound is shown to be significant and must be accounted for when interpreting source physics from acoustic observations.

How a tectonic earthquake may wake up volcanoes: Stress transfer during the 1996 earthquake–eruption sequence at the Karymsky Volcanic Group, Kamchatka

A large tectonic earthquake occurred on Kamchatka peninsular on New Year's Day of 1996 along a SW–NE trending fracture system. Just two days after the earthquake and at a distance of about 10–20 km to the north, a simultaneous eruption of two separate volcanoes followed. These were Karymsky Volcano and Akademia Nauk Volcano, the latter having its first eruption in historical records. In this paper I use numerical models in order to elaborate the static stress transfer between the earthquake and the volcanic system during the sequence that culminated in the January 1996 volcano-tectonic events. The models were designed to consider (i) the geodetically identified pre-eruptive period of doming in order to calculate stress changes at the nearby SW–NE trending fracture zone, and (ii) the January 1996 Mw 7.1 earthquake in order to calculate the dilatation and stress changes at the magma plumbing system. The results suggest that stress changes related to year-long inflation under the volcanic centers increased the Coulomb failure stress at the active faults and thus encouraged the earthquake. The earthquake, in turn, prompted dilatation at the magmatic system together with extensional normal stress at intruding N–S trending dikes. Also, field measurements confirmed the presence of N–S oriented fractures above the dike. Unclamping of the N–S oriented fractures allowed magma to propagate and eventually to trigger the twin-eruption at the volcanoes Karymsky and Akademia Nauk. These findings imply that successful hazard evaluations at volcanoes elsewhere require consideration of the seismo-tectonic framework and large earthquake cycles.

Non-linear explosion tremor at Sangay, Volcano, Ecuador

A detailed analysis of discrete degassing pulses, chugs, at Sangay volcano, was performed on seismic and infrasonic records to determine the physics of the conduit. Infrasonic chugging signals appear as repetitive pulses with small variations in amplitude and time lag. An automated time-domain analysis was developed to measure with high precision time intervals and amplitudes at different wave arrivals, reducing the possibility error associated with hand picking. Using this automated method, a strong positive correlation of acoustic amplitude with repose time between individual pulses on chugging signals of Sangay was found on numerous oscillating sequences. Frequency gliding of apparent harmonic frequencies generally trends from high to low frequency at Sangay, in contrast to trends at Karymsky Volcano, Russia. A new description of chugging events using wavelet transform methods, appropriate for non-stationary signals, shows subtle changes in the waveforms relate to physical processes in the volcano. A system of non-linear feedback, based on choked flow at the vent, is postulated as the most likely source of this volcanic tremor.

On the relation between infrasound, seismicity, and small pyroclastic explosions at Karymsky Volcano

Ground‐ and atmospheric‐propagating elastic waves are integrated with digitized video to reconstruct important parameters during the onset of eruptions at Karymsky Volcano in 1999. Muzzle velocities, which range from 10 to 55 m/s for 34 analyzed explosive events, are found to be very well correlated with eruption velocities synthesized from infrasonic trace data. Acoustic modeling proposed here invokes a linear acoustic source consistent with a 3‐m piston that accelerates upwards. Timing of acoustic arrivals relative to video records of material emission is used to constrain fragmentation sources depths, which are assumed to be coincident with infrasound generation. These sources are generally shallow, with an observed vertical range of about 15 m. Systematic changes in source depth are observed during two nights of data collection and are attributed to variations in the depth of the magma free surface. Relative timing of acoustic and seismic arrivals is used to identify the presence of seismicity prior to fragmentation. This seismicity is emergent and low intensity, but significant because it precedes the presumed fragmentation events by variable amounts up to 4 s. The primary short‐period seismic phases appear coincident with the initiation of fragmentation and infrasound generation. Because of the complexity of the seismic Green's function, it is not possible to correlate amplitude from a specific seismic pulse with observed eruption intensity.

Experimental study of plagioclase rim growth around anorthite seed crystals in rhyodacitic melt

The purpose of this study was to replicate experimentally the growth of new rims around highly anorthitic plagioclase core phenocrysts, analogous to the incorporation of xenocrysts into a silicic magma body through magma mixing. Aniakchak rhyodacite forms the bulk starting composition, and phase-equilibria experiments constrained the pre-eruption magma conditions to be ∼110 MPa and 870-880 °C. The experimental runs were seeded with Great Sitkin anorthite (An 9 1 - 9 5 ) crystals. New rim growth of An 2 8 - 3 8 plagioclase occurred at rates between 3.5 (′0.3) x 10 - 1 0 to 60.6 (′20.0) x 10 - 1 0 cm/s at pressures and temperatures from 50 to 150 MPa and 825 to 880 °C. The values in parentheses are ′1σ standard deviation. Microlite crystallization (An 2 7 - 4 1 ) occurred in all experiments within the plagioclase stability field, and their growth rates varied from 4.4 (′1.3) x 10 - 1 0 to 65.7 (′10.1) x 10 - 1 0 cm/s. The rim and microlite growth rates are similar to one another within each experiment, and microlite number density (N v ) is correlated approximately inversely with rim growth rates. Microlite crystallinities increased from 4.2 to 49.7 vol% as a function of increasing ΔT e f f up to 95 °C. The results indicate growth-dominated crystallization at low ΔT e f f , and nucleation dominated crystallization at high ΔT e f f , in agreement with previous studies. Assuming the experiments apply to nature, the rim growth rates can provide a minimum estimate on how fast magma mixing can occur. Rims that are 10 to 100 μm wide can grow in ∼10 days to 4 months, recording fast mixing timescales as long as eruption occurs shortly after mixing. The growth rate estimates presented here generally agree with those derived from sodic rims growing around anorthite cores after mixing between basalt and andesite prior to the 1996 eruption of Karymsky volcano, Kamchatka.

Disturbances in groundwater chemical parameters related to seismic and volcanic activity in Kamchatka (Russia)

Abstract. Starting from 1992 geochemical data are being collected with a mean sampling frequency of three days in the form of the pH value and of the most common ions and gases in the groundwater in one deep well located in Petropavlovsk, the capital city of Kamchatka (Russia). On 1 January 1996 a strong eruption started from the Karymsky volcano, that is located about 100km far from the well, in the north-northeastern direction. At the same time, a large earthquake (M=6.9) occurred in the Karymsky area. On 5 December 1997 a very large earthquake (M=7.7) occurred offshore, at a distance of 350km from the well and towards the same direction. The analysis of the geochemical data shows clear variations in the raw temporal trends on both cases. For the first event, a clear premonitory phase appeared; for the second one, some pre-seismic variations could be revealed but permanent modifications of the chemistry of the water subsequent to the earthquake are very clear. In both cases the feature of the geochemical variations is consistent with an afflux of new water in the aquifer connected with the well and with an escape of the Carbon dioxide gas from the ground in different directions. A schematic model able to justify such a phenomenology and the connections of the geochemical variations with the previous tectonic activities is proposed.

The 1996 Eruption of Karymsky Volcano, Kamchatka: Historical Record of Basaltic Replenishment of an Andesite Reservoir

The simultaneous eruption in 1996 of andesite from Karymsky volcano and of basalt from the Academy Nauk vent 6km away appears to provide a case of mafic recharge of an andesite reservoir for which the time of recharge is exactly known and direct samples of the recharging magma are available. The explosive phreato-magmatic eruption of basalt was terminated in less than 24h, whereas andesite erupted continuously during the following 4 years. Detailed petrological study of volcanic ash, bombs and lavas of Karymsky andesite erupted during the period 1996–1999 provides evidence for basaltic replenishment at the beginning of the eruptive cycle, as well as a record of compositional variations within the Karymsky magma reservoir induced by basaltic recharge. Shortly after the beginning of the eruption the composition of the matrix glass of the Karymsky tephra became more mafic and then, within 2 months, gradually returned to its original state and remained almost constant for the following 3 years. Further evidence for basaltic replenishment is provided by the presence of xenocrysts of basaltic origin in the andesite of Karymsky. A conspicuous portion of the plagioclase phenocrysts in the Karymsky andesite has calcic cores, with compositions and textures resembling those of plagioclases in the Academy Nauk basalt. Similarly, the earlier portion of the andesite of the eruption sequence contains rare olivines, which occur as resorbed cores in pyroxenes. The composition of the olivine matches that of olivines in the Academy Nauk basalt. The sequence of events appears to be: (1) injection of basaltic magma into the Karymsky chamber with immediate, compensating expulsion of pre-existing chamber magma from the Karymsky central vent; (2) direct mixing of basaltic and andesitic magmas with dispersal of phenocrysts associated with the basalt throughout the andesite so that newly mixed magma appeared at the vent within 2 months; (3) re-establishment of thermal and chemical equilibrium within the reservoir involving crystallization in the new hybrid liquid, which returned the melt composition to ‘normal’, formed rims on inherited calcic plagioclase, and caused the resorption of dispersed olivine xenocrysts. Taken together, these findings indicate that the Karymsky magma reservoir was recharged by basalt at the onset of the 1996 eruptive cycle. The rapidity and thoroughness of mixing of the basalt with the preexisting andesite probably reflects the modest contrast in temperature, viscosity, and density between the two magmas.

Explosions and periodic tremor at Karymsky volcano, Kamchatka, Russia

SUMMARY The explosions of Karymsky volcano often produce signals containing a sequence of repeating pulses recorded on acoustic and seismic sensors, known as chugging. The amplitudes of these pulses correlate with the time interval between pulses. For a given measured acoustic pressure, seismic amplitudes take on arbitrary values up to a specific, empirically determined threshold. Conversely, events with a small seismic amplitude yielded acoustic waves with large variations and large-amplitude seismic events corresponded to large acoustic waves. These observations are not consistent with a source modelled by a resonating conduit. Rather, a model consisting of a sequence of discrete pulses explains the data and provides a framework for understanding the dynamics of degassing at the vent. The physical model for chugging involves a time-varying narrowing vent where gasses are released in a series of oscillations which appear to be harmonic but instead are modelled as short-term transients, or discrete pulses, suggestive of choked flow.

Detection of eruption cloud with DTII derived from GMS-5 VLSSR data

On January 2, 1996 two eruption clouds from Karymsky volcano group in Kamchatka Peninsula were detected in the imageries of VISSR (Visible and Infrared Spin Scan Radiometer) aboard the fifth Japanese Geostationary Meteorological Satellite, GMS-5. The cloud drifting ENE was brighter than that drifting SSE in the imagery of visible channel. The ENE cloud was recognizable in the infrared imagery, while the SSE cloud was not. Although ash-bearing eruption cloud is generally discriminated in the imagery of DTII (Differential Thermal Infrared Imaging) made from the data of two infrared window channels of GMS-5 VISSR, the ENE cloud was not discriminated with DTII. The data of in situ and radio sounding observations revealed that the height of the ENE cloud was around 6.3 km above sea level and originated from the crater in the Karymskoe Lake side, containing abundant ice particles, while the height of the SSE cloud was around 2.7 km above sea level. This eruption cloud was from the crater near the summit of the volcano, containing abundant ash (silicate glass). The directions of the eruption clouds coincided with those of the prevailing winds at the cloud heights. It is considered that, although the ENE cloud contained abundant ash, the radiative characteristics of the ash was greatly reduced by ice coating on ash particles. The advantage of DTII is rather reduced in the cold area due to the low temperature of the Earth's surface.