The 2,288 m Mutnovsky is one of the most active volcanoes in S Kamchatka.  It was formed by four coalescing stratovolcanoes that erupted basalts to dacites.  Activity here began 80 ka and continued through to the present.  Recent eruptions have been phreatic, with the last magmatic eruption in 1848.  The volcano has a vigorous hydrothermal system that has altered volcanic rocks throughout its history.  That active hydrothermal system is being used to power a geothermal electrical generation plant on the N slope of the edifice. 

Mutnovsky is located just 15 km SE from neighboring Gorely which had a caldera-forming eruption 39 ka.  They tap different magma sources and erupt chemically dissimilar magmas.  They are not considered to be related.  Granyia covered Mutnovsky in a great 2016 post.  Today’s will take a little more regional perspective. 

The region is sparsely populated with only a single major road running S from Petropavlovsk along the E part of the peninsula.  There are only 97 living within 30 km of Mutnovsky.  Over 250,000 live within 100 km.  Most of these are in Petropavlovsk and surrounding towns, 70 km NE.

Climate is classified as subarctic, just a bit cooler than a humid continental climate.  Average daily highs are 6.3° C, lows 0.5° C.  It is quite wet, with nearly 120 cm of precipitation / year.  Average snow depth during the seven-month winter is 47 cm.

Petropavlovsk is the largest city in Kamchatka.  It and its surrounding towns have a population of 250,000, perhaps half the population of the Kamchatka Krai (the peninsula and the Koryak Autonomous Okrug N of it on the Siberian mainland).  In terms of population and weather, it is somewhat similar to Anchorage in Alaska.

The city was visited by Cossacks in 1697 and founded by Vitus Bering in 1740.  It is located on the Avacha Bay, a large, sheltered bay at the mouth of the Avacha River.  The region had significant military importance during the time of the Soviet Union.  After its fall, the economy is mostly based on fishing, crabbing and logging.  The surrounding volcanoes are generally accessed by helo, though there are some unimproved roads and trails available.  A geothermal plant on the N flanks of Mutnovsky supplies a third of electrical needs for Petropavlovsk. 

Volcanic monitoring and warnings in this part of the world are handled by KVERT (Kamchatkan Volcanic Eruption Response Team), part of the Russian Institute of Volcanology and Seismology.  KVERT maintains a close working relationship with AVO (Alaska Volcano Observatory) and the USGS.  Like more government funded and supported scientific activities, it is continually involved in the yearly budget wars.  Some years go better than others. 

Region

Volcanoes in this part of Kamchatka seem to be arrayed in closely spaced groups.  Just N of Petropavlovsk, we have the closely spaced Avachinsky – Koryaksky group.  Another 42 km NNE from that group we have the Zupanovsky – Dzenzursky group.  S of Petropavlovsk, we have the Karymshina volcanic complex.  This complex contains the volcano for today’s post, Mutovsky.  It stretches N and W to include Gorely, Tolmaechev Dol, Opala, Bolshaya Ipelka, and the Karymshima Caldera between Mutnovsky and Petropavlovsk.  The next volcanic group to the S is Khodutka. 

Most of these groups warrant a separate post centered around their main member, something the reader should expect in the future.  Given the sheer number of closely spaced volcanic groups and their members, I will limit the regional review to the volcanic systems mentioned above.  All distances will be measured from Mutovsky.

Avachinsky – Koryaksky  

The Avachinsky – Koryaksky volcanic group is located some 100 NNE from Mutnovsky, some 30 km NE from Petrovpavlovsk.  Like most volcanic groups in this part of Kamchatka, activity has migrated E over time, with the youngest volcano, Avachinsky anchoring the group on the E.  To the W of Avachinsky, we have Koryaksky, Kozelsky, Arik and Aag.  The entire line measures roughly 25 km between volcanic peaks oriented toward the NW.  The older volcanoes are heavily eroded. 

2,741 m Avachinsky is considered active, erupting at least 16 times in recorded history.  The largest of these were a pair of VEI 4s in 1926 and 1945.  The most recent eruption was a VEI 1 in 2001.  The volcano has an active hydrothermal system with fumaroles and other activity in the crater.  Neighboring Koryaksky, is taller at 3,456 m.  It is still active with fumaroles and a hydrothermal system.  The most recent eruption a VEI 2 ending in 2009.  The pair is treated as a single volcanic system and is a member of the Decade volcanoes list due to its proximity to Petropavlovsk.

Like most stratovolcanoes in Kamchatka, Avachinsky erupts violently and has an unstable cone.  Both Avachinsky and Kozelsky have collapse scars from major flank collapses and debris avalanches.  Kozelsky has an amphitheater that is breached to the NE.  Avachinsky collapsed to the S, 40 – 30 ka, with the avalanche covering 500 km2.  Neighboring Petropavlovsk is built on that debris field.  Avachinsky rebuilt its cone in two stages 18 and 7 ka.  Most recent eruptions are explosive, with pyroclastic flows and hot lahars going SW, directed by the collapse scarp. 

Karymshina volcanic complex

The big volcanic structure in the Karymshina volcanic complex is the 15 x 25 km Karymshina caldera, formed in a massive eruption 1.78 Ma.  The eruption produced over 800 km3 of rhyolite ignimbrite.  There are perhaps 12 resurgent domes surrounding the caldera dating 2.2 – 0.5 Ma.  It is located some 39 km NNW from Mutnovsky.  The Bolshe – Banny geothermal field is located on the NW edge of the caldera.  There are multiple older volcanic structures in close proximity to the caldera that erupted dacites, basalts and rhyodacites. 

Recently active neighboring volcanic systems are not formally classified as resurgent activity but may more properly be a reflection of continued volcanic activity of this region.  There are several hydrothermal systems associated with Karymshina whose names may be mistaken for the larger caldera system.  These include Bolshe – Bannaya, Mal, Bannaya, Karymchina, Karymshina and Verkhne – Paratunka. 

Activity at Karymshina has been long-lived, proceeding in three phases starting 4.0 Ma.  Each phase was separated by about a 1 Ma hiatus.  Eruptions took place 4.0 – 0.5 Ma.  Initial eruptions continued through 3.3 Ma.   Precaldera eruptions formed basaltic andesitic and dacitic volcanoes.  The second phase was the climatic Karymshina ignimbrite 1.78 Ma, which produced an estimated 800 km3 of rhyolite.  The third phase extruded domes around the caldera ring facture 0.9 – 0.5 Ma. 

Post-caldera eruptions are chemically similar to the 1.78 Ma ignimbrite and may have erupted residual melts from the underlying caldera-wide crystal mush.  The mush is heated up by periodic basaltic intrusions to remain semi-molten for more than 1.0 Ma.  The size of the caldera, the underlying caldera, the duration of volcanism, and crystal-rich nature of eruptive products are similar to the North American ignimbrite flareup 30 – 20 Ma and the current Andean ignimbrite flareup. 

There are no thick ash layers from the 1.78 Ma eruption found in Pacific cores.  Cores from the Okhotsk Sea have not yet been taken.  It is possible that most of the material erupted as ignimbrites rather than plumes. 

Vilyuchinsky

Vilyuchinsky (Vilyuchik) is 2,173 m steep-sided young stratovolcano located some 27 km NNE from Mutnovsky.  The distance would put it close to the SE rim of the Karyshina caldera, though it is not described as a resurgent system.  It was built prior to 10 ka, which is thought to be the most recent eruption.  That eruption produced airfall and a lava flow.  Landslides, lahars and rock avalanches have impacted areas below the slopes.  The volcano has an active hydrothermal system with hot springs and sulfur vapor.  A lahar triggered by Typhoon Elsa killed at least two climbers in 1981, sweeping away a vehicle they were driving. 

Gorely

Gorely is the immediate neighbor to Mutnovsky, located 15 km NW.  It is a 1,799 m massif constructed by five overlapping small stratovolcanoes along a WNW trending line.  The group is built in a 9 x 13 km caldera formed 40 – 38 ka.  Post caldera activity built at least 40 cinder cones.  There are three major rift zones across the complex.  Another young stratovolcano is located on the SW flank.  The complex covers over 650 km2. 

Activity over the last 10 ka has been frequent mild to moderate explosive eruptions with at least 6 major lava flows.  Over the last 10 ka, explosive activity and lava flows filled much of the caldera.  The length of quiet periods grew over the last 6 – 2 ka.  Over the last 650 years, frequent eruptions included strong explosions and lava flow effusion.  Historic eruptions have been moderate Vulcanian and phreatic explosions.

The edifice is described as a shield, with the ancestral Pra-Gorely 20 – 25 ka in diameter.  It is topped with the 9 x 13 km diameter caldera that ejected at least 100 km3 during its formation some 40 – 38 ka.  There is some dispute about the size of the eruption as VOGRIPA carries it as a VEI 7.5 ejecting 225 km3 of material.  Post caldera activity built Young Gorely, with three stratocones and 11 associated craters. 

The most recent eruption was a VEI 1 in 2010.  It opened a new vent on the inner SW wall of the crater.  Two previous eruptions in 1984 and 1980 were VEI 2 and VEI 3 respectively.  There have been several episodes of increased seismic activity and tremor following the 2010 eruption. 

The main volcano is a ridge about 3 km long with a chain of 11 craters.  It was formed by merging of several stratocones and covers some 150 km2.  There are multiple lakes, fumaroles and cinder cones on the slopes of the ridge.  A few of the craters are filled with acid lakes.  Blue Lake in the bottom of the E crater changes color with volcanic activity, blue when quiescent and boiling muddy gray when active. 

The currently active crater is called Active, with an orange acid lake.  There are multiple active fumaroles around the lake.  Climbing into this crater is not recommended due to unstable slopes and SO2 emissions from the fumaroles. 

An eruption some 2,000 years ago extruded lava flows onto the N flanks of the volcano.  There are at least 14 lava caves among the flows.  Some of the lava flows extend over 10 km. 

Tolmachev Dol

Tolmachev Dol (Tolmachev Plateau) is a broad volcanic highland located some 44 km NW from Mutnovsky, between Gorely and Opala.  It tops out at 1,021 m, including numerous recent cinder cones and lava flows.  The lava field covers a broad area on both sides of Lake Tolmachev, in a wide depression between Opala and Gorely.  The ancestral Tolmachev stratovolcano is at the SE side of the lake.  The last major eruption was a VEI 5.0 4.6 ka from the Chasha crater in the N part of the plateau, ejecting some 1 km3 of rhyolitic tephra.  The most recent eruption was from a cinder cone in the NW part of the plateau 1. 7 – 1.6 ka. 

Opala

Opala is a relatively young 2,439 m steep-sided stratovolcano located some 58 km WNW from Mutnovsky.  It is located midway between the Tolmachev Dol volcanic field to the E and the large, heavily eroded Bolshaya Ipelka to its W.  It has erupted andesitic – dacite lavas and tephras over the last 10 ka.  It is located at the N end of the 12 x 14 km Opala caldera formed 40 ka. 

The most recent major eruption was a VEI 5.7 in 610 AD that created the Barany (Baranii) Amphitheater on the SE flank.  The eruption deposited 3 – 5 km3 rhyolite tephra.  The 2 x 2.5 km crater is filled with a 1 km diameter post collapse lava dome.  There have been mild explosive eruptions from the summit and flank vents.  There are no known tephras from the recent eruptions.  The most recent eruption took place at the summit some 300 years ago.

The 610 AD major eruption took place in multiple phases, stopping and starting more than once, mixing explosive and effusive phases.  The eruption deposited rhyolite tephras across much of Kamchatka.  There were pyroclastic flows ejected during this eruption.  The eruption vent in the Barany Amphitheater is filled with obsidian lavas chemically identical to the rhyolite tephras. 

Phase 1 of this eruption ejected a lithic – rich pumice fall, followed by ashfall from an 18 – 20 km Plinian plume and pyroclastic flow when the plume collapsed.  The eruption resumed with Phase 2 after a 5-6 hour pause.  Phase 3 repeated Phase 1.  The final phase 4 extruded obsidian lavas.  Phases 1 – 3 lasted some 60 – 80 hours including the pause. 

There was a debris avalanche some 10 – 7 ka (early Holocene) from new Opala into the surrounding caldera.  It traveled 8 km S of the summit.  A smaller landslide on the S slope took place before a tephra and lava eruption some 3.5 ka. 

The magma was very close to being decompressed (degassed) during the eruption, which led to pauses during the eruption as it varied between explosive and effusive emissions, eventually switching to effusive with dome extrusion at the end.   

The Opala caldera was formed by multiple caldera forming eruptions, the most recent of which was Opala IV, 40 ka, which ejected some 250 km3 of rhyolite.  Most of the material was ejected as tephras, with pyroclastic flows toward the end as the column collapsed.  Prevailing winds carried the plume NNE.  Thickness of fall deposits was 20 – 30 cm at 300 – 320 km from the vent.  This was the largest eruption in Kamchatka over the last 50 ka. 

Bolshaya Ipelka

Bolshaya Ipelka (Ipelka) is a massive, heavily eroded volcanic shield located W of Opala, some 83 km WNW from Mutnovsky.  Its 32 x 42 km footprint tops out at 1,194 m.  It is located W of the current volcanic front in Kamchatka and thought to be Pleistocene in age.  The volcano is heavily eroded, cut by deep glacial valleys flowing from the summit during past glacials.  The summit is the most heavily eroded. 

Ascha

Asacha is a complex group of Pleistocene to recent volcanoes located some 27 km WSW from Mutnovsky.  The group includes the ancestral Asacha shield volcano, Zheltyi stratovolcano to the E, the young 1,910 m Asacha stratovolcano and the young Tumanov lava cone.  The group is located on a fault bound crustal block.  The most recent volcanism in this group took place at young Asacha and Tumanov. 

There are at least 10 domes on the flanks of the volcanoes and seem to have extruded throughout the period of activity of the complex.  Recent activity built cinder cones and associated lava flows along the W and S flanks of the complex.  A major volcano-tectonic earthquake took place near Zheltyi in 1983.

Khodutka

The Khodutka volcanic complex is the final group of regional volcanoes we will touch on in this section.  The young Khodtuka stratovolcano was formed toward the end of the last glacial just SE of the older Priemysh stratovolcano.  There are at least 10 explosion craters, small lava cones and domes located on its flanks.  There are Holocene cinder cones to the W.  The Khodutkinsky maar on the WNW flank was created 2.8 ka.  Its eruption deposited tephra across much of S Kamchatka.  Formation of the twin maar also produced small pyroclastic flows, followed by lava flows and domes.  The most recent summit eruption took place 2.5 – 2.0 ka.  The most recent eruption in 1933 emplaced a dome in the E crater.

There is a landslide crater and related deposits on the NE slope.  It is younger than 2.5 ka, as there are no marker tephras on its surface. 

The volcano is known for its extensive hydrothermal system, including the Khodutka Springs geothermal field in an explosion crater on the NW flank of the Priemysh volcano.  Eugene Kaspersky calls Khodutka’s natural hot springs the very best in the world.  His Dec 2021 post on a visit has photos of a hot lake with what he calls perfect temperature water for bathing.  It is even drinkable. 

Mutnovsky Volcano

Mutovsky is a complex of 4 composite cones referred to as Mutnovsky I – IV.  They have been active for at least the last 80 ka.  Each stage probably reflects the evolution of a small shallow magma reservoir.  Transition from one stage to the next shifts the location of the eruptive center and perhaps the reservoir by as much as 1 km.  All stages except for the current produced magmas ranging from basalts to dacites. 

Mutnovsky I is the oldest of the eruptive centers, starting 80 – 60 ka.  It erupted basalts, basaltic andesites, andesites, dacites and pyroclastic rocks.  Total volume is around 58 km3.  There is no significant change in volcanic rock between various eruptive centers.

Mutnovsky II was active 40 – 30 ka.  It is located 3 km SE from Mutnovsky I.  It produced 24 km3 of lavas and pyroclastics and also produced parasitic cones on its flanks.  Volcanic rocks vary from basalts to dacites.  One paper describes its relationship to the older structure as a “twin volcano of the Somma – Vesuvius type.” 

Mutnovsky III was relatively small compared to the older centers at 5 km3.  It is constructed from alternating lava flows and tephras with parasitic cones on its flanks similar to the older centers.  Volcanic rocks here vary between basalts to rhyodacites.  The 1.5 x 2.0 km summit caldera was created by an eruption ejecting 2.0 – 2.5 km3 of pumice.  Its caldera is now partly filled with lava flows from Mutnovsky IV.  There is also an intra-caldera basaltic andesite cone and rhyodacite extrusion.  Final activity in the caldera was extrusion of a dacite dome some 4.0 ka.  This cycle ended with eruption of dacite pyroclastic flows and a dome within its crater.  The crater has been enlarged by explosion, collapse and/or erosion.  It is now occupied by a glacier that may be the main recharge source for the hydrothermal system.  There is a breach in the crater cut by a river that exposes a dike swarm. 

The youngest composite cone is Mutovsky IV, active for the last 11 ka.  It is located 1 km SSW from the older centers.  So far, it has erupted some 3.8 km3 of basalts and basaltic andesites.  More evolved magmas have not erupted from here yet.  There is a 1.3 km diameter crater at the summit which is either a small caldera or a collapse feature.  The crater is almost completely filled with glacial deposits.  The youngest volcanic deposits in the crater are basaltic andesite scorias and pyroclastics from a 2000 eruption sequence.  The last large explosive eruption created the Active Funnel, whose walls are altered basaltic andesites. 

There is a distinct chemical difference between Mutnovsky eruptive products and those of neighboring Gorely, a mere 15 km W.   The subducting slab is 120 km below the surface at Gorely as the slab dives steeply beneath the crust.  The magma chamber is estimated to be 3.0 km below the surface, 3.0 km in diameter. 

The extinct Skalistaya and Dvugorbaya volcanoes, and heavily eroded, somewhat younger Zhirovsky volcanoes are located N and NE of Mutnovsky.  These surround the plateau where the Mutnovsky Geothermal Field and thermal sites are located.  Gorely is the nearest active volcano to Mutnovsky.

Hydrothermal

Mutnovsky has a large hydrothermal system fed by local precipitation and by a glacier in one of its craters.  There is a large hydrothermal field of commercial value on its N slopes.  Altered rock of the volcano are prone to landslides and have produced a number of wet debris avalanches followed by lahars.  One of the largest of these (over 0.5 km3) extended 10 km.  Its deposits are typical hummocky topography with large blocks 5 – 15 m in a matrix of altered rock.  The avalanche took place 500 – 1000 AD and was accompanied by a phreatic eruption. 

The Mutnovsky III crater has intense fumarole activity arranged in a ring, perhaps defining the conduit margin of the final dacite dome.  The phreatic explosion in 2000 at the edge of the adjoining Mutnovsky crater reopened a large pre-existing sub crater.  This appears to have been caused by a dike propagating upwards intersecting with the hydrothermal system.  There is a direct connection between geothermal production and active magma beneath the volcano. 

A scientific drilling project to sample a suspected directly connected magma – hydrothermal system between the active craters and the geothermal field was proposed in 2006.  The goal was to test connectivity between them.  The other scientific interest is the deposition of various metals and minerals by the active fumarole system.  These have been called “a unique natural chemical reactor” where 35 previously unknown hydrothermal minerals have been discovered. 

The Active funnel is a small crater with steep walls and a flat bottom.  It is the most active crater of the volcano and has the most powerful and hottest fumaroles.  The Bottom Field is located at the lowest part of NE crater at the bottom of a former lake.  Upper Field is located above the Bottom Field under the glacier.  The distance between Bottom and Upper Fields is only 200 m, though the gasses differ sharply in composition.

There are several additional thermal sites with boiling pots, steam jets and hot springs on the N slopes of the volcano.  All gas vents have temperatures close to boiling with low concentrations of chlorides. 

Geothermal

The Mutnovsky Geothermal Field extends 6 -7 km N of Mutnovsky.  There are tens of relatively shallow geothermal wells 1 – 2.5 km deep producing fluids from a 240 – 300° C aquifer that feed a 60 MW power plant.  It is the largest geothermal power station in Russia.  As an aside, the Soviet Union pushed geothermal energy in much of the developing world 1950 – 1990.  It appears they obtained much of that expertise with geothermal exploration on Kamchatka. 

The geothermal field was discovered in 1960.  It has fumaroles as hot as 620° emitting a continuous SO2-rich plume.  Mutnovsky craters emit thermal energy greater than 1,000 MWt with temperatures above 600° C.  The cooling rate is comparable with recent dome emplacement at Mount St Helens, implying a robust magma convection within the conduit. 

Exploration began in 1978 with 89 exploratory wells.  Flow tests from production wells were done 1983 – 1987.  Modeling confirmed a potential for 50 MWe production.  The 12 MWe pilot plant was put into operation in 1999.  It was followed in 2022 by the Mutnovsky 50 MWe power plant, 8 km NNE from the Mutnovsky II crater.  This plant provides a third of Petropavlovsk’s electric power. 

Eruptions

Mutnovsky is a quite active system.  For example, between 7550 and 100 BC, there were at least 20 confirmed eruptions.  Most of them were VEI 2, with an occasional VEI 3.  Over the next 1,000 years, there were only 4 eruptions, three VEI 2 and a VEI 3.  Between 1000 AD and 1900, activity increased, with 8 eruptions, most of them VEI 2.  The 19^th Century was active, with 5 of the eruptions in the second half of it.  Activity continued into the 20^th Century with 4 eruptions by 1920, three more by 1930, and three more by 1950.  There was a month long VEI 2 in 1960 – 1961 and a four-month long period of unrest in 2000 listed as a pair of eruptions, a VEI 1 in Mar and VEI2 in Jun.  The last eruption of juvenile material was in 1848.  Eruptions since then have all been small phreatic events or seismic crisis. 

The Smithsonian GVP Bulletin Reports lists multiple large rock avalanches within the summit crater 17 – 18 Sept 1993.  There were explosions from a vent in the central part of the crater the ejected boiling mud several meters above the vent.  Hikers and other visitors were advised to stay out of the crater until further notice.  The next report in 1996 reported a fumarole plume rising 1 km above the crater.

Mutnovsky Active Crater.  Video courtesy The Trek Blog 

Two minor phreatic explosions took place at Mutnosky 17 Mar 2000.  The short explosions put two gas and steam plumes 1 km above the volcano.  The plumes dispersed within 30 minutes after the eruptions.  Activity took place 0700 – 1700.  There was a corresponding shallow seismic event two hours later followed by a low frequency volcanic tremor.  A second episode of tremor took place on 1 Apr, though there was no notable emissions. 

Subsequent helo observations found the explosions took place in the N crater of the volcano.  It had been active before the mid-1950s and was filled with snow and ice afterwards.  The eruption had over 20 years of visible precursors.  Over that time, heat from the main crater increased, creating new fumaroles and heating up existing fumaroles.  An alpine glacier started moving.  There was also a 3 – 5x increase in sulfur, chlorine and fluorine chemicals in the Vulcannaya River which drains the fumarole fields of the NE and SE craters.  Seismicity continued for months afterwards prompting concerns that the minor explosions were precursors to something larger.

All this was further complicated by KVERT (Kamchatkan Volcanic Eruption Response Team) temporarily suspending operations due to budget wars.  KVERT works hand in hand with AVO (Alaska Volcano Observatory) to provide information on volcanic activity in Kamchatka.  Prevailing winds generally carry ash up the Aleutians along international jet airways, so a suspension of KVERT’s activity is a concern.

Increased fumarole activity continued Jun – Oct 2000.  Volcanic tremor was slightly above background levels until a sharp increase on 26 Jun.  Seismicity indicated a short, vigorous eruption (likely phreatic) on that date.  By 4 Jul, tremor decreased to background levels.  Weak fumarole activity continued afterwards, putting plumes 200 – 500 m above the volcano on two occasions in Jul.  Occasional volcano-tectonic earthquakes continued along with gas and steam plumes on 9 Aug, 30-31 Aug, 1 Sept, 7 Sept, 8 – 9 Oct.  The 8 Oct explosions put plumes 800 – 1,000 m above the crater. 

Tectonics

Mutnovsky, located some 70 km SW of Petropavlosk is part of the Eastern Volcanic Front, the easternmost of three major volcanic chains on Kamchatka.  The belts represent evolution of the volcanic arc over the last 30 Ma.  Volcanoes along this front are all 90 – 100 km above the top of the subducting slab.  We did a top-level review of Kamchatka tectonics in 2015, which would be a good place to start.  Tectonics in this part of Kamchatka is driven by subduction of the Pacific Plate beneath the Eurasian (or Okhotsk) Plate.  Subduction takes place at the Kuril Trench E of the peninsula, with the Pacific Plate subducting around 8 cm/year.  The subduction angle and depth of the plate increases significantly under Mutnovsky and just to its W.  The Avachia transform fault comes ashore N of Petropavlovsk. 

Two low velocity anomalies have been imaged in this part of Kamchatka.  The first is under Zupanovsky – Dzenzursky.  Other nearby volcanoes are located at the margins of this anomaly.  The second one is located beneath Gorely and Mutnovsky.  Other volcanoes near these two are located at the margins of the anomaly.  The anomalies are thought to be feeding magma to the volcanoes above them.  The anomaly below Gorely and Mutnovsky is mushroom shaped, reaching a height of 30 km below the surface.  Both Gorely and Mutnovsky can be fed directly from the mantle. 

The 2019 Binderman et al paper suggests that the Karymshina magmas were formed by the action of a weak plume on the underside of the crust starting some 20 Ma.  A deep crustal hot zone allowed partial melting of the crust, which includes a crustal component to buoyant, hot magma.  This would rise through the crust, stalling out as a shallow magma chamber.  The deep crust hot zone would provide a constant source of magma recharge and heat to the developing magma chamber at shallow depths.  The crystal mush is periodically resupplied with high silica, high water content, magma from the deep crustal hot zone.

Basalt production rate is estimated around 200 km3/km/Ma for this portion of the volcanic arc.  Over 20 Ma, the mantle melting heated and thickened the crust.  This showed up as instabilities in the Moho, leading to at least two delamination events separated by 1 Ma.  The first of these was around 15 Ma.  The second was triggered by the first.  They produced a surge of mantle melting leading to eruption of 1,500 km3 of magmas on the surface.  These events occurred after the heating, thickening, and steady intrusion of basalts destabilized the system.  By 3 Ma after the initial instability, the system returned to stability. 

The next delamination event took place 10 Ma later, 5 Ma when crust thickness decreased from an initial 45 km to its current 38 km under the complex, up to 5 km less than surrounding area, suggesting material below the caldera delaminated into the mantle.  Falling colder material disrupts the hot plume creating a lull in upwelling basalt production.  The system quickly recovers after a few Ma.  The duration of the delamination events is similar to the duration of volcanism at Karymshina.

Conclusions

Mutnovsky is a known active volcano.  While recent eruptions have been phreatic, it has a large, active magma and hydrothermal system.  Previous cycles of activity have progressed from basalts to dacites.  The current cycle is still erupting basalts and basaltic andesites.  The volcano has a vigorous hydrothermal system used to power the largest geothermal plant in Russia.  Expect activity from Mutnovsky to continue or even increase in the foreseeable future. 

Additional information

Isotopic and petrologic investigation, and a thermomechanical model of genesis of large-volume rhyolites in arc environments:  Karymshina volcanic complex, Kamchatka, Russia, Binderman, et al, Jan 2019

The Opala IV:  an explosive caldera-generating super eruption, which was the largest in the last 50000 years, IV Melekestsev, Jan 2016

Explosive volcanism of Kamchatka, Ivanov, et al

The magma-hydrothermal system at Mutnovsky volcano, Kamchatka peninsula, Russia, Eichelberger, et al, Jul 2009

Geochemical and geo-electrical study of mud pools at the Mutnovsky volcano (South Kamchatka, Russia): behavior of elements, structures of feeding channels and a model of origin, Bessonova, et al, Feb 2012

Connections between arc volcanoes in central Kamchatka and the subducting slab inferred from seismic tomography, Bushenkova, et al, Feb 2023

Physical and chemical conditions of the formation and evolution of late Pleistocene – Holocene magmas of the Gorely and Mutnovsky volcanoes, southern Kamchatka, Chashchin, et al, Aug 2011

Sublimate speciation at Mutnovsky volcano, Kamchatka, Zelenski & Bortnikova, Mar 2005

Geochemistry of volcanic and hydrothermal gases of Mutnovsky volcano, Kamchatka:  evidence for mantle, slab and atmosphere contributions to fluids of a typical arc volcano, Zelinsky & Taran, Aug 2009

Melt inclusion evidence for magma evolution at Mutnovsky volcano, Kamchatka, Robertson, et al, Nov 2013

Connections between arc volcanoes in central Kamchatka and the subducting slab inferred from local seismic tomography, Bushenkova, et al, Mar 2023

Analysis of magma injections beneath Mutnovsky volcano (Kamchatka), Kiryukhin, et al, Feb 2018

Efflorescent sulphates with M+ and M2+ cations from fumaroles and active geothermal fields of Mutnovsky volcano (Kanchatka), Zhitova, et al, May 2022

Hydro-mechanical modeling of magma injections in NE sector of Mutnovsky volcano (Kamchatka), Kiryukhin & Tshchiya, Feb 2022

Evolution of Mutnovsky volcano, Kamchatka with implications for arc pluton growth, Simon, et al, Dec 2011

Hydrochemistry of thermal sources, Mutnovsky volcano, south Kamchatka (Russia), Bortniikova, et al. Jan 2008

Output of thermal energy from Mutnovsky volcano (Kamchatka) and thermal feeding of Mutnovsky hydrothermal system, OV Verina, Jan 2007

Poster – SO2 gas emission of Mutnovsky and Gorely volcanoes (Kamchatka): Satellite data and ground based observations, Melnikov & Ushakov, Feb 2014

Boiling mud pots: origin and hydrogeochemistry (Donnoe and North Mutnovsky fumarolic fields, Mutnovsky volcano; south Kamchatka, Russia), Bortnikova, et al, Apr 2010

Mutnovsky geothermal power complex in Kamchatka, Britvin, et al, May 2000