The Kamchatka Volcanoes of tour #805.

These brief notes refer only to those volcanoes in the central sector of the Eastern Kamchatka Volcanic Belt, which are those that may be seen on the excursion. They are listed from north to south.

Kronotsky. A beautifully symmetrical andesitic cone 3528 m high; it has been quiet since some minor gas eruptions in 1923. 

Krasheninnikov. A large cone, 10 km across and 1857 m high, has two calderas in its summit. Each caldera is 1 km across; one is largely filled by a cinder cone with its own summit crater and small lava flows, and the other is flooded with cold lava. Activity is recent but unrecorded. 

Kikhpinych. A stratovolcano 1552 m high, which last erupted in 1550. Rhyolites and dacites form an old eroded edifice, and a younger summit cone of andesites and basalts has a small central crater. Present activity includes a few small summit fumaroles. 

Uzon Caldera. This large complex caldera has evolved through much of the last two million years. An early shield of basaltic lavas collapsed in the first caldera about 40,000 years ago, when huge sheets of welded and unwelded ignimbrite were formed; the geothermal activity of the Valley of Geysers now lies over the marginal faults of this caldera. A second caldera collapsed in the western half of the first one, and produced the Belaya dacite dome and more acidic tuffs. A third minor collapse created the depression that is now largely filled by lake sediments, and the adjacent tuff-ring that contains the Dalneye maar lake. Geophysical data has identified an underlying magma chamber with its top about 5 km down. There are numerous active hot springs, mud pools and small geysers on the floor of the third collapse. Part of the extinct Uzon volcanic cone survives on the caldera rim. Close to the northwest, the cones of Taunschyts and Unana are also inactive.

Bolshoi Semlyachik. An extinct and eroded stratovolcano, now 1720 m high. An andesitic volcano grew first, and then collapsed into a caldera as it produced dacite ignimbrites. The last eruption was in 4450 BC, since when it has had only fumarole activity.

Maly Semlyachik. A truncated cone, 1560 m high, stands inside an older caldera 6 km across. Its summit crater, formed by explosions and collapse in 1804, is 500 m across and 170 m deep to a hot lake, with fumaroles around its margin. Its last explosive vulcanian eruption was in 1952.

Karimsky. Currently the most active volcano on Kamchatka, the modern cone has been formed within the last 5300 years and now rises to 1486 m. The 700 m high active cone is formed of andesitic pumice ash, bombs and spatter, armoured with flows of blocky lava. It is currently erupting (and has been for about 500 years) in Strombolian style, whereby blasts of steam, smoke, ash and lava bombs rise to heights of 500-1000 m above the summit crater; each blast lasts only about a minute, and they occur at intervals of 5-15 minutes, accompanied by minor earthquakes; lava sometimes flows from the crater. This pattern is temporarily disrupted by occasional larger eruptions; in November 1998 an ash column reached a height of 6000 m. Some eruptions produce new vents close to the summit; these then evolve into the dominant crater. The Karimsky cone stands inside a caldera 7700 years old whose walls still stand nearly 100 m high; the older Dvor caldera survives as a truncated fragment to the north.

Academia Nauk. This caldera is 50,000 years old, is now intersected by the younger Karimsky caldera, and contains the hot waters of Karimsky Lake. An underwater dacitic vent erupted explosively in 1996 (simultaneously with a major Karimsky eruption), producing an ash cloud about 8000 m high, and leaving a crescentic peninsula in the lake's northern half.

Zhupanovsky. This large compound volcano of andesites and basalts is a coalesced group of four cones rising to 2958 m. The highest summit, to the east, has a crater 1000 m across that is filled with ice; hot solfataras have bored shafts (70 m across) up though the ice, and then coated them with sulphur. A western parasytic cone has a crater with fumaroles, and is the only vent that produces lava during the vulcanian eruptions, of which the last was in 1959. The nearby cones of Dzendzur and Zhupanovsky Vostryaky are inactive and eroded.

Avacha. An active conical stratovolcano 2741 m high. A large early cone of andesites and basalts collapsed in stages into calderas. About 30,000 years ago, a massive lateral blast followed the collapse of its southwest flank; this left coarse debris deposits 150m thick that now survive beneath the the northern part of Petropavlovsk. The crater that this eruption left has been almost completely filled by a cone largely of pyroclastics but with the fronts of basaltic andesite lava flows sticking out around its base, mostly within the last 5000 years. The central crater of this younger cone has produced 14 historical eruptions. A powerful vulcanian eruption in 1945 left the crater 250 m deep and 330 m across. The most recent eruption was in 1991, when lava filled the crater and overtopped the rim to produce a flow a kilometer long down the southern slope. This lava plug is still warm, and fumaroles and solfataras emerge round the margin of its dome within the crater; if past eruption patterns repeat themselves, the plug is likely to be removed explosively within the next 100 years. Gravity surveys show that the top of its magma chamber is only 2000 m below sea level. The adjacent eroded cone of Kozelsky is extinct.

Koryaksky. A tall symmetrical stratovolcano of andesite 3456 m high; it is built of welded and unwelded pyroclastics, with subordinate lavas, some of which are basaltic andesites. A small eruption in 1956 produced pyroclastic flows from the summit crater and a radial fissure; since then activity has been limited to fumaroles, but periodic increases in seismicity (including one in late 1997) indicate that future eruptions may be expected. The cones of  Koryaksky is likely to collapse at some time in the next few thousand years; it this follows the style of the collapse of Avacha 30.000 years ago, it will cause massive destruction to the Yelisovo area.

Viluchinsky. A beautiful and symmetrical andesitic cone, 2173 m high, is now almost inactive, and erosion will eventually destroy its fine profile.

Gorely. A massive shield volcano 1830 m high. Massive andesite lava accumulation in the Early Pleistocene was followed about 33,000 years ago by production of about 120 km3 of ignimbrite accompanied by caldera collapse. Basalts and basaltic andesites then created five volcanoes that coalesced to form most of the modem mountain between 8000 and 6000 years ago; this largely filled the caldera, but sections of the old caldera walls remain visible just outside the shield. Subsequent activity has been on a reduced scale, producing both lavas and tephras; these are exposed in the walls of the summit complex of craters. Recent eruptions have been explosive; in 1981 ash covered an area of 500 km2, and the last eruption was in 1986 when a cloud of steam and ash rose 600 m.

Mutnovsky. A complex of four superimposed volcanoes with a summit 2322 m high. Each cycle of activity produced a large cone, before dying and being followed by another whose centre was shifted; it is largely formed of basaltic andesites, with a high proportion of more acidic pyroclastics. Mutnovsky #1 formed about 45,000 years ago; its caldera is now eroded to open out on the north side of the mountain. Mutnovsky #2 grew to the south in the Late Pleistocene, collapsed in a caldera, and then grew a new cone that forms the present summit. Mutnovsky #3 produced basalts and differentiated dacites and rhyolites (about 35% as lavas and 65% as pyroclastics with included lahars), in between the cones of #1 and #2; its huge caldera contains the active fumarole fields that are partly overrun by its own glaciers. Mutnovsky #4 is a small crater in the edge of the #3 caldera, and is also filled with glacier ice. The active crater also lies in the rim of the #3 caldera; it last erupted explosively in 1960, and still contains powerful fumaroles.

Opala. A very large stratovolcano 2475 m high standing in a caldera which collapsed 35,000 years ago. Its most recent explosive eruption was in 1776.

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