Shiveluch

There are three elements of the volcano: the stratovolcano Old Shiveluch (Старый Шивелуч); an ancient caldera; and the active Young Shiveluch (Молодой Шивелуч), with an elevation of about 2,800 meters (9,200 ft).[9] Shiveluch is one of Kamchatka's largest and most active volcanic structures.[1] It is a stratovolcano composed of alternating layers of solidified ash, hardened lava and volcanic rocks.[10]

Shiveluch began forming about 60,000 to 70,000 years ago during the Late Pleistocene, and it has had at least 60 large eruptions during the Holocene.[1] During this era, the most intense period of volcanism — including frequent large and moderate eruptions — occurred around 6500–6400 BC, 2250–2000 BC, and AD 50–650. This coincides with the peak of activity in other Kamchatka volcanoes. The current active period started around 900 BC. Since then, the large and moderate eruptions have been following each other at 50-to-400-year-long intervals.[11] Chemically a full spectrum of subduction-zone lava types occur: basalt, mafic andesite, two-pyroxene andesite, hornblende-hypersthene andesite, hornblende andesite, hornblende dacite, rhyolite.[12]

Since mid-2022, volcanologists were expecting an imminent large eruption of Shiveluch due to the unstable state of its lava dome.[14] A strong eruption occurred on April 11, 2023 at 00.54 local time.[15][16] A progressive increase in activity was observed since March 28 in the form of continued extrusion, fumarole activity, and ash emissions.[17] During the initial paroxysmal explosive phase on April 11, the volcano ejected a cloud of volcanic gas and ash that reached a height of 20 km (12 mi) and spread over an area of 108,000 km² (42,000 sq mi).[18][17] Pyroclastic flows from the eruption traveled up to 19 km (12 mi) away from the volcano.[17] The next day, other summit explosions followed, the eruption column of one of which reached an altitude of 10 km (6.2 mi). The initial phase resulted in the region's largest ashfall in 60 years. The Federal Air Transport Agency assigned the eruption a “red” (maximum) hazard code.[19] Because the height of the eruption columns reached the stratosphere, 200,000 tons of sulfur dioxide were released into the upper atmosphere.[17] According to authorities, this eruption, with the exception of heavy ashfall, did not lead to any damage to local settlements and transport infrastructure.

Analysis of radar images from satellites on April 15 showed that the main eruption occurred as a result of the collapse of the lava dome of the volcano to the south, with the formation of a 2 × 2.6 km (1.2 × 1.6 mi) collapse scar in its place. Initially, the collapse process was triggered by a breach of the dome at its base and by the subsequent lateral explosion to the southeast. Thus, the eruption classifies as Peléan.[20] Since April 12, the activity of the volcano decreased, but the eruption continued in the form of ash ejections of lower intensity and height, and strong fumarole activity continued. Infra-red satellite images on the 16th showed that the volcano is forming a new lava dome inside its new crater.[21]