Avachinsky Kamchatka, Russia
Location: 53.2N, 158.8E
Elevation: 8,990 feet (2,741 m)
Avachinsky (on the right) is one of the most active stratovolcanoes on
the Kamchatka peninsula. It consists of a younger cone inside the rim
of an older caldera. Avachinsky has been classified as a Somma volcano
based on its similarities with Vesuvius. Avachinsky has
erupted at least 16 times since 1737. A large (VEI=4)
explosive eruption occurred at Avachinsky in 1945. The most recent
eruption was in 1991 and produced lava flows, a dome, and mudflows.
Koryaksky is on the left. Photograph by Jack Lockwood, U.S. Geological
Survey.
Avachinsky was built in several stages. Eruptions of andesite and
then basalt created a
volcanic cone. Later, the caldera
and its graben were
formed. Then, domes
and, finally, the present Avachi cone was formed inside the caldera.
The southern portion of the caldera has been destroyed by
faulting and has opened the caldera on this side. The main crater is situated in the top of
the active cone of Avachinskaiasopka. A strong, explosive eruption
occurred in 1945,creating a steep walled crater with a diameter of 1082
ft (330 m) and a depth of about 853ft (260 m). Its southern ridge rises
197 ft (60 m) over the northern.
Fumaroles exist on the bottom of the crater and on the outer
slopes near the northwestern rim. The crater's appearance changed in
width and depth from eruption to eruption.
Fifteen individual lava flows exist on the present Avachi cone,
most of these being located on its southern slopes. Only their leading
fronts are visible when they stick out from underneath Avachinsky's
pyroclastic deposits and
drift material. These streams have a blocky appearance. These streams,
reaching 2.5-3.1 miles (4-5 km) inlength and up to 6.2-9.3 miles (10-15 km)
in thickness, are oftenbordered by swells which makes them look like
narrow grooves.
Eruptions from Avachinsky are mostly explosive and are often
accompanied by avalanches and mud flows.
Source of Information:
Simkin, T., and Siebert, L., 1994, Volcanoes of the World: Geoscience
Press, Tucson, Arizona, 349 p.
Voldavetz, V.I., and Piip, B.I., 1947, Kamchatka and continental areas of
Asia: Catalog of Active Volcanoes of the World: Rome, IAVCEI, 8, 110 p.
Vlodavetz, V.I. and Piip, B.I., "Catalogue of the Active Volcanoes of the
World Including Solfatara Fields: Part VIII, Kamchatka and Continental
Areas of Asia,"International Volcanological Association, Napoli, Italy,
110 pp., 1959.
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