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Active volcanoes / Aktive vulkaner:
Amukta, Alaska
Symmetrical snow-capped Amukta stratovolcano in the central Aleutian Islands is located at the northern side
of an arcuate caldera-like feature along the coast of the 8-km-wide island of the same name.
The 1066-m-high stratovolcano overlies a broad shield volcano and is topped by a 400-m-wide crater.
Amukta has had several eruptions since the late 18th century from both summit and flank vents. .
The undissected stratovolcano of Amukta volcano composes most of nearly circular, 7.7-km-wide Amukta Island. The cone, about 5.8 km in basal diameter and topped by a 0.4 km wide summit crater, appears on synthetic-aperature radar imagery to be built upon a 300+ meter high, east-west trending arcuate ridge. Extensions of that ridge on the southwest and east sides of the island indicate an older caldera approximately 6 km in diameter and open to the sea on the south side. No hot springs or fumaroles have been reported from Amukta. Sekora (1973, p. 29) reports the presence of a cinder cone near the northeastern shore of the island. (AVO) However, the volcano has been statistically forecasted for eruption within a year (Nov.2004). (SWVRC)
Well documented reports of historical Amukta volcanism are sparse; activity was noted from 1786 to 1791, and again in 1876 (Coats, 1950). Petroff (1884, citing Grewingk, 1850) lists activity at Amukhton in 1770, presumably the same volcano; conversely, Dall (1870, citing Grewingk, 1850) describes a cessation of activity at Amukta in 1770. On February 13, 1963 an eruption occurred involving the central crater and one or more parasitic vents; both ash and lava were produced (Anchorage Times, February 11, 1963; Decker, 1967). Persistent low clouds obscured the exact source of the lava, but the flow was seen to extend from the west side of the cone southwest into the sea at Traders Cove (Bulletin of Volcanic Eruptions, 1963). In early July 1996, a passing ship reported a 1-km high plume of "ash
and smoke" (Neal and McGimsey, 1997). On August 28 Mt. Cleveland,
100 km to the northeast, was also active and winds were blowing towards
Amukta. In late August and early September, 1987, a commercial pilot
observed a 10.5-kilometer-high eruption plume rising through cloud cover
near Amukta Island. On September 4, another pilot observed a small dark
ash plume issuing from the summit of Amukta (Smithsonian Institution,
1987). On Sept. 18, yet another pilot reported a 300m-high ash plume. |
