Amak 1796
Start: 1796 [1]
Event Type: Other
- Active; type of activity not specified [1]
- Lava flow [2]
Description: Grewingk (1850, translated 2003 by Fritz Jaensch) reports that in 1796, Amak "with active crater (?)." Grewingk also writes that Amak has been dormant at least since 1804, when Krusenstern viewed the island. Marsh (in Wood and Kienle, 1990) states that "granular, blocky leveed flows have erupted in historic times."
From Marsh and Leitz (1978): "The younger series of flows issued from a central vent located slightly south of the initial crater. These lavas breached the initial summit crater on the south and, at least in part, flowed down pre-existing glacially-cut valleys. These flows are chaotic, and wholly comprised of large angular blocks ranging in size from 0.1 m to several meters. Most blocks show traces of having been sheared and granulated. The lava is dark gray with a porous and sugary texture. At the outer margin of the southern flank this series has an apparent thickness of about 100 m. Moss and lichen growth on these flows, confirm that two periods of eruption produced this younger series. A thin layer (1 cm) of volcanic ash caps some of the larger blocks; this ash is probably from nearby Shishaldin volcano on Unimak Island, which has been active intermittently for at least the last 200 years (Coats 1950)."
"According to Funk (1973) the latest period of glaciation in this area was about 6,700 years B.P. The small U-shaped glacial valley cut into the older series was probably excavated during this period of glaciation. The older flows also show no sign of being extruded beneath ice. Thus Amak is probably not much older than 6,700 years. Early explorers (Dall 1897) reported volcanic activity on Amak during 1700-1710 and 1796 but report that by 1867 all activity had ceased. The younger series of flows was, surely, extruded during these times."
From Marsh and Leitz (1978): "The younger series of flows issued from a central vent located slightly south of the initial crater. These lavas breached the initial summit crater on the south and, at least in part, flowed down pre-existing glacially-cut valleys. These flows are chaotic, and wholly comprised of large angular blocks ranging in size from 0.1 m to several meters. Most blocks show traces of having been sheared and granulated. The lava is dark gray with a porous and sugary texture. At the outer margin of the southern flank this series has an apparent thickness of about 100 m. Moss and lichen growth on these flows, confirm that two periods of eruption produced this younger series. A thin layer (1 cm) of volcanic ash caps some of the larger blocks; this ash is probably from nearby Shishaldin volcano on Unimak Island, which has been active intermittently for at least the last 200 years (Coats 1950)."
"According to Funk (1973) the latest period of glaciation in this area was about 6,700 years B.P. The small U-shaped glacial valley cut into the older series was probably excavated during this period of glaciation. The older flows also show no sign of being extruded beneath ice. Thus Amak is probably not much older than 6,700 years. Early explorers (Dall 1897) reported volcanic activity on Amak during 1700-1710 and 1796 but report that by 1867 all activity had ceased. The younger series of flows was, surely, extruded during these times."
References Cited
[1] Grewingk's geology of Alaska and the Northwest Coast of America [edited by Marvin W. Falk, translation by Fritz Jaensch published 2003], 1850
Grewingk, Constantine, 1850, Grewingk's geology of Alaska and the Northwest Coast of America [edited by Marvin W. Falk, translation by Fritz Jaensch published 2003]: Rasmuson Library Historical Translation Series 11, Fairbanks, AK, The University of Alaska Press, 242 p.[2] Geology of Amak Island, Aleutian Islands, Alaska, 1979
Marsh, B. D., and Leitz, R. E., 1979, Geology of Amak Island, Aleutian Islands, Alaska: Journal of Geology, v. 87, n. 6, p. 715-723.Complete Eruption References
Volcanoes of the world [2nd edition], 1994
Simkin, Tom, and Siebert, Lee, 1994, Volcanoes of the world [2nd edition]: Tucson, Arizona, Geoscience Press, 349 p.
Hard Copy held by AVO at FBKS - CEC shelf
Geology of Amak Island, Aleutian Islands, Alaska, 1979
Marsh, B. D., and Leitz, R. E., 1979, Geology of Amak Island, Aleutian Islands, Alaska: Journal of Geology, v. 87, n. 6, p. 715-723.
Grewingk's geology of Alaska and the Northwest Coast of America [edited by Marvin W. Falk, translation by Fritz Jaensch published 2003], 1850
Grewingk, Constantine, 1850, Grewingk's geology of Alaska and the Northwest Coast of America [edited by Marvin W. Falk, translation by Fritz Jaensch published 2003]: Rasmuson Library Historical Translation Series 11, Fairbanks, AK, The University of Alaska Press, 242 p.
Hard Copy held by AVO at FBKS - CEC shelf