Moffett Intermediate Ash
Start: 6960 yBP ± 100 Years [1]
Stop: 4460 yBP ± 180 Years [1]
Event Type: Explosive
Description: Waythomas and others (2003) tentatively identify Moffett Volcano as the source of the Intermediate Ash, observed on Adak Island and also called AD-4 by Kiriyanov and Miller (1997).
From Kiriyanov and Miller (1997): "AD-4 ash is 4-8 cm thick and consists of pumice gravel and lapilli with a maximum size of 3 cm, small amounts of gray clay- and silt-size materials and fine-grained sand, and a large amount of rock fragments 0.5-0.8 cm in size. The coarser material is concentrated in the middle of the ash layer. Distinctive features of this ash are a considerably large amount of rock debris (13%), absence of pyroxenes, and a very small content of green and brown hornblendes (1-2%). The inferred age of the ash is 4500-4600 14C years (Table 1 [in original text])."
From Okuno and others (2012): "The lntermediate tephra-fall deposit consists of pumice and lithic fragments with a cross-laminated ash bed. It is 43cm thick and contains a large amount of dense lithics with a maximum size (ML) of 3.8cm."
From Waythomas and others (2001): "A thick lapilli tephra deposit about the same age as the Intermediate Ash is present at locality 00CW06 northeast of Kanaga Volcano (fig. 9 [in original text]) but is not recognized elsewhere on Kanaga Island. Radiocarbon ages associated with Kanaga Island tephra T7 match those of the Sandwich Ash (fig. 13 [in original text]); however, the T7 deposits consist of massive sand-size felsic tephra with granule-size juvenile lapilli at the base (sec. 99CW75, fig. 9 [in original text]) or a single thin lapilli bed (sec. 99CW83, fig. 9 [in original text]) and do not exhibit the sequence massive gray fine ash/oxidized granule lapilli/massive gray fine ash that characterizes the Sandwich Ash on Adak Island. Thus, we are uncertain whether tephra T7 and the Sandwich ash are the same tephra deposit..."
From Kiriyanov and Miller (1997): "AD-4 ash is 4-8 cm thick and consists of pumice gravel and lapilli with a maximum size of 3 cm, small amounts of gray clay- and silt-size materials and fine-grained sand, and a large amount of rock fragments 0.5-0.8 cm in size. The coarser material is concentrated in the middle of the ash layer. Distinctive features of this ash are a considerably large amount of rock debris (13%), absence of pyroxenes, and a very small content of green and brown hornblendes (1-2%). The inferred age of the ash is 4500-4600 14C years (Table 1 [in original text])."
From Okuno and others (2012): "The lntermediate tephra-fall deposit consists of pumice and lithic fragments with a cross-laminated ash bed. It is 43cm thick and contains a large amount of dense lithics with a maximum size (ML) of 3.8cm."
From Waythomas and others (2001): "A thick lapilli tephra deposit about the same age as the Intermediate Ash is present at locality 00CW06 northeast of Kanaga Volcano (fig. 9 [in original text]) but is not recognized elsewhere on Kanaga Island. Radiocarbon ages associated with Kanaga Island tephra T7 match those of the Sandwich Ash (fig. 13 [in original text]); however, the T7 deposits consist of massive sand-size felsic tephra with granule-size juvenile lapilli at the base (sec. 99CW75, fig. 9 [in original text]) or a single thin lapilli bed (sec. 99CW83, fig. 9 [in original text]) and do not exhibit the sequence massive gray fine ash/oxidized granule lapilli/massive gray fine ash that characterizes the Sandwich Ash on Adak Island. Thus, we are uncertain whether tephra T7 and the Sandwich ash are the same tephra deposit..."
References Cited
[1] Volcanic ashes of Adak Island, Aleutian Islands, Alaska [Vulkanicheskiye peply na o-ve Adak (Aleutskiye o-va, SShA)], 1997
Kiriyanov, V. Y., and Miller, T. P., 1997, Volcanic ashes of Adak Island, Aleutian Islands, Alaska [Vulkanicheskiye peply na o-ve Adak (Aleutskiye o-va, SShA)]: Volcanology and Seismology [Vulkanologiya I Seysmologiya], v. 19, n. 1, p. 52-77.[2] Geology and late Quaternary eruptive history of Kanaga Volcano, a calc-alkaline stratovolcano in the western Aleutian Islands, Alaska, 2003
Waythomas, C. F., Miller, T. P., and Nye, C. J., 2003, Geology and late Quaternary eruptive history of Kanaga Volcano, a calc-alkaline stratovolcano in the western Aleutian Islands, Alaska: in Galloway, J. P., (ed.), Studies by the U.S. Geological Survey in Alaska, 2001, U.S. Geological Survey Professional Paper PP 1678, p. 181-197.
full-text PDF 1.5 MB [3] Holocene Tephra Layers on the Northern Half of Adak Island in the West-Central Aleutian Islands, Alaska, 2012
Okuno, M., Wada, K., Nakamura, T., Gualtieri, L., Sarata, B., West, D., and Torii, M., 2012, Holocene Tephra Layers on the Northern Half of Adak Island in the West-Central Aleutian Islands, Alaska, in West, D., Hatfield, V., Wilmerding, E., Lefevre, C. and Gualtieri, L. (eds.): The People Before: The Geology, Paleoecology and Archaeology of Adak Island, Alaska, Oxford, UK, p. 61-75.Complete Eruption References
Volcanic ashes of Adak Island, Aleutian Islands, Alaska [Vulkanicheskiye peply na o-ve Adak (Aleutskiye o-va, SShA)], 1997
Kiriyanov, V. Y., and Miller, T. P., 1997, Volcanic ashes of Adak Island, Aleutian Islands, Alaska [Vulkanicheskiye peply na o-ve Adak (Aleutskiye o-va, SShA)]: Volcanology and Seismology [Vulkanologiya I Seysmologiya], v. 19, n. 1, p. 52-77.
Geology and late Quaternary eruptive history of Kanaga Volcano, a calc-alkaline stratovolcano in the western Aleutian Islands, Alaska, 2003
Waythomas, C. F., Miller, T. P., and Nye, C. J., 2003, Geology and late Quaternary eruptive history of Kanaga Volcano, a calc-alkaline stratovolcano in the western Aleutian Islands, Alaska: in Galloway, J. P., (ed.), Studies by the U.S. Geological Survey in Alaska, 2001, U.S. Geological Survey Professional Paper PP 1678, p. 181-197.
full-text PDF 1.5 MB 
Holocene Tephra Layers on the Northern Half of Adak Island in the West-Central Aleutian Islands, Alaska, 2012
Okuno, M., Wada, K., Nakamura, T., Gualtieri, L., Sarata, B., West, D., and Torii, M., 2012, Holocene Tephra Layers on the Northern Half of Adak Island in the West-Central Aleutian Islands, Alaska, in West, D., Hatfield, V., Wilmerding, E., Lefevre, C. and Gualtieri, L. (eds.): The People Before: The Geology, Paleoecology and Archaeology of Adak Island, Alaska, Oxford, UK, p. 61-75.
