Moffett Sandwich Ash
Start: 4390 yBP ± 150 Years [1]
Stop: 3825 yBP ± 105 Years [1]
Event Type: Explosive
Description: Waythomas and others (2003) tentatively identify Moffett Volcano as the source of the Sandwich Ash, observed on Adak Island and also called AD-3 by Kiriyanov and Miller (1997).
From Kiriyanov and Miller (1997): "AD-3 ash ranges between 1.5 and 17 cm (average 10-12 cm) in thickness and consists of a gray silt-size particles, inequigranular sand, and pumice lapilli up to 5 cm (mainly 1 cm) in size. The thickness of this ash layer varies considerably from section to section. The particle size of this ash generally grows larger westward. In some of the sections, this ash was fond to be intercalated with a layer of humus sandy loam. Apparently, these two ash layers were ejected from the same vent during different eruptions with a small time interval between them. Characteristic features of this ash (Fig. 5 [in original text]) are a high glass content (76%), absence of green hornblende, and the low contents of pyroxenes (3%) and brown hornblende (2%). The carbon-14 age of the ash was found to be ~2000 years (Table 1 [in original text])."
From Okuno and others (2012): "The Sandwich tephra-fall deposit covers a 74cm thick sequence of tephra-soil complexes, is 20cm thick, and comprises alternating lenses of ash and pumice (MP is 0.9cm). As Kiriyanov and Miller (1997) noted, the thickness and lithology of the Sandwich tephra vary from section to section, and humus loams are intercalated in the tephra in some places. The ash and pumice beds of the Sandwich tephra infill the erosion gully in the humic soil layer, which contains the Sandwich pumice lapilli at Site 2 on the southern slope of Adagdak Volcano (Figure 4.6 [in original text]). We attribute this humus layer to a contemporaneous reworking associated with the eruption of the Sandwich tephra and thus consider this humic layer as a pseudo-soil. Two fine grained tephra layers: the YBO (5cm thick) and Forty Year (6cm thick) are located as tephra-soil complexes between the Sandwich tephra and the ground surface (Figures 4.2 and 4.5 [in original text])."
From Kiriyanov and Miller (1997): "AD-3 ash ranges between 1.5 and 17 cm (average 10-12 cm) in thickness and consists of a gray silt-size particles, inequigranular sand, and pumice lapilli up to 5 cm (mainly 1 cm) in size. The thickness of this ash layer varies considerably from section to section. The particle size of this ash generally grows larger westward. In some of the sections, this ash was fond to be intercalated with a layer of humus sandy loam. Apparently, these two ash layers were ejected from the same vent during different eruptions with a small time interval between them. Characteristic features of this ash (Fig. 5 [in original text]) are a high glass content (76%), absence of green hornblende, and the low contents of pyroxenes (3%) and brown hornblende (2%). The carbon-14 age of the ash was found to be ~2000 years (Table 1 [in original text])."
From Okuno and others (2012): "The Sandwich tephra-fall deposit covers a 74cm thick sequence of tephra-soil complexes, is 20cm thick, and comprises alternating lenses of ash and pumice (MP is 0.9cm). As Kiriyanov and Miller (1997) noted, the thickness and lithology of the Sandwich tephra vary from section to section, and humus loams are intercalated in the tephra in some places. The ash and pumice beds of the Sandwich tephra infill the erosion gully in the humic soil layer, which contains the Sandwich pumice lapilli at Site 2 on the southern slope of Adagdak Volcano (Figure 4.6 [in original text]). We attribute this humus layer to a contemporaneous reworking associated with the eruption of the Sandwich tephra and thus consider this humic layer as a pseudo-soil. Two fine grained tephra layers: the YBO (5cm thick) and Forty Year (6cm thick) are located as tephra-soil complexes between the Sandwich tephra and the ground surface (Figures 4.2 and 4.5 [in original text])."
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.
