Event Name : Moffett Sandwich Ash
|Start: 4390 (± 150 Years) || Years BP C-14 (raw) || |
|Stop: 3825 (± 105 Years) || Years BP C-14 (raw) || |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])."