Makushin A'a flow
Start: 40000 yBP ± 6000 Years [1]
Event Type: Effusive
- Lava flow [1]
Description: From McConnell and others (1998): "Plagioclase-dominant (up to 27 vol.%), two-pyroxene andesitic a’a flow. The end of the flow extends from above Bishop Point Valley to above Koriga Point. Rubbly surface characteristic of a’a flows is still evident at lower elevations. This flow is overlain by the younger Qmbp flows above Bishop Point Valley and Qag above Koriga Point. The matrix is microcrystalline plagioclase and magnetite and the mineralogy also includes minor (<1 vol.%) olivine. Clinopyroxene overgrowths of orthopyroxene are common as are crystal clots of plagioclase and clinopyroxene. 40Ar/39Ar age determinations place its deposition at 40+/-6 ka (table 2 [in original text])."
References Cited
[1] Geologic map of the Makushin volcanic field, Unalaska Island, Alaska, 1998
McConnell, V. S., Beget, J. E., Roach, A. L., Bean, K. W., and Nye, C. J., 1998, Geologic map of the Makushin volcanic field, Unalaska Island, Alaska: Alaska Division of Geological & Geophysical Surveys Report of Investigation 97-20, unpaged, 2 sheets, scale 1:63,360.
Complete Eruption References
Geologic map of the Makushin volcanic field, Unalaska Island, Alaska, 1998
McConnell, V. S., Beget, J. E., Roach, A. L., Bean, K. W., and Nye, C. J., 1998, Geologic map of the Makushin volcanic field, Unalaska Island, Alaska: Alaska Division of Geological & Geophysical Surveys Report of Investigation 97-20, unpaged, 2 sheets, scale 1:63,360.