Alaska Volcano Observatory
Jarvis reported activity
EVENT SPECIFIC INFORMATION
Event Name : Jarvis 1630000 yBP
|Start: 1630000 (± 420000 Years) || Years BP K-Ar || |Description:
|Eruption Product: || other ||
From Richter and Smith (1976): "Dacite andesite and dacite flows. Thick sequence of thin to medium flows with minor interbedded tuffs and breccias representing main cone-building stage of Jarvis volcanoes which extend into the McCarthy D-7 and Nabesna A-6 quadrangles. Rocks are dark gray, and pinkish gray. Chiefly two-pyroxene dacitic andesite containing hypersthene, augite, plagioclase, and rare olivine phenocrysts in a felty plagioclase-rich matric. In southwest corner of quadrangle sequence is cut by numerous dark-colored dikes probably chiefly of andesite composition. K-Ar date (M.A. Lanphere, written commun., 1974) on plagioclase indicates age of 1.63+/-0.42 m.y. (Sample 72-ARh-307a)."
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