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Almost 0.9 cubic kilometers (dense-rock equivalent) of rhyodacite tephra, lava domes, and lava
flows erupted from numerous vents on the southwest, southeast, and northeast flanks of South
Sister volcano during late Holocene time. Eruptions occurred during two brief episodes between
2300 and 2000 carbon-14 years B.P., separated by a dormant interval of as long as several
centuries. The eruptions of each episode were probably fed by dikes, on the basis of the
following: the alignment of vents, the chemical uniformity of eruptive products, and
stratigraphic evidence that the eruptions of each episode occurred over a short interval of
time.
-- Scott, 1987
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[Map,20K,InlineGIF]
