USGS/Cascades Volcano Observatory, Vancouver, Washington
Pelican Butte, Oregon
Map, Major Volcanoes of the Southern Oregon Cascades
Wood and Kienle, 1990, Volcanoes of North America: United States and Canada:
Cambridge University Press, 354p., p.199-200,
Contribution by James G. Smith
Pelican Butte is a normally polarized, steep-sided andesite
built on faulted
Pliocene and early Pleistocene
carved a steep canyon and broad
cirque in the northeast flank of the volcano, lowered the summit some tens of
meters, and exposed a lava-filled intrusive conduit. However, the volcano's
original shape is largely preserved.
Pelican Butte (20 cubic kilometers)
is volumetrically one of the larger Quaternary volcanoes between
Crater Lake and
it is larger by one-third than the nearby more scenic
Two analyzed samples contain 58 and 60 percent SiO2.
Two types of andesite make up most of the volcano. Thick platy flows are most
common low on the mountain. These glassy flows traveled far down the slopes of
Pelican Butte following preexisting channels. Phenocryst minerals are
plagioclase, augite, hypersthene, and locally olivine; all are inconspicuous and
collectively make up no more than a few percent of the lava.
The second type of andesite forms thin flows that have scoriaceous and blocky
tops. Lava of this type is common near the summit of Pelican Butte. It is
typically fine-grained and vesicular. Small snow-white plagioclase phenocrysts
of sodic labradorite are characteristic. ...
Pelican Butte's summit is high, the mountain is
detached from the axis of the
Cascades, and it formed on top of a system of down-to-the-east normal faults
with large displacements that delineate the east side of the Cascade Range at
this latitude. For these reasons, views from its summit are impressive. It
offers a 180 degree panorama of Cascade Peaks from just south of
Crater Lake past
and onto the volcanoes in the Mountain Lakes Wilderness. ...
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08/21/00, Lyn Topinka