Is there any information on Tumac Mountain, some 20km ESE of Mt.
Rainier? This mountain is an obviously recent cinder cone, with crater
intact and apparently sits on an older shield volcano. Is it a parasite
on Mt. Rainier and how old is it? Incidentally, the Mt. Adams complex ,
when view from the NW, also appears to rest atop an ancient shield.
Jonathan Martin
Hi Jonathan,
I've looked in both "Volcanoes of North America" and "Volcanoes of the
World", and couldn't find any mention of Tumac Mountain. Perhaps it is a
flank vent of Mt. Rainier? Neither of these books lists all the vents of
the volcanoes. As for having a cinder cone sitting on top of a lava
shield, that's kind of a common occurrence. Either the cone grows during
the entire eruption, and manages to keep from being buried by the more
voluminous shield, or it is a late additions--the result of higher
fountaining at the end of the eruption.
On a larger scale, it is also possible for strato volcanoes to be built on
much more extensive lava shields. "Volcanoes of North America" says of
the Washington strato volcanoes: "...with only one (Mount Adams) having
significant nearby basaltic volcanics. In marked contrast, Oregon has six
generally smaller stratovolcanoes, but the entire state is traversed by a
40-50 km-wide band of basaltic to andesitic lava shields..." You're a
good observer.
Sincerely,
Scott Rowland
PS, by the way there is a Mt. Rainier home page by the USGS
Cascades Volcano Observatory.
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