
The "Big Pumice Cut" as seen from highway 395. The
lowermost vegetation-covered layer is highly weathered, bouldery,
Sherwin Till.
This is overlain by a gently-dipping, 9-15 foot thick layer of well-sorted air
fall tuff. Overlaying the air fall tuff is
a much thicker ash flow tuff
with horizontal bedding. At the very crest of the hill is a thin layer of
outwash gravel. Several
prominent "clastic dikes" cut the tuff layers.