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ening by erosion along the main stream. The lower part of the valley of
Kast creek is unusually deep and steep sided. This stream has cut through
igneous rocks to underlying sediments and in these softer rocks it has
rapidly cut its way down to a normal steep gradient, whereas the upper
slopes of the canyon have been worn down only a relatively small amount
because the rocks are more resistant. Falls on Canyon and Falls creek are
caused by horizontal beds of hard, siliceous argillites.

The course of Falls creek in the vicinity of Anyox is south parallel to
the strike of the rocks. The lower 8 miles of the valley also follows a
fault. The smaller streams in the vicinity are related to the bedrock struc-
ture only in a minor degree, as glacial deposits have disorganized the earlier
stream pattern.

The large valley occupied in the north by American creek and lower
Bear river, and in the south by Portland canal, has for most of its length
the steep-sided character of a glacially modified valley. It follows the
strike of the rocks for part of its length, the contact of the Coast Range
intrusives for another part, and a major fault for much of its length. The
valley of Upper American creek is V-shaped, and the valley takes on the
glacial U-shape a short distance north of Bear river. The valley originated
long before the Pleistocene but has been greatly modified by glacial ero-
sion. The ice did not move south from the head of American creek but
entered the valley from the sides mainly along upper Bear river, Bitter
and Glacier creeks, and Marmot and Georgia rivers. Upper Bear River
valley is a through valley between the lower Bear River valley and the
Nass River drainage basin. It is not known whether this was a through
valley prior to the Pleistocene or was cut largely by ice. If cut mainly by
ice this could have taken place only at a time when ice covered the interior
to considerable depth, for Meziaden lake lying in the valley 10 miles east
of the head of Bear river is 1,200 feet or more lower than the divide.

West of Bear River ridge the north-south valley occupied by Divide
and Long lakes is a through valley between Bowser river and Copper creek,
a branch of Cascade creek. The divide is at an elevation of 3,000 feet and
the pre-Pleistocene divide was probably lowered by ice erosion. The part
of Cascade creek between Harris creek and Long lake is a recent diversion
from a former course south to Cooper creek. This diversion was probably
caused by glacial accumulations in the valley south of Long lake.

The Salmon River-Bowser River valley is also a north-south through
valley with a present ice summit about 2,800 feet high. The valley is prob-
ably not the course of pre-Pleistocene drainage from the interior as it is
not very large and has certainly been enlarged by ice erosion. Ice from the
interior has not moved south along the valley to any extent, for at the
southern end of the valley only the higher slopes are U-shaped.