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CHAPTER II
GENERAL CHARACTER OF THE AREA
TOPOGRAPHY

Aiken Lake map-area lies almost entirely within the Omineca Moun-
tains of the Central Plateau and Mountain area of the Interior system of
the Canadian Cordillera (Bostock, 1948, pp. 42-44). The extreme north-
east corner of the map-area extends into the Rocky Mountain Trench of
the Eastern system of the Cordillera.

The Omineca Mountains of the map-area are characterized by irregu-
lar, dissected mountain units, ranging in size from single peaks to composite
masses of 10 by 20 miles, with little general tendency to form well-defined
ranges. The mountain massifs are arranged in a more or less rectangular
pattern, with a northwest-trending axis, and are separated by straight
or broadly curving, relatively wide-floored, steep-sided valleys, the larger
of which measure as much as 10 miles between mountain summits on either
side (See Plate I). Most of the mountains of the eastern and northern
parts of the area have smooth profiles and rounded summits, although the
local relief is just as great and the over-all slopes as steep as elsewhere,
and the Russel Range contains several rugged peaks. The general charac-
ter of the landscape becomes increasingly precipitous toward the south-
west, culminating in rugged, alpine topography around the headwaters of
Osilinka, Tutizika, and Mesilinka Rivers.

River, and have an altitude of about 8,060 feet. The lowest point is in
the Rocky Mountain Trench at 2,150 feet above sea-level. Local relief

The highest peaks in the map-area lie near the headwaters of Osilinka
between mountain summits and adjacent valley floors is relatively uniform
for the entire area, and varies between 3,500 and 4,000 feet.

DRAINAGE

Aiken Lake map-area lies entirely within the Arctic Ocean watershed,
and is drained by Finlay River and its tributaries. The main rivers flow
east and southeast. Owing, however, to the characteristic asymmetrical
profile produced by more intense glacial erosion on the northeast slopes of
the mountains, the drainage within each mountain group is predominantly
to the northeast.

The large valleys have relatively gentle gradients for a mountainous
terrain, and the heavily loaded larger rivers have all developed a complex
system of meanders and shifting bars (Plate II A), in sharp contrast with
the steep, turbulent, actively down-cutting character of the tributary
streams and headwaters of the main streams. A common feature of the
larger tributaries, most of which flow in valleys left by glacial erosion
in a hanging relation to the trunk valleys, is the presence of long canyons