Landforms of British Columbia 1976 - Department of Geography

The plain in British Columbia extends for 100 miles along the Yukon Border and
for 20 to 30 miles south of it.
The Liard Plain was completely covered by glacial ice, which moved across
it. The present surface is very largely the product of glacial processes, and the
effect of post-glacial erosion is to be seen only in the 50 to 100 feet of incision
along the major streams. As the ice moved across the plain, it shaped and modelled
bedrock and drift alike in drumlin-like forms parallel to the direction of ice move-
ment (see Plate XXXVIIA) . Numerous depressions were gouged, which now are
occupied by the many shallow lakes dotting the plain. Eskers and morainal features
are clearly displayed on air photographs and topographic maps or may be seen a
short distance south of the Alaska Highway at a point 20 miles east of Lower
Post (see Plate XVA).
It is evident that ice escaping northward from the Cassiar Mountains flowed
northward down the Dease River valley and swung northeastward around the
northern end of the Horseranch Range to flow northeastward (north 67 degrees
east) and eastward across the Liard Plain past Mount Monckton (3,948 feet)
(see Fig. 10). Some ice may at one stage have moved southeastward up the
Rocky Mountain Trench toward Aeroplane Lake. Escape from the plain evidently
was eastward down the valley of the Liard River past the Hotsprings (Mile 497)
and northeastward across the Liard Plateau from the vicinity of Smith River Airport.
[Reference: Gabrielse, H., “ McDame,” GeoZ. %wv., Cunudu, Paper 54-10.1
[Photographs: B.C. 893: 102; B.C. 954:82, 87, 88, 117; B.C. 955:9, 59.1
CENTRAL PLATEAU AND MOUNTAIN AREA
The Central Plateau and Mountain Area comprises the Stikine Plateau,
Skeena Mountains, Nass Basin, Hazelton Mountains, Cassiar Mountains, and the
Omineca Mountains.
STKINE PLATEAU
The Stikine River, between the Coast Mountains on the west and the Cassiar
Mountains on the east, drains a large area of dissected plateau country named
the Stikine Plateau. On the north the Stikine Plateau merges in the Yukon Plateau
along an arbitrary line between Atlin and Teslin Lakes. It is bounded on the west
by the Boundary Ranges, on the south by the Skeena Mountains, into which it
passes by transition through a progressively more elevated belt of greater dissection
(see Plate XIXB) , and on the east by the Stikine Ranges and the northern Omineca
Mountains. For the most part, the Stikine Plateau lies below the level of the
surrounding mountains on the west, south, and east.
The Stikine Plateau is subdivided into seven units having distinct geographic
and geologic characteristics. These are the Tahltan Highland and the Taku,
Kawdy, Nahlin, and Tanzilla Plateaus north of the Stikine River and the Klastline
and Spat&i Plateaus to the south.
Tahltan Highland
The Tahltan.Highland (see Plates XVB and XLVIIA) extends southeastward
along the western side of the Stikine Plateau between the Taku River and the head
of the Iskut River. It is a transition zone between the plateaus and the Boundary
Ranges of the Coast Mountains. The highland is about 5 miles wide on the Taku
River and widens southward to a maximum of about 30 miles where crossed by
the Stikine River.
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