Landforms of British Columbia 1976 - Department of Geography

snowline reached a low altitude along the coast between Cape Caution and Banks
Island, as revealed by cirque basins at sea-level in the Kitimat Ranges and Hecate
Lowland. This was a large centre of ice accumulation from which ice moved east-
ward and northeastward across the Interior Plateau and also westward across the
Hecate Depression.
Ice accumulated at the various centres as mountain, cirque, and valley glaciers
that eroded their typical landforms. All the mountain belts exhibit in varying de-
grees glacial landforms produced by cirque, mountain, and valley glaciers. Areas of
highest summits in the Coast Mountains, Columbia Mountains, and the Rocky Moun-
tains display these features to the greatest extent (see Plates XIIA and XXX).
Ice accumulated gradually by the coalescing of numerous ice-tongues into ice-
caps, and the rounded ridges and domed summits characteristic of mountain ice-cap
erosion are displayed over wide areas in the Kitimat Ranges (see Plate XA) , in parts
of the Cassiar and Omineca Mountains, and in the Hart Ranges. This type of topog-
raphy may have been partly destroyed or completely obliterated in some areas by
intense late-stage cirque and alpine glaciation.
Eventually the entire Cordilleran region was covered with ice whose surface
reached a maximum elevation over the southern interior of more than 8,000 feet.*
At this stage of maximum ice coverage, movement of the ice was largely independent
of the underlying topography, and was controlled to a large extent by climatic factors.
Ice Movement
Ice moved across British Columbia from the Coast Mountains, and in the
plateau areas of the interior it left evidence of its direction of movement in the
orientation of drumlins and flutings (see Plate XXV), The ice moved in a general
easterly direction across the Nechako and Fraser Plateaus (see Fig. 10). Farther
to the north, ice moved southeastward parallel to Babine Lake and then swung
eastward in a great arc south of Stuart Lake. From the area between Whitesail
Lake and Anahim Lake, ice moved eastward and northeastward across the Nechako
Plateau to the Rocky Mountains. From Chilko Lake, Taseko Lakes, and Williams
Lake ice moved northeastward and northward to join the main flow, which in part
overrode the Misinchinka and Hart Ranges between the McGregor and Peace
Rivers (see Plate XXXVIB) and debauched onto the Alberta Plateau in a fan-
shaped area west of Dawson Creek.
Farther north ice moved onto the Nahlin, Kawdy, Teslin, and Nisutlin
Plateaus and moved generally in a northwesterly direction over the plateaus into
Yukon Territory. On the east side of the Cassiar Mountains ice moved north-
eastward and eastward across the Liard Plain (see Plate XXXVIIA), escaping
down the valley of the Liard River and across the surface of the Liard Plateau.
On the Thompson Plateau, south of an ice divide which lay between Clinton
and Williams Lake, ice moved southeastward and southward across the surface
of the plateau to escape southward into the State of Washington.
Elsewhere the ice has recorded the direction of its movement by the landforms
it created, and one may discern that ice moved southward down the Iskut River
valley from the vicinity of Kinaskan and Kakiddi Lakes; southward through the
Nass Basin and down the Nass, Skeena, and Kitimat River valleys; northwestward
through Hecate Strait and westward through Dixon Entrance past the northern part
of Graham Island; westward from the mainland across the northern end of
Vancouver Island; southward and southeastward down the Strait of Georgia and
southwestward across the southern end of Vancouver Island; and, as the Puget
Lobe, southward down Puget Sound into Washington.
* Glacial Map of Canada, Geol. Sure., Canada, Map No. 1253~. 1968.
102