Landforms of British Columbia 1976 - Department of Geography

anges farther west. The ranges south of Taku River, at the head of the Whiting
River, and between the heads of the Sheslay, Tahltan, and Chutine Rivers, are ex-
tremely rugged. The slopes below 3,500 and 4,500 feet are heavily forested, and
scenic features of glacial origin, such as cirques, hanging valleys, and over-steepened
slopes are everywhere present.
The Boundary Ranges reach their greatest heights in the granite peaks of Mount
Ratz (10,290 feet), Mussel1 Peak (10,260 feet), Noel Peak ( 10,040 feet), and
Kates Needle ( 10,002 feet) north of the Stikine River. South and west of Bowser
Lake the highest summits are Mount Jancowski (9,800 feet) and Mount Patullo
(8,951 feet), but elsewhere in the ranges the summits range between 7,000 and
8,500 feet in elevation. The fact that the summits are close to the coast and that
the streams draining them fall rapidly to sea-level emphasizes the great relief in the
mountains.
In the ranges between Stewart and Mount Foster (north of Skagway) a very
high percentage of the area is under a cover of glacial ice, through which isolated
peaks project as nunataks. The Taku Icefield (see Plate XLIA) is a very large ice-
field which extends southward from Skagway to the Taku River. From it the Meade,
Eagle, and Mendenhall Glaciers and others flow westward to the sea, the Llewellyn
Glacier flows eastward to Atlin Lake, and the Tulsequah Glacier flows southward to
the head of Tulsequah River. Another extensive icefield lies north of Iskut River
and south of the heads of Scud River and Mess Creek; other icefields lie between
the Unuk and Salmon Rivers and between the heads of the Kitsault and Bear Rivers.
Timberline is at an elevation of 3,500 to 4,000 feet, and below that level the
slopes are heavily forested and underbrush is dense.
The ranges have been heavily glaciated, the high peaks have matterhorn forms
produced by well-developed cirque glaciation, peaks and ridges below about 6,500
feet are rounded and subdued by the effects of ice-sheet erosion, and valley walls
have been steepened and spurs truncated so as to produce typical U-shaped profiles,
The steep topography, combined with heavy undergrowth below timberline, makes
the region exceedingly ditlicult for ground travel.
During the Pleistocene the land was heavily loaded with ice, and near the coast
was submerged beneath the sea. Deposits of marine origin occur at elevations up to
100 feet above present sea-level along the Taku River, and terraces and benches up
to 500 feet above sea-level may be delta deposits of marine origin that indicate a
submergence of 500 feet. In the Alice Arm and Portland Canal areas, marine clays,
deltas, and old beaches now at a considerable height above sea-level indicate a maxi-
mum submergence there of 485 feet below present sea-level.
The ranges are crossed by the Taku, Whiting, Stikine, Iskut, Unuk, Bear, and
Kitsault Rivers. These are antecedent rivers whose valleys, incised before the Pleis-
tocene, served as main drainage-ways for the westward flow of glacial ice. The val-
leys were over-deepened by the passage through them of very large amounts of ice,
with the formation of the many hanging valleys which are characteristic of the region.
Cirque erosion was an important phase of the late stage of glaciation, and large well-
developed cirque basins carved on the north and northeast sides of peaks and ridges
are characteristic of the landscape.
A remarkable feature of the ranges between Portland Canal and the Nass River
is the abundance of northeasterly trending lineaments in the granitic rocks. These
are marked by Observatory Inlet and by the Kincolith, Iknouk, and Nass Rivers, as
well as by numerous minor topographic features visible on aerial photographs.
[References: Kerr, F. A., “ Taku River Map-area,” Geol. Surv., Cunudu, Mem.
248, 1948; Kerr, F. A., “ Lower Stikine and Western Iskut River Areas,” GeoZ.
Surv., Canada, Mem. 246, 1948.1
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