Landforms of British Columbia 1976 - Department of Geography

The amount of relief is governed by the elevations at which the rivers are
flowing, and these in turn are controlled by various lake-levels, such as 1,379 feet
at Lower Arrow Lake, 2,235 feet at Kinbasket Lake, 1,753 feet at Slocan Lake,
2,400 feet at Trout Lake, and 1,765 feet rit Kootenay Lake.
The ranges north of Trout Lake are extremely rugged and have high relief.
The peaks are sharp and are separated by deeply incised glaciated valleys. There
are few interconnecting ridges. The high peaks projected through the Pleistocene
ice-sheet and still hold numerous icefields and glaciers which have sculptured the
summits in typical fashion. The sedimentary and metamorphic rocks of the region
have a northwesterly trend, which controls the direction of the ranges and has im-
posed a trellis-like pattern upon the drainage.
South of Trout Lake the area is largely underlain by intrusive rocks, which
Cairnes remarks in the Slocan Mountains “ show the strong relief characteristic of a
mountainous topography in a late adolescent stage of erosion. The areas of
Nelson granite and Kaslo series arc norma!ly more rugged and sharper in outline
than those underlain by sediments of the Sloan series.“* The Sloan Ranges are
characterized by long, uniformly steep, heavily timbered slopes rising through about
5,000 feet to angular peaks and sharp narrow interconnecting ridges. Cirqw glaciers
have sculptured the peaks, and high ridges and valley glaciers have facetted the spurs.
South of Nelson the several ranges comprising the southern Selkirk Mountains
do “ not show the rugged alpine topography of the Slocan, Lardeau, and n~ore north-
erly ranges of the system The mountains of the southern Selkirks [see Plate XXIXBI
are more subdued and rounded than those of the north with fewer rugged peaks and
serrated ridges and without the youthful glacial forms due to higher uplift and more
recent sculpture by mountain glaciers. In this portion of the Selkirks there are.
practically no glaciers and the ranges form a transition belt of mountains connecting
the high and rugged Canadian Selkirks with the low, subdued mountain ranges of the
same system which border the Columbia lava plain in Washington state. . .
Glacial forms, including cirques, a&es, trough-shaped valleys, truncated spurs,
hanging valleys, roches moutonn&es, and valley terraces, are prominent topographic
features in the landscape.“t
[References: Wheeler, .J. O., “ Rogers Pass Map-area,” Geol, Surv., Canada,
Paper 62.32; Little, H, W., “Nelson Map-area (West Half),” Ge01. SIUV., Canada,
Man. 308, 1960; Gunning, H. C., “ Geology and Mineral Deposits of Big Bend
Map-area,” Geol. Surv., Canada, Sum. Rept., 1928, Pt. A, pp. 136-193; Walker,
.I. F., and Bancroft, M. F., “ Lardeau Map-area,” Geol. Surv., Canada, Man. 161,
1930; Cairnes, C!. E., “ Slocan Mining Camp,” Geol, Surv,, Canada, Man. 173,
1934; Drysdale, C. W., “Ymir Mining Camp,” Geol. Surv., Canada, Man. 94,
1917; Walker, J. F., “ Geology and Mineral Deposits of Saltno Map-area,” Geol.
Swv., Canada, Mem, 172, 1934; Fyles, J. T., and Eastwood, G. E. P., “Geology
of the Fergoson Area,” B.C. Dept. of Mines, Bull. No. 45, 1962.1
[Photographs: B.C. 489:82, 107.1
Purcell Mountains
The Purcell Mountains occupy an elongate triangular area 190 miles long and
50 miles in maximum width. The Purcell Mountains lie east of the Selkirk Mountains
and are separated from them by the long through valley occupied by the Beaver
River, Duncan River, Duncan Lake, and Kootenay Lake. On the east they adjoin
the Rocky Mountain Trench.
‘ caimes, c. E., Gd. .SrJ,“., ca”da, kkn In, 1934, p. 2*.
+ mydale, c. w., Gd SU,“., can”da, Mml. 94, WI,, p, 7.
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