Landforms of British Columbia 1976 - Department of Geography

Adams, and Shuswap Rivers and their tributaries into large polygonal upland tracts.
The valley sides are commonly steep because of glacial erosion, and the total relief
may be fairly great even though the local relief in the uplands is moderate.
The Shuswap Highland reaches heights of 8,945 feet at Mount Mahood, 9,000
feet at Trophy Mountain, 8,640 feet at Dunn Peak, 7,390 feet at Pukeashun Mow-
tain, and 6,749 feet at Park Mountain. The high points are progressively lower to
the south, Most ridges and summits are rounded, and despite the height of much of
the terrain the country lacks the jagged sawtooth profiles of the mountains to the east.
The effects of glaciation in the region were largely to soften and reduce the
upland relief while steepening and deepening the valleys. Cirque glaciation on north-
eastern exposures was a minor feature.
Numerous large lakes, such as Murtle, Adams, Shuswap, and Mabel Lakes,
occupy some of the major valleys of the area, and these, as well as the rather extraor-
dinary pattern of the drainage, quite obviously diverted from its pre-glacial flow, are
legacies of PIeistocene ice occupation.
[References: Jones, A. G., “ Vernon Map-area,” Geol, Surv., Canada, Mem.
296, 1959; Ugkxv, W. L., “ Geology of the North Thompson Valley Map-area:
Geol. Surv., Camdu, Sum. Rapt., 1921, Pt. A, pp. 72-106; Walker, J. F., “Clear-
water River and Foghorn Creek Map-area,” Geol. Surv., Canada, Sum. Rept., 1930,
Pt. A, pp. 125-15311
[Photographs: B.C. 359:103; B.C. 487:lll; B.C. 490:19, 39.1
Okmagan Highland
The Okanagan Highland (.w Plate XXVIIIB), the most southerly of the three
highland subdivisions, extends southward from the Coldstream Valley for 85 miles
to the 49th pamlIe and thence into the State of Washington. It lies between the
Monashee Mountains on the east and the Thompson Plateau on the west. The east-
ern boundary of the Okanagan Highland is the valley of the Kettle River. The west-
ern boundary has been drawn arbitrarily and is somewhat difficult to define, because
there are no natural features to follow between Penticton in the Okanagan Valley
and Lumby in the Coldstream Valley.
The Okanagan Highland includes rounded mountains and ridges and gentle
open slopes on an upland surface reaching 7,118 feet at Mount Moore, 7,000 feet
at Jubilee Mountain, 7,603 feet at Big White Mountain, 7,004 feet at Greyback
Mountain, 7,550 feet at Baldy Mountain, and 7,372 feet at Ape? Mountain. The
area is drained and dissected by the Okanagan and Kettle Rivers and their tributaries.
Much of the area is underlain by gently dipping Shuswap gneisses, the differential
weathering of which has produced gentle step-like slopes.
Pleistocene ice covered the highland, but erosion by it was not great; some
rounding of surfaces was effected and a widespread mantle of drift was deposited.
Meltwater channels developed at successively lower elevations along the sides of
Okanagan Valley as the elevation of the ice surface was reduced. Marginal lakes
formed along the sides of the melting ice lobe and streams deposited their loads in
them as deltas and accumulations of silt. These latter form the white cliffs which
are particularly prominent along southern Okanagan Lake (1,123 feet). The late
glacial history and the origins of many minor topographic features are described in
detail in British Columbia Department of Mines and Petroleum Resources Bulletin
No, 46, 1962.
[References: Nasmith, H., “ Late Glacial History and Surficial Deposits of the
Okanagan Valley, British Columbia,” B.C. Dept. of Mines, Bull. No. 46, 1962;
Reinecke, L,, “ Physiography of Beaverdell Area, ” Gtd. Sm., Canada, Mu% Bull.
No. 11, 191521
[Photographs: B.C. 804:45; B.C. 805: 14.1
74