Landforms of British Columbia 1976 - Department of Geography
Landforms of British Columbia 1976 - Department of Geography
Landforms of British Columbia 1976 - Department of Geography
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I<br />
.<br />
The Purcell Mountains (see Plate XXXIA) include some extremely high and<br />
rugged mountainous country, and the highest peak, Mount Farnham (11,342 feet),<br />
is only slightly inferior in height to Mount Sir Sanford ( 11,590 feet), which is the<br />
highest in the Selkirk Mountains. The ranges at the north end <strong>of</strong> the Purcell Mountains<br />
gradually increase in summit level south from Beavermouth, reaching their<br />
maximum heights in the area between the heads <strong>of</strong> Bugaboo and Findlay Creeks in<br />
Mount Farnham (11,342 feet), Jumbo Mountain (11,217 feet), Hamill Peak<br />
( 10,640 feet), and Mount Findlay ( 10,780 feet). The northern ranges are inferior<br />
in height to the ranges in the Selkirk Mountains due west in Glacier Park, whereas<br />
due west <strong>of</strong> the highest Purcell Mountains lie the somewhat lower Slocan Ranges <strong>of</strong><br />
the Selkirks. South <strong>of</strong> Mount Findlay, summit heights diminish gadually, Mount<br />
Loki (9,090 feet), northeast <strong>of</strong> Riondel, and Mount Evans (8,949 feet), southwest<br />
<strong>of</strong> St. Mary Lake, being the highest. At the International Boundary the summit<br />
heights arc in the vicinity <strong>of</strong> 7,000 feet and the topography is comparatively subdued.<br />
The axis <strong>of</strong> the mountains lies closer to their western margin than to their<br />
eastern. Westward drainage is by short steep streams, whereas eastward drainage<br />
is on gentler gradients by longer tributaries. Along the east side <strong>of</strong> Kootenay Lake<br />
the tributary creeks flowing in narrow deep valleys have carved out a series <strong>of</strong> narrow<br />
ridges running east and west, ranging in elevation from 7,000 feet on the ends<br />
overlooking the lake to 8,000 feet and higher on the eastern ends.<br />
The mountains are drained by tributaries <strong>of</strong> the head <strong>of</strong> the <strong>Columbia</strong> River<br />
and by the Kootenay River and its tributaries. Kootenay Lake at 1,755 feet elevation<br />
and <strong>Columbia</strong> Lake at 2,852 feet elevation are significant heights in the drainage<br />
systems, above which the mountains rise to a maximum regional relief <strong>of</strong> about<br />
8,000 feet.<br />
The Purcell Mountains are underlain by sedimentary and metamorphic rocks,<br />
largely <strong>of</strong> Proterozoic age but extending upward into the Lower Palazozoic, which<br />
are intruded by batholiths <strong>of</strong> granitic rocks. The sedimentary and metamorphic<br />
rocks comprise thick quart&e, argillaceous quart&e, argillite, and limestone members;<br />
the lithology is far more uniform in the Purcell Mountains than in the Selkirks.<br />
The rocks are involved in overturned and frequently complex folds about axes which<br />
regionally have an arcuate plan, being northeasterly in the south, northerly in the<br />
central ranges, and northwesterly in the north. The trends <strong>of</strong> individual ranges are<br />
controlled by this fundamental bedrock structure.<br />
The northern ranges contain rugged high peaks which are massive and bold<br />
when composed <strong>of</strong> quartzite or granite, and sharp and pinnacled when composed <strong>of</strong><br />
slates. The highest peaks projected above the Pleistocene ice-sheet, whose level lay<br />
at 8,000 feet in the north and at about 7,000 feet in the south. The peaks were<br />
shaped by intense cirque glaciation, and active cirqw glaciers are still present on<br />
some <strong>of</strong> the highest peaks. The summits are separated by deep, steep-sided glaciated<br />
valleys, and interconnecting ridges are few and mostly serrate. In the southern Purcell<br />
Mountains south <strong>of</strong> Mount Findlay and Skookumchuck Creek “ the mountains<br />
up to 7,000 feet are rounded and well wood& to the summit, higher ones are commoody<br />
extremely rugged, and those carved out <strong>of</strong> gmnite or massive quart&es are<br />
climbed only with extreme difficulty. Near the International Boundary few peaks<br />
rise above 7,000 feet and the topography is comparatively subdued. To the north,<br />
where the elevation <strong>of</strong>.the higher peaks is 8,000 or 9,000 feet, the terrain is extremely<br />
rugged. A feature that causes the abrupt relief and consequent steepness <strong>of</strong> the<br />
mountains is the deeply incised valleys that reach far back into the heart <strong>of</strong> the<br />
range.“*<br />
” Glacial striae, erratics, and glacial debris occur at all elevations,up to 8,000<br />
feet.<br />
* Rice, H, M. A, f&o,. sm., Cm7d.T. blem. 2% ,94,, p, *<br />
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