Landforms of British Columbia 1976 - Department of Geography

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It flows out the west arm of Kootenay Lake and crosses the Selkirk Mountains to join the Columbia River at Castlegar. This southern looping of the Kootenay River and the northern looping of the Columbia around the north end of the Selkirk Moun- tains are not normal stream patterns and probably are the result of post-glacial diver- sion and major stream piracy. The details of drainage history are not fully known, and the partial interpretation that headward erosion of the ancestral Columbia River beheaded and captured part of the head of Kootenay River to form the “ Big Bend ” of the Columbia only suggests what the general explanation might be. Smaller tributaries of the Columbia that drain an important part of southern British Columbia are the Kettle, Okanagan, and Similkameen Rivers. These rivers drain the southern parts of the Monashee Mountains and the Interior Plateau. COASTAL DRAINAGE A number of rivers in the western part of British Columbia rise on the eastern side of the Coast Mountains and flow westward through them to the sea. Of them the largest are the Alsek, Taku, Stikine, Nass, Skeena, Dean, Bella Coola, Klinaklini, and Homathko Rivers, of which the Stikine, Nass, and Skeena are the largest. The Stikine River rises in Laslui Lake (about 3,900 feet elevation) in the southern part of the Spatsizi Plateau and flows 335 miles westward across the Stikine Pla- teau and through the Coast Mountains to the sea, a few miles north of Wrangell, Alaska. During its course acmss the plateau it is joined by the Klappan, Tanzilla, Tuya, and Nahlin Rivers, which drain much of the Stikine Plateau. In the Boundary Ranges close to the Alaska Border it is joined by the Iskut River, which drains the southern part of the Tahltan Highland and a segment of the Boundary Ranges. The river has a normal dendritic pattern, which developed during the long period of erosion in the Tertiary and which was maintained against the Pliocene uplift of the Coast Mountains. An interesting and scenic stretch of the Stikine River is the Grand Canyon upstream from Telegraph Creek, through which the. river flows for 40 miles, in part between near-vertical lava walls rising to heights of several hundred feet. The canyon was eroded in Recent time by the river after jt was forced from its old valley by the outpouring of fluid basaltic laws from Mount Ed&a (see p. 50). The Nass River rises at about 3,900 feet on the eastern side of the Klappan Range in the northern part of the Skeena Mountains. It flows southwestward for about 236 miles to the ocean at Nass Bay on Portland Inlet (see Plate XLVIIB). The river drains part of the western side of the Skeena Mountains and flows through the Nass Basin, where it is joined on the north by the Bell-Irving River and on the south by the Cranberry River. Much of its drainage basin is within an area of heavy precipitation, so that despite the fact that its drainage area is less than half that of the Stikine, its average flow is comparable. The river downstream from Aiyansh for a length of about 5 miles is flanked on the south by vertical cliffs of black basaltic lava of very recent age. The lava is derived from a small cone on Tseax Creek 3 miles east of Lava Lake, from which flows and scoriaceous material poured northward down the creek valley, forming a lava plain where the larger valley of the Nass was reached and forcing the Nass River against the northern side (see p. 57). The Skeena River rises at an elevation of more than 4,000 feet in the northern Skeena Mountains east of the head of the Nass River. It flows southward and westward for 360 miles to the sea just south of Prince Rupert (see Plate XLIIIB), It drains most of the Skeena Mountains, the western part of the Nechako Plateau, the Bulkley and Nass Ranges, and the northern Kitimat Ranges by its chief tributaries, the Babine, Kispiox, Bulkley, Zymoetz, Kitsumkalum, and Ecstall Rivers. 112
Its pattern of flow within the mountains has developed normally, and in the Skeena Mountains the valleys are in part controlled by bedrock structures. Where the river drains the western part of the Nechako Plateau by the Babine and Bulkley Rivers, it has done so by stream piracy and through glacial derangement of tributaries that formerly were part of the Nechako River drainage. The Stikine, Nass, and Skeena Rivers drain most of northwestern British Columbia. They have maintained their courses across the Coast Mountains and, with their steep gradients, have expanded their drainage basins at the expense of the Yukon, Mackenzie, and Fraser systems, which surround them. There is no doubt that the coastal rivers will continue to maintain this trend. [References: Andrew, G. S., “ British Columbia’s Major River Basins,” Trans., 14th B.C. Nalural Resources Conference, 1963, pp. 23-43; British Co- lumbia Atlas of Resources, 1956, Map No. 4, Glacial Geology, and Map No. 8, Water; Mathews, W. H., “Glacial Lakes and Ice Retreat in South Central British Columbia,” Trans., Roy. Sm., Canada, Vol. 38, Sect. 4, 1944, pp. 39-57; Camsell, C., “Grand Canyon of Fraser River,” Trans., Roy. Sot., Canada, Sect. 4, 1920, pp. 45-59; Schofield, S. J., “Origin of the Rocky Mountain Trench,” Trans., ROY. SK., Canada, Sect. 4, 1920, pp. 61-97; Dawson, G. M., “Later Physiograpbic Geology of the Rocky Mountain Region,” Trans., Roy. Sm., Canada, Sect. 4, 1889; Water Power of Canada, Dept. of Northern Affairs and National Resource 1958; Water Powers of British Columbia, Dept. of Lands and Forests, 19.54; Water Resources Paper No. 128, “Pacific Drainage,” Dept. of Northern Affairs and Nationnl Resources; Water Resources Paper No. 127, “Arctic and Western Hudson Bay Drainage,” Dept. of Northern Affairs and National Resources.1 [Photographs: B.C. 395:17; B.C. 522:113; B.C. 695:lll; B.C. 899:92; B.C. 1087:30; B.C. 1402:lO; B.C. 1407:64.1 COASTLINE OF BRITISH COLUMBIA British Columbia is flanked to seaward by the continental shelf of North America. The sharply defined edge of the platform runs from Dixon Entrance along the west coast of the Queen Charlotte Islands, past Queen Charlotte Sound, and 10 to 30 miles offshore west of Vancouver Island. On the west side of Moresby Island the coast falls off steeply along a fault which bounds the continental platform there and which may extend southeastward along the edge of the platform west of Vancouver Island. Dixon Entrance, Hecate Strait, Queen Charlotte Strait, and the Strait of Juan de Fuca lie on the continental shelf, which is crossed by troughs glacially excavated to depths below 100 fathoms. The Pacific coast of British Columbia is essentially a structurally controlled fiord coastline. The deeply indented coastline (see Plate XLVIA), the flooded glaciated valleys (see Plate XLVIB), and the glacial cirques at and below sea-level (see Plate VIA) are characteristic features of glaciated coastlines in mountainous regions. The coastline was submerged by ice loading during the Pleistocene, and has only recently emerged. Recent marine shells in the Fraser Valley at an elevation of 575 feet above sea-level demonstrate the amount of post-glacial emergence of the coastline there. It is thought that at present the sea-level and land are in equilibrium. SHORELINE FEATURES The recent emergence of the present coastline from beneath its covering of Pleistocene ice, less than 11,000 years ago, accounts for the general lack of shoreline features of marine origin. Beaches are scarce because the bedrock exposed 113
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Bulletin 48 Landforms of British Co
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The technical references are believ
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PAGE Chapter II.-Physiographic Subd
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FIQ. ILLUSTRATIONS 1. Landform map
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PLATE PAOE XVIII. (33) Stikine Plat
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PLATE XXXVIIB. (70) Rocky Mountain
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traveller. If he SO wishes, his enj
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pendants which, because of their se
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As Iava cools and consolidates, it
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are lithologic differences from pla
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mentary rocks are folded and faulte
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Field work by members of the Geolog
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BIBLIOGRAPHY Alden, W. C.: “ Phys
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The western boundary of the Eastern
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INSULAR MOUNTAINS The Insular Mount
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H. C., “ Geology and Mineral Depo
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The extreme northeastern tip of Gra
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the strait. It is suggested that th
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The lowland consists of many low, w
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anges farther west. The ranges sout
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Pacific Ranges The Pa&c Ranges (see
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Columbia. The mountains along the 4
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ones, and widening and deepening th
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south end of Teslin Lake, which sep
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Between the Taku &nd Sheslay Rivers
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The tuyas consist of nearly horizon
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sloping areas of upland remain undi
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mostly in the Babine Range. The roc
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to Eutsuk Lake on the southern side
Page 59 and 60: I These valleys are at a fairly hig
Page 61 and 62: Detailed studies made around severa
Page 63 and 64: The area is drained by the Finlay,
Page 65 and 66: Plateau and the Nechako Plateau, an
Page 67 and 68: iver in pre-Pl&ocene time or whethe
Page 69 and 70: dissected upland surface of the pla
Page 71 and 72: Thompson and North Thompson River v
Page 73 and 74: Adams, and Shuswap Rivers and their
Page 75 and 76: highlands, but the main effects of
Page 77 and 78: eda Rivers on the west and the Colu
Page 79 and 80: The amount of relief is governed by
Page 81 and 82: “ Striae, roches moutonn&s, and l
Page 83 and 84: The boundary between the Rocky Moun
Page 85 and 86: [References: Price, R. A., “ Fern
Page 87 and 88: 8,820 feet, and the lowest point in
Page 89 and 90: margin of the Rocky Mountains% it s
Page 91 and 92: Devonian limestones that are thrust
Page 93 and 94: locally, as a rule only on the nort
Page 95 and 96: Dept. of Mines and Petroleum Remmx?
Page 97 and 98: CHAPTER III.-SPECIAL ASPECTS OF THE
Page 99 and 100: movement, and regional studies of t
Page 101 and 102: Both the Atlas of British Columbia
Page 103 and 104: ase of the Sumas till in the Fraser
Page 105 and 106: British Columbia includes the drain
Page 107 and 108: The Parsnip and Finlay Rivers were
Page 109: upper Fraser River is the result of
Page 113 and 114: materials. Along the west coast of
Page 115 and 116: , Pleistocene probably has been bet
Page 117 and 118: A small volcanic cone with associat
Page 119 and 120: ‘I , titularly for those interest
Page 121 and 122: The Pinchi fault and its northweste
Page 123 and 124: component of the discordant pattern
Page 125 and 126: APPENDIX B.-GLOSSARY * Aggrade-to b
Page 127 and 128: Lineation-in rock the parallel orie
Page 129 and 130: INDEX The place names listed are th
Page 131: 85 126 :: :: 116
Page 134 and 135: Quam Quartz ~ountam Queen Bess, Mou
Page 136: 138
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Landforms of British Columbia 1976 - Department of Geography

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