Landforms of British Columbia 1976 - Department of Geography

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(15,300 feet) on the Alaska-British Columbia Boundary, the highest peak in British Colmbia; Mount St. Elias (18,008 feet) on the Alaska-Yukon boundary; and Mount Logan (19,850 feet) in southwestern Yukon, the highest peak in Canada and second only to Mount McKinley (20,300 feet) in the Alaska Range, the highest peak in North America. In British Columbia the St. Elias Mountains extend along the Alaska-British Columbia Boundary between Mount Fairweather and Mount Jette. Their boundary with the Coast Mountains is along the Tatshenshini, Kelsall, and Chilkat Rivers. Within British Columbia they comprise the Fairweather Ranges, Icefield Ranges, Alsek Ranges, and the Duke Depression. The mountains along the Alaska-British Columbia Boundary southwest of a line drawn from the head of Tarr Inlet along Melbern Glacier to the Alsek River cuhninate in Mount Fairweather (15,300 feet) (see Plate I), and constitute the Fuirweuther Ranges. The ranges lie in a coastal belt of heavy precipitation and are very largely covered with glaciers and snowfields. Much of the height of the Fair- weather Ranges is due to Pleistocene and Recent uplifts totalling as much as 5,000 feet. The valley of the Alsek River (see Plate IIA) , the only breach in the mountain front between Cross Sound and the Copper River, serves as the southeastern and eastern boundary of the Icefield Ranges, which extend northwestward from the Alsek River to Mount St. Elias and Mount Logan and for the most part lie within Yukon Territory. These ranges, too, are very largely covered with glaciers and snowfields and, together with the Fairweather Ranges, constitute one of the least explored sections of the Province. The AZsek Ranges extend southeastward from the Alsek River and lie to the east of the Fairweather Ranges. They are separated from the Coast Mountains on the northeast by the Kelsall and Tatshenshini Rivers. In contrast to the Fair- weather and Icefield Ranges they are considerably lower in general summit level, about 6,500 to 8,500 feet in elevation, and they carry a much smaller mantle of snow and ice. Their serrate peaks have been sculptured by cirque action, and the major valleys especially have been modified strongly by the movement of ice along them. The creeks and rivers are heavily charged with sediments from melting glaciers, and most streams are aggrading; they flow in intricate and ever- changing courses over their valley trains (see Plate 11~). The valley flats of the lower Alsek and Tatshenshini Rivers are more than a mile wide and present formidable barriers to travel by foot. The low timberline and general lack of vegetation in many parts, coupled with many evidences of stagnant and receding ice, give the appearance of a land just emerging from its glacial cloak. The Duke Depression, a physiographic unit more prominently developed in the Yukon, is a belt of broad smooth slopes, almost plateau-like in character. The general trend of the depression is parallel to the Kluane Ranges, which lie along its northeastern side and which are separated by it from the main mass of the St. Elias Mountains. However, the extension of the Duke Depression into British Columbia is only a very minor feature and is represented by the uppermost reaches of the Tatshenshini River valley at an elevation between 3,000 and 4,000 feet. [References: Watson, K. dep., “ Squaw Creek-Rainy Hollow Area,” B.C. Dept. of Mines, Bull. No. 25, 1948; N.T.S. Sheet 114~, Tatshenshini River.] [Photographs: B.C. 687:58, 76; B.C. 688:13, 31, 35, 82; B.C. 691:26.] 29
INSULAR MOUNTAINS The Insular Mountains comprise the Queen Charlotte Mountains on the Queen Charlotte Islands and the Vancouver Island Mountains on Vancouver Island. Queen Charlotte Mountains The Queen Charlotte Mountains consist of two units-the Queen Charlotte Ranges, which form the mountainous backbone of the Islands and lie mostly along their western side, and the Skidegate Plateau, an elongated belt of plateau-like country flanking them on the east. The Queen Charlotte Mountains lie to the southwest of a more or less direct line drawn from Copper Bay at the northeast end of Moresby Island, south of Dead Tree Point, thence through Juskatla Inlet and past the south end of Naden Harbour to Beresford Bay. This boundary separates the low-lying northeastern corner of Graham Island, the Queen Charlotte Lowland, from the section of greater relief which includes the rest of the Islands. The Queen CharZotte Ranges (see Plate IIB), of which only the San Cristoval Range is named, extend southeastward from RemelI Sound to Cape St. James. The eastern margin of the ranges, between Vertical Point on Louise Island and Rennell Sound, closely follows a zone of faulting. Only the Slatechuck Mountain mass, part of the main ranges, lies east of the fault zone. The highest peaks on the Islands are Mount Needham (3,500+ feet) in the southwestern part of Graham Island, Mount Kermode (3,500+ feet) on the west side of Louise Island, Mount de la Touche (3,600+ feet) just south of Tasu Sound, and an unnamed peak (3,700+ feet) just south of Mosquito Lake. The general summit elevation diminishes southward as the ranges plunge into the sea at Cape St. James. The core of the ranges between Tasu Sound and Nagas Point and of the high range between Skidegate Charmel and Rennell Sound is granitic. Much nf the rest of the ranges is underlain by Triassic and Jurassic volcanic rocks. Despite the fact that their maximum relief is only about 3,700 feet, the Queen Charlotte Ranges are extremely rugged, tbeir serrate peaks having been sculptured by cirque glaciers long since melted away. The cirque erosion has produced topo- graphic forms at all elevations down to and below sea-level. The Skidegate Plateau, some 10 miles wide and 100 miles long, is a dissected plateau whose eastward sloping surface reaches 2,500 feet elevation (see Plate 11~). It is bounded by the Queen Charlotte Ranges on the west and the Queen Charlotte Lowland on the east. It extends between Louise Island on the southeast and Beres- ford Bay at the northwestern tip of Graham Island. From Louise Island northward to Yakoun Lake the surface of the plateau cuts across Mesozoic rocks; farther north tilted Paleocene lavas underlie the plateau surface.* The Islands show signs of intense glaciation. An ice-sheet with a local centre of accumulation, rather than one of mainland derivation, sculptured the terrain below 3,000 feet. Only matterhorn peaks above that height may have projected through the ice-sheet as nunataks. In a late stage, glaciers moved westward and eastward from an ice divide lengthwise of the Islands. Eastward-moving ice modified the topography north of Cumshewa Inlet and coalesced with other glaciers to move northward and northwestward across the Queen Charlotte Lowland and finally westward out to sea across the Lowland past the northern end of the Skidegate Plateau (see Fig. 10). * Personal communication, A. Sutherland Brown. 30
Page 1 and 2: Bulletin 48 Landforms of British Co
Page 3 and 4: The technical references are believ
Page 5 and 6: PAGE Chapter II.-Physiographic Subd
Page 7 and 8: FIQ. ILLUSTRATIONS 1. Landform map
Page 9 and 10: PLATE PAOE XVIII. (33) Stikine Plat
Page 11 and 12: PLATE XXXVIIB. (70) Rocky Mountain
Page 13 and 14: traveller. If he SO wishes, his enj
Page 15 and 16: pendants which, because of their se
Page 17 and 18: As Iava cools and consolidates, it
Page 19 and 20: are lithologic differences from pla
Page 21 and 22: mentary rocks are folded and faulte
Page 23 and 24: Field work by members of the Geolog
Page 25 and 26: BIBLIOGRAPHY Alden, W. C.: “ Phys
Page 27: The western boundary of the Eastern
Page 31 and 32: H. C., “ Geology and Mineral Depo
Page 33 and 34: The extreme northeastern tip of Gra
Page 35 and 36: the strait. It is suggested that th
Page 37 and 38: The lowland consists of many low, w
Page 39 and 40: anges farther west. The ranges sout
Page 41 and 42: Pacific Ranges The Pa&c Ranges (see
Page 43 and 44: Columbia. The mountains along the 4
Page 45 and 46: ones, and widening and deepening th
Page 47 and 48: south end of Teslin Lake, which sep
Page 49 and 50: Between the Taku &nd Sheslay Rivers
Page 51 and 52: The tuyas consist of nearly horizon
Page 53 and 54: sloping areas of upland remain undi
Page 55 and 56: mostly in the Babine Range. The roc
Page 57 and 58: 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
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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
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British Columbia includes the drain
Page 107 and 108:
The Parsnip and Finlay Rivers were
Page 109 and 110:
upper Fraser River is the result of
Page 111 and 112:
Its pattern of flow within the moun
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
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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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