Landforms of British Columbia 1976 - Department of Geography

More documents

Recommendations

Info

ice movement. Elongate drumlins and glacial flutings are clearly visible in air photographs of the lowland, but their relief is only very slight, and consequently they are not represented by the SOO-foot contours on the present 4-m& topographic maps. Aerial photographs show extensive areas of ground moraine and pitted out- wash, with lakes occupying the undrained depressions and a complex of glacial m&water channels related to the disappearance of the last ice (see Plate XLA). Many of these charnels are occupied by small streams quite unrelated in size to the charnels that they occupy. The complexities of Pleistocene and post-Pleistocene history have yet to be disclosed by detailed studies on the ground and of aerial photographs of the region. [References: Douglas, R. J. W., and Norris, D. K., “ Fort Liard and La Biche Map-areas,” Geol. Swv., Canada, Paper 59-6; Camsell, C., and Malcolm, Wyatt, “Mackenzie River Basin,” GeoJ. Surv., Canada, Mem. 108,1919.1 [Photographs: B.C. 1194:SO, S9,77; B.C. 1198:71,72; B.C. 1200:27, 80; B.C. 1201:33,41,48.1
CHAPTER III.-SPECIAL ASPECTS OF THE BRITISH COLUMBIA LANDSCAPE British Columbia spans a thousand-mile length of the Canadian Cordillera and of the vast cordilleran mountain chain that extends along the western side of North America. Its position is not unique, and yet certain features of the landscape give the Province a special flavour and set it apart topographically from the rest of the Cor- dillera. These features are five in number. No other large segment of the Cordillera has been so completely covered during the Pleistocene with glacial ice, as a conse- quence of which the landscape in all parts of the Province shows the effects of glacial erosion and deposition. The pre-glacial topography, the product of erosion by the various river systems, shows deviations from normal river patterns that are the result of stream piracy on a major scale. The fiord coastline is taken very much for granted by the local inhabitants, yet it is comparable in dimension and grandeur to the world- famous coasts of Norway, Patagonia, New Zealand, and elsewhere. To these special features of landscape-namely, glaciation, drainage, and coastline-may be added Tertiary volcanic activity and lineaments. Of these, none is in any way unique or restricted to this region, but they nevertheless combine to give distinction and charac- ter to British Columbia landscapes. In the following pages these five features are treated separately to unify and give meaning to the scattered references made to them in Chapter II. GLACIATION IN BRITISH COLUMBIA There is abundant evidence that the earth’s climate has been continuously changing in an extremely complex way. Warm periods have been succeeded by cold, and more than once in the geologic past conditions have been sufhciently severe to produce a glacial period. The latest of these refrigerated periods began with the Pleistocene epoch, about one million years ago. The Pleistocene is the time interval on the geological calendar when glaciation was widespread, not only in British Columbia, but over large areas in the northern and southern hemispheres. Even in regions that were not glaciated there was sufhcient change in the Pleistocene climate to one that was cool and moist so that the plants, animals, and physical history were affected. A background knowledge of glaciation is important in the consideration of landforms in British Columbia because the Province was intensely glaciated during the Pleistocene. Almost the entire Province was covered by ice which, at.its maximum extent, covered all but some of the highest mountain peaks and parts of the northern and southern Rocky Mountains. The topography everywhere shows the effects of glacial erosion and deposition. In this Province, as in eastern North America, Europe, and other parts of the northern hemisphere, the glacial history was probably complex, but the visible effects of glaciation are almost entirely those of the last, Wisconsin stage. Glaciation in British Columbia resulted in the eventual accumulation of enough ice to form an ice-sheet of continental dimensions. The growth, culmination, and decline of this Cordilleran ice-sheet was in response to world-wide factors of climatic control. Climatic cycles during the Pleistocene produced cyclic advances and reces- sions of glaciers and resulted, in some parts of the world, in four glacial stages of ice advance separated by three interglacial stages of ice recession and partial deglacia- tion. Glaciation in British Columbia differed from much of the rest of Canada in that the ice-sheet occupied an initially mountainous terrain. In mountain regions the cycle of glaciation is considered to begin with the formation of small cirque glaciers 99
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 and 28:
The western boundary of the Eastern
Page 29 and 30:
INSULAR MOUNTAINS The Insular Mount
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
Page 95: Dept. of Mines and Petroleum Remmx?
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 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
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
show all

Landforms of British Columbia 1976 - Department of Geography

Create successful ePaper yourself

Delete template?

Save as template?