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Landforms of British Columbia 1976

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Landforms of British Columbia 1976 Landforms of British Columbia A Physiographic Outline bY Bulletin 48 Stuart S. Holland 1976 FOREWORD British Columbia has more variety in its climate and scenery than any other Province of Canada. The mildness and wetness of the southern coast is in sharp contrast with the extreme dryness of the desert areas in the interior and the harshness of subarctic conditions in the northernmost parts. Moreover, in every part, climate and vegetation vary with altitude and to a lesser extent with configuration of the land. Although the Province includes almost a thousand-mile length of one of the world’s greatest mountain chains, that which borders the north Pacitic Ocean, it is not all mountainous but contains a variety of lowlands and intermontane areas. Because of the abundance of mountains, and because of its short history of settlement, a good deal of British Columbia is almost uninhabited and almost unknown. However, the concept of accessibility has changed profoundly in the past 20 years, owing largely to the use of aircraft and particularly the helicopter. There is now complete coverage by air photography, and by far the largest part of the Province has been mapped topographically and geologically. In the same period of time the highways have been very greatly improved, and the secondary roads are much more numerous. The averagecitizen is much more aware of his Province, but, although knowledge has greatly improved with access,many misconceptions remain on the part of the general public as to the precise meaning even of such names as Cascade Mountains, Fraser Plateau, and many others. This bulletin is an authoritative account of the major land subdivisions of British Columbia. It defines the boundaries of the vario’us mountain, plateau, or plain areas, many of them for the first time. Agreement has been reached with the Canadian Permanent Committee on Geographical Names, with Provincial Govern- ment officials, and with geologists and the various sorts of map-makers whose knowledge of the Province is most thorough. In particular, close attention has been paid to H. S. Bostock’s “ Physiography of the Canadian Cordillera, with Special Reference to the Area North of the Fifty-fifth Parallel,” which has heretofore been the chief authority, and any departures from that work have been fully discussed with Dr. Bostock. The form of presentation, and much of the subject-matter, is a reflection of the mind and the interests of the writer, who is a field geologist with a broad knowl- edgeof the Province. Thus the reader is aware throughout of the principal processes that have formed the land as we now see it, and of the reasons for much of the character of the scenery and landforms. Concluding are five short essaysthat are written to clarify the text, and a complete glossary of terms. This bulletin is more than an enunciation of physical boundaries and is, it is hoped, a source book for the better knowledge and understanding of the face of British Columbia. The average reader will surely find much to interest him, though he may care little about the precise boundaries of the Spat&i Plateau, the Tagish Highland, or of other places he may never visit. Literally thousands of air photographs have been examined in the preparation of this bulletin, and many of the finest photographs available have been chosen to illustrate each subdivision mentioned in the table of contents. It is suggestedthat the reader study the photographs and their captions and refer to the text (Chapter II) for further description. The five essaysof Chapter III are written to be read alone, but constant reference to the illustrations and descriptive text makes them more interesting. This is not the sort of bulletin to be read and digested at one sitting. The technical references are believed to be complete. There are, however, publications such as The Canadian Alpine Journal, Canadian Geographic Journal, and others that have not been mentioned but will furnish interesting auxiliary read- ing. This bulletin, it should go without saying, should spur interest in the general study of geology and physiography. H. SARGENT, Chief, Mineralogical Branch. TABLE OF CONTENTS P.&GE Chapter I.-Introduction . -----.- -- . ..---- . ----.-..--..---- ----- ---.----.---.--- ------.---- ---- 13 Development of Landforms .--------.-.------..---------.-. ------ -.--.--- -- ------- -------------.- -- 13 Influence of Process.....--- ------- --------- -- .--- ------ ----..-.- --- -------- -..- -------------- 14 Influence of Bedrock--------.--.-.-.----- --- ------------------.. ---- ---- ------ ----- ---------- 15 Influence of Orogenic History.--------------- -- -----------------------. ---------- ----- 21 Summary of Physiographic History of British Columbia.-..-------------------...- 22 System of Subdivision.----...-.---.-.-... ~.----- .-.-.- ---~--~------- ---------.-.. -- ---.. ----- ----...- 23 Previous Work- ---------- --.-.-------- ------- ---------.-------------------------..--------- ------ 23 Sources of Information .--.-.-.-.-.---- ------.- -------- --------. --- -----.-.------------ -----.. 24 Selection of Boundaries----------.- ---- .-....- ------.-.--- .--.-...---- ------- ---.-- --- ----.- 24 Illustrations .--.----------.----------.------ ----.--- ----.-..- ------- ..------.---..-.-........--.---.-.------- 25 Bibliography --.-----..--.-.-.-..--..--------.-..-----.---------------.--.- -- -.-. - -----..-..--..-.-.-------- 26 Chapter II.-Physiographic Subdivisions of British Columbia-..---------..--------..-- 27 A. Canadian Cordillera..--------.-.. ---- -------- ---- -.------- ------.--.-.-.....-.....-.-.....-.-..-- 27 I. Western System..... ..--..----------- -----------.----------.-.--.........-...--..-..--.---..- 28 Outer Mountain Area.-.-----.-.. ---.- ---.--.-------.-------.------.--.---.--..-----.- 28 St. Elias Mountains .--..--....--------- -------- ---- ---- ----~~~--~.------ ----... 28 Fairweather Ranges------..----------------------..--.---..-------..- 29 Icefield Ranges-------V----.-.------ -- --------------..- ...-----------.--- 29 Alsek Ranges.---- - .-.------- ---- -------------. --..-.--.-- - --------- ----- 29 Duke Depression-.------. ------ .---- --- -.-... - -.-....-.------- --------... 29 Insular Mountains .-..--.--..--..-~~-~-----~-.....~~~~~.-..-..- - ----------- --- 30 Queen Clmd&te Mountains .-----------.--- ---- -.- ------------ ----. 30 Queen Charlotte Ranges------ -------------~ ---.- ------- -.--- 30 &idegate Plateau.---.-.------- -------. -..-....- - -...-.--- - ----- 30 Vancouver Island Mountains .~~~~~~~~~~~-.-.~~~.------- ------ -.-.- 31 Vancouver Island Ranges.--- ---- -...---..------- ---- -.-.- 31 Alberni Basin ..-..---.-.-----------------------..-------------.---32 Estevan Coastal Plain .-------------.-.-.-.....---------- ---..- 32 Coastal Trough .-------.-.-----.------- - -.-- ------- ----.---------.--.--- ----. .--.-------- 32 Hecate Depression.---- ..----.--.------- -----.--- ---- -..--.-- -- --------- ----- 33 Queen Charlotte Lowland .----- -.-.-.------------.----------------.- 33 Argonaut Plair-- ------...-------..-...--..-.-..-------..----.----34 Nahwitti Lowland ..------------- --------..-. - --..---.----------- ------ 34 Suquash Basin..-..--- ------- ------.-.---.--.---.----- ----- ------ 34 Hecate Lowland..-------------.---------------------..- - ------------.-- 34 Milbanke Strandflat------------.------.-.-.-.-- ----- --------- 35 Georgia Depression.--------------.------.-------.--------.--.-- ---.--.-------.- 35 Georgia Lowland .---....------------------------------..-- -- ------.. -.- 36 Fraser Lowland ..--------- -------------------- -.-------------- ---- 36 Nanaimo Lowland .---------------- ----- ---- -----------------.-------- 37 Coast Mountain Area--------.-----..----------- ---------------- ---- ------- -- --.- ---- 38 Coast Mountains .-.---- -...-------------.-.----------------...- ------ ---------- 38 Boundary Ranges---------------------------------- -----...--.-------- 39 Kitimat Ranges.--.------------------------------- -----------.---.------- 41 Pacific Ranges-- .-.----.------ ------- -- ------- ------- .---.------------ 42 Chilcotin Ranges------ ----------------. -.----------.-.-- 43 Cascade Mountains..------.-.-.-- ----- -- -------------- ------~ -.----- 43 Physiographic History of the Western System--------------------.---.--- 45 5 PAGE Chapter II.-Physiographic Subdivisions of British Columbia-Co&nued A. Canadian Cordillera-Continz.& II. Interior System.-------- ------- ..-----.-- --.--------- -...------.------- ---.----- ------ ----- 46 Northern Plateau and Mountain Area .--.-------.------- -----------------.--- 46 Yukon Plateau ..-.--- -.-...-.--- ---- -....---.-------..----- ----.----- -- ----------- 47 Tagish Highland.----.-.------...------- ------ ---!---- ---- --- -------..-- 47 Teslin Plateau------ -- --------.--------- ---------------------- ------------- 47 Nisutlin Plateau.-----.--...--...-.---- --- ---... - ---- ------ --------- ------ 48 Liard Plair------.------..---- --------~~-- ..--.... -- ---- -- ------..-- --.-------- - ---- 48 Central Plateau and Mountain Area ..-.--------------- ---..--.---------------- 49 Stikine Plateau.-.-----..-.--...-- ----.-- ..-.-. ------.--- ------.------------ ----- 49 Tahltan Highland .-.-.---..--......-----~~~------~---- ------------ ----- 49 Taku Plateau.-.----...---.....--.... ------~~~--- -.-.---- .----- ------------- 50 Kawdy Plateau..-...---.-.- -. ..-..---- ---- -- --..- -- --..------------.---- 5 1 Atsutla Range.----..-...-..-- --- ---- -- --...-.-.----- ----------.--- 52
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