page_title: Canadian Rockies
section_title: Geology
hierarchical_section_title: Canadian Rockies / Geology
caption_attribution_description: Sodalite-aegirine-albite pegmatite (field of view ~7.1 cm across) from the Ice River Complex of British Columbia, Canada. Blue = sodalite Very dark green = aegirine pyroxene Whitish = albite/sodium plagioclase feldspar Here’s an unusual rock that represents a cavity-filling in a pegmatitic syenite. The syenite host rock is dominated by large, whitish albite crystals (= sodium plagioclase feldspar, NaAlSi3O8) (see left &amp; right edges of photo). The cavity fill has nice, large, bluish sodalite crystals (= sodium chloro-aluminosilicate, Na8(AlSiO4)6Cl2)). Surrounding each sodalite is a radiating spray of very dark green needles of aegirine pyroxene (= sodium iron silicate, NaFeSi2O6). The rock comes from southeastern British Columbia’s Ice River Complex. The Ice River is an 18-kilometer long, 29-square kilometer, backward J-shaped alkaline igneous intrusion emplaced in Cambro-Ordovician passive-margin limestones and shales. Age: ~356 million years (Tournaisian Stage, Early Mississippian)
context_page_description: The Canadian Rockies or Canadian Rocky Mountains comprise both the Alberta Rockies and the B.C. Rockies in the Canadian segment of the North American Rocky Mountains. They are the eastern part of the North American Cordillera, which is a system of multiple ranges of mountains which runs from the Prairies to the Pacific Coast. The Canadian Rockies mountain system comprises the southeastern part of this system, lying between the Interior Plains of Alberta and northeastern British Columbia on the east to the Rocky Mountain Trench of BC on the west. The southern end borders Idaho and Montana of the United States. In geographic terms, the boundary is at the Canada–United States border, but in geological terms it might be considered to be at Marias Pass in northern Montana. The northern end is at the Liard River in northern British Columbia.
  The Canadian Rockies have numerous high peaks and ranges, such as Mount Robson and Mount Columbia. The Canadian Rockies are composed of shale and limestone. Much of the range is protected by national and provincial parks, several of which collectively comprise a World Heritage Site.
context_section_description: The Canadian Rockies are quite different in appearance and geology from the American Rockies to the south of them. The Canadian Rockies are composed of layered sedimentary rock such as limestone and shale, whereas the American Rockies are made mostly of metamorphic and igneous rock such as gneiss and granite.
  The Canadian Rockies are overall more jagged than the American Rockies, because the Canadian Rockies have been more heavily glaciated, resulting in sharply pointed mountains separated by wide, U-shaped valleys gouged by glaciers, whereas the American Rockies are overall more rounded, with river-carved V-shaped valleys between them. The Canadian Rockies are cooler and wetter, giving them moister soil, bigger rivers, and more glaciers. The tree line is much lower in the Canadian Rockies than in the American Rockies.
caption: Sodalite-aegirine-albite pegmatite specimen, Ice River Complex, an intrusion partly in Yoho National Park. Field of view ≈7.1 cm across.
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