Landforms of British Columbia 1976 - Department of Geography
Landforms of British Columbia 1976 - Department of Geography
Landforms of British Columbia 1976 - Department of Geography
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pendants which, because <strong>of</strong> their sedimentary laminations, tend to produce an<br />
oriented topography.<br />
Some intrusions have a primary gneissic structure, which is the result <strong>of</strong> parallel<br />
orientation <strong>of</strong> minerals, and which may be stmiciently pronounced to influence the<br />
topography. A common feature <strong>of</strong> large batholiths, and one well illustrated in the<br />
Coast Intrusions, is the presence on a regional scale <strong>of</strong> well-developed joints. These<br />
fractures are sticiently prominent to influence the orientation <strong>of</strong> valleys and ridges<br />
and to give a pronounced rectilinear pattern to the topography (see Plates VIA<br />
and XLVIII) .<br />
Figure 2. Diagram showing the main areas <strong>of</strong> intrusive igneous rock.<br />
Areas <strong>of</strong> dominantly intrusive rocks are shown in Figure 2. Such rocks occupy<br />
a very large area in the Coast Mountains, and their presence explains similarities in<br />
topography that extend over a length <strong>of</strong> almost 1,000 miles. Intrusive rocks are<br />
extensively exposed in the Cassiar-Omineca Mountains, across the southern part <strong>of</strong><br />
the Province, and in the southern part <strong>of</strong> the <strong>Columbia</strong> Mountains. Smaller areas<br />
<strong>of</strong> intrusive rock are scattered throughout the interior <strong>of</strong> <strong>British</strong> <strong>Columbia</strong> from the<br />
International Boundary to the Yukon Border, and on Vancouver Island and the<br />
Queen Charlotte Islands.<br />
Intrusive rocks, wherever they occur and despite. local peculiarities <strong>of</strong> erosion,<br />
impart a characteristic appearance to the landforms developed on them.<br />
(2) Sedimentary rocks consist <strong>of</strong> successions <strong>of</strong> similar or diverse beds. In<br />
general, they consist <strong>of</strong> layers a few feet, or possibly tens or even hundreds <strong>of</strong> feet,<br />
thick, with physical characteristics that may persist for many miles. When the sedimentary<br />
beds are flat lying or only very gently dipping, the topography has a dis-<br />
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