Landforms of British Columbia 1976 - Department of Geography

material and are resistant to erosion. Their response to erosion is similar to that
of granitic rocks but differs in the one important respect that they possess mineral
orientation and structural characteris’tics that give alignment and orientation to the
landforms. The foliation may be gently or strongly folded, and this dilference may
be reflected in the topography. Thus, structurally controlled dip slopes in the
Shuswap terrain are gently dipping in contrast to the more steeply dipping slopes
in the Horseranch Range.
Figure 7. Diagram showing the main areas of foliated metamorphic rocks.
The main area underlain by foliated metamorphic rocks is the Shuswap
terrain, shown on Figure 7 as extending northward from Osoyoos to Quesnel Lake
and T&e Jaune. Similar rocks border Carp Lake, extend in a belt northwestward
from the Wolverine Range, underlie the Horseranch Range in northern British
Columbia, and form roof pendants in the Coast Mountains.
INFLUENCE OF OROGENIC HISTORY
Landforms reflect the deformation that a region has experienced. The funda-
mental reason for the difference between the gentle relief of the Interior Plains
and the varied and rugged topography of the Cordillera is the difference in type
of crustal movement that the two regions have undergone. In the Plains Region,
since early Paheozoic times, movements have always been vertical (epeirogenic) ,
with only minor warping of the crust. Because of this fact the sedimentary rocks
laid down in that region are still flat lying or only very gently tilted (&e Plate
XXXVIII). In contrast, movements within the Cordillera have been erogenic
(mountain-building), that is, compressive or tangential to the crust, so that sedi-
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