Effects of Plate Boundary Variations on Elevation, Coast Mountains, British Columbia

Abstract

New Geographic Information Systems (GIS) analysis reveals that the width and height of the elevated topography of the Coast Mountains in British Columbia is largely controlled by the type of adjacent plate boundary. This research documents a strong spatial correlation between topographic characteristics of the Coast Mountains and the transition from a subduction zone to a transform margin on the coast of British Columbia. A sharp change in the topography was observed just near Bella Coola, where the plate boundary switches from a subduction zone in the south to a transform boundary in the north. The south part of the mountain range is distinctly different from the north; the high peaks are concentrated in the south. All of the peaks between 2500 and 4000 meters occur solely in the south part of the mountain range. In addition, all of the topography in the southern part of the range is higher and forms a dense 150 kilometer-wide band of high elevation (>2000 m) that runs through the center of the southern part of the range. The north segment of the Coast Mountains contains very few peaks above 2200 meters. These few peaks are widely scattered, and do not form a persistent topographic feature. The abrupt change in topography occurs where the plate boundary changes from a subduction zone to a transform fault. This spatial relation implies that topography in the south is being held at higher elevations due to the subduction zone?s intense compressional forces.