May 17, 2003
The photo above shows Mt. Rundle, located in the Rocky Mountains of British Columbia, Canada. In the Earth's early stages of continent building, what is now North America consisted mainly of a granite batholith. Relatively recently, about 170 million years ago, several strings of volcanic islands collided with the west coast of North America. Sedimentary layers that had piled up in the Pacific Ocean became folded and faulted (thrust faults) by the compression of the collision, resulting in the formation of the Rocky Mountains. A side view of the sedimentary layers that were thrust upwards during the mountain building process is shown on the photo. British Columbia would have been about 300 km wider (188 miles) if the collision and resulting folding had not occurred.