The rocks that form the Insular Superterrane are allochthonous, meaning they are not related to the rest of the North American continent. They consist of a series of volcanics, intrusions and sedimentary rocks from the collision of an ancient island arc called the Insular Islands.[1] The exact collision of the Insular Islands remains uncertain.[1]
The region is noteworthy as it has the greatest physiographic relief from the depths of Queen Charlotte Sound (which had been a coastal plain during the last ice age) to the heights of the Wrangell - Saint Elias Mountains. In general the region is extremely rugged with very little flat land except in certain regions (e.g. the east coast of Vancouver Island).
The region is thickly forested, having a temperate year round climate, with many of the world's largest trees.