Insular Belt

It represents the Late Cretaceous to Eocene accretion of what is known as the Insular Superterrane (formed from repeated accretion of multiple terranes) to the North American continent.

The rocks that form the Insular Superterrane are allochthonous, meaning they are not related to the rest of the North American continent.

[1] The exact collision of the Insular Islands remains uncertain.

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.

The region is thickly forested, having a temperate year round climate, with many of the world's largest trees.