Iron Dike

The Iron Dike

A Geologic Wonder of Colorado


Outcrop of 1.3-billion-year-old Iron Dike's dark gabbro on Trail Ridge road. Click to enlarge image.

Iron Dike at Steep Mountain Image: Stefan and Richard Hollos Click to enlarge image

Iron Dike intrusion into nearby granite Image: Stefan and Richard Hollos Stefan Hollos shown. Click to enlarge

Iron Dike on south side of Steep Mountain - Image: Stefan and Richard Hollos Click to enlarge image

About 1.3 billion years ago, the crust was extended in a northeast-southwest direction. Molten material intruded the older Precambrian igneous and metamorphic rocks forming dikes trending in a northwest-southeast direction. Most of the dikes are dark igneous rocks such as gabbro.

A striking example of these dikes is the sixty-eight-mile-long Iron Dike, which intruded 1.3 billion years ago and extends from south of Boulder northeastward across Rocky Mountain National Park.


The distinctive gabbro of the Iron Dike along Trail Ridge Road in Rocky Mountain National Park. Image: V. Matthews Click image for enlarged close-up view

Last Updated: 1/24/2013 2:48 PM