ⓘ Lewis Overthrust

                                     

ⓘ Lewis Overthrust

The Lewis Overthrust is a geologic thrust fault structure of the Rocky Mountains found within the bordering national parks of Glacier in Montana, United States and Waterton Lakes in Alberta, Canada. The structure was created due to the collision of tectonic plates about 170 million years ago that drove a several mile thick wedge of rock 50 mi eastwards, causing it to overlie softer Cretaceous age rock that is 400 to 500 million years younger.