Geology

I guess I should start by saying I'm no expert in geology, but Glacier National Park has a very interesting geological history. It has some of the oldest and best preserved exposed sedimentary rock, evidentially on the planet! And what's really strange is that during the time these mountains were forming, this old rock, dating from 1.6 billion to 800 million years old, was actually thrust on top of much younger and softer rock over an unbelievable distance of 50 miles. It's called the Lewis Overthrust, and the older rock is amazingly over 1,400 million years older than the stuff under it! The old rock is the kind visible in the upper left of the photo.