The rocks in Glacier National Park’s mountains reveal ancient seabeds and rivers and volcanic activity from billions of years ago, noted geologist Kurt Constenius, a Whitefish native and geologist with the University of Arizona during a September lecture.

Speaking during the park's Science and History Day, Constenius went over a few of the formations in Glacier, which date back to as long as 1.6 billion years ago. Scientists believe that at one point the park was likely connected to Australia.

At that time, North America was a much different place, a rather large land mass with huge drainages that once flowed north and then south. Eventually, the landscape rose up into mountains.

Geologists can track these shifts by studying the various rock formations and also through dating zircon crystals through their radioactivity.

Much of the geological record is fairly straightforward, but there’s a wildcard in play, Constenius said. A formation known as the Sheppard uplift, which features black rock with cobbles, holds the potential link to Australia. It will take some more digging to determine definitively if that’s the case.

The mountains of Glacier, created by the Lewis Overthrust, were formed roughly 150 million years ago, and slowly at that.

According to Glacier’s website, plates of crust collided on what was then the western edge of North America. That collision began a process of mountain building that would continue for nearly 90 million years.

In the area that would become Waterton-Glacier International Peace Park, massive forces uplifted a slab of rock several miles thick. The bottommost layer of this slab is roughly 1.6 billion years old, and it was pushed east for 50 miles over rock only 70 million years old. Geologists estimate that this movement occurred at a rate of less than half an inch every year. When the slab finally came to a halt, the layer on top was over a billion years older than the rock beneath it.

The Lewis Overthrust Fault is not only Glacier’s most famous geological feature, it’s also major evidence of the tectonic events that created the mountains here in the Crown of the Continent. As a result of the uplift, erosive forces accelerated and over several million years removed the upper layers of material, exposing the rock formations evident in the park today. 

However, other events were occurring at the same time as the overthrust. Folding warped many of the formations into synclines and anticlines, bending the rock upward and downward like an S-curve. Multiple smaller faults also curved, cracked and broke different layers in various places throughout the park.

The casual visitor can see evidence of the overthrust at places like Marias Pass. The fault can be seen on Summit and Little Dog Mountains as a thin tan line of rock roughly halfway between the peak and the ground below, the National Park Service notes.