Alberta Montana
Glacier National Park in Montana and Waterton Lakes National Park in Canada are known jointly as the Waterton-Glacier International Peace Park. The international border running through them isn’t the only boundary line here, though. The park boundaries also represent the dividing line between the U.S. Rockies and the Canadian Rockies.
Looking down on Waterton-Glacier, you will see steep-sided mountains with many horizontal layers. Rivers and lakes here tend to be bright blue because of the fine glacial rock flour in the water.
The rocks found here are more similar to those in the Canadian Rockies than the rocks found throughout the U.S. Rockies, which are primarily volcanic and metamorphic. In Waterton-Glacier, the layers are mostly sedimentary rocks deposited in shallow seas between 1.6 billion and 800 million years ago. Finding sedimentary rocks that old is unusual, as most get transformed into metamorphic rocks over long periods—a result of burial, heat, and pressure or mountain-building activity.
Sedimentary rocks are also known for containing fossils, created when organisms of creatures get preserved by burial in sediments and hardened over time. However, the rocks in Waterton-Glacier are too old to contain plant or animal fossils—they were laid down before complex life evolved on Earth. The only fossils found in these rocks are stromatolites: layered biomasses formed in shallow water by colonies of cyanobacteria. Such colonies—among the earliest life-forms to evolve on the planet—have been found in rocks dating back 3.5 billion years and can be found today thriving in similarly shallow water environments all over the world.
These tiny organisms had a big impact on the early days of Earth. Cyanobacteria use sunlight to convert carbon dioxide from seawater into oxygen. This process creates particles of calcium carbonate, which help cement the stromatolite mats and build the massive deposits of carbonate-rich rocks found in the park. The production of oxygen by the cyanobacteria helped create the oxygen-rich atmosphere that gave rise to many early life-forms.
The Waterton-Glacier International Peace Park straddles the border between the United States and Canada, and the dividing line between the U.S. Rockies and Canadian Rockies.
Not all the rocks in Waterton-Glacier are ancient. Some layers date to the more recent Cretaceous Period, but curiously, they underlie the older rocks. One of the basic principles of geology is that younger rocks sit on top of older rocks; the reversal here is evidence of a tremendous geologic upheaval. During the formation of the Rocky Mountains, a region of rock several miles thick and several hundred miles long, now known as the Lewis Overthrust, was shoved fifty miles eastward, coming to rest over the top of older rocks in what is now Glacier National Park.
You might spot this breathtaking area en route to Kalispell, Montana, or Calgary, Alberta.
