How America rifted apart 750 million years ago

During sunrise, Sinopah Mountain is perfectly reflected in Two Medicine Lake in Waterton Glacier. The colorful pebbles in the foreground are mind-boggling 1500 million years old and contain the first life forms of planet Earth, the reef-forming stromatolites.
At that time, the archaic North American continent was a barren land with shallow seas, streams and mud. Cyanobacteria built the first reefs on Earth that fossilized into stromatolithes. Wave action formed ripple marks and even tiny impact craters of raindrops into mud are preserved in these rocks. This provides a snapshot from a world 1000 million years before the first animals would appear.
Here, the continent repeatedly started and failed to split apart along a north south trough. This formed a rift valley where sediments from the surrounding land accumulated to a total thickness of 13 miles (21 km) making it one of the largest sediment deposits on Earth, called the Belt rocks. Around 750 million years ago, the western part of ancient North America drifted away forming its own continent, today known as Antarctica. The Northern Rockies we know today consist of these Belt rock sediments. The uplifting started 80 million years ago. The mountains reflect in a lake that formed after the last ice age within a glacial trough.