From the parking lot at Bow Summit, a short, paved trail leads to one of the most breathtaking views you could ever imagine. Far below the viewpoint is Peyto Lake, an impossibly intense green-colored lake whose hues change according to the season. Before heavy melting of nearby glaciers begins (June–early July), the lake is dark blue.
As summer progresses, meltwater flows across a delta and into the lake. This water is laden with fine particles of ground-rock debris known as “rock flour,” which remains suspended in the water.
The mineral content of the rock flour is not responsible for the lake’s unique color; rather, it’s created by the particles reflecting the blue-green sector of the light spectrum. Therefore, as the amount of suspended rock flour changes, so does the color of the lake.
© Andrew Hempstead, from Moon Western Canada, 3rd Edition