Lake McDonald is the largest of the more than 700 lakes that make up Glacier National Park in Montana. McDonald has a surface area of 6,823 acres, and it is also the longest (more than 9 miles) and the deepest (450+ feet). But as impressive as all those numbers are, it’s the lake’s shoreline that I find the most amazing. Lake McDonald is famous the world over for its beautiful, multi-colored pebbles. The rocks range in color from reds and yellows to greens to blues. The candy-colored pebbles are found in great abundance on the shore and under the water on the western side of the lake. And the fact that the lake enjoys (?) year-long low temperatures that prohibit the growth of plankton, the water is crystal clear, showing off all those beautiful colors beneath the surface.
“The color of the rocks is determined by the presence or absence of iron. The bright red rocks found along the Grinnel Glacier trail were deposited in a shallow ocean environment where the iron was oxidized by the tidal exposure to the air. Rocks with this coloration often have old ripple marks or ancient mud crack lines.
The rich green-colored rocks were formed in deeper water than the red rocks. Although these rocks contain the same quantities of iron-bearing minerals, they did not have the same exposure to oxygen and the amount of oxidization was limited.” Glacier-Waterton International Peace Park by Vicky Spring and Tom Kirkendall
We are very much looking forward to planning a family trip there. Our 5-year-old niece is particularly obsessed with rocks (I thoroughly expect her to grow up to be a geologist), and I know it’s really going to thrill her. We’d better bring an empty suitcase for rocks!
You can check out all the beautiful lakes of Glacier National Park on their website.