Mark Wilson July 15th, 2010
LOGAN, UTAH–Logan Canyon cuts perpendicularly through the Bear River Range in Cache County, northern Utah. It neatly dissects a complex section of Paleozoic sedimentary rocks in the Logan-Huntsville Allochthon noted in my last post. Conveniently, US Highway 89 runs through the length of the canyon providing spectacular views of the quartzites, dolomites and limestones.
After exiting the canyon in the east, Highway 89 meets a most unusual body of water with a prosaic name: Bear Lake. Running north-south across the Utah-Idaho border, Bear Lake is one of the oldest existing lakes in North America. Studies of its sediments show the lake has existed for at least 220,000 years, and maybe more. Its water is strangely blue because it contains lots of dissolved calcium carbonate from the surrounding limestone mountains in its watershed. The lake was formed by tectonic processes, sitting now in a half-graben which is still active. Its human history is interesting too — in the early 19th Century it was a gathering point for mountain men, including Jim Bridger and my hero Jedediah Smith.