The Henrys Lake Mountains are a mixture of Paleozoic sedimentary rocks and volcanic materials including rhyolite and basalt with some Precambrian metamorphic rocks thrown in for good measure. The range, which was forced up with the uplifting of the Rocky Mountains, has most recently been shaped by glaciation and the nearby Henrys Fork and Island Park calderas and the collapsed volcanoes that preceded them. One of these volcanoes covered more than 6,000 square miles of Idaho and Montana with red-hot ash and other materials. North Targhee Peak is the highest summit in the Idaho portion of the range.
The Henrys Lake Range is located just west of Yellowstone National Park. As part of the greater Yellowstone ecosystem it is prime habitat for grizzly bears. In fact, my climbing partners and I were charged by a young grizzly on the day the day we climbed Targhee Peak. We highly recommend you visit the National Park Service’s Staying Safe Around Bears page before venturing into the Henrys Lake Range.