The North Fork of the Big Wood drainage is the hiking epicenter of the Boulder Mountains. The main canyon accesses two large tributaries, the West Fork of the North Fork (WFNF) and the East Fork of the North Fork (EFNF). The hikes ascend dramatic, steep-walled canyons that access multiple alpine cirques ringed by the highest peaks in the range. The West Pass Trail begins at a junction 1.7 miles out the North Fork of the Big Wood.
The underlying geology of the North Fork of the Big Wood River is a combination of sedimentary and volcanic rock. Neither is particularly durable, and both rock units tend to break apart. A wide variety of individual rock units provide a wash of reddish and brown hues that blend together in large, sweeping faces of talus and scree in the upper elevations. Below tree line much of the underlying rocks are covered with forests and soil, but canyon walls are consistently steep down to the valley floor.
Nestled beneath four 10,000-foot and 11,000-foot peaks, Window Lake lies in a dramatic, high alpine basin. The route to the lake is entirely off-trail and requires map and navigation skills.
From an elevation of 8,400 feet where the WFNF Trail emerges into the headwaters basin, cross the West Fork and gain the sharp ridge to the hiker’s right of the creek draining the lake. Work up this forested ridge for 600 feet before scrambling through a band of broken cliffs around 9,200 feet. From here it’s a straightforward rising traverse into the creek and up a narrow, rock-filled gorge to the shores of Window Lake. Winter snow holds along the creek, and alpine buttercups and March marigold fringe the lake in mid-June.
Reference: All content excerpted from Exploring Sun Valley - A Comprehensive Guide to the Boulder, Pioneer, and Smoky Mountains by Idaho River Publications.
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