Chasm Lake Trail

Chasm Lake Trail is a hard 8.4-mile out-and-back from Longs Peak Trailhead, with about 2,360 feet of climbing. It follows the East Longs Peak Trail to a signed junction, then branches toward the lake in a high cirque beneath Longs Peak. Allow roughly seven hours with breaks; the trailhead is already around 9,300 feet, so the altitude adds to the effort. This is a destination hike, not a warm-up for the Longs Peak summit route. At the junction, take the Chasm Lake branch; the route toward Boulder Field and the Keyhole keeps climbing elsewhere.

The first miles climb steadily through dense lodgepole pine, spruce and fir. Short side paths lead toward Eugenia Mine and the Goblins Forest and Battle Mountain backcountry campsites; stay on the main trail. Around 2.2 miles, the trees shrink into krummholz, the twisted, stunted growth at the forest-to-tundra edge. Longs Peak, Mount Meeker and Mount Lady Washington come into view. Beyond the trees, the path crosses rugged Mills Moraine and gets rougher underfoot. Trekking poles help on this sustained climb, but you will still need to watch your footing.

At roughly 3.4 miles, leave the East Longs Peak route at the signed Chasm Lake junction. The branch traverses the wall of a deep gorge, with views down to Peacock Pool and Columbine Falls, then passes above the waterfall and crosses a small alpine basin. This section eases off compared with the climb behind you. The lake stays hidden until the last rise: the final tenth of a mile climbs sharply over rock up the headwall. Cairns mark more than one line. Expect easy scrambling and some route-finding; this is the part to skip if steep, uneven rock makes you uneasy.

At the top, Chasm Lake sits in a glacial cirque between Longs Peak and Mount Lady Washington. The sheer east face of Longs Peak, known as the Diamond, rises more than 2,400 feet over the water. Mount Meeker and the Keyboard of the Winds add to the southern view. The payoff is the change from the narrow gorge and boulder slope to a lake tucked beneath enormous walls. At the shore, rocks make the footing uneven and a little scrambling is needed for some viewpoints. For a photo, keep the lake in the foreground and the Diamond above it; that scale is the reason this route is memorable.

Start early to leave room for a long climb and to reduce your exposure to afternoon thunderstorms. Above treeline there is little shelter from sun, wind or quickly changing mountain weather. Carry food and enough water for the full outing; no dependable potable-water stop was identified along the route. The Longs Peak Trailhead lot is small, and roadside overflow is limited; both can fill early on busy summer weekends. A park entrance pass is required year-round. Timed entry rules change by season, so check the current Longs Peak access requirement before driving in. Pets are prohibited on park trails. The first ascent of Longs Peak came in 1868, when John Wesley Powell and William Byers climbed the mountain; its name comes from Major Stephen H. Long, whose 1820 expedition saw it from a distance.