Rocky Mountain National Park: Chasm Lake

For the ultimate view of Longs Peak's 1,000-foot Diamond Face, climb to Chasm Lake on this 8.2-mile out-and-back that tops out above treeline.

From the Longs Peak Trailhead, follow a wide path that climbs steadily through ponderosa pine toward Chasm Lake and the summit of Longs. This trailhead is more remote than others in the national park, but as the gateway to the park's only fourteener, it can be a veritable highway of hikers in July and August.

Switchbacks occasionally edging mountain streams eventually reach treeline just past mile two. From here, the trail heads across a wide, rocky basin toward Longs Peak, which is now in view. Crest a small ridge at mile 3.2—this is a great place to drop your pack for a quick snack, photo op, and use the privy, if necessary. (Why not? It has no roof and a great view of Longs' 1,000-foot Diamond Face.)

From here, edge left down into the valley that leads up to the Diamond. In early to mid summer, cross a patch of snow on the descent to columbine-lined stream crossings in front of the patrol cabin that sits at the base of the class-II scramble. Chasm Lake is still out of view.

South of the cabin, scout out cairns on the rock above. Although other routes through the short cliff-bands are doable, the cairns mark the easiest route, and it's a good practice to stay on the designated trail.

In five or ten minutes, summit your scramble to impressive views of the Diamond and icy Chasm Lake at its base. Shoo away aggressive marmots and chipmunks as you search for climbers on the Diamond and Ship's Prow, to the left.

INFO For information on permits, current trail and camp conditions, and wilderness guidelines, go to

PERMIT A wilderness permit is required for all overnight camping in the backcountry. Reservations accepted ($20 administrative fee for permits during peak season).

CONTACT Rocky Mountain National Park, (970) 586-1206;

-Mapped by Jenn Fields and Chris Hood

Trail Facts

  • Distance: 13.2



Location: 40.271774, -105.55645

Trailhead and Longs Peak Ranger Station is well equipped with modern toilets, but can be very crowded on summer weekends.


Location: 40.274994, -105.56411

Turn left at the Y-junction half a mile from the trailhead.


Location: 40.272994, -105.570524

Pass the spur trail that leads to a backcountry campsite.


Location: 40.273212, -105.580032

Cross an upper branch of Alpine Creek on two sturdy wooden bridges.


Location: 40.270432, -105.578568

Around 10,700 feet, the steep, stair-stepped trail crosses treeline. Look for the Twin Sisters across the valley.


Location: 40.270691, -105.581444

Lift your eyes off the trail and start watching for views of Longs Peak's Diamond Face to the southwest.


Location: 40.270828, -105.584282

Turn left at Y-junction following signs for Chasm Lake.


Location: 40.267544, -105.5914

Above treeline, the rocky path is cairn-marked in some stretches. Pass a cairn here.


Location: 40.265656, -105.592537

Turn left at this Y-junction. The well-traveled path to Longs Peak veers right at this point.


Location: 40.265625, -105.591949

Privy: This outhouse has excellent 360 views. Go even if you don't have to.


Location: 40.264234, -105.594825

Peacock Pool is the small lake to the south; Chasm Lake is out of view, beyond the moraine to the southwest.


Location: 40.258827, -105.600601

Bear left for yet another photogenic privy before your arrival at the lake.


Location: 40.258704, -105.601074

Patrol cabin: Hopefully you'll never need to meet the rangers that work here.


Location: 40.258176, -105.602844

Chasm Lake: Bring binoculars to seek out climbers ascending the Diamond Face. Turn around and retrace your steps to the trailhead.


Location: 40.271749, -105.556254

Longs Peak Trailhead © Jenn Fields


Location: 40.274189, -105.577948

The trail crosses and parallels several creeks before it reaches treeline. © Jenn Fields


Location: 40.273223, -105.579793

A sturdy bridge eases the crossing of an upper branch of Alpine Creek. © Jenn Fields

Valley View

Location: 40.270423, -105.578377

At treeline, a hiker scopes out the valley below. © Jenn Fields


Location: 40.270702, -105.58121

The trail turns rockier above treeline. Longs Peak looms above and left. © Jenn Fields

Longs Peak And Mount Lady Washington

Location: 40.270669, -105.58269

Catch glimpses of Longs Peak and Mount Lady Washington in the distance as you push west.


Location: 40.270767, -105.584063

All of the trail junctions on this route are well-marked. © Jenn Fields


Location: 40.265642, -105.592368

The trail to Chasm Lake continues left from here, straight for Longs Peak. © Jenn Fields


Location: 40.265634, -105.59182

Pretty view from the privy © Jenn Fields

Peacock Pool

Location: 40.264259, -105.594653

Peacock Pool © Jenn Fields

Columbine Falls And Longs Peak

Location: 40.263306, -105.596478

Catch views of Columbine Falls backdropped by Longs Peak as you continue to the west.


Location: 40.258823, -105.600548

Columbine burst from between rocks beneath Chasm Lake in mid-July. © Jenn Fields

Patrol Cabin and Ship's Prow

Location: 40.258585, -105.600758

Patrol Cabin: Say hi to the rangers as you pass -- hopefully you'll never have to meet them on a rescue. © Jenn Fields


Location: 40.25829, -105.601691

Follow the cairns. They mark the easiest way over this class-II scramble. © Jenn Fields

Chasm Lake

Location: 40.258176, -105.602758

Chasm Lake

Location: 40.257861, -105.603032

Because of its high altitude and relative lack of sunlight (Mount Hood and Mount Lady Washington block most afternoon sun), Chasm Lake holds ice deep into summer.