Trail Run Project Logo

blueBlack Chasm Lake

  4.7 ( 59 ) Favorite

Navigate on-trail with our free app

iOS App Store Android App Store


8.2 mile 13.3 kilometer out and back
72% Runnable


Ascent: 2,766' 843 m
Descent: -2,766' -843 m
High: 11,675' 3,559 m
Low: 9,430' 2,874 m


Avg Grade: 13% (7°)
Max Grade: 50% (26°)


No Dogs
Driving directions Take a virtual tour
Zoom in to see details
Map Key

Trail shared by Brian Smith

A must-do RMNP run that leads to and from an incredible alpine lake.

Brian Smith

Features Birding · Lake · River/Creek · Views · Wildflowers · Wildlife


This run offers many of the draws of the Longs Peak run in a much shorter, easier to manage package. Although you'll not achieve the same "top of the world" views on offer from Longs Peak, you'll still work for some stunning views from an alpine glacial tarn.

Need to Know

Given that the exceedingly popular Longs Peak run originates from the same trailhead, be prepared for crowds. The Longs Peak Trailhead can also fill up quickly on nice days, so plan to start early if possible.

Once you get out of the subalpine forest, there is very little shade or protection from the wind so use the sunscreen and have the lip balm handy. Even in the summer months, a lightweight long-sleeve shirt is recommended.


Start running up the Longs Peak Trail from the trailhead. The trail is rocky and has steps created by trail crews the whole way. It is moderately steep as it switchbacks its way to a junction with Eugenia Mine Trail, roughly 0.5 miles in. Longs Peak Trail continues ascending above Alpine Brook, eventually crossing it at mile two. Shortly thereafter, you'll reach a junction with Jims Grove Trail and begin to emerge above tree line. Continue on Longs Peak Trail for another 0.8 miles to the Chasm Lake Trail. Turn right onto Chasm Lake Trail.

This trail contours gently along the south face of Mills Moraine providing excellent views below of Peacock Pool and Columbine Falls along the Roaring Fork river. The gentle positive grades give way to equally gentle negative grades before the trail shows its second, and much more drastic character.

After crossing the upper reaches of the Roaring Fork River, at roughly mile 3.7, this trail begins to climb very steeply and will require some scrambling up the outer side of the "wall" that holds the lake.. This short but strenuous pitch is well worth it as you are quickly rewarded with the absurd views at Chasm Lake.

From the lakeshore, you'll be able to view the majestic "Diamond," one of the steepest and most iconic rock faces in Colorado. Located on the east face of Longs Peak, The Diamond rises roughly 2400' straight up.

There are privies located approximately at the intersection of Chasm Lake Trail and Longs Peak - Keyhole Route and also just below Chasm Lake next to a Ranger station (small rock building) in the marshy area,

Flora & Fauna

This run begins in a subalpine ecosystem which occupies elevations approximately between 9,000 and 11,000 feet. A typical subalpine forest may consist mostly of subalpine fir and Engelmann spruce. as you transition above treeline, you'll be entering the alpine ecosystem.

Here, many plants are dwarfed, but their few blossoms may be full-sized. Cushion plants, looking like ground-hugging clumps of moss, escape the strong winds blowing a few inches above them. Cushion plants may also have long taproots extending deep into the rocky soil. Many flowering plants of the tundra have dense hairs on stems and leaves to provide wind protection or red-colored pigments capable of converting the sun's light rays into heat.

Keep a close look in the marshy area between the lakes for the fast moving Pika, resembling a small rabbit with short ears and the lumbering marmot that resembles a beaver with a fox tail. The pika usually makes a short squeaking sound as it initiates its movements.

History & Background

Chasm Lake sits in a semi-circular, steep sided scar, known as a cirque, that is indicative of the top of a glaciated valley. A moraine (as in Mills Moraine) is a field of debris left behind by a glacier as it melts that it scraped and tore from the walls of the valley it moved down.


Rate This Featured Run

Rate Quality

   Clear Rating

Rate Difficulty

Share This Run

Check In


Aug 18, 2018
Jason White
Great for trail running. Medium technical rating. Lots of steps and tall rocks but navigable. I went on a cloudy day, was cool. 8.2mi
Jul 29, 2017
Jen McMurtrey
Jul 28, 2017
Kelly Tuomala
Jul 25, 2017
Mysticmerl1 None
Jun 25, 2017
Dave Richter
Great hike! Beautiful views 8.4mi
Jun 16, 2014
Liz Scordato
So good

Trail Ratings

  4.7 from 59 votes


  4.7 from 59 votes
5 Star
4 Star
3 Star
2 Star
1 Star


in Colorado


315 Views Last Month
13,441 Since Jan 29, 2015
Intermediate/Difficult Intermediate/Difficult



Trail Run Project is part of the REI Co-op family,
where a life outdoors is a life well lived.

Shop REI Running