Bunsen Peak Trail

Bunsen Peak Trail is a 4.6-mile out-and-back from Bunsen Peak Trailhead 1K4 to the summit area and the higher eastern high point, then back the same way. Plan on two to three hours and about 1,300 feet of climbing. It makes a satisfying half-day near Mammoth: the views start early and keep widening, but the steady uphill and loose rock near the top make this more demanding than the mileage suggests. Slow down on the descent; the last slope is where the footing gets loose and the tread less obvious.

A shorter 4.2-mile description turns back around the main summit area. To reach the higher eastern point beyond the communications building, continue about 0.2 mile farther; that is the full 4.6-mile walk represented here. Stay on the same trail and return to the trailhead. Descending the far side to Old Bunsen Peak Road creates a longer loop, while Osprey Falls is a separate hike from that road.

The small unpaved lot is about five miles south of Mammoth, just south of Golden Gate and across from Glen Creek Trailhead. Spaces are limited and can fill in summer. There is no water or restroom at the lot or on the route, so stop in Mammoth first. The usual hiking season is summer and fall; in winter, trailhead access requires a snow-coach drop-off or skiing from the Upper Terrace parking gate. Pets are not allowed, and bikes use the road route rather than this summit trail.

From the lot, the path leaves the gated old road almost immediately and climbs through lodgepole pine. The switchbacks keep the grade manageable, but they do not make it flat. A view toward Kingman Pass and Mammoth opens after roughly a third of a mile, so you can get a taste of the route without committing to the summit. By about the first mile, the trees open toward Swan Lake Flats, Gardners Hole and the Gallatin Range.

Higher up, the path reaches open ground in the area burned in 1988. New lodgepole pines are returning among fireweed, Indian paintbrush and whortleberry. Near Cathedral Rock, look back toward Mammoth Hot Springs, Fort Yellowstone and Everts Bluff. This section changes the feel of the climb: less forest around you, more of the basin spread out below.

The last switchbacks cross loose, shifting talus and the route is harder to pick out, so keep an eye on the tread. The communications building is the first obvious marker near the top, but the slightly higher eastern summit is worth the extra steps; a small cement survey marker identifies the high point. From the ridge, the view takes in Swan Lake Flats, the Gallatin Mountains, Blacktail Deer Plateau and the Yellowstone River Valley. For a summit photo, frame Swan Lake below the snowy range rather than just the sky.

The communications equipment up here supplies Mammoth and nearby communities, an unusual bit of working infrastructure at the end of a scenic climb. The peak is named for German chemist Robert Bunsen, who studied geysers and invented the Bunsen burner. Grizzly bears frequent the area; carry bear spray where you can reach it and know how to use it.