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Delta Mountains, AK: Castner Glacier

Witness the effects of climate change on a challenging trek in the Delta Mountains.

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There’s more to the Alaska Range than Denali National Park and its heavily regulated backcountry: Discover equally impressive sections of Alaska’s namesake range east of the park’s main entrance. There you’ll find the Delta Mountains, with a million acres of lower-elevation but equally glaciated peaks.

This 20.5-mile round-trip up the Castner Glacier takes you into the heart of it all. In addition to stunning views of soaring ridgelines and glacial icefalls, you’ll also get a firsthand look at the profound effects of climate change. The Castner Glacier is losing ice mass rapidly, literally collapsing in on itself, and much of the central glacier has become a deep trench with water flowing between icy, muddy banks.

The route begins from asphalt roadside along the Alaska Pipeline, and climbs up massive glacial moraines of the Castner to the spectacular cirque of the Silvertip Icefield. There’s no trail to follow, and simple routefinding mistakes can cost you time and effort (download our field-scouted GPS tracklog to eliminate the guesswork). Despite being almost entirely on the glacier proper, the trip does not require crampons, ice axes, or ropes, because most of the ice is bare and hard with minimal crevasses, or buried entirely under moraine rubble. You will, however, need good fitness, cross-country routefinding skills, and bear awareness–grizzlies prowl the alder and willow thickets of the lower glacier.
Begin by walking away from the highway up a fading roadbed on the left/north side of Castner Creek. Within a half mile you’ll encounter the glacier toe, where the creek emerges from beneath a hard ice wall. Climb up talus ramps left of the stream to the rim above, and begin working your way east-northeast toward an obvious 100-foot-high dirt cone a mile distant. From the cone, turn right; drop down across the deep slumping glacier center on mud, loose talus, and bare ice, then climb an obvious ramp to reach the vegetation-covered bench on the far side. Follow this bench east-northeast through willow thickets and across collapsing muddy ground, all of which overlies the ice.
By following the line of least resistance, you’ll eventually encounter faint trail that appears and disappears. Follow it past several ponds and decent emergency campsites as the terrain flattens out and travel becomes easier. After 7.9 miles you’ll finally reach bare ice. A superb campsite sits atop the medial moraine here, with expansive views of all three upper forks of the Castner, and the blocky, ice-clad, 9,500-foot summits that surround it, like Silvertip, Black Cap, and White Princess. In good weather, this makes a superb base from which to explore the glacier-floored upper cirques.
The northern fork is short, but ends in a broad snow cirque beneath serac-draped icefalls on Mt. Silvertip. The southern, M’Ladies Fork can be traveled for at least seven miles without ice gear by following its medial moraines, but easy travel ends below a steep pass leading to the remote, 20-mile-long Johnson Glacier. The central/eastern fork leads into the Silvertip Icefield, which is surrounded by steep, cliffy walls and dominated by a view of the shining snow pyramid of White Princess.
In bad weather, you’ll definitely want to check out the tiny Thayer Hut, located on a high isolated bench overlooking the glacier junction, and invisible from all approaches until the last 200 yards of a steep, loose talus ascent. This small, rustic, four-person Alaska Alpine Club hut offers superb views and an excellent refuge from storms, but it’s amenities are limited to a Coleman stove, lantern, flat plywood floor, and dry roof. It is strictly first come, first served. Be prepared to share on weekends or holidays. When it was first finished in 1964, the Thayer Hut was only 100 feet above ice level; now, it’s 400. At this rate of melting, the Castner Glacier, like many of its neighbors, could disappear within 50 years. But for now, it’s one of the most stunning and easily accessed glacier basins in all of Alaska.

–mapped by Steve Howe
PERMITS: None needed, but use of the Thayer Hut ($1/person/night) requires advance contact with, and prepayment to the Alaska Alpine Club ( We recommend an additional donation for hut upkeep and expanding the hut network.

MORE INFO: BLM Glennallen Field Office, 907-822-3217;

To Trailhead

From Anchorage, drive 186 miles north on AK 1 to Glennallen. Turn left and go 107 miles on the Richardson HWY to milepost 218. Just north of the bridge across Castner Creek, look for a gravel road heading upriver. Follow it for a .25 mile to the trailhead campsites.

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