Mount St. Helens: Worm Flows Route (Winter Route)

This challenging summit climb up Mount St. Helens leads hikers past waterfalls and lava flows to the edge of a smoldering crater.

Named for the rivers of rocky lava that surround the trail, the 10.8-mile Worm Flows route ascends nearly 5,700 feet to the summit of Mount St. Helens. Although challenging, this standard winter and spring route provides a non-technical climb for experienced hikers craving sweet summit views and a chance to practice basic mountaineering skills.
Start at the Marble Mountain Sno Park and follow the cross-country ski trails through forests of Douglas fir (bleached stumps and fallen logs still clutter the forest floor). Roughly 2 miles in, leave the forest and pass views of Chocolate Falls, a 40-foot waterfall along Swift Creek. From here, the trail crosses an increasingly barren landscape of mudflows and rock, where large posts and occasional cairns mark the way. Navigate through the jumbled lava flows, then push beyond cloud level toward St. Helens' false summit. (On clear days, scan the horizon for Mount Adams and Mount Hood.)
The route crests the crater's crescent-shaped rim at mile 5, which reveals dramatic views of Spirit Lake and Mount Rainier. (Make sure to look down into the caldera—the lava dome burps clouds of steam and sulfur into the air.) Take in the scene, then continue west along the rim to the true summit, a mound of rocks at 8,365 feet. Savor more sweet views before turning around for the return trip back to the trailhead.
Caution: The ash and loose gravel that covers the trail is slick. Depending on the conditions, consider using crampons along the snowy stretches.
-Mapped by Nathan and Jeremy Barnes,

Trail Facts

  • Distance: 17.1



Location: 46.130624, -122.171466

The trail starts out at the north end of the parking area at Marble Mountain Sno Park. Hike north and follow the blue arrows.


Location: 46.158157, -122.174095

After 2.3 miles, check out 40-foot Chocolate Falls. Take a break here to change gear and rest before starting the climb to the summit.


Location: 46.174222, -122.180696

After 3.65 miles, stop for a break on the landing. A small weather antenna serves as a trail marker. From here, continue north as you head for the summit.


Location: 46.182118, -122.18535

Depending on conditions, crampons may be necessary on the Smith Glacier.


Location: 46.190193, -122.190749

Catch the first peek of the crater rim. Continue west along the rim to reach the highest point on the mountain.


Location: 46.191069, -122.194319

The true summit lies at 8,365 feet. On the way down, save time with some controlled glissades over the snow fields.

Crater West

Location: 46.191032, -122.194158

View of the west side of the crater.

Trail Marker

Location: 46.136014, -122.169685

Sign indicating Worm Flows route.

Chocolate Falls

Location: 46.158157, -122.17387

The 40-foot plunge at Chocolate Falls.

Mount St. Helens

Location: 46.16081, -122.176552

Snow covered Mount St. Helens on the way up.

Creek in Lava Flow

Location: 46.166576, -122.175136

Glacial runoff splashing down a lava flow.

Foggy Ridge

Location: 46.168211, -122.175736

Climbers working their way up a ridge through the cloud level.

Weather Antenna

Location: 46.174363, -122.181015

Looking down at the weather antenna and landing.

Glacier Crossing

Location: 46.186724, -122.188568

Hikers trekking across the Smith Glacier.

Top of Smith Glacier

Location: 46.188387, -122.188911

Looking down Smith Glacier to the clouds below.

Crater East

Location: 46.190987, -122.194051

View of the east side of the crater.