Thunder Creek Trail

Thunder Creek drains one of the largest glacier systems in the contiguous United States, and the trail that follows it south from Diablo Lake is among the most impressive old-growth forest walks in the Pacific Northwest. The creek runs a remarkable turquoise color derived from glacial flour — finely ground rock particles suspended in meltwater from the Skagit, Neve, and Boston glaciers above. Western red cedar and Douglas fir reach 6 to 8 feet in diameter along the lower valley, their root systems draped in thick moss that muffles sound and turns the forest floor luminescent green after rain. The trail gains elevation gradually as it moves south, crossing several tributary creeks on sturdy log bridges and passing through a grove of ancient cottonwood near the McAllister Creek junction. Bears are frequently sighted along Thunder Creek corridor, and the dense vegetation supports one of the highest black bear densities in the park. The turnaround at the 6-mile mark reaches a designated campsite with views up-valley toward the peaks of the Skagit Range, visible above the treeline through a gap in the old-growth canopy.