Beginning at Obsidian Trailhead, Obsidian Trail #3528 heads southeast on a gradual to steep uphill course. The trail begins in a mixed Lodgepole Pine and Hemlock alpine forest before reaching the boundary of the Obsidian Limited Entry area and the Three Sisters Wilderness. An Obsidian Limited Entry Permit is required to enter the Obsidian Limited Entry Area, and can be reserved at recreation.gov. The trail continues uphill, entering an open old growth forest before switching back up an old lava flow. Views of the Three Sisters and other surrounding mountains are available on this lava flow. After passing through the flow, the trail crosses White Branch Creek, then heads uphill through alpine forests and meadows, crossing many streams along the way. The trail reaches its terminus at the Pacific Crest Trail #2000.