The next canyons are Desolation Canyon and Gray Canyon, two back-to-back canyons that total 120 miles in length. Desolation is the deepest and longest of the canyons of the Green, while Gray (earlier known as Coal Canyon) is lower but narrower. The Green leaves Gray Canyon just above the town of Green River, Utah, and flows through an open area for about thirty miles before entering the last of the canyons it traverses, Labyrinth and Stillwater canyons. As the names suggest, these are quietwater canyons, where the river loops in sinuous curves around towering cliffs of sandstone. The Green meets its sister stream, the Colorado, at the end of Stillwater Canyon, in the middle of what is now Canyonlands National Park.
The Green traverses several different vegetation and fauna zones during its course through Utah, ranging from high mountains in the north to slickrock deserts in the south. Pines, firs, and groves of aspen are common in the higher parts, while pinyon and juniper are predominant below the mountains. In the lower elevations, shadscale, sagebrush, cactus, and desert shrubs are most common. Cottonwoods, tamarisk, and willows are the predominant members of the riparian plant community throughout the river's length. Likewise, fauna follow typical life zones. Elk, deer, bighorn sheep, coyotes, rabbits, squirrels, and other small rodents, and an occasional bobcat or cougar are found along the Green. Snakes, lizards, toads, and other reptiles are common near the river, less common away from it. Bird life, especially along the river corridor, is abundant, as the river is part of the main north-south flyway for some waterfowl.