 Like most other major drainages within the Sky Lakes Wilderness, Seven Lakes Basin and the deep canyon of the Middle Fork of the Rogue River were carved by the massive ice fields that covered the highest elevations of the Cascades.Approximately 6,700 years ago, when Mount Mazama exploded, collapsed, and formed the caldera of Crater Lake, some of the vast amount of rock and ash thrown into the air landed in the northern portion of the Sky Lakes Wilderness, creating the pumice-covered Oregon Desert.Many plant species thrive in the Sky Lakes Wilderness, including nearly two dozen tree species.