The islands are volcanic in origin, and their highest peak, Mt. Kartala (2,360 m/7,743 ft), located near the southern tip of the island of Grande Comore, is an active volcano. In the center of Grande Comore lies a desert lava field; to the north, a number of volcanic peaks rise from a plateau nearly 600 m (2,000 ft) in altitude. The island of Anjouan, to the southeast, has steep hills reaching heights of nearly 1,500 m (5,000 ft) in a central volcanic massif. Mohéli, to the west of Anjouan, has wide and fertile valleys, with a ridge in the center that reaches about 580 m (1,900 ft) above sea level, and a thick forest cover.