a mountain range in the Northern Altai in the Gorno-Altai Autonomous Oblast; the water divide of the Biia and Katun’ rivers. Length, 90 km; maximum elevation, 2,615 m (Mount Al’bagan).
The Iolgo Range is composed of limestones, sandstones, shales of the Lower Paleozoic, and tuffaceous rocks of the Middle Paleozoic with granite faults. Middle-altitude mountain relief dominates. The eastern slopes are covered by taiga with spruce, fir, and cedar; the western slopes have forests with birch, pine, and larch. Alpine and subalpine meadows, alpine tundra, and rock streams are found above 1,700 m.