Lake Tahoe

Snow, rain, and streams filled the southern and lowest part of the basin, forming the ancestral Lake Tahoe. Modern Lake Tahoe was shaped and landscaped by the scouring glaciers during the Ice Age (the Great Ice Age began a million or more years ago). Many streams flow into Lake Tahoe, but the lake is drained only by the Truckee River, which flows northeast through Reno and into Pyramid Lake in Nevada.