Mayo Glacier, named by Perito Moreno, is located in the most rugged and narrow portion of the Southern Patagonia Icefield. The glacier covers a total area of 40.1 km² (15.4 sq miles) and is 14.5 km (9 miles) long. Its distinctive feature are the ogives – alternating bands of light and dark ice on a glacier usually found in crevasses – where its slope is high and thickness is low. Dust is deposited into cracks during summer and snow layers serve as a protection in winter. The debris bands resulting from rock avalanches are also noteworthy.