WAIANAE RANGE

mountains paralleling the western coast of Oahu, Hawaii, U.S. The range is the oldest area of volcanic activity on the island. It is 22 miles (35 km) long and 9 miles (14 km) wide and is composed of three lava groups. The original caldera, 3 miles (5 km) wide and 5 miles (8 km) long, was at the head of Lualualei Valley (near Kolekole Pass) but was buried through submergence and erosion. Composed mainly of basaltic rock, the range is heavily eroded. Its western slopes are steep and precipitous and indented by deep valleys such as the Nanakuli, Lualualei, Waianae, Makaha, and Keaau. Its eastern slopes are more gradual and approach the central Schofield Plateau with small, narrow valleys. The range's northern part ends in steep, coastal cliffs (750-1,000 feet [200-300 m]), while its southern slopes have an even gradient as they near the coastal plain. Mount Kaala (4,020 feet ), the highest point on Oahu, is at the head of Makaha Valley; it has a flat, swamp-filled, semicircular plateau 1 mile (1.5 km) in diameter. Kolekole Pass, 3 miles (5 km) south, is an important link between the west coast and the fertile central plateau.