The four volcanic masses whose coalescing bases form the island of Hawaii are substantially alike in petrographie composition; all of them bear cinder cones on their flanks, and lava flows from all of them have extended far into the sea, and also inland to join their neighbors. As regards their topographic expression, they form two groups. Mauna Loa and Hualalai have remarkably flat, smooth profiles and summit craters; Mauna Kea and Kohala are rugged masses sharply incised by canyons and have no topographic feature to indicate the major source of the materials of which they are constructed. The two giant domes, Mauna Loa and Mauna Kea, reveal these differences clearly.
The profile of Mauna Loa extends from the coast as an almost unbroken curve with a gradient averaging about 600 feet to the mile nearly to the rim of the active crater, Mokuaweoweo, at an altitude of 13,680 feet.1 . . .