A brief summary of the geography, climate, and geomorphology is given. Streams develop slowly after the extinction of a volcano because of the high permeability of the rock. Once established they cut rapidly because of the steep slopes and fractured condition of the rock. Stream erosion varies enormously on different slopes of the same mountain due to the great differences in rainfall and to other causes. Six reasons are given for the development of amphitheater-headed valleys. Marine erosion has formed cliffs as much as 1,000 feet high on the leeward side and 3,000 feet high on the windward side of some of the domes. The islands have undergone a complex series of emergences and submergences leaving marine fossiliferous limestone up to 1,070 feet above sea level and valleys drowned more than 1,200 feet. Twelve terrace levels are recognized. Some are definitely eustatic.
A synopsis is given of the present knowledge of the geology of each volcanic mountain, as well as a table of the rock units, and geologic maps of all major islands. The volcanoes pass through four major phases between birth and extinction and are built around one minor and two major rift zones. The volcanoes began their history above sea level in the Tertiary. Most of them became dormant either before or during the early Quaternary. Activity was renewed in the late Quaternary. Mauna Kea was glaciated in the late Pleistocene. The character of each islet in the archipelago is tabulated.
