Hawaii hotspot created at least 129 volcanoes, more than 123 of which are extinct volcanoes, seamounts, and atolls, four of which are active volcanoes, and two of which are dormant volcanoes. They can be organized into three general categories: the Hawaiian archipelago, which comprises most of the U.S. state of Hawaii and is the location of all modern volcanic activity; the Northwestern Hawaiian Islands, which consist of coral atolls, extinct islands, and atoll islands; and the Emperor Seamounts, all of which have since eroded and subsided to the sea and become seamounts and guyots (flat-topped seamounts). Hawaiian volcanoes are characterized by frequent
Ingalba, Big Bush and Pucawan Nature Reserves Ordovician geology of quartzite, shale, slate, phyllite and schist. There is an indistinct boundary with the Upper Silurian geology predominant in Big Bush and Ingalba Nature Reserves. These areas consist of sandstone, shale, siltstone, slate, conglomerate and limestone, with some volcanics. Abundant but poorly preserved fossil graptolites are found in a disused quarry in Pucawan Nature Reserve. These fossils (an extinct group of oceanic colonial organisms) have been dated from the late Ordovician period. The soils are of intermediate loamy texture. Crest soils are mostly shallow, with broken shales and siltstone present on the surface. On the gentle slopes and