The geology of the Hawaiian Islands. This illustration shows the archipelago and underwater topography of the Hawaiian Islands. These volcanic islands, located in the northern Pacific Ocean, have formed as volcanoes rising from a mantle hot spot under the sea floor some 5500 meters below sea level. There are eight main islands (as pictured here): Big Island (Hawaii Island), Maui, O'ahu, Kaua'i, Moloka'i, Lana'i, Ni'ihau, and Kaho'olawe. The highest point is the peak of the Mauna Kea volcano (on Big Island), at 4205 meters elevation.