Paleontology and geology
The Cenozoic: The Hawaiian Islands are composed almost entirely of lava flows, the oldest of which are found on Kauai at the northwest end of the island chain and are just over 5 million years old. The youngest rocks occur on Hawaii (southeast end of the island chain), which still has active volcanoes.
Fossils of marine organisms are known only from the Quaternary rocks of the main islands of Kauai, Oahu, Molokai, Lanai, and Maui. These fossils represent animals that lived on the sea floor during times when sea level was higher than it is today. There are also some Early Quaternary (Pleistocene) reefs built by algae, modern species of corals, molluscs, and foraminifera, exposed along the shores of Oahu, especially along the Waianae coast. In addition to these marine fossils, bones of land birds are reported in Quaternary dunes and sinkholes.