The geologic event forming the Marianas archipelago occurred during the eocene epoch, a time when dinosaurs had already become extinct, plants, fishes and invertebrate mammals had developed and the major mountains of the world had begun to rise. Man would not appear for another 25 to 50 million years, a period so distant from the present as to equal 350,000 to 700,000 human life spans. A theory known as plate tectonics presumes that the Asian continent and the North and South American continents are moving and that the Lithosphere (crust) of the continents are composed of different material. The edge of these plates are believed to be moving  in such a manner that one moves under the other and the cataclysmic forces that result push material upward to form islands. The CNMI Guide would like to thank Mr. William H. Stewart for providing all the information used in these pages.