For centuries, naturalists also thought that the oldest rocks on Earth were on the ocean floors. They believed that the present-day ocean basins formed at the very beginning of the Earth's history and throughout time they had slowly been filling by a constant rain of sediment from the lands. Data gathered since the 1930's have enabled scientists to view the seafloor as relatively youthful and geologically dynamic, with mountains, canyons, and other topographic forms like those found on land.
The seafloor is no more than 200 million years old a young part of the globe's crust compared to the continents which may contain rocks nearly 20 times that age. Marine geological studies were of extreme importance in providing the analytical evidence for sea floor spreading and plate tectonics during World War II. The ocean floor is the last essentially unknown frontier and the detailed portraying in support of both military objectives and economic objectives which drives the research.