The Atlantic Ocean is thought to be the youngest of all oceans. It was formed about 180 million years ago when a large continent called Pangea and ruled by dinosaurs, split down the middle. The split formed two separate landmasses now known as North and South America to the west, and Eurasia and Africa to the east. The separation of one landmass into two occurred as the result of the horizontal movement of the continental plates - a process known as continental drift. This widely accepted theory of the formation of the Atlantic Ocean stems from a broader theory known as plate tectonics. The theory of plate tectonics states that the earth’s crust is comprised of huge plates of solid rock slowly moving at about the same rate as a fingernail grows. If these plates move apart, oceans form between them. If they collide, mountains form. The movement of continental plates also causes volcanic activity and earthquakes. As the continental plates that lie to the sides of the Atlantic continue to pull apart, the Atlantic grows, at a rate of about 1.8 - 2.4 centimetres per year.