Another Continental Break Up
Although a collision of continents caused the formation of the Appalachian Mountains, the present-day margin of North America is the result of a reversal in crustal plate movement. After the continents collided, the masses began to pull apart. About 240 million years ago, at the beginning of the age of the dinosaurs, a new ocean basin began to form the present-day Atlantic. The Atlantic Ocean is still widening today, with the ocean crust pulling apart at the mid-Atlantic Ridge.
Encyclopedia ID: p1545
