When two oceanic plates converge, the denser plate will end up sinking below the less dense plate, leading to the formation of an oceanic subduction zone. Old, dense crust tends to be subducted back into the earth. An example of a subduction zone formed from a convergent boundary is the Chile-Peru trench.

Fossils of similar organisms across widely disparate continents encouraged the revolutionary theory of continental drift. Continental drift describes one of the earliest ways geologists thought continents moved over time. Today, the theory of continental drift has been replaced by the science of plate tectonics.

In the early part of the 20th century, scientists began to put together evidence that the continents could move around on Earth’s surface. The evidence for continental drift included the fit of the continents; the distribution of ancient fossils, rocks, and mountain ranges; and the locations of ancient climatic zones.

This movement in the mantle causes the plates to move slowly across the surface of the Earth. About 200 million years ago Pangaea broke into two new continents Laurasia and Gondwanaland. Laurasia was made of the present day continents of North America (Greenland), Europe, and Asia.

How did Wegener’s theory of continental drift differ from the current theory of plate tectonics? Wegener’s theory did not explain how the continents could move. Wegener attempted to explain the movement of continents but could not identify a source of force strong enough.

Plates Collide When two plates carrying continents collide, the continental crust buckles and rocks pile up, creating towering mountain ranges. The Himalayas are still rising today as the two plates continue to collide. The Appalachian Mountains and Alps also formed in this way.