Divergent BoundariesĪt divergent boundaries in the oceans, magma from deep in the Earth's mantle rises toward the surface and pushes apart two or more plates. These types of collisions can also lead to underwater volcanoes that eventually build up into island arcs like Japan. In addition, the diving plate melts and is often spewed out in volcanic eruptions such as those that formed some of the mountains in the Andes of South America.Īt ocean-ocean convergences, one plate usually dives beneath the other, forming deep trenches like the Mariana Trench in the North Pacific Ocean, the deepest point on Earth. As the overlying plate lifts up, it also forms mountain ranges. These convergent boundaries also occur where a plate of ocean dives, in a process called subduction, under a landmass. Mount Everest, the highest point on Earth, may be a tiny bit taller tomorrow than it is today. As the mash-up continues, the mountains get higher. India and Asia crashed about 55 million years ago, slowly giving rise to the Himalaya, the highest mountain system on Earth.

Where plates serving landmasses collide, the crust crumples and buckles into mountain ranges. They move at a rate of one to two inches (three to five centimeters) per year. The movement of the plates creates three types of tectonic boundaries: convergent, where plates move into one another divergent, where plates move apart and transform, where plates move sideways in relation to each other. Most geologic activity stems from the interplay where the plates meet or divide. (This includes the crust and uppermost part of the mantle.) Churning currents in the molten rocks below propel them along like a jumble of conveyor belts in disrepair.

The plates make up Earth's outer shell, called the lithosphere. The tiny Juan de Fuca plate is largely responsible for the volcanoes that dot the Pacific Northwest of the United States. Though smaller in size, the minors are no less important when it comes to shaping the Earth. Six of the majors are named for the continents embedded within them, such as the North American, African, and Antarctic plates. There are a few handfuls of major plates and dozens of smaller, or minor, plates.

Divergent boundary definition