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What Features Are Caused by Plate Tectonics?

The contour of the Earth's surface is formed by the movement of massive plates of rock, called tectonic plates, that form the lithosphere under the crust. The mantle below these plates is composed of gelatinous molten rock that moves the earth above it as it flows. As the plates move, they collide in different ways, pushing and pulling the crust to form different land formations. The formations created are determined by the way the plates converge and diverge.

Converging Plate Boundaries
- Plates converge in two ways. When plates simply converge, they push against each other, folding and crinkling material. Material is pushed upward to form mountains. The Himalaya Mountains in south-central Asia are an example of plate convergence. This mountain range is the result of the convergence of the head-on collision of the Indo-Australian and Eurasian plates. In some areas, the plates slide underneath each other rather than push against each other. This process is known as "subduction."
Subducting Plates
- Subduction occurs when one plate slides under another plate, forming a trench where the plates converge. The upper plate is pushed upward, forming mountains. The heat from the friction of these plates melts material that is being subducted. The melted material forms pools, which sometimes harden underground. Some of these pools push to the surface, creating volcanoes. These volcanic ranges can be seen around the world. If you look at a map of volcanic regions, you will see they form a ring around the globe. This ring is referred to as the "Ring of Fire" in the Pacific Ocean. Volcanic mountain ranges, island chains and archipelagos are formed through subduction. The mountains of coastal Washington state are subduction zone mountains. By destroying old crust, subduction zones create room for new crust to be formed in divergent boundaries.
Divergent Plate Boundaries
- Divergent boundaries are formed where plates pull away from each other. When these boundaries happen on sea floors, they create new crust and spread the ocean floor. As the plates pull away from each other a rift is formed. Magma forces its way up through the rift where it cools, becomes brittle and cracks. New magma will force its way up, spreading the newly created surface material. On land, rifts form at divergent boundaries and faults form on either side of the rift. Material in the center of the rift begins to fall, forming rift valleys. Water flows into the valleys, forming long lakes or lake chains. When the material falls below sea level, new oceans form. The Red Sea is an example of a rift valley where an ocean is being formed.
Other Plate Boundaries
- Conservative, or transformation, boundaries are where plates are sliding by each other. These boundaries do not destroy or create crust material, but form faults instead. Over time, they do change the position of the land. Earthquakes are frequent along these plate boundaries. In some regions, more than two plates meet and move in different ways, creating complicated landscapes. The Mediterranean-Alpine region is an example of complicated land structures caused by the movement of more than two plates.

Nature