Plate Interactions

There are three types of tectonic plate boundaries. They are the divergent plate movement, the convergent plate movement and the transform plate movement.

Divergent plate movements, where the plates move apart from one another, occur mostly on ocean floors at constructive plate boundaries. The drifting apart of the plates at the spreading zones creates new lithosphere when basaltic magma rises up from the gaps and cools and solidifies on the ocean floor. This process, commonly known as sea floor spreading, forms a chain of mountains of heights 2000m to 4000m called mid-oceanic ridges. An example is the Mid-Atlantic Ridge. Earthquakes may occur along these boundaries and volcanic activity also takes place when the magma forms submarine rift volcanoes.

Convergent plate movement, which takes place at destructive plate boundaries, involves the movement of plates coming towards each other. At these boundaries, one plate is thrust under the other in a process known as subduction. These movements, which are often not smooth, generate powerful earthquakes and creates a line of subduction volcanoes along the overriding plate. Ocean trenches may be formed such as the Peru-Chile Trench. At some plates margins, The overriding plate scrapes a thick mass of sediment off the descending plate, a process which over time forms long chains of fold mountain ranges.

Transform plate boundaries, where plates slide horizontally past each other, neither creates nor destroys lithosphere. Powerful earthquakes take place at these plate boundaries. One example is the San Andreas Fault in California, United States.

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