Plate tectonics are a relatively new theory that has revolutionized the way geologists think about the Earth. According to the theory, the surface of the Earth is broken into large plates. The size and position of these plates change over time. The hypothesis of continental drift was largely developed by the German Alfred Wegener The edges of these plates, where they move against each other, are sites of intense geologic activity, such as earthquakes, volcanoes, and mountain building. Plate tectonics is a combination of two earlier ideas, continental drift and sea-floor spreading. Continental drift is the movement of continents over the Earth's surface and in their change in position relative to each other. Sea-floor spreading is the creation of new oceanic crust at mid-ocean ridges and movement of the crust away from the mid-ocean ridges. Plate Boundaries are located around the boarder of the plate. It is where the plates collide. There are different types of Boundaries, Divergent Plates transform boundary Subduction boundary and collisional boundary. A divergent boundary occurs where two plates move apart, allowing magma, or molten rock, to rise from the Earth's interior to fill in the gap. The two plates move away from each other like two conveyor belts moving in opposite directions. Plate area is increased as the plates move apart. Plate movement takes place laterally away from the plate boundary, which is normally marked by a rise or a ridge. The ridge or rise may be offset by a transform fault. Presently, most divergent margins occur along the central zone of the world's major ocean basins. The process by which the plates move apart is referred to as sea floor spreading. The Mid-Atlantic Ridge and East Pacific Rise provide good examples of this type of plate margin. Also known as spreading boundary. The rate at which each plate moves apart from a divergent margin varies from less than 50 mm per year to over 90 mm per year and ca...
