Beginning of Essay
The land below us is always in motion. Plate tectonics studies these restless effects to give us a better understanding of the Earth and its past. New molten rocks are poured out in the form of magma from the mid-ocean ridges. The rock is recycled and re-entered ....

Middle of Essay
.... Each complete cycle, called a convection cell, drives the plate in the direction of the cell. How does a ‘solid’ mantle move? The mantle may be solid but, as with most solids, it will deform if long-term stress is applied. Presently, there are more than fourteen plates in the Earth’s crust. Upwelling hot magma flows out from mid-ocean ridges and then cools down when exposed to the cooled environment outside; the layer of cooled magma forms the lithosphere. When magma flows out from the ridges, the crust is fractured and a new ocean floor is built spreading perpendicularly away from the ridge. Because of this constant upwelling, the ocean i ....