The lithosphere comprises the crust and the upper section of the mantle. It forms the rigid exterior of the Earth, which is composed of the crust, mantle and core.
The lithosphere is fragmented into a series of massive tectonic plates. While continental plates range from around 93 to 124 miles in thickness, oceanic plates are much thinner and roughly only around 50 to 62 miles thick. These plates constantly move but at a very slow pace. The border that forms between two moving plates can be a transform, divergent or convergent boundary. The majority of geologic events, such as earthquake, volcanic eruptions and geothermal activities, occur along plate boundaries.