Two types of lithospheric plates make up the surface of the Earth, land-based continental plates and ocean-based oceanic plates. Continental plates are made up of granite types of rock with high mineral quantities of silica and aluminum. These plates are lighter than ones found beneath the surface of the oceans. Basaltic rocks are the main ingredient of oceanic plates, which contain high levels of magnesium and aluminum, according to the University of Wisconsin - Stevens Point.
The lithospheric plates that make up the Earth's surface are constantly moving because of a process called a convection cell. During this process, the molten rock close to the Earth's core is heated and begins to move upwards towards the surface of the Earth, pushing cooler rock downward as it travels upwards. After reaching the surface, the hot volcanic rock cools and slowly begins to sink back down towards the Earth's core, where it repeats its heating process and again moves to the surface of the Earth. The rock that makes up the plates of the planet are also thought to complete small convection cell processes to ensure the rock continually moves. Where hot volcanic rock surges to the surface of the Earth and forces its way through the lithosphere to push molten rock onto the Earth's surface, a ridge push is said to have taken place.
The constant movement of the lithospheric plates requires plate activity to interact with other plates in areas where the surface of the Earth is fractured. In the majority of cases,, the Earth's plates overlap, with one plate sitting on the top of another. In some instances these plates can become jammed against each other without the ability to overlap. During these moments, heat and pressure builds up until the plates move in a dramatic, sudden way that results in an earthquake.
The plates of the lithosphere are different weights and sizes, due to their thickness and the type of rock that they are made up of. In order to maintain the balance of the Earth, the plates of the lithosphere move continuously to maintain an equal weight distribution.
