The Earth is divided into three layers: the crust, mantle and core. The bark is the most superficial of the planet and they distinguish continental and oceanic crust. The continent has an average thickness of 30-40 kilometers and the ocean has a thickness much smaller, between 5 and 9 kilometers. The second layer is the mantle, which extends from the cortex to reach some 2,900 kilometers deep. It is believed that the establishment of this area mainly involved the peridotites, rocks composed of oxygen, silicon, iron and magnesium, among other things. Finally, is the core that extends from the mantle to the center of the planet at 6371 km depth, and is composed primarily of iron.
In the constitution of the substances involved continental crust as lava, sediment from the continents and granite, whereas oceanic layer are mainly oxygen, silicon, aluminum and magnesium.
The continental crust is composed of blocks of granite, lava flows and sediment.