Earth’s Structure

Earth’s interior is composed of several layers. The inner core is a solid layer composed of heavy metals such as iron and nickel. These metals are under intense pressure and extreme temperatures. The outer core is composed of the same material, but is slightly cooler and under less pressure. The mantle is composed of mostly silicon and oxygen, as well as some iron. This layer is solid but has the ability to flow gradually with changes in pressure. Earth’s crust is solid rock, mostly made of granite on the continents and basalt in the ocean.

Earth’s crust and the top rigid layer of the mantle are known as the lithosphere. The solid but mobile portion of the upper mantle is the asthenosphere. Due to convection currents, heat from within the Earth causes the lithosphere to move gradually above the asthenosphere, creating the variety of landforms that are seen on Earth.