Layers of the Planet Earth

Crust

• The outer layer of the Earth is called the crust. It is made up of the ground materials that are visible on the Earth's surface such as soil and rocks, and the seabed that lies beneath the oceans. The Earth's crust is quite rigid and thin compared to the other layers. This top layer ranges in thickness across the planet. Beneath the beds of the Earth's oceans it is just over 3 miles thick. Beneath the continents it averages about 20 miles in thickness, but beneath the planet's tallest mountain ranges it is as thick as 60 miles.

Mantle

• The mantle is the Earth's thickest layer and is located beneath the crust. It is approximately 1,800 miles thick and is divided into an upper and lower section. Pressure and temperatures increase farther inside the Earth, so the lower section of the mantle is hotter than the upper. The cooler, top section of the mantle is more solid, forming a thin crust over the lower section. The lower section is semi-solid rock so hot that it moves like lava. The flow of heated rock in the mantle has cracked the Earth's crust into sections. The continents are on these sections and they float slowly on the mantle's moving current.

Outer Core

• The outer core is beneath the mantle. It is the only purely liquid layer in the Earth's makeup. This liquid layer is composed mostly of iron, with some sulfur and nickel. The outer core is about 1,400 miles thick and reaches temperatures between 7,200 and 9,000 degrees Fahrenheit. The liquid layer moves and flows with the rotation of the Earth; this movement creates the Earth's magnetic field.

Inner Core

• The inner core lies at the very center of the planet. This deepest layer is a core ball of iron mixed with small amounts of nickel, sulfur and other elements. It is approximately 1,500 miles across and is located about 3,200 miles beneath the surface of the Earth. Scientists estimate the temperature of the inner core to be between 9,000 and 13,000 degrees Fahrenheit. Although the core is nearly as hot as the surface of the sun, its metal does not melt because of the enormous pressure placed on it by the Earth's other layers.