2. An Overview The Earth is made of 5 main internal layers and one external layer (the atmosphere). This diagram shows the locations and approximate thicknesses of each internal layer.

3. The Atmosphere Technically, the very outermost layer of the Earth is the one that we live in—the atmosphere. The atmosphere contains all the air we breathe and the weather we experience. Although we often use the term “air,” the atmosphere is made out of many gases like: nitrogen (78%), oxygen (21%), and other gases like argon and carbon dioxide (1%). Since there isn’t a distinct boundary between the atmosphere and outer space, it is generally stated that the atmosphere is around 100 km thick but it can extend up to 480 km if you count the very thinnest parts. Temperature also varies a great deal in the atmosphere, depending on what altitude you are at but it can get as cold as - 90° C.

4. The Crust The crust is the rocky, outermost layer of the earth. Oceans and soil sit on top of the crust. This layer is divided into two types: oceanic crust and continental crust. The crust is relatively thin compared to the earths others layers. Oceanic crust averages 7 km in thickness, while continental crust can be as thick as 100 km. The temperature of the crust at the surface depends on where you are at. But the temperature of the crust can be up to and 400 degrees Celsius in its deepest parts. The crust is completely solid and is composed of rock with many less dense elements like oxygen, silicon and aluminum.

5. The Asthenosphere (Upper Mantle) Below the crust is the mantle. The top part of the mantle is a special layer called the asthenosphere or upper mantle. The asthenosphere is about 180 km thick and much hotter than the crust (about 500 degrees Celsius). While it is technically still a solid, the rock in this layer is hot enough and under enough pressure that it flows like asphalt. A solid that can flow like this is called a plastic. Another example of a plastic is silly putty. The fact that the asthenosphere is a plastic has a major impact on the crust. It is this layer that causes the tectonic plates of the crust to move and, therefore, is the reason why we have earthquakes. This layer is composed of rock that has significant amounts of denser materials like calcium, magnesium and iron.

6. The Mantle (Lower) The lower or main part of the mantle is the largest layer of the Earth and is about 2300 km thick. The temperature in the lower mantle is much greater than the upper mantle (about 2000 degrees). Even though this layer is hotter than the asthenosphere, the lower mantle is actually a solid. It is a solid because the great amount of pressure at this depth keeps the molecules from moving like a liquid. The lower mantle is composed of many of the same materials as the upper mantle with the addition of a significant amount of iron.

7. The Outer Core The core of the Earth is divided into two parts. The outer core lies beneath the mantle and can reach temperatures up to 5000 degrees Celsius. Due to high temperatures, all its components are in a liquid state. The outer core is 2200 Km thick. This layer is composed of melted iron, melted nickel, and sulfur. Because it is liquid, it flows constantly. This flowing metal in the outer core is responsible for creating the Earth’s magnetic field. This field surrounds the Earth and is important not only in navigating, but in protecting us from harmful solar radiation.

8. The Inner Core The inner core is located at the very center of the earth and is approximately 1200 km thick. Like the outer core, it is composed of iron and nickel. The temperatures at the core of the earth can reach almost 11,000 degrees Celsius, that’s hotter than the surface of the sun! Because of the immense pressure at the center of the planet, the iron and nickel cannot flow and the inner core remains a solid. The pressure is so powerful, that if you were to journey to the center of the Earth, you would be squished into something the size of a marble!

9. Patterns in Earth’s Layers