Earth’s Composition and Layers


Earth is divided into four major systems.  They are the atmosphere, hydrosphere, geosphere, and biosphere. The biosphere consists of all the organisms on Earth and the environments in which they live whether it is in the ocean or on land. All of Earth’s systems are interdependent of each other. For example, you have learned that the volcanic activity in the geosphere helped formed Earth’s present atmosphere. The geosphere is the area from the surface of the Earth down to its center.

The geosphere consists of four different layers.  The crust is outermost layer. It is the thinnest of the layers.  The crust consists of many different pieces called plates. The crust ranges from 45 miles thick on land to 7 miles thick under the oceans.

The mantle lies below the crust.  It is the largest layer of the Earth. The mantle makes up 80% of the Earth’s total volume and almost two thirds of the Earth’s mass.  The mantle is about 1800 miles thick.  The core is located in the center of the Earth, just below the mantle.  The core can be divided into two sections which are the outer core and inner core.  The outer core is very hot and temperatures can reach 9000oF.  The outer core consists of the metals iron and nickel that remain in liquid form due to the heat.  The outer core is about 1400 miles thick.

The inner core is about 780 miles thick. It consists of mostly solid nickel and iron. The inner core is hotter than the outer core.


diagram of earth layers


Review activity:  Determine which category each description belongs to.

Categories to choose from:  Crust, Mantle, Outer Core, Inner Core

  1.  A shell surrounding the entire Earth
  2. Asthenosphere
  3. Temperature is almost equal to the surface of the sun
  4. Made up of rock and soil
  5. Protects us from the heat inside the Earth
  6. About 1400 miles think
  7. 2/3 of the Earth’s mass
  8. Center of the Earth
  9. Magnetic field is produced in this layer
  10. Molten rock
  11. Consists of continental plates
  12. Solid nickel and iron
  13. Liquid metal
  14. Consists of ocean plates
  15. About 780 miles thick
Click to reveal the answers.

1.  Crust
2.  Mantle
3.  Inner core
4.  Crust
5.  Crust
6.  Outer core
7.  Mantle
8. Inner core
9.  Outer core
10.  Mantle
11.  Crust
12.  Inner core
13.  Outer core
14.  Crust
15. Inner core