Earth Study Guide

1. Earth is the only known planet with life on it. It also has an atmosphere, seasons, and water.

2. Earth takes one year (365 days) to revolve around the Sun.

3. Earth is the fifth largest planet in the solar system.

4. The Sun is at the center of the solar system. All the planets revolve around it.

5. orbit- the Earth’s path around the Sun. It travels in a long oval shape called an ellipse.

6. axis- an imaginary line through the center of the planet (from pole to pole) on which the Earth “spins”

7. Earth spins on its axis once every 24 hours.

8. There are three parts of the Earth:

1.) crust

2.) mantle

3.) core

9. crust- surface of the Earth that is a thin layer of rock. It ranges from three miles thick under oceans to 22 miles thick under mountains.

10. mantle- beneath the crust, it is a layer of very hot melted rock about 1,800 miles thick

11. core - found in the center of the Earth, it has two parts:

a. outer core - made of lava

b. inner core - solid