Scientists believe that is an example of an internal force that changes the earth’s crust.

Scientists believe that plate tectonics is an example of an internal force that changes the Earth’s crust.

Plate tectonics is a theory that describes the motion of seven large plates, and many other smaller plates of the Earth's lithosphere. When they collide they can make mountains or we can feel their motion as earthquakes. Their motion is responsible for the continental shift and it made our continents look the way they look today.

the rub-al-khali is also known as the arabian desert and the "empty quarter"