Geographers, geologists, and many other scientists study the movement of the plates and the changes they cause in order to understand how the earth is continually being reshaped. You will study various types of tectonic forces. (Helpful Hint: This movement of the plates is sometimes called the continental drift.)

The internal forces that shape the Earth's surface begin beneath the lithosphere. Rock in the asthenosphere is hot enough to flow slowly. Heated rock rises, moves up toward the lithosphere, cools, and circulates downward. Rising above this circulation system are the tectonic plates, large moving pieces of the earth's lithosphere.

Interactive exercise. Assistance may be required. Look carefully at the image below and click on lithosphere and asthenosphere.

Activity

Video segment. Assistance may be required. Watch this video to get an understanding of plate tectonics and tectonic forces:

Source: The Early Earth and Plate Tectonics, Michaelfreudiger, YouTube

After watching the video answer the following questions (feel free to watch the video again if you missed something):

Interactive exercise. Assistance may be required.
  1. Match the earth's events to the corresponding time period.
  2. In your notes, explain how the two causes of heat below the earth's surface (convection flow and radioactive heat) affect the movement of plates above the earth's surface.