<img src="https://d5nxst8fruw4z.cloudfront.net/atrk.gif?account=iA1Pi1a8Dy00ym" style="display:none" height="1" width="1" alt="" />
Dismiss
Skip Navigation
Our Terms of Use (click here to view) and Privacy Policy (click here to view) have changed. By continuing to use this site, you are agreeing to our new Terms of Use and Privacy Policy.

4.8: Tectonic Plate Motions

Difficulty Level: Basic Created by: CK-12
Atoms Practice
Estimated2 minsto complete
%
Progress
Practice Tectonic Plate Motions
Practice
Progress
Estimated2 minsto complete
%
Practice Now

What is tectonics?

Dividing the lithosphere into plates is one thing. Having the plates move around on the planet is another! A conveyor belt is a good analogy for how a plate moves. How the plates move and where they move is the "tectonics" half of plate tectonics.

Plate Motions

Scientists have determined the direction that each plate is moving (Figure below). Plates move around the Earth’s surface at a rate of a few centimeters a year. This is about the same rate that fingernails grow.

Earth's plates are shown in different colors. Arrows show the direction the plate is moving.

How Plates Move

Convection within the Earth’s mantle causes the plates to move. Mantle material is heated above the core. The hot mantle rises up towards the surface (Figure below). As the mantle rises it cools. At the surface the material moves horizontally away from a mid-ocean ridge crest. The material continues to cool. It sinks back down into the mantle at a deep sea trench. The material sinks back down to the core. It moves horizontally again, completing a convection cell.

Plates move for two reasons. Upwelling mantle at the mid-ocean ridge pushes plates outward. Cold lithosphere sinking into the mantle at a subduction zone pulls the rest of the plate down with it.

Seafloor spreading takes place as plates move apart from each other at a mid-ocean ridge. Mantle convection drives seafloor spreading.

Summary

  • Plates move by seafloor spreading
  • Seafloor spreading is driven by mantle convection.
  • Plates move as if on a conveyor belt.

Practice

Use this resource to answer the questions that follow.

Tectonic Plate Movement at http://www.youtube.com/watch?v=prfgw8uKXA8 (3:18)

  1. What would the Earth look like without the biosphere and atmosphere?
  2. What are plates?
  3. How fast are the plates moving?
  4. What happens at the ridges?
  5. What are subduction zones?
  6. What heats Earth's interior?

Review

  1. Describe how convection takes place in the mantle.
  2. How does mantle convection cause seafloor spreading?
  3. How does seafloor spreading move plates?

Vocabulary

convection cell

Hot material rises and cool material sinks in a circular pattern.

seafloor spreading

Mechanism for moving continents. The formation of new seafloor at spreading ridges pushes lithospheric plates on the Earth's surface.

Image Attributions

Show Hide Details
Description
Difficulty Level:
Basic
Grades:
6 , 7
Date Created:
Jan 04, 2013
Last Modified:
Jul 06, 2016
Files can only be attached to the latest version of Modality
Reviews
83 % of people thought this content was helpful.
6
Loading reviews...
Load More (7)
Please wait...
Please wait...
Image Detail
Sizes: Medium | Original
 
SCI.ESC.341.1.L.1