Lesson 1 Earth's Moving Surface

Earth's Moving Surface

Chapter 4- Lesson 1

Plate Tectonics

• The theory of plate tectonics states that Earth's surface is broken into large, rigid pieces that move with respect to each other.

• These plates move slowly and can form volcanoes and mountains and cause earthquakes.

Multiple Choice

What is the theory of plate tectonics?

• The theory of Earth's surface being broken into large pieces that move.

• The theory of how the Earth was made.

• The theory of how magma is formed.

Earth's Layers

• The lithosphere includes the crust and the uppermost part of the mantle. This layer is rigid and does not bend easily.

• Below the lithosphere is a partially melted portion of the mantle called the asthenosphere. This layer is hotter than the lithosphere and bends easier.

Tectonic Plates

• There are 15 large tectonic plates.

• 7 of these tectonic plates are considered major tectonic plates due to their size.

Multiple Choice

How many tectonic plates are there?

• 7

• 15

Divergent Boundary

A boundary where two plates move away from each other. (divergent = divide)

The boundary between the North Amercian Plate and the Eurasian Plate is a divergent boundary.

Convergent Boundary

• A boundary where two plates toward each other. (convergent= collide)

• Subduction is the process that occurs when one tectonic plate moves under another.

• The Pacific Plate is being subducted under the North American Plate adjacent to Alaska.

Transform Boundaries

• A boundary where plates slide past each other.

• The boundary between the Pacific Plate and the North American Plate in California is an example of this boundary.

Multiple Choice

At a divergent boundary, plates move

• towards each other.

• away from each other.

• by sliding past each other.

Multiple Choice

At at convergent boundary, plates move

• toward each other.

• away from each other.

• by sliding past each other.

Multiple Choice

At a transform boundary, plates move

• towards each other.

• away from each other.

• by sliding past each other.

Measuring Plate Movement

• Plates move so slowly, it wasn't until the 1970s that scientists and engineers developed a way to measure their movement.

• The movement of the continents is measured by the Global Positioning System (GPS), which uses satellites to track moving objects.

• Even though the movement of the plates is slow, the changes are dramatic. About 200 million years ago, all of the continents were together in a super continent called Pangea. As the plates separated, the Atlantic Ocean was formed.

Why do tectonic plates move?

• Convection occurs in the Earth's asthenosphere, just below the lithosphere causes plates to move.

• Convection is the circulation within fluids caused by differences in density and thermal energy.

• When subduction happens, this also allows for plate movement ans the colder, more dense plate moves below another plate.

Open Ended

Why do tectonic plates move?

Open Ended

What questions do you still have about plate tectonics?