1. Chapter 17 Plate Tectonics
Section 17.3
The Theory of Plate Tectonics

2. Vocabulary Divergent Boundary: Convergent Boundary:
A plate boundary where two plates move away from each other.
Convergent Boundary:
A plate boundary where two plates move toward each other.
Transform Boundary:
A plate boundary where two plates move past each other in opposite directions.

3. Vocabulary Plate: Plate Tectonics:
A section of the lithosphere that slowly moves over the asthenosphere, carrying pieces of continental and oceanic crust.
Plate Tectonics:
The theory that pieces of Earth’s lithosphere are in constant motion, driven by convection currents in the mantle.

4. Vocabulary Fault: Rift Valley:
A break in Earth’s crust where slabs of rock slip past each other.
Rift Valley:
A deep valley that forms where two plates move apart.

5. Introduction
The lithosphere is broken into separate sections called __________.
True or False: Plates can carry continents or parts of the ocean floor but not both.
False
plates

6. A Theory of Plate Motion
What is a scientific theory?
A scientific theory is a well-tested concept that explains a wide range of observations.
State the theory of plate tectonics.
Pieces of Earth’s lithosphere are in constant, slow motion, driven by convection currents in the mantle.
True or False: The theory of plate tectonics explains the formation, movement, and subduction of Earth’s plates.
True

7. Plate Boundaries
True or False: Crust is both created and destroyed along a transform boundary.
False
Most divergent boundaries occur at the ________________.
When two plates collide, what determines which plate comes out on top?
The density of the plate determines which plate comes out on top.
mid-ocean ridge

8. Plate Boundaries Convergent Boundaries
Types of
Plates Converging
Result
Oceanic/Oceanic
Subduction occurs.
Oceanic/Continental
Ocean plate
sinks.
Continental/Continental
Mountain Ranges
form.

9. The Continent’s Slow Dance
About how fast do plates move?
Plates move from about one to ten centimeters per year.
True or False: The pieces of the super continent Pangaea began to drift apart about 225 million years ago.
True