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Chapter 7 Plate Tectonics
Section 3: The Theory of Plate Tectonics
Standard: S6E5.e: Recognize that lithospheric plates constantly move and cause major geological events on
Earth’s surface.
I. Plate Tectonics
A. What is plate tectonics? The theory that the Earth’s lithosphere is divided into tectonic plates that
move around on top of the asthenosphere.
II. Tectonic Plate Boundaries
A. What are the three types of plate boundaries?
1. What is a convergent boundary? When two tectonic plates collide
2. What are three types of Convergent Boundaries?
a. Continental – Continental Collisions: when two continental plates collide, they buckle
and thicken, which pushes the continental crust upward.
b. Continental – Oceanic Collisions: when a plate with oceanic crust collides with a plate
with continental crust, the denser oceanic crust sinks into the asthenosphere.
c. Oceanic – Oceanic Collisions: when two oceanic plates collide, one of the oceanic
plates is subducted or sinks under the other plate.
3. What is Subduction? Old ocean crust gets pushed into the asthenosphere, where it is
remelted and recycled.
4. What is a divergent boundary? When two tectonic plates separate
5. What is the most common type of divergent boundary? mid-ocean ridges
6. What is a transform boundary? when two tectonic plates slide past each other horizontally
7. What is an example of a transform boundary? the San Andreas fault in California where the
Pacific plate and North American Plate are sliding past each other.
III. Possible Causes of Tectonic Plate Motion
A. Convection: hot rock from deep within the Earth rises, but cooler rock near the surface sinks, causing
the oceanic lithosphere to move sideways and away from the mid-ocean ridge
IV. Tracking Tectonic Plate Motion
A. How do scientists track plate movement? GPS to track the movement of the plates