Plate Tectonics Study Guide
Concepts to Know





















The lithosphere includes all of the crust and part of the mantle.
Density is a measure of how much mass there is in a volume of a substance.
As oceanic crust moves away from the mid-ocean ridge, it cools and becomes more dense.
The supercontinent that began to break apart about 225 million years ago is called Pangaea.
A rift valley forms along a divergent boundary on land.
Fossils of tropical plants found on an island in the Arctic Ocean are evidence for Wegener’s
hypothesis of continental drift.
The process that continually adds new material to the ocean floor is sea-floor spreading.
The asthenosphere is the part of the mantle that can bend like plastic.
A transform boundary is a place where two plates slip past each other.
Heat transfer by movement of a heated fluid is called convection.
Molten material erupts through a valley of mid-ocean ridge.
Alfred Wegener was the first to propose the theory of continental drift.
The transfer of energy through space is called radiation.
In the convection current of a pan of soup, the cooler, denser fluid sinks to the bottom.
Scientists who study the forces that make and shape the planet Earth are called geologists.
Earth’s lithosphere is broken into separate sections called plates.
Subduction is the process by which oceanic crust sinks beneath trenches.
Scientists rejected Wegener’s theory because he could not explain what force pushes or pulls
continents
Continental crust consists mainly of the rock granite.
A break in Earth’s crust where rocks slipped past each other is called a fault.
Know the layers of Earth: crust, mantle, outer core, and inner core
Essay



Where is the bottom of the lithosphere located compared to the Earth’s layers?
o In the mantle just below the crust since the lithosphere includes the crust, and the top
part of the mantle.
What is the major difference between the inner and the outer core?
o The outer core is molton while the inner core is solid.
What is divergent boundary, convergent boundary, and transform boundary?
o Divergent boundary: a place where two plates move apart, or diverge
o Convergent boundary: the place where two plates come together, or converge
o Transform boundary: is a place where two plates slip past each other, moving in
opposite directions



Compare and contrast three different kinds of convergent boundaries.
o One kind is when two plates carrying oceanic crust collide. In this case, the denser plate
subducts below the less dense plate at a deep ocean trench. A second kind is when a
plate carrying oceanic crust collides with a plate carrying continental crust. In this case,
the oceanic plate plunges beneath the continental plate. In a third kind, two plates
carrying continental crust collide. In this case, neither plate is subducted. Instead, the
collision squeezes the curst into mountain ranges.
Describe what scientists now know about Earth that would have answered the scientists who
rejected Wegener’s theory.
o Scientists did not believe Wegener because he could not provide an explanation for the
force that moves continents. Scientists now know that convection currents in the
mantle cause the movements of plates on Earth’s surface, and those plates carry the
continents with them.
What accounts for the difference in density between oceanic and continental crust?
o Oceanic crust is made mostly of basalt, while continental crust is made mostly of
granite. Since basal is denser than granite, oceanic crust is denser than continental
crust.