Name: _________________________________
Date: __________________________________
Chapter 10: Plate Tectonics
Section 2: The Theory of Plate Tectonics
How Continents Move
•
Plate tectonics - the ___________________________ that explains how large pieces of the
lithosphere, called _____________________, move and change shape.
•
Lithosphere - the solid, __________________________________ of Earth that consists of the
crust and the rigid upper part of the mantle.
•
Asthenosphere - the solid, _________________________________ of the mantle beneath the
lithosphere; made of mantle rock that flows very slowly, which allows tectonic plates to move
on ___________________________ of it.
•
The lithosphere forms the thin
outer shell of Earth and is broken into
several blocks, or
____________________________________.
•
The tectonic plates ride on
the asthenosphere in much
the same way that ____________________
____________________float on water.
•
Tectonic plates can include continental crust, ________________________________________,
or both.
•
Continents and oceans are _______________________________ on the moving tectonic plates.
Tectonic Plates
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Scientists have identified about __________________________ tectonic plates and many
smaller plates.
Plates are often bordered by major surface features, such as ___________________________
or deep trenches in the oceans.
Scientists identify plate boundaries primarily by studying
__________________________________________________________________________.
The locations of ______________________ can also help identify the locations of plate
boundaries.
Name: _________________________________
Date: __________________________________
The boundaries of tectonic plates do not always match the outlines of continents
Types of Plate Boundaries
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Tectonic plate ____________________________ may be in the middle of the ocean floor,
around the edges of continents, or even within continents.
The ______________________ types of plate boundaries are
o divergent boundaries
o convergent boundaries
o transform boundaries
Each plate boundary is associated with a characteristic type of
__________________________________________________________.
Divergent Boundaries
o Divergent boundary - the boundary between
tectonic plates that are
________________________________________
from each other.
o Magma rises to the surface and cools to form the
warm, light rock that sits _______________________
than the surrounding sea floor because it is less dense.
o The narrow valley that forms where the plates separate is a
______________________________.
Convergent Boundaries
o Convergent boundary - the boundary between tectonic plates that are
_______________________________.
o When oceanic lithosphere collides with continental
lithosphere, the denser oceanic lithosphere
_______________________, or sinks under the less
dense continental lithosphere.
o The region along this plate boundary is called a
_____________________________________.
Name: _________________________________
Date: __________________________________
o

When two plates that are made of continental lithosphere collide, the colliding edges
_________________________ and __________________________, which cause uplift
that forms large mountain ranges.
o When two plates that are made of oceanic lithosphere collide, one plate subducts under
the other plate, and a _______________________________________________ forms.
A chain of volcanic islands, called an island arc, may form.
Transform Boundaries
o Transform boundary - the
boundary between tectonic
plates that are sliding past
each other
____________________________.
o Plate edges at a transform
boundary ___________________
_____________________ each
other in a series of sudden
spurts of motions that are felt
as __________________________.
o Short segments of a mid-ocean
ridge are connected by transform
boundaries called _____________________________________________________.
Causes of Plate Motion
 The movement of tectonic plates is part of the
_____________________________________________________________________________.
 Convection is the movement of heated material due to differences in _____________________
that are caused by differences in _______________________________.
o The convection process can be ______________________ by boiling water in a pot on
the stove. As the water at the bottom of the pot is heated, the water at the bottom
expands and becomes less dense than the cooler water above it. The cooler, denser
water ________________________, and the warmer water rises to the surface to
create a cycle called a ________________________________________.
 Mantle Convection
o Scientists think that Earth is also a __________________________________________.
Energy generated by Earth’s core and radioactivity
within the mantle heat the mantle material.
This heated material rises through the cooler,
denser material around it.
o As the hot material rises, the cooler, denser
material flows away from the hot material and
sinks into the mantle to replace the rising material.
o As the ____________________________________
_________________________________________,
the overlying tectonic plates move along with it.
Name: _________________________________
Date: __________________________________
Reading Check
 How may density differences in the rock at a mid-ocean ridge help to drive plate motions?
Slab Pull
• Where the lithosphere cools and becomes dense enough, it begins to subduct into the
__________________________________________________.
• As the leading edge of the plate sinks, it pulls the rest of the plate along behind it. The force
exerted by the sinking plate is called _________________________________________.
• In general, plates that are subducting move __________________________ than plates that are
not subducting. This evidence indicates that the _____________________________________ of
the subducting lithosphere is a strong driving force for tectonic plate motion.