Download Guided Notes on the Theory of Plate Tectonics

Guided Notes on the
Theory of Plate Tectonics
Chapter 17, Section 3
1. State the theory of plate
tectonics in its entirety

The earth’s crust and rigid upper mantle
are broken into enormous slabs called
plates. These plates move in different
directions and at different speeds and this
movement is caused by the Earth’s
internal heat.
2. What are the 3 types of movement
that can occur at plate boundaries?

Plates can come together, or converge

Plates can move away from each other, or
diverge

Plates can move horizontally past each
other
3. Divergent boundaries are places
where 2 tectonic plates are moving
apart. Most divergent boundaries are
found on the seafloor, where they
form ocean ridges.
4. The process of seafloor spreading
along a divergent boundary may
cause an ocean basin to grow wider.
5. A divergent boundary formed on a
continent is called a rift valley, which
is a long narrow depression in
continental crust.
6. Convergent boundaries are places
where 2 tectonics plates are moving
toward each other.
3 Types of Convergent Boundaries
1.
Continental-Continental
One continental plate converges with
another continental plate. Neither plate
is forced downward and a folded
mountain range is formed.
3 Types of Convergent Boundaries
2. Oceanic-Oceanic
Oceanic crust converges with oceanic crust.
One plate is forced downward, resulting in
a deep-sea trench and an island arc of
volcanoes.
3 Types of Convergent Boundaries
3.
Oceanic-Continental
An oceanic plate converges with a
continental plate and the oceanic plate is
forced downward. A trench forms along
with a volcanic mountain range on the
edge of the continent
What is subduction?
 Subduction
is the process of one
crustal plate descending beneath
another.
Where does it occur?
 Subduction
occurs at a
subduction zone, where one plate
descends beneath another.
How does it happen?
 If
one oceanic plate becomes
denser than another plate
(because it is cooler), then it will
descend below the other plate as
they converge.
What forms as a result of it?
 A deep-sea
trench and an island
arc of volcanoes form at
subduction zones.
When subduction occurs between
a continental and oceanic plate…
When an oceanic and continental plate
converge, the oceanic plate is subducted
because it is denser.
 A trench is formed along the coast of the
continent, along with a series of volcanoes
along the edge of the continental plate.

10. When two continental plates
converge, the colliding edges of the
continents are crumpled and uplifted
to form a mountain range.
11. A transform boundary is a place
where two plates slide horizontally
past each other.
12. What happens to crust at a
transform boundary?

Crust is only deformed or fractured. It is
neither subducted or uplifted. Transform
boundaries are characterized by long
faults and shallow earthquakes.