Download PHYSICAL GEOLOGY OF CANADA

Introduction to Plate
Tectonics
Plate Tectonics
 The
theory of plate tectonics best
explains the evolution of the earth’s
landforms.


A German scientist
named Alfred Wegener
first proposed the
Theory of
Continental Drift in
1912.
200 million years ago
all the continents were
grouped together in
one large land mass
called Pangea.

The earth’s crust is divided into 20 plates.

The plates move
because they are
resting on the
partially melted
rocks of the
asthenosphere.

Slowly flowing
convection currents
move the plates in
various directions.
Three Basic Boundaries
Converging Plate Boundaries
Two plates moving
toward each other
 The collision can
cause the
lithosphere to be
pushed up into a
mountain range.

 Example:
The Himalayas formed
from India pushing northward into
China.
Subduction Plate Boundaries

A type of converging plate boundary
where one plate is plunged downward
under the overriding plate.

When an
oceanic plate
collides with a
continental
plate, the
lighter ocean
plate is
subducted
underneath the
continental
plate.
 Forms
a mountain chain and a deepsea trench.
 Deep & strong earthquakes.
Main Convergent Boundaries

The Ring of Fire is a volcano & earthquake
zone that encircles the Pacific Ocean.
EQ Magnitude less than 5.0
Earthquake and
Volcano Data
EQ Magnitude 5.0 to 6.9
EQ Magnitude 7.0 and above
Volcano
Diverging Plate Boundaries:

Two plates are
moving away from
each other

The Mid-Atlantic
Ridge is the
spreading center,
which separates
the North American
Plate from the
Eurasian Plate and
the South
American Plate
from the Africa
Plate.
 The
MAR was formed by the
solidification of magma as the older
rock moves aside.
Main Divergent Boundaries
Transform Plate Boundaries
 Two
plates are sliding
past one another –
causes earthquakes

Example:
San
Andreas
Fault
has
resulted
from the
North
American
Plate
sliding
past the
Pacific
Plate.