8. CONTINENTAL DRIFT
Alfred Wegener's theory that the continents were
once a single supercontinent called Pangaea (all
land).
Over time this super continent slowly broke apart
into what we have today
9. CONTINENTAL DRIFT
The Theory of Plate Tectonics starts
with another idea… Continental Drift.
The Earth once had a single land mass
called Pangaea that broke apart into
pieces that drifted away to become the
major continents of today.
10. EVIDENCES THAT PROVE
CONTINENTAL DRIFT
Identical types of fossils found in Africa
and South America
Continents can “piece”together with the
same rock formations
Glacial deposits left by same sheet of
ice
11. PLATE TECTONINCS
Theory of Plate Tectonics - The theory of plate
tectonics, the crust is broken up into
sections/pieces that move on top of the liquid
mantle (asthenosphere).
Tectonic Plates – these sections/pieces of
crust are called plates
12. How do the plates move?
One hypothesis is that large
convection currents within
the mantle move the plates.
Movement is caused by
differences in temperature
causing a rising and sinking
cycle.
Convection Currents
13. The lithosphere is divided into 7
major and minor plates. Plates move
at different speeds in different
directions. Plate boundaries are
where two plates meet.
14. 3 TYPES OF PLATE TECTONIC
BOUNDARIES
i. CONVERGENT BOUNDARIES
ii. TRANSFORM BONDARIES
iii.DIVERGENT BOUNDARIES
15. Divergent Boundaries occur where
plates move apart. There are two types
of divergent or constructive boundaries:
Mid-Ocean Ridge
Rift Valley
16. Mid- Ocean Ridge : New ocean floor,
mountains, earthquakes and volcanic
action occur when an ocean plate
spreads apart (Mid-Atlantic Ridge: largest
mountain range in the whole world.
17. Rift Valley : Continent starts to split
apart forming a rift valley and eventually
a seaway and then an ocean. Volcanic
activity and earthquakes occur in these
areas. (Ex: African Rift Valley)
18. Convergent Boundaries form when two
tectonic plates come towards each other.
There are three types of convergent boundaries
or destructive boundaries.
Continent – Continent
Ocean – Ocean
Continent – Ocean
19. Continent –Continent : Mountains form
and earthquakes occur when
continental plates run into each other
and fold upwards. (Ex: Himalayas and
Alps)
20. Ocean Plate-Ocean Plate: Volcanic
island arcs, trenches & earthquakes
occur when older ocean plate subducts
under a younger ocean plate.
(Ex: Japan, Aleutian Islands-off Alaska,
Philippines, Tonga Islands, Marianas
Trench).
21. Ocean Plate-Continent Plate:
Mountains, volcanoes and earthquakes
occur as an ocean plate subducts under
a continental plate. The Oceanic plate
melts; less dense-magma rises to form
volcanoes. (Ex: Andes, Cascade Range,
Sierra Nevada)
22. Strike-slip or transform boundaries
occur where two plates slide along side
each other. Earthquakes occur in these
areas (Ex: San Andreas Fault in
California).
Transform Boundary San Andreas Plate Movements
23. PANGEA
Pangea, also spelled Pangaea, in
early geologic time, a supercontinent
that incorporated almost all the
landmasses on Earth.
