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Plate Tectonics
The Crust
• This is where we live!
• The Earth’s crust is
made of:
Continental Crust
Oceanic Crust
- thick (10-70km)
- buoyant (less dense
than oceanic crust)
- mostly old
- thin (~7 km)
- dense (sinks under
continental crust)
- young
Plate Tectonics
• Pieces of the lithosphere that move
around
• Each plate has a name based on the
name of the continents and oceans
nearby.
• Fit together like jigsaw puzzles
• Float on top of mantle
Evidence of Pangea
Evidence of Pangaea
1.Fossils of animals and plants living
on separate continents
2.Rock deposits
3.Ancient mountain ranges
4.Glacial deposits
5.Continental drift
Continental Drift
-Alfred Wegener
Continents were once a
single land mass that
drifted apart.
-He called this
supercontinent Pangea,
Greek for “all Earth”
-Could we use today’s maps
50,000 years from now?
Why or Why not?
http://members.enchantedlearning.com/subjects/astronomy/planets/earth/Continents.shtml
Names & Locations of the tectonic plates
Tectonic Plates
Types of Plate Boundaries
Ocean-Ocean Plate Collision
• When two oceanic plates collide, one runs
over the other which causes it to sink into the
mantle forming a subduction zone→ trench.
• The subducting plate is bent downward to
form a very deep depression in the ocean
floor called a trench.
• The worlds deepest parts of the ocean are
found along trenches.
– Ex: The Mariana Trench is 11 km deep!
Continent-Oceanic Crust Collision
• Causes SUBDUCTION → volcanoes
Volcanoes are formed by:
- Subduction - Rifting - Hotspots
Ring of Fire
-An area in the Pacific Ocean (Pacific Plate)
where many Earthquakes and volcanic
eruptions occur. California
Continent-Continent Collision
• Forms folding of crust →mountains,
• Ex: European Alps, Himalayas
Divergent Boundaries
• Spreading ridges, rift valleys
– As plates move apart new material is erupted to
fill the gap
Sea Floor Spreading
Sea Floor Spreading
• Mid Ocean Ridges – underwater
mountain chains that run through the
Earth’s Basins
• Magma rises to the surface
and solidifies and new
crust forms
• Older Crust is pushed
farther away from the
ridge
Transform Boundaries
• Where plates slide past each other
• Causes a fault → earthquakes
Above: View of the San
Andreas transform fault in
California. It is caused by
the Pacific Plate sliding on
the North American Plate.
Where do earthquakes from?
Figure showing the tectonic setting of earthquakes
What do the locations of Volcanoes
and Earthquakes tell us?