Transcript PLATE TECTONICS

Plate Tectonics
The word “tectonic”
means
“to build.”
So the evidence is
• 1. Coastlines seem to fit like a puzzle.
• 2. Matching mountain chains on separate
continents.
• 3. Matching rock formations on separate
continents.
• 4. Fossils of plants and animals on separate
continents.
Plate tectonics is
Geez… 50
a relatively
new
is
SOOOOO
scientific
concept,
OLD!!!
introduced
50 years
ago
Most scientists say there are
about 17 plates.
How do we know where the plate
edges are?
What makes these plates move?
• Giant lithospheric ants?
• A funky beat?
• How ‘bout CONVECTION?
Click on the lamp.
Plate Tectonics
•The plates consist of an outer layer of
the Earth, the lithosphere,
Oh Behave
•which is cool enough to behave as a
rigid shell.
•Occasionally the hot asthenosphere of
the Earth finds a weak place in the
lithosphere to rise as a plume
•PLATE BOUNDARIES!!!
There are THREE types of plate
boundaries:
I. DIVERGENT Boundaries
• where new crust is generated as the
plates pull away from each other.
• These occur mostly in the ocean
• Rocks of crust feel tension stress
Click below for an animation of
divergent boundaries.
• Click!
DIVERGENT
Boundaries
• Results in the following:
1. Volcanoes
a. mafic magma and lava
b. islands are made
2. Earthquakes
3. Mountain chains
4. Rift zones or Valleys
5. Geothermal activity
DIVERGENT
Boundaries
• Examples include:
1. Mid-Atlantic Ridge
2. Iceland
3. East African Rift Valley
4. East Pacific Rise
DIVERGENT
Boundaries
• The Evidence is that
the Sea Floor is
spreading
1. Earth’s magnetic
field reverses every
million years
2. New magnetic rock
in the ocean floor
looks different.
So the sea floor must be spreading!
• Click here for an animation online.
Evidence of sea floor spreading
• Click here for an animation, explaining how
scientists know the sea floor is spreading.
SO WHAT?!?
So what is slowly happening to the Atlantic
Ocean????
That’s right…it’s getting BIGGER!
Another animation here!
mmm… hot
syrup
2. CONVERGENT boundaries
-- where crust is destroyed as one
plate dives under another.
This is also known as a
SUBDUCTION BOUNDARY!
Convergent Boundaries
• Boundary in which two plates meet
• Rocks of crust feel compression stress
• Types of Convergent boundaries are shown
in the table
• All can result in earthquakes
Plates Involved
Ocean
meets
_continent_
Description
The denser ocean plate
subducts and melts
under the continental
plate.
Picture
Example
Andes Mtns
_Mt. St. Helens_
Vesuvius
_ocean__
meets
Ocean
The denser ocean plate
_subducts__.
Continent
meets
Continent
The continental plates
do not subduct, they
_collide__ and push up
on each other.
Japan
Marianas _Trench_
_Himalayas_
SO WHAT?!?
So what is slowly happening to
the Pacific Ocean????
That’s right…it’s getting
SMALLER!
Animation!
a number of long narrow,
curving trenches thousands of
kilometers long and 8 to 10 km
deep cutting into the ocean
floor. Trenches are the deepest
parts of the ocean floor and are
created by subduction. Animation!
Burn baby burn,
Disco inferno!!!
Let’s see an animation! Wouldn’t that be grand?!
3. TRANSFORM boundaries -
- where crust is neither
produced (created) nor
destroyed
TRANSFORM boundaries
• A boundary in which two plates
slide laterally past one another.
• Most are found on the ocean floor
but some are on coastlines.
• Rocks of crust feel a lot of stress
TRANSFORM boundaries
• Results in:
1. Earthquakes
2. No volcanoes (volcanoes DO
NOT form along transform
boundaries)
TRANSFORM boundaries
• Examples include:
1. Haiti
Haiti is situated to the north of the
Caribbean Plate, on a transform
(slip/conservative) plate boundary with
the North American Plate. The North
American plate is moving west. This
movement is not smooth and there is
friction between the North American
Plate and the Caribbean Plate. Pressure
builds between the two plates until it is
released as an earthquake.
TRANSFORM boundaries
• Examples include:
2. San Andreas Fault in
California
SO WHAT?!?
So what is really going
to happen to western
California?
Part of California will
end up in the Pacific
Ocean
zone between two plates sliding
horizontally past one another is called
a transform-fault boundary
 Most transform faults are found on
the ocean floor. They commonly offset
the active spreading ridges, producing
zig-zag plate margins
San Andreas fault zone in California
4. Hot Spot
• Not a plate boundary!
• This is a place where there is a plume
of magma under the middle of a plate.
It can push up through the plate as the
plate moves across the stationary hot
spot
4. Hot Spot
• Results in any or all of the
following:
• Geothermal geysers
• Volcanoes
• Earthquakes
4. Hot Spot
• Examples include:
• Hawaiian Islands
• Yellowstone
Volcanoes and the Hawaiian
Islands
Animation!
Visualizing Eruptions
Disco Stu is
tellin’
YOU…
This is the
last
Hawaiian
Island
above
water, all
the rest are
DOWN
LOW!!!
A Review of Plate Boundaries
• Click here!