Transcript plate tectonics

PLATE TECTONICS
Why the Earth is Like It Is
Plate tectonics is the theory that Earth's outer layer is made up
of plates, which have moved throughout Earth's history. The
theory explains the how and why behind mountains, volcanoes,
and earthquakes.
Continental Drift
Continental Drift: Alfred Wegener's theory that all continents were once
connected in a single, large landmass (called Pangaea) that broke apart
about 200 million years ago and drifted slowly to their current positions.
What Did
The Earth
Look Like
In The
Past?
What evidence do we have that the
continents have moved?
Fossil Clues:
Fossils of similar plants and animals have been found on
continents that are now very far apart, but were perhaps
once joined together.
Climate clues:
Evidence of glaciers can be found on land that is now
tropical, because that land was once located in a colder
region of our planet.
Rock Clues:
Similar rock structures can be found on continents that are now
far apart, again suggesting that they could have once been joined.
Rocks found in the eastern US are similar to those found in
western Europe.
Tectonic Plates World Map (link)
Major Tectonic Plates:
Do land features continue to change?
Are the continents still moving?
The earth’s tectonic plates continue to
gradually move even today. The plates
interact. Where one plate meets
another, is called a boundary.
How do we know?
Hot Spots
(Hawaii,
Yellowstone)
Volcanoes and Earthquakes
Ring of Fire – very active
region of subduction
Why Do Plates Move?
Plates are “pushed”
and “pulled” over the
surface of the Earth
due to unbalanced
forces.
When convection
currents reach the
surface, plates are
pushed apart
As the plates move
away from each
other, part of them
are pulled into the
Earth’s mantle
Plates Move Toward Each Other
This is called Convergent Boundary – these are
destructive boundaries since they deform the plates
Continent/Continent
Ocean/Continent
Ocean/Ocean
Convergence creates mountains
Most volcanoes (but not all) form along Convergent boundaries,
as one plate is pushed under another and the old crust melts.
As two plates rub against one another, a number of small and
large earthquakes could occur near convergent boundaries.
http://geology.com/nsta/convergent-plate-boundaries.shtml
Convergence – Moving Together
Trenches
Mountains
Structural
Mountains
Volcanic
Mountains
Plates Move Away From Each Other
This is called Divergence – these are constructive
boundaries since they produce new land
Africa and Arabia
Mid-Atlantic Ridge
North America
and Eurasia
http://geology.com/nsta/divergent-plate-boundaries.shtml
Divergent Boundaries
Most often takes place at ocean ridges.
As the two sides of the crust move away from each other, magma
wells up from the Earth's interior.
It then solidifies into rock as it is cooled by the sea, creating new
ocean floor. Causes some volcanoes and earthquakes to form.
The ridges are zones of intense volcanic activity. In addition to
forming at the bottom of oceans, these divergent boundaries
can also form on continents.
When this happens, a line of volcanoes emerges.
Divergence – Moving Apart
Rift Valley –
if the land is
above water
Sea Floor
Spreading –
when the land is
below water
Plates Move Side By Side - ***SHIFTING
This is called Transform Boundary – Transform boundaries neither
create nor consume crust. Rather, two plates move against each other,
building up tension, then releasing the tension in a sudden and often
violent jerk. This sudden jerk creates an earthquake.
The San Andreas Fault is undoubtedly the most famous transform
boundary in the world. To the west of the fault is the Pacific plate,
which is moving northwest. To the east is the North American Plate
which is moving southeast.
http://geology.com/nsta/transform-plate-boundaries.shtml
San Andreas Fault
Is a continental transform fault that runs a length
of roughly 1,300 km (800 miles) through
California.
Review clip
(click on the link above)
Review
Divergent: Boundary between two plates that
are moving apart.
Convergent: Boundary between two plates that
are pushing together.
Transform (Strike-slip): Boundary between two
plates that are sliding past one another. ***
Causes Earthquakes
Subduction Zone: The area where one plate
pushes down under another. Volcanoes are
often created by this.
As two continental plates move toward
each other, what landforms would you
expect to see?
Volcanoes
B. Cliffs
C. New Land
D. Mountains
A.
As two continental plates move toward
each other, what landforms would you
expect to see?
Volcanoes
Incorrect
These form at edges of plates or over
hot spots
A.
As two continental plates move toward
each other, what landforms would you
expect to see?
Cliffs
Incorrect
These are erosional landforms or minor
uplift areas
B.
As two continental plates move toward
each other, what landforms would you
expect to see?
New Land
Incorrect
Forms when plates move apart
C.
As two continental plates move toward
each other, what landforms would you
expect to see?
D.
Mountains –
correct because 2
continental
masses will push
into each other
and “crumple” the
edges to form
mountains
Where would you find the newest
land on Earth?
A.
B.
C.
D.
In areas of continental convergence
In areas where two ocean plates come
together
In areas where plates are moving apart
In areas where two plates are sliding past each
other
Where would you find the newest
land on Earth?
In areas of continental convergence
Incorrect
Mountains would form here from existing land.
A.
Where would you find the newest
land on Earth?
In areas where two ocean plates come
together
Incorrect
You would find trenches in this area.
B.
Where would you find the newest
land on Earth?
In areas where two plates are sliding past each
other
Incorrect
You would find land movement but not new
land being formed
D.
Where would you find the newest
land on Earth?
In areas where plates are moving apart
Correct
When plates move apart it is due to magma
reaching the surface. When magma cools new
land is formed.
C.