Transcript Plate Tectonics*what is it?

PLATE TECTONICS AND
CONTINENTAL DRIFT
AUGUST 30, 2016
FALCON FOCUS
SOLVE THE PUZZLE ON THE NEXT SLIDE
ESSENTIAL QUESTION
What evidence supports that at one time the
continental plates were together as Pangaea?
Plate Tectonics…what is it?
Plate tectonics is the theory that explains
the formation, movement and subduction
of Earth’s plates
How do the Plates move?
• The plates of the Earth move because of
Convection Currents in the asthenosphere
rising and causing the movement.
What happens when the plates move?
• No plate can budge without affecting
the other plates surrounding it.
• As the plates move, they collide pull
apart, or grind past each other
producing changes in the Earth’s
surface.
What kind of Changes?
Volcanoes!
Mountain ranges!
Earthquakes!
Sea-trenches!
Where are these plates?
IN THE LITHOSPHERE!
PROOF or it didn’t happen…
EVIDENCE #1
The continents used
to fit together like
puzzle pieces before
the plates moved them
apart
Scientists call this
Supercontinenet: PANGAEA
How do I say that?? PAN-GEE-UH
 Continental drift was Wegener’s theory
that all continents had once been joined
together in a single landmass and have
drifted apart since.
 Wegener named this supercontinent
Pangaea.
 Wegener’s theory was rejected by
scientists because he could not explain
what force pushes or pulls continents.
Continental drift video clip
Wegener
1880-1930
earthobservatory.nasa.gov
Alfred Wegener first proposed the theory of
continental drift.
As the plates continued to move and
separate, OCEANS formed
Landmasses collided and split apart until
they ended up where they are now
PROOF or it didn’t happen…
EVIDENCE #2
Fossils on different continents are similar to
fossils on continents that were once connected.
When the continents split, different life forms
developed.
Continents that were once connected also have
identical landform shapes and features and
identical rock formations
PROOF or it didn’t happen…
EVIDENCE #3
Most features on land and in the ocean are the result of
geological activity and earthquakes along plate
boundaries (where the pieces meet).
• The exact patterns depend on HOW the plates are
moving… together – apart – or sliding.
What else do we know?
The plates are still moving!!
Though they move VERY SLOWLY 
between 1-10 centimeters per year
What else do we know?
There are places within the lithosphere where
magma rises and leaks through the crust
This is called a HOT SPOT and is where volcanic
activity occurs.
HOTSPOTS are how the Hawaiian islands were
formed!!
CONVERGENT PLATE BOUNDARY
AUGUST 31, 2016
FALCON FOCUS - REVIEW CHECK
• What are two evidences of the continental drift theory?
• What is Pangaea?
• Where are the tectonic plates located?
• What part of the Earth do tectonic plates float on?
• How do tectonic plates move?
ESSENTIAL QUESTION
What landforms result from a Convergent
Boundary?
Plate Boundaries
Plates float on the upper mantle (Asthenosphere)
They move due to Convection Currents
The edges of the different plates meet at lines called
Boundaries
At the border of plate boundaries are….
FAULTS—breaks or cracks in the
Earth’s crust
Types of Boundaries
There are 3 different types of
boundaries that occur because of their
different movement
 Convergent Boundaries
 Divergent Boundaries
 Transform Boundaries
Convergent Boundaries
 2 plate boundaries come together or
collide
 A collision is when two plates hit
each other
CRUST
CRUST
What happens when they hit?
• The DENSITY of the crustal plates
colliding determines if either…
A) One plate goes under the other
B) The plates rise up
Either way…. An Earthquake can always (and
often does) occur when two plates interact
Collisions
PREDICTION TIME: Basalt (what
Oceanic Crust is made out of) is
more dense than Continental Crust.
What do you think will happen
to the plate that is MORE
dense?
SUBDUCTION ZONE
CRUST INVOLVED: OCEANIC & CONTINENTAL
MOVEMENT: More dense plate (Oceanic) slides
under or sinks below the less dense Continental
plate.
FORCE/STRESS ON THE ROCK: Compression
(push or squeeze rocks)
LAND FORMS:
– Trenches, crust going below into the mantle melts and
recycles
– Island arcs and volcanic arcs (small mountain ranges)
SUBDUCTION ZONE
SUBDUCTION ZONE
TRENCHES
ISLAND ARC
VOLCANIC ARC
MOUNTAINS & VOLCANOES
• CRUST INVOLVED: CONTINENTAL & CONTINENTAL
• MOVEMENT: Both plates buckle and push up
• FORCE/STRESS ON THE ROCK: Compression (push or squeeze
rocks)
• LAND FORMS:
Mountain ranges
Volcanoes
AND EARTHQUAKES!
• INCRUST INVOLVED: CONTINENTAL and push up
• FORCE/STRESS ON THE ROCK: Compression (push or squeeze
rocks)
DIVERGENT AND TRANFORM
BOUNDARIES
SEPTEMBER 1
FALCON FOCUS
With reference to the types of crusts, describe
how converging boundaries are formed.
ESSENTIAL QUESTION
WHAT LANDFORMS RESULT FROM A DIVERGENT
BOUNDARY?
Landforms from Convergent
Boundaries
i.
Deep ocean trench – includes oceanic and
continental plates; as oceanic subducts, it pulls
the front edge of the continental plate.
ii. Volcanoes – includes oceanic and continental;
continental plate melts due to friction and
extreme heat; melted plate rises up through
crust and cools when it reaches surface
iii. Volcanic island arc- includes only oceanic plates;
subduction occurs
iv. Folded mountains – includes only continental
plates; collision occurs; no subduction
PEER/PAIR ASSIGNMENT
To your favorite Rap beat, compose a lyric to
describe the types of boundaries (convergent,
divergent and transform).
You will be graded on content, creativity and
performance.
Presentation – tomorrow
Lyrics MUST be typed!!!
Divergent Boundaries
 The place where two
plates move apart—or
diverge—is called a
divergent boundary
 Most divergent
boundaries occur at the
mid-ocean ridge—so
crust is forming
 When divergent
boundaries occur on land,
a rift valley is formed
Divergent Boundaries
A plate boundary where two plates move away from each other.

RIFTING
causes
SEAFLOOR SPREADING
How is the rock pulled at Divergent
Boundaries?
Rock gets THIN in the middle as it is
pulled apart.
This STRESS is called
What happens when the rock SNAPS from
the Stress of Tension?
A Normal Fault (fault is a break in Earth’s
Rock drops down as it breaks
crust)
What happens next at Divergent Boundaries?
• A geologic feature or
event…
May form RIFT
VALLEYS on
continents
SEA-FLOOR SPREADING
in the ocean
Helpful Hints…
• Divergent is like “dissecting” or “dividing”
• If you pull warm bubble gum or silly putty, it will
thin in the middle until it is stressed so much that
it breaks.
• Happens on land
& under H2O
Features of Divergent Boundaries
• Mid-ocean ridges
• rift valleys
• fissure volcanoes
TRANSFORM BOUNDARY
SEPTEMBER 2, 2016
FALCON FOCUS
Can you match the
boundary name
correctly with its
diagram?
A._____________
B._____________
C._____________
ESSENTIAL
QUESTION
WHAT LANDFORMS RESULT FROM A
TRANSFORM BOUNDARY?
Transform Boundaries
 Along transform
boundaries crust isn’t
created or destroyed
 At a transform
boundary the two
plates slip past each
other
Transform Boundaries
A plate boundary where two plates move past each
other in opposite direction.
How is the rock broken at Transform
Boundaries?
• Rock is pushed in
two opposite
directions (or
sideways, but no
rock is lost)
• This stress is
called SHEARING
What happens next at Transform Boundaries?
• May cause
Earthquakes
when the rock
snaps from the
pressure.
• A famous fault @
a Transform
Boundary is the
San Andreas Fault
in California.
San Andreas Fault, CA
What happens when the rock is sheared (or
“cut”) from the Stress of Shearing?
• A STRIKE-SLIP FAULT
• Rocks on each side of the fault slip past
each other as they break.
Helpful Hints…
• Shearing means cutting (“Shears” are like
scissors)
• Transform boundaries run like trains going
past each other in different directions & they
shake the ground!
Plate Boundaries:
• Correct Answers:
A.Divergent
B. Convergent
C. Transform
Station Work
1. WHAT IS THE THEORY OF PLATE TECTONICS?
2. WHAT IS A RIFT VALLEY? HOW IS IT FORMED?
3. WHAT TYPES OF PLATE MOVEMENT OCCUR AT
PLATE BOUNDARIES
4. WHAT MAJOR EVENT BEGAN ABOUT 225 MILLION
YEARS AGO?
5. LABEL ALL THE BOUNDARIES ON FIGURE 5
(OVERHEAD) AS TRANSFORM, CONVERGENT OR
DIVERGENT.