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TRANSCRIPT
Plate Tectonics
Goal 2.1
Lesson 1
Plate Tectonics: An Overview
Think About It…
Look at the map below. Which two
continents look like they‘d fit together?
Focus Question…
How do Earth’s tectonic plates cause…
…volcanoes to form? …earthquakes to occur?
…Earth’s surface features to form?
Continental Drift… 1. What is the theory
of continental
drift?
The
continents
had once
been joined
as a single
landmass that
split (drifted)
apart. http://rosalieee.files.wordpress.com/2009/01/pangea-continental-drift.jpg?w=596&h=489
Continental
Drift…
2. What was
Pangaea?
the
ancient
super-
continent
http://pubs.usgs.gov/gip/dynamic/historical.html
3. Evidence Supporting Continental
Drift…
a. the puzzle-like fit continents on either side
of the Atlantic Ocean
http://earthscience.wordpress.com/2007/04/13/day-143-continental-drift-puzzle/
Evidence Supporting Continental
Drift… Rocks and Fossils
b. Rock formations
& fossils on both
sides of the
Atlantic Ocean
match.
http://choralemaacher.lu/continental-drift-evidence-mountains
Evidence Supporting Continental
Drift…Fossils
http://abyss.uoregon.edu/~js/images/fossil_break.gif
Evidence Supporting Continental
Drift…Climate
c. Climate changes...
Coal deposits in
Antarctica (warmer
and farther north)
Glacial erosion in India,
Africa, and Australia
(colder and farther
south)
http://blue.utb.edu/paullgj/physci1417/Lectures/Gondwanaland_Glaciations.JPG
Seafloor Spreading…
1. The theory of seafloor spreading
states…
new ocean crust is formed at the ridges
and destroyed at trenches.
Seafloor Spreading…
http://higheredbcs.wiley.com/legacy/college/levin/0471697435/chap_tut/images/nw0125-nn.jpg
How we know what’s down there!
http://marinesciencetoday.com/2009/05/06/new-antarctic-sonar-images-reveal-clues-to-sea-level-rise/
https://directory.eoportal.org/web/eoportal/satellite-missions/t/topex-poseidon
2. Preview of the Ocean Floor…
a. An ocean ridge is…
vast, underwater mountain range – the
longest on Earth!
b. A deep sea trench is…
narrow, elongated depression in the
ocean floor - deepest part of the ocean –
11 km deep!
See next slide…
The Ocean Floor…
Evidence for Seafloor Spreading…
a. Ocean rocks and sediments are
younger at the midocean ridges.
Evidence for Seafloor Spreading…
b. Magnetism –
Basalt provides an accurate
record of ancient
paleomagnetism.
i. Earth has had a series of
magnetic reversals or
changes in its magnetic field.
ii. These are recorded in the
ocean floor.
The magnetic pattern on
either side of a midocean
ridge is a mirror image.
DRAW ME!!
DRAW ME!!
How Seafloor Spreading Occurs…
Step 1: Magma rises and fills the gap.
Step 2: Magma solidifies to form new crust.
Step 3: New crust is continually made and pushes the
older crust to the outer edges of the ocean.
http://www.uwsp.edu/geo/faculty/ritter/glossary/S_U/sea_flr_spread.html
See next slides…
A Bigger View!
http://www.moorlandschool.co.uk/earth/tectonic.htm
The Theory of Plate Tectonics…
1. The theory of plate
tectonics …
Earth’s rigid
crust and upper
mantle is broken
into large plates.
http://geology1a-1.wikispaces.com/Plate+Boundary+images+and+captions
2. Plate Boundaries…(Add to
Lesson 1.)
a. Divergent – plates separate
b. Convergent – plates are moving toward each other
c. Transform – slide horizontally past each other
Click here to investigate the boundaries…
http://geology.com/plate-tectonics.shtml
The Plates…
Australian plate - pink or lighter orange, Nazca & Scotia plates – lighter blue
Lesson 2
Plate Tectonics – Divergent
Boundaries
Think About It…
Why do some parts of Earth have
volcanoes and earthquakes and
others don’t?
Focus Question…
What geologic activity occurs at
a divergent plate boundary?
Plate Boundaries: The Big Pic…
http://geology1a-1.wikispaces.com/Plate+Boundary+images+and+captions
Divergent Boundary…
1. A divergent boundary is one
where the plates are separating
or moving apart.
2. Geological Processes
a. High heat flow – magma pushes up into
the rift valley.
2. Geological Processes
b. Volcanoes – formed by the magma
rising at the rift valley
2. Geological Processes
c. Earthquakes – caused by the magma
breaking rocks on its way to the surface
Divergent Boundaries…
3. Divergent boundaries form rift valleys
where… magma rises, solidifies, &
pushes plates apart. DRAW ME!!
Divergent Boundary…
4. The underwater
mountain range
formed at
divergent
boundaries in
every ocean is…
The midocean
ridge
5. Examples - Iceland…
East Africa Rift Valley…
http://geology.com/articles/east-africa-rift.shtml
The Midocean Ridges
http://earthguide.ucsd.edu/eoc/teachers/t_tectonics/p_midoceanridges.html
Lesson 3…
Convergent Boundaries
Think About It…
Where do many of our most
devastating earthquakes occur?
Focus Question…
What geologic activity occurs at
a convergent plate boundary?
Plate Boundaries: The Big Pic…
http://geology1a-1.wikispaces.com/Plate+Boundary+images+and+captions
Convergent Plate Boundaries…
• There are 3 types of convergent plate boundaries – depending on their locations… – Ocean/continental
– Ocean/ocean
– Continental/continental
We will look at each type separately…
Convergent
Boundaries:
Ocean/Ocean
1. Subduction is…
… the process of one plate going under another.
The process of subduction creates a deep-sea trench.
2. The underground edge of the subducting plate melts because… it is pulled deep into Earth’s crust.
Melted crust rises to form a volcanic island arc.
Effects of Plate Snapping…
3. Two devastating
effects of a
plate snapping
back are…
a. Earthquakes
b. Tsunamis
• See clips…
http://d3sdoylwcs36el.cloudfront.net/map_of_thye_areas_hit.gif
http://tsunami2004videoarchive.com/tsunami_video_key_video.htm
Convergent Boundaries:
Ocean/Ocean
4. The type of fault found at this
boundary is…
… reverse
http://www.artinaid.com/wp-content/uploads/2013/04/ReverseFault.gif
Convergent Boundaries:
Ocean/Ocean
http://www.indiana.edu/~geol116/week7/conver.jpg
Let’s
Draw! DRAW ME!!
Convergent Boundaries:
Ocean/Ocean
5. Examples of
this are…
a. Mariana
Islands
b. Japan
c. Indonesia
Convergent Boundaries:
Ocean/Ocean – Another Example
The Japanese Islands
Convergent Boundaries:
Ocean/Continental
1. The oceanic plate subducts under the
continental plate. (It is denser.)
2. A volcanic mountain range forms on
land above the subduction zone.
3. Examples include Andes Mountains (S.
America) and the Cascade Mountains
in N. America)
Convergent Boundaries:
Ocean/Continental
http://www.100destinos.com/imagenes/los-andes-chile.jpg
http://www.worldtravelattractions.com/cascades-cascade-range/
The Andes of S. America
The Cascades of N. America
Convergent Boundaries:
Ocean/Continental
http://elearning.stkc.go.th/lms/html/earth_science/LOcanada4/403/images/3_1.jpg
Let’s
Draw! DRAW ME!!
Convergent Boundaries:
Continental/Continental
1. A folded mountain range is formed when two
continental plates collide. (They are both too
thick to go under.)
2. Examples include the Himalaya Mountains
and the European Alps.
Let’s
Draw!
DRAW ME!!
The Appalachian Mountains and
the Piedmont…
• They started as a continental fragment and a volcanic island arc about 700–600 mybp.
– The continental fragment moved west & became the Blue Ridge Province. (500-400 mybp)
– The island arc moved west & became the Piedmont Province. (400-300 mybp)
– The folded Valley and Ridge (c/c) formed when the N. American and African plates collided. (300-260 mybp)
Lesson 4
Transform Boundaries
Transform Boundaries… 1. Transform refers to “moving across.”
2. At transform boundaries, crust is only deformed or fractured.
3. Volcanoes and mountains don’t form here because there is NO vertical movement of the plates.
4. The type of faults formed here are called strike-slip faults
5. Transform boundaries are characterized by shallow earthquakes.
DRAW ME!!
Haiti, 1/2010 (7)
6. Examples include:
San Andreas Fault in California
Haiti
Plate Boundary Activity…
• http://geology.com/plate-tectonics.shtml
Causes of Plate Movements…
1. Large-scale
motion in the
mantle drives
the movement
of the plates.
http://www.nakedscience.org/mrg/Plate%20Tectonics%20Lecture%202_files/image018.jpg
Causes of Plate Movements…
2. Definitions…
a.Mantle – layer of
Earth beneath
the crust
b.Asthenosphere
– partially molten
layer of the
mantle
Causes of Plate Movements…
Definitions…
c. Convection –
transfer of thermal
energy by the
movement of heated
matter
d. Convection current
– pattern of motion
produced by warmer
matter moving up and
cooler matter sinking
http://library.thinkquest.org/C003124/images/convect.jpg
Causes of Plate Movements…
3. The tectonic plates move by…
a.… The rising part of the convection
current spreads out as it reaches the upper
mantle which lifts and splits the lithosphere
at divergent plate boundaries.
b.… The downward part of the convection
current creates a sinking force that pulls
tectonic plates downward at convergent
boundaries.
Causes of Plate Movements…
3. The tectonic plates move by…
c. … Ridge push - the force created by the
weight of the uplifted ridge which pushes an
oceanic plate towards a trench. (at a
subduction zone)
d. … Slab pull - process in which the weight
of the subducting plate helps pull the trailing
lithosphere into the subduction zone.
Causes of Plate Movements… DRAW ME!!
Causes of Plate Movements…
http://www.fas.org/irp/imint/docs/rst/Sect2/Sect2_1b.html