Download Theory of Plate tectonics

Theory of Plate Tectonics
Oceans 11
But first…a little about the
internal structure of the Earth
A Brief look Earth’s 2 major layers
Earth’s Internal Structure
•
•
•
•
Earth can be divided into 3 main layers:
Crust (outside of Earth)
Mantle
Core (very inside)
Earth’s Crust
• Crust is the outermost layer.
• Two Parts of Crust:
– Continental crust
• Mainly granite
• Up to 75km thick
• Density 2.6g/cm3
– Oceanic crust
• Made up of basalt rock (type of volcanic rock)
• Up to 8 km thick
• Density 3.0g/cm3
The Mantle
• The mantle is the next layer.
• This zone is about 2900km thick and makes up
great 82% of Earth’s volume.
• Fragments of the mantle have been brought to
the surface by volcanic eruptions.
Earth’s Core
• Earth’s core is extremely hot – hot as the
sun!
• Divided into two parts.
– Outer Core
• Liquid iron and nickel
– Inner Core
• Solid iron
Now let’s look at the Theory of
Plate Tectonics…
Plate Tectonics – brief history
• 1912
– Alfred Wegener,
German geophysicist and
meteorologist
– Wegener thought that all
landmasses formed one
supercontinent
approximately 225 mya
“Pangaea” meaning all
earth.
Wegener’s research:
•
•
•
•
Geologic record (rock strata)
Fossil record
Climatic record of continents
A KEY FINDINGS:
– Southern America & Africa have many
similarities
• Large coal deposits
Resistance…
• Wegener was met with a lot
of skepticism from other
scientists and the church.
• 1950 to 1960’s
– Geologic Discoveries:
• Similar fossils on each
continent
• Same age rock on coast lines
• It wasn’t until the 1960’s
that Wegener’s theory was
accepted and coined
Theory Plate Tectonics
Animation of Continental Drift
• http://education.sdsc.edu/optiputer/flash/p
angea_4.htm
PANGEA
Definition of Plate Tectonics
• Tectonic – Greek meaning “building” or
“construction”
• Refers to the configuration of Earth’s crust
as a result of internal forces.
Plate Tectonic Processes
• Include:
– Upwelling of magma
– Crustal plate movements
– Sea-floor spreading
– Subduction of crust
– Earthquakes
– Volcanic activity
– Warping, folding and faulting of crust.
Earth’s Plates
• Plates are made up of:
– Continental crust
– Oceanic crust
• These plates float upon the moving
asthenosphere.
• Plates move 1 to 19 cm per year
– Movement of plates are a result of convection
currents in the asthenosphere
– http://education.sdsc.edu/optiputer/flash/convection.htm
Earth’s Plates
• What do you notice about the relationship
between volcanoes(red), earthquakes
(yellow) and location of plate boundaries?
3 Main types of Plate Boundaries
1. Divergent plate boundary
2. Convergent plate boundary
3. Transform plate boundary
Divergent Plate Boundaries
• Plates separate (move away from each other)
• Almost always occurs between two ocean plates.
• When ocean plates separate, new crust is formed through the
upwelling of magma. This is called sea-floor spreading.
– http://education.sdsc.edu/optiputer/flash/seafloorspread.htm
– Mid-oceanic ridges
– http://www.planetseed.com/files/flash/science/features/earth/livingplanet
/plate_boundaries/en/index2.html?width=570&height=475&popup=true
• Iceland, "the land of fire and ice", is being split by an
oceanic ridge that surfaces to create an oceanic island (left
and below) in the North Atlantic Ocean.
• Red triangles show Iceland's active volcanoes, including
Krafla. Reykjavik is Iceland's capital.
Divergent Plate Boundaries
• Something
interesting!!!
• Great Rift Valley in
Africa
• A continental plate is
breaking up!
• Convection currents
under the crust are
pulling this area apart!
•
http://www.youtube.com/watch?v=
w7Y2R4KBwvo
Convergent Plate Boundaries
• These plate boundaries can occur between:
– Oceanic and Continental plates
• “Subduction Zones”
•
http://www.planetseed.com/files/flash/science/features/earth/livingplanet/plate_boundaries/en/index2.html?wi
dth=570&height=475&popup=true
– Continental and Continental plates
• Mountain building
•
http://www.planetseed.com/files/flash/science/features/earth/livingplanet/plate_boundaries/en/index2.html?wi
dth=570&height=475&popup=true
Transform Plate Boundaries
• These are where plates move side-to-side.
• Trigger earthquakes
•
http://www.planetseed.com/files/flash/science/features/earth/livingplanet/plate_bound
aries/en/index2.html?width=570&height=475&popup=true
Your Task
• Complete the “checking your
understanding” questions and hand in.
• Complete the Plate Tectonic Map Activity