Plate Tectonics. What is Plate Tectonics? The Earth’s crust and upper mantle are broken into...
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Transcript of Plate Tectonics. What is Plate Tectonics? The Earth’s crust and upper mantle are broken into...
Plate TectonicsPlate Tectonics
What is Plate Tectonics?What is Plate Tectonics?• The Earth’s crust and upper mantle are
broken into sections called plates.• Plates move around on top of the mantle
like rafts.
The CrustThe Crust• This is where we live!
• The Earth’s crust is made of:
Continental Crust
- thick (10-70km)- buoyant (less dense than oceanic crust) - mostly old
Oceanic Crust
- thin (~7 km)- dense (sinks under continental crust)- young
World PlatesWorld Plates
What are tectonic plates made of?What are tectonic plates made of?
• Plates are made of rigid lithosphere.
The lithosphere is made up of the crust and the upper part of the mantle.
What lies beneath the tectonic plates?What lies beneath the tectonic plates?
• Below the lithosphere (which makes up the tectonic plates) is the asthenosphere.
Plate MovementPlate Movement• “Plates” of lithosphere are moved around by
the underlying mantle convection currents.– Also, gravity pulls harder on the more dense
oceanic plates.
Questions...Questions...
• What causes plates to move?• How is a convection current
formed?
Questions...Questions...• What is the theory of plate tectonics?• What is the lithosphere?• What is the asthenosphere?• What is the connection between the
two?• What are the two types of plates?
Plate BoundariesPlate Boundaries
• Divergent
• Convergent
• Transform
Three types of plate boundary
• Seafloor Spreading– As plates move apart new material is erupted to
fill the gap
Divergent Boundaries
Age of Oceanic Crust
Courtesy of www.ngdc.noaa.gov
• Iceland has a divergent plate boundary running through its middle
Iceland: An example of continental rifting
• Two plate that are colliding • There are three styles of convergent
plate boundaries– Continent-continent collision– Continent-oceanic crust collision– Ocean-ocean collision
Convergent Boundaries
• Forms mountains, e.g. European Alps, Himalayas
1. Continent-Continent Collision
Himalayas
• Called SUBDUCTION
2. Continent-Oceanic Collision
• Oceanic lithosphere subducts underneath the continental lithosphere
• Oceanic lithosphere heats and dehydrates as it subsides
• The melt rises forming volcanism
• E.g. The Andes
Subduction
• When two oceanic plates collide, one runs over the other causing it to sink into the mantle forming a subduction zone.
• The subducting plate is bent downward to form a very deep depression in the ocean floor called a deep-sea trench.
• The deepest parts of the ocean are found along trenches. – The Mariana Trench is 11 km deep!
3. Ocean-Ocean Collision
• Where plates slide past each otherTransform Boundaries
Above: View of the San Andreas transform fault
Questions...Questions...• What are the three types of
boundaries?• What direction do plates go for
each?• Which boundary has a subduction
zone…what occurs at a subduction zone?
Side EffectsSide Effects• Earthquakes and
volcanoes transfer energy from Earth’s interior to the surface.• Earthquakes –
mechanical energy• Volcanoes – thermal
and mechanical energy