Plate Tectonics
Geological Forces• There are 3 types of force that are involved
in the movement of large areas of crust.
❖ Compression ~ force that pushes land
masses together
❖ Tension ~ force that pulls land masses
apart
❖ Shear ~ force applied when land masses
slide past each other horizontally
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Ocean Topography
• Ocean Ridges- underwater mountains;
longest mountain range on Earth
• Trenches- Narrow depression in the
seafloor
• How do they form?
Seafloor Spreading
• Seafloor spreading: when new ocean
crust is formed
• Formation of new crust
➢ Magma is forced towards the surface
➢ As the ridge separates the magma fills
the gap created
➢This will continue to happen and new
ocean crust will continue to generate
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Plate Tectonics
• Plates: huge, mobile pieces of crust that
cover the Earth.
➢Move because of convection currents
➢Energy (thermal) comes from the core
(internal) to drive plate movement.
➢There are 3 types of plate boundary
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Divergent Boundaries
• Divergent Boundaries- two tectonic
plates move apart
➢Occur in Ocean ridges
➢Seafloor spreading
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Transform Boundaries
• Transform Boundaries
➢Plates slide horizontally
➢Responsible for most earthquakes
➢Ex. San Andreas Fault
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Look at California…
What is so interesting?Transform boundary at the San Andreas Fault
Convergent Boundaries
• Convergent Boundaries: 2 tectonic plates
move towards one another
➢When 2 plates collide the denser plate
descends below the other plate
➢This process is called subduction
➢There are 3 types of convergent plate
interaction…
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Convergent Boundaries
• Oceanic-Oceanic:
➢Forms an ocean trench
• Oceanic-Continental:
➢Oceanic plate is more dense so it is
subducted. Produces trenches & volcanic
arcs
• Continental-Continental
➢The crust are unable to subduct due to rocks
so the continents collide and form massive
mountain regions. 10
Convergent Boundaries
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11/21/2019 Free Template from www.brainybetty.com 12
Know Your Boundaries!!
Lithosphere divided into 10
major tectonic plates—
know the continental ones
and the Pacific plate!
Plate Movement
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Ring of Fire!!