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!!