Theory of Plate Tectonics (1960)

Earth’s lithosphere

consists of rigid, but moving masses called

tectonic plates

Tectonic Plates

Lithosphere Outer shell of Earth that is

made of rigid crust and upper mantle

• Broken into moving

tectonic plates

2 Types of Lithosphere Oceanic Crust

Made up of the ocean floor

Continental Crust

Made up of continental landmasses.

Oceanic Crust vs. Continental Crust

CONVECTION

How do the plates move?!

Convection currents

• Unequal heating from the Earth’s core causes hotter magma to rise and cooler magma to sink down towards the core and heat up

http://youtu.be/ryrXAGY1dmE

https://www.youtube.com/watch?v=ryrXAGY1dmE

Plate Boundaries

There are 3 main ways that the plates

interact.

Points of interaction are called boundaries

3 Types of Plate

Boundaries…

1. Divergent Boundaries Where two plates are

moving apart,

magma rises and fills space between plates creating new

crust as it cools

CRUST IS GAINED

Divergent boundaries

2.Transform Boundaries

• Plates horizontally slide past one another

3. Convergent Boundaries

When two plates collide

CRUST IS LOST

•There are 3 types….

1. Continental + Oceanic Convergence=

SUBDUCTION ZONE

• When an oceanic plate collides with a continental plate

• One plate subducts under the other forming a trench

SUBDUCTION ZONE

2. Cont. + Cont. Convergence

• Two continental plates collide

• The plates crumple and uplift

• Form folded mountain ranges

2. Cont. + Cont. Convergence

3. Oceanic to Oceanic Convergence

• Trenches form as one plate subducts and melts

• Magma rises to the surface along the trench and slowly forms an island chain called an ISLAND ARC

SUBDUCTION ZONE

1. Divergent boundaries

• 1. Mid-ocean ridges: Underwater mountain range

that winds throughout the

Earth’s oceans. It is the 40,000

miles long

New Crust Forms Here As Crust is Pulled Apart

2. Rift Valley: When the crust is pulled or ‘rifted’ apart, valleys form with steep walls

Transform Boundaries

Earthquakes occur when

stress is too great from plates sliding, causing fracture to form in the crust

Example: San

Andreas Fault

Boundary Features

1. Volcanoes

Volcanoes Subduction and its

resulting gas chemical reactions, causes hot lava, ash and gas to

return to the atmosphere

2. Island Arc

Island Arc

Magma rises to the surface along the trench and slowly forms an island

Trench

3. Trench

Deep depression in the ocean floor caused by

subduction

4. (Folded) Mountains

Appalachian Mountains

Himalaya Mountains

Folded Mountains

Appalachian Mountains

As compressional force increases, folded mountains form

http://www.pbs.org/wgbh/aso/tryit/tectonics/#

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