Tectonic Plates

Plate Tectonics

• Pieces of the lithosphere that move around• Each plate has a name• Fit together like jigsaw puzzles• Float on top of mantle similar to ice cubes

in a bowl of water

Continental Drift• Alfred Wegener 1900’sContinents were once a single land mass that drifted apart.

• Fossils of the same plants and animals are found on different continents

• Called this supercontinent Pangea, Greek for “all Earth”

Pangea

Evidence of Pangea

Sea Floor Spreading

Sea Floor Spreading

• Mid Ocean Ridges – underwater mountain chains that run through the Earth’s Basins

• Magma rises to the surface and solidifies and new crust forms

• Older Crust is pushedfarther away from the ridge

Two Volunteers to Demonstrate

Sea Floor Spreading

How Plates Move

http://pubs.usgs.gov/gip/dynamic/unanswered.html

Different Types of Boundaries

Animations

Divergent Boundary – Arabian and African Plates

Arabian Plate

African Plate

Red Sea

Divergent Boundaries

• Places where plates are coming apart• Forms a central valley called a rift• Earthquakes occur along the faults• Volcanoes form where the magma reaches the

surface.• Plate separation is a slow process. For example,

divergence along the Mid Atlantic ridge causes the Atlantic Ocean to widen at only about 2 centimeters per year.

Animation

Divergent Boundary – Iceland

Divergent Boundary - Oceanic

Divergent Boundary - Continental

Convergent Boundary• Places where plates crash

or crunch together

• Collisions are very slow and last millions of years

• Mountains, earthquakes, and volcanoes form where plates collide

• Rockies in North America, the Alps in Europe, the Pontic Mountains in Turkey, the Zagros Mountains in Iran, and the Himalayas in central Asia were formed by plate collisions

Convergent Boundary – Indian and Eurasian Plates

Indian Plate

Eurasian Plate

Himalayas

Transform Boundaries• Places where plates slide past each other

• Marked in some places by linear valleys where rock has been ground up by the sliding

Transform Boundary – San Andreas Fault in California

Subduction Zone• When two oceanic plates collide, the younger of the two plates,

because it is less dense, will ride over the edge of the older plate. 

Review

• Name the 3 main layers of the Earth.• What is a tectonic plate?• What was Pangea?• What is Sea-Floor spreading?• Name the three different types of plate

boundaries and one location on Earth for each one

1. In your basket you should have wax paper, a plastic spoon, fruit roll-up and a graham cracker

2. I will come around and put a small amount of icing on your wax paper.

1. Divergent Boundary– Notice how the

frosting is exposed and pushed up where the plates are separated?

– This is how magma comes to the surface where plates are moving apart at divergent boundaries

– When plates begin to pull apart

1. Continent-Oceanic Convergent Boundary

– The graham cracker represents the continental crust, which is thicker and less dense than oceanic crust (fruit roll-up).

– After you complete Step 3, the oceanic plate will be subducted below the continental one.

1. Continent – Continent Convergent Boundary

– This is when two continents collide

– Notice how the wet edges crumble?

– This is how mountains are made at convergegnt plate boundaries.

– When continents move toward each other, there is nowhere for the rock to go but up.

Snack Tectonics

1. Transform Boundary