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’s Continents 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”
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 pushed farther away from the ridge Two Volunteers to Demonstrate
Divergent Boundary –Arabian and African Plates
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
Convergent Boundary•Places where plates crash orcrunch together•Collisions are very slow andlast millions of years•Mountains, earthquakes, andvolcanoes form where platescollide•Rockies in NorthAmerica, the Alps inEurope, the Pontic Mountainsin Turkey, the ZagrosMountains in Iran, and theHimalayas in central Asiawere formed by plate
Convergent Boundary – Indian and Eurasian Plates Himalayas
Transform Boundaries•Places where plates slide past each other•Marked in some places by linear valleyswhere 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 cracker2. 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.