Plate Tectonics

Benjamin Franklin in 1782 wrote The crust of the earth must be a float on a liquid interior Thus the surface of the globe would be capable of being broken by the violent fluid on which it rests.

Plate Tectonic Theory Plate Tectonic theory helped to explain the formation of the earth’s plates and continental drift

Plate Example Take a hard-boiled egg and crack its shell. The egg could be seen as a tiny model of the Earth. The thin shell represents the Earth's crust, divided into plates; within the shell is the firm but slippery mantle.

Plate Tectonic Theory Plate tectonic theory states that pieces of Earth’s lithosphere, called plates, move about slowly on top of the asthenosphere

The Force to move a Continent Convection is the process that moves Continental Plates As heat moves outward from the earth’s interior, convection currents rise in the mantle These currents spread out beneath the lithosphere, dragging plates with them

The Force to move a Continent As the rock cools, it sinks back to the bottom of the mantle, reheats and floats up again

Sea Floor Spreading Sea Floor Spreading takes place at the boundary of the oceanic plates As Convection pulls plates apart magma rises up threw new cracks. Magma piles up and solidifies, slowly forming a long chain of mountains on the ocean floor, called an oceanic ridge. This new rock land moves plates farther apart.

There are basically two types of plates. Oceanic plates Continental plates Not this kind!

What Are Oceanic Plates? Oceanic plates, as the name goes, are crusts which 'carry' the oceans above it. It is made of lighter but denser materials than the continental crust. This explains why they tend to subduct, or sink under continental crust when the two collide due to plate tectonics

What Are Continental Plates? Continental plates are crust that have continents (Large land masses) and some areas of ocean on them. They are usually named after the continents they 'carry'. Because they are made of lighter and less dense substances, they normally do not subduct.

What is Subduction? Just like cars on a road The earth’s plates sometimes have accidents CRASH SITE

What is Subduction? Subduction is the sliding of one plate under another.

Three Types Of Plate Movements Convergent Divergent Transform

Convergent Plate Movement When two plates move towards each other, they would collide. This is called a convergent plate movement.                        

When A Continental And Oceanic Plate Collide When a continental plate and an oceanic plate collide, The impact of the collision also causes cracks to form in the crust. The heat and pressure from the mantle forces the acidic magma to rise up these cracks. As the magma continues to rise up the cracks, it escapes onto the surface and solidifies, building up a volcano.

Transform Plate Movement A transform plate movement is one where two plates slide laterally past each other. However, movement is not smooth due to friction between the rocks of the two plates. Tension and pressure is built up at the transform boundary. When there is sufficient buildup of pressure, rocks in the plates break and get jerked apart. This results in earthquakes

Divergent Plate Movement A divergent plate movement occurs when two plates move away from each other. Magma from the mantle underneath the crust to rise up the surface to cool and solidify at the plate boundary.

Mid Ocean Shelf When you go swimming in a lake, you expect the middle to be the deepest part Not in the ocean Deep drop offs just of shore called ocean shelf

Mid Ocean Ridge A chain of under water mountains and Volcanoes just off the ocean shore

Mountain Building Fold mountains, such as the Appalachian Mountains in the eastern United States, and the Swiss Alps in Switzerland, form when two plates collide head on, and their edges crumble

The Result Sea floor spreading is force that moves the earth’s plates Carrying along with them the continents giving use the force required to complete continental drift theory.