Plate Tectonics

4 Main Layers• The earth is divided into fourfour main layers

based on composition and state of matter.

A. Inner Core

• Solid- It is very hot, but it is a solid because it is under so much pressure from all of the layers above it.

• Made of SolidSolid IronIron - - very dense dense metal

B. Outer Core

• Liquid

• Made of Iron and Iron and NickelNickel

C. Mantle• Liquid- peanut

butter-like consistency. It can flow and move, but is almost solid in places.

• Made of lighter elements.

• Convection Convection CurrentsCurrents occur in the mantle.

D. Crust

• Solid, rocky.

• We live on the crust

• Made of mostly Oxygen and SiliconOxygen and Silicon.

• Made up of rocks and sediments.

• Divided into PlatesPlates that move around on the mantle.

II. Convection in the Mantle• A. Since the mantle is

liquid, the material can flow. Convection Convection currentscurrents cause the material to move around.

• B. Convection Current- when material is heatedheated, it becomes less denseless dense and rises. Then it coolscools, becomes more more densedense and sinks again.

III. Plate Tectonics• A. The solid, outer part of the crust and

upper mantle is called the LITHOSPHERE.

• B. The lithosphere floats on the liquid-liquid-like part of the mantlelike part of the mantle, which is called the ASTHENOSPHERE.

The lithosphere is broken into sections called PLATES. The plates get carried along as the asthenosphere moves due to convection currentsconvection currents, like a raft in a river.

IV. Alfred Wegener• A. Alfred Wegener believed the crust of

the earth moved as early as the 1800s, but he couldn’t explain what made them move. He called his idea CONTINENTAL DRIFT. He thought the plates moved because of 4 reasons:

• # 1- the shapesshapes of the continents look like they fit together like a puzzle.

• PangeaPangea- supercontinent when all the continents joined together.

• # 2- FossilsFossils on on continents continents

besidebeside each other each other match up.match up.

• # 3- RockRock types and Mountain rangesMountain ranges on continents beside each other match upmatch up.

• # 4- WarmWarm climateclimate fossils are found in Antarctica, and there is evidence of glaciersglaciers in places that are now tropical. A possible explanation is the continents moved.

Glossipteris- fern fossil found in Antarctica