PLATE TECTONICS

Plate Tectonics The Theory of Plate Tectonics states that the surface of the earth is broken up into a few large plates and many smaller ones

Plate Tectonics

These solid plates float on the semisolid mantle The plates interact with each other in three major ways: –Pull away from each other “Divergent” –Move towards each other “Convergent” –Slide past each other “Transform Fault”

Plate Tectonics Divergent Examples: –Atlantic Ocean Mid-Ocean Ridge –Red Sea –Iceland –African Rift Valley

Plate Tectonics

Convergent –Oceanic- continental –Oceanic-Oceanic –Continental- Continental

Plate Tectonics Oceanic-Continental –Ocean plate sinks under the continental plate Subduction Forms a Trench Forms a Continental Volcanic Arc Earthquakes –Examples: West coast of the United States and South America

Plate Tectonics Oceanic-Oceanic –One Ocean plate sinks under the other Subduction Forms a Trench Forms a Volcanic Island Arc Earthquakes –Examples: Japan Caribbean Islands

Plate Tectonics Continental-Continental –Continent crashes into Continent No subduction after Continents hit. Forms Mountains Earthquakes –Examples: Himalayas Appalachia Urals

Plate Tectonics Transform Fault –One plate grinds past another Deforms the surface Earthquakes –Examples: San Andreas Fault Anatolian Fault – Turkey Chaman Fault - Pakistan

Plate Tectonics Evidence for Plate Tectonics –Paleomagnetism The natural remnant magnetism in rock bodies When rock solidifies from the molten state the magnetic crystals that form align with the magnetic field of the earth. The Earths magnetic field has flipped many times in the past. This shows up as alternating strips of polarity in the rocks of the seafloor.

Plate Tectonics Evidence for Plate Tectonics –Earthquake patterns Most earthquakes happen along plate boundaries and happen at different depths according to the type of boundary. –Ocean Drilling Data on age of seafloor crust supports seafloor spreading. –Hot Spots Hawaiian Island chain supports the idea that the plates are moving.

Plate Tectonics Mechanisms of Plate Tectonics –Slab-Pull and Ridge-Push Slab-Pull – As the slab sinks down into the mantle it pulls the rest of the plate after it. Ridge-Push – The push of the magma from the mantle at the ridge causes the material at the top of the ridge to fall down the sides of the ridge. –Mantle Convection Currents of rock moving in the earths interior over millions of years. –Cool rock sinking – Hot rock rising