PLATE TECTONICS The Unifying Theory of Earth Science

Plate Tectonics  Explains  Mountains  Volcanoes  Earthquakes  Oceans  Valleys  The surface of the earth

Plate Tectonics  Surface features are caused by processes within the earth  Central Idea of all Science  Observations can be explained as the result of regular, natural processes

Earth’s Interior  Studied by analyzing  Seismic Waves React differently depending on the material  Meteorites Same composition as the Earth’s interior

Layers of the Earth  Inner Core: solid iron and nickel  Outer Core: liquid iron and nickel  Mantle: dense, ultramfic magma and semi-molten rock  Crust: rigid outer layer of rock  Arranged by density

Crust  Very thin  Solid Rock  Oceanic Crust: 3-8 miles (5-12 km)  Continental Crust: miles (24-40 km)  Scientists can study directly  8 miles: deepest humans have ever gone  Continental crust is thicker and less dense

Mantle  Magma and rock miles below surface (160 – 2900 km)  Plastic rock  Solid that can bend and flow Toothpaste; silly putty  Very dense (ultramafic)  Very hot  Radioactive decay produces a lot of heat

Mantle  Lithosphere: upper mantle + crust  Asthenosphere: layer of mantle below lithosphere  Heat moves by  Convection: movement of heated particles  Conduction: transfer of energy through contact

Core  Outer Core  Liquid metal – iron an nickel Swirls to produce earth’s magnetic field  Inner Core  Solid due metal to enormous pressure

Continental Drift  Developed by Alfred Wegener ~ 1915  Continents move on the oceanic crust  All were once joined to form Pangaea  Supported by  Geologic formations (mountains etc.)  Fossils  Climate

 Gathered evidence from around the world  Died on an expedition to Greenland

Geologic Evidence  Similarities between rocks and mountains on each side of the Atlantic Ocean  Same composition of minerals  Evidence of similar forces and stresses

Fossil Evidence  Same species of worms, dinosaurs, ferns, etc found on distant continents

Climate Evidence  Glaciers and coal deposits show that climate of continents was very different in the past

Continental Drift  Not accepted at the time  No mechanism for movement  Continents are not hard enough to push through oceanic crust  Magnetic evidence added after Wegener’s death

Magnetic Evidence  Rocks record the magnetic field of the earth from when they first cool  What is cooling of magma called?  Magnetic minerals = compasses  Align with the poles in molten rock  Locked in place once rock crystallizes

Magnetic Evidence  Rocks less than 800,000 years old point toward North Pole  Rocks 800,000 to 2,500,000 years old point in opposite direction  Normal and reversed polarity

Magnetic Reversals

Magnetic Evidence  Rocks from different continents did not agree on location of the poles  Either the poles moved, the continents moved, or both  Only the continents moved while the poles remained stationary

Magnetic Evidence  Continents seemed to move over history  Wegener’s theory began to become popular  Still no mechanism for the movement or explanation about how continents could push through oceans