Download Plate Tectonics

Plate Tectonics
. Theory of how the continents moved apart ( Continental Drift) driven bySeafloor Spreading
. Tectonics - important motions of Earth’s Crust
. Plates- Make up the crust
Tectonic Plates
. Crust made up of 12 or so plates
 study of movement/ formation of these plates
Continental Drift
. Theory that all continents are moving across Earth’s surface
Evidence:
1. Fossils
2. Glacial Striations/Grooves
3. Rock deposits
4. Jigsaw puzzle of Modern Continents
Creation Of Continental Drift
. Alfred Wegener - 1912
. Continents were together at one point ---> “ Pangea” -- “All Earth”
. Over millions of years ---> continents split apart
. Wegener discredited because he was a meteorologist and he could not explain a force for
moving plates
Wegener Revisited
. 1960- Harry Hess introduced a possible force to Wegener’s theory
. During WWII - he concluded that the magma may be surfacing at “ Mid Ocean ridhes” causing
sea-floor spreading
. Sea floor spreading ---> Convection in mantle is driving force
Moving Continents: Convection
. Lithosphere ( Crust) - approximately 100 km. Thick
. Crust is thicker under continents than Ocean basins
. Lithosphere “ floats” on the upper layer of the mantle - Asthenosphere
. Heated magma rises from core--> Convection currents move the plates of the lithosphere
around
Seafloor Spreading
. Plates moving apart at center of Atlantic oceans and other locations
Evidence:
. Separation shows us rocks on both sides of ridge have:
. Similar composition and age
. Similar mineral alignment of magnetic particles towards normal and reverse polarity
. Distinct shape of ocean floor with the ridge
Earth’s Layers and the Mohorovich Interface( Moho)
Four layers: Crust
Mantle
Outer Core
Inner Core
. Moho. - point that separates liquid mantle from solid crust above
Tectonic Features
Divergent - rift valleys and ridges, fault block mountains, volcanic mountains
. New crust forming
. Frequent but weak earthquakes
Ex. Mid- Atlantic Ridge
Convergent
. Subduction Zone
. Trenches, folded mountain ranges, volcanic and mountain ranges, island arcs and fault block
mountain ranges
. Strong deep earthquakes
. Old crust is being pushed under and remelted ( Re-cycled)
Ex. Marianas Trench
Transform
. Fault Block mountains
. Frequent strong earthquakes
Ex. San Andreas Fault
. A lot of friction
. No crust made or destroyed
Plate to Plate Convergence
Ocean- Continent: More dense oceanic gets sub-ducted ( pushed underneath)
Ocean- Ocean- Older, colder , denser of 2 plates gets subducted
Continental- Continental: More dense, older of 2 gets partially subducted
. Leads to high folded of fault block mountains ( ex. Himalayas)