2Plate TectonicsThe Theory of Plate Tectonics is a theory that describes the formation, movements, and interactions of Earth’s lithospheric plates that move on the asthenosphere.
3Theory of Plate Tectonics The Theory of Plate Tectonics explains why earthquakes and volcanoes are likely to occur in particular locations and how new crust forms along the ocean floor.
4Earthquakes and volcanic activity occur primarily at the location of plate boundaries. Plate boundaries are where 2 plates are pushing toward, pulling away, or sliding past each other. The strain and friction causes fractures in the earth, where earthquakes occur and where the fractures allow molten rock to flow to the surface.
5Evidence for plate tectonics was also found in igneous rocks which recorded the direction of Earth’s magnetic field.
6Mid-ocean ridge is a long chain of volcanic mountains on the ocean floor with a deep central valley. The mid-ocean ridge always shows the magnetic orientation of the North and South poles.
7Mid-ocean RidgeA pattern of bands on either side of the mid-ocean ridge show the changes in magnetic orientation.
8Mid-ocean RidgesRocks at the center of the mid-ocean ridge are the youngest.Mid-ocean ridges are boundaries where plates are moving apart.(so the farther the rocks are from the mid-ocean ridge the the rocks are).older
93 Main Hypothesis Which Cause of Plate Movement: Mantle Convection,Ridge Push, andSlab Pull
10Mantle Convection:Mantle Convection - the transfer (convection) of heat from Earth’s inner and outer cores moves the plates (like a convection belt)
11Ridge PushRidge Push – occurs at the Mid-ocean Ridges- The hot molten magma rises up at the mid-ocean ridges and as it cools and hardens into a denser rock, the rock pushes out and slides down the ridge, allowing more new hot molten material to flow out of the mid-ocean ridge.
12Slab Pull – occurs at a subduction boundary. Slab Pull - Scientists believe this Slab Pull is the greater factor out of the three theories.Slab Pull – occurs at a subduction boundary.- The denser, heavier plate sinks underneath the other less dense plate. The edge of the subduction plate is much colder and heavier than the mantle, so it continues to sink and pull the rest of the plate along down with it.
13CONTINENTAL DRIFTAlfred Wegener proposed a hypothesis called Continental Drift which said the continents have drifted, or moved from one location to another over time.
14Continental Drift was proven by: The shapes of the continents seem to match up (fit together like puzzle pieces)
15Continental Drift was proven by: Certain fossils are on different continentsExample: Mesosaurus – reptile that lived about 270 mya, fossils found only in parts of South America and Africa – could have only happened when the 2 continents were once joined).
16Continental Drift was proven by: Mountain chains found on 2 continents and would have matched up if the continents were joined.Example: Appalachian Mountains – run along the eastern coast of US and through Great Britain.
17Pangaea – the giant supercontinent that existed about 200 mya.
22Divergent Boundary Plates are moving apart Occurs at Mid-ocean Ridges and at Rift Valleys (seafloor spreading)Rift valley = deep valleys at the center of a mid-ocean ridge.Volcanic activity (underwater) and earthquakes take place along this boundary.Hot springs also come up from hydrothermal vents on the ocean floor.
24Divergent Boundary East Pacific Rise (Pacific Ocean) Transform faults run along the mid-ocean ridges
25Convergent Boundary Plates are moving toward each other. 2 Types of Convergent BoundariesSubductionCollision
26Convergent Boundary Subduction occurs at: ocean to ocean plate moving toward each otherOcean to continental plates moving toward each otherOceanic crust is denser than continental crust, so oceanic crust will subduct underneath the continental plateDeep sea trenches are formedVolcanic island arcs are formedEarthquakes occur
27Convergent Boundary - Subduction Islands of Indonesia (ocean to ocean)Mariana Islands (ocean to ocean)Mariana Trench (Pacific plate moving underneath the Philippine Plate)
28Convergent Boundary - Subduction Mariana Islands –Philippine and Pacific plates colliding (ocean to ocean)
29Convergent Boundary Collision Boundary occurs at: Continental to continental plate moving towards each otherBuilds high mountain chainsEarthquakes occur along these boundaries
31Convergent Boundary - Collision Our Appalachian Mountains were also formed this way long ago, but are not currently being formed. (rounded mountain tops – been weathered and eroded down)
32Convergent Boundary - Collision Himalaya Mountains (sharp and jagged peaks)
33Transform Boundary 2 plates are sliding past each other. Earthquake activity occurs here
34Transform Boundary San Andreas Fault (in California) Movement isn’t the same along all parts of the fault. Some parts can move up to 5cm/yr, while others haven’t moved in over a century.North Anatolian Fault (in Turkey)Fracture zones along mid-ocean ridges