Austin Mills 6 th Period Mrs. Turner

1. Plate Tectonics Austin Mills6th Period Mrs. Turner

2. Continental Drift • Wegner’s Theory - hypothesized that the continents were slowly drifting around the Earth • Evidence - There are different continents now, which we’re connected in Pangaea, also fossil evidence on continents being similar to other continents • Problems – Geophysicist argued the ocean floor was not strong enough to hold the continents

3. Supercontinent Theory • Supercontinent Cycle - geologic cycle in which the Earth's continents alternatively merge into a single supercontinent • Pangaea and Panthalassa – Pangaea was the Supercontinent, and Panthalassa was the surrounding ocean • Accretion - process by which water vapor in clouds forms water droplets

4. Supercontinent Theory Continued • Rifting - linear zone where the Earth's crust and lithosphere are being pulled apart • Plate Movement Affecting Climate – By changing Ocean Currents • Example • Japan’s Coastline moving 13 feet

5. Theory of Plate Tectonics • Lithosphere – comprises of the crust and the portion of the upper mantle • Asthenosphere - comprises the crust and the portion of the upper mantle • How Plates Move – Convection moves the plates around • Three Types of Plate Boundaries - Divergent boundaries; Convergent boundaries; and Transform boundaries

6. Theory of Plate Tectonics Cont. • Isostasty - Equilibrium in the earth's crust such that the forces tending to elevate landmasses balance the forces tending to depress landmasses • Isostatic Adjustment – Earth can move up or down • Stress – Produces the Earthquakes and Volcanoes

7. Divergent Boundary • Sea Floor Spreading - extend the crust in a direction perpendicular to the fault trace. • Landforms – Mid-Ocean Ridges - Equilibrium in the earth's crust such that the forces tending to elevate landmasses balance the forces tending to depress landmasses • Example – Off South America Coast in Pacific Ocean

8. Paleomagnetism • Magnetic Reversals - North pole is transformed into a South pole and the South pole becomes a North pole. • Magnetic Symmetry - presence of identical parallel lines on each side of the Mid-Atlantic Ridge

9. Normal Faults • Normal Faults - Extend the crust in a direction perpendicular to the fault trace. • Related Landforms – Landforms with perfect faults in them where the plates are joining • Example – Great Rift Valley

10. Convergent BoundarySubduction Zones • Continental & Oceanic Crust - Oceanic crust is primarily composed of mafic rocks, or sima, which is rich in iron and magnesium. It is thinner than continental. • Mt Fuji – Japan • Mt. Osorno

11. Volcanoes • Magma - mixture of molten or semi-molten rock, volatiles and solids that is found beneath the surface of the Earth. • 3 Conditions magma forms • 1. Decrease in Pressure 2. Increase in Pressure 3. increase in the amount of water in the asthenosphere

12. Lava - molten rock expelled by a volcano during an eruption and the resulting rock after solidification and cooling • Volcano - opening, or rupture, in a planet's surface or crust, which allows hot magma, volcanic ash and gases to escape from the magma chamber. • Common Locations – Where Tectonic Plates smash into eachother. • Pacific Ring of Fire – Ring of active volcanoes encircling the Pacific Ocean

13. Pyroclastic Material • a cloud of ash, lava fragments carried through the air, and vapor. • Viscosity - measure of the resistance of a fluid which is being deformed by either shear stress or tensile stress. • How magma contents produce explosive eruptions • Explosive eruption occurs, from the magma building up inside, until it fills so much it finally explodes from being under pressure.

14. Types of Volcanoes • Shield - usually built almost entirely of fluid lava flows. They are named for their large size and low profile • Cinder Cones - bowl-shaped crater at the summit and only grow to about a thousand feet.

15. Composite - crater at the summit which contains a central vent or a clustered group of vents. • Caldera - most powerful and catastrophic types of volcanoes in a category by themselves.

16. Oceanic & Oceanic Crust • Outermost layer of Earth's lithosphere that is found under the oceans and formed at spreading centers on oceanic ridges Landforms Produced • Pacific Ocean

17. Collision Zones • Continental & Continental crust - When two oceanic plates collide, the younger of the two plates, because it is less dense, it will ride over the edge of the older plate. • Compression and uplift – Plates compressing and uplifting from one another • Landforms Produced • Himalayas • Cape Fold Mountains

18. Transform Boundary • Reverse Faults - Convergent zones are thrust or reverse faults, and divergent zones are normal faults • Strike-slip Faults - Strike-slip faults are vertical (or nearly vertical) fractures where the blocks have mostly moved horizontally. • Tension - two plates move against each other, building up tension, then releasing the tension

19. Sheer Stress - Shear stress causes two planes of material to slide past each other. This is the most common stress found at transform plate boundaries. • Related Landforms • Fault Block Mountains • Pennsylvania Appalachians • Utah • Grabens • Owens Valley

20. Earthquakes • Elastic Rebound - The release of strain energy by the abrupt movement of a fault with a resultant earthquake. • Seismology - branch of science concerned with earthquakes and related phenomena • Seismograph - instrument that measures and records details of earthquakes, such as force and duration. • Focus – The focus of an earthquake is the point in the earth where the earthquake rupture or fault movement actually occurred. • Epicenter -point on the earth's surface vertically above the hypocenter

21. Seismic Waves - waves of energy that travel through the core of the earth or other elastic bodies • Body Waves - waves of energy that travel through the core of the earth or other elastic bodies • Example : Longitudinal or Compression Waves

22. P Waves - move through material by squeezing and stretching the material in the same direction as the wave • Example – Compressional Waves • S Waves - moves as a shear or transverse wave, so motion is perpendicular to the direction of wave propagation • Example- Shear Waves

23. Surface Waves - a seismic wave that is trapped near the surface of the earth. • Ex. – Any wave trapped at the surface

24. Earthquakes not from movement wat plate boundaries - An intraplate earthquake is an earthquake that occurs in the interior of a tectonic plate, whereas an interplate earthquake is one that occurs at a plate boundary. • Ex. Missouri & Tennessee

25. Magnitude • The magnitude is a number that characterizes the relative size of an earthquake. • Example – Measuring on Richter’s Scale.

26. Intensity • The intensity is a number (written as a Roman numeral) describing the severity of an earthquake in terms of its effects on the earth's surface • The Mercalli intensity scale is a seismic scale used for measuring the intensity of an earthquake.

27. Tsunami • series of water waves caused by the displacement of a large volume of a body of water, typically an ocean or a large lake • Ex. Japan March, 2011

28. Other Related Landforms • Hot Spots • Hawaii • Dome Mountains • Castle Dome Mountains • Black Dome Mountain