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Plate Tectonics

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FC: Plate Tectonics | by Noel Hofseth

1: Part 1 (Chapters 10 & 11)

2: The main problem with Wegener's hypothesis of Continental Drift was the lack of a mechanism. He did not have an explanation for how the continents moved. | Wegener's theory of Continental Drift | Wegener's theory was that the continents had once been joined, and then over time had drifted apart. The coasts of the continents surrounding the Atlantic ocean could, if the continents were moved closer, fit together like a jigsaw puzzle.

3: Wegener's Supercontinent Theory | The supercontinent cycle is a geologic cycle where the Earth's continents alternatively merge into a single supercontinent, split into numerous continents, then merge again. | Pangaea is a supercontinent that existed during the Paleozoic and Mesozoic eras about 250 million years ago, before the component continents were separated. Panthalassic Ocean, was the vast global ocean that surrounded the supercontinent Pangaea .

4: Accretion is a process by which material is added to a tectonic plate or a landmass | Rifting is where the Earth's crust and lithosphere are being pulled apart | Examples Madagascar

5: Theory of Plate Tectonics | The lithosphere includes the crust and the uppermost mantle, which constitute the hard and rigid outer layer of the Earth. | The asthenosphere is a portion of the upper mantle just below the lithosphere that is involved in plate tectonic movements and isostatic adjustments. | Plates at our planet’s surface move because of the intense heat in the Earth’s core that causes molten rock in the mantle layer to move. It moves in a pattern called a convection cell that forms when warm material rises, cools, and eventually sink down. As the cooled material sinks down, it is warmed and rises again.

6: 3 Plate Boundaries Divergent, Convergent, and Transform | Isostatsy is the state of gravitational equilibrium between the earth's lithosphere and asthenosphere such that the tectonic plates "float" at an elevation which depends on their thickness and density. | Isostatic Adjustment is the rise of land masses that were depressed by the huge weight of ice sheets during the last glacial period. | Stress in the lithosphere provides strong constraints on the forces acting on the plates.

7: Divergent Boundary | Sea-Floor Spreading- process that occurs at mid-ocean ridges, where new oceanic crust is formed through volcanic activity and then gradually moves away from the ridge. | Paleomagnetism | Magnetic Reversals- A change in the Earth's magnetic field resulting in the magnetic north being aligned with the geographic south, and the magnetic south being aligned with the geographic north. | Magnetic Symmetry- When the sea-floor spreads, it's symmetrical.

8: Normal Faults- a planar fracture or discontinuity in a volume of rock. Energy release associated with rapid movement on active faults is the cause of most earthquakes, such as occurs on the San Andreas Fault, California.

9: Convergent Boundary | Subduction Zones | Continental + Oceanic Crust Layer of igneous, sedimentary, and metamorphic rocks which form the continents and the areas of shallow seabed close to their shores. | Volcanic landforms are controlled by the geological processes that form them and act on them after they have formed. Thus, a given volcanic landform will be characteristic of the types of material it is made of, which in turn depends on the prior eruptive behavior of the volcano. | Oceanic + Oceanic Crust Part of Earth's lithosphere that surfaces in the ocean basins. Oceanic crust is primarily composed of mafic rocks, or sima, which is rich in iron and magnesium.

10: Collision Zones | Continental + Continental Crust Convergent margins neither plate subducts. The two plates converge, buckle, fold, and fault to form complex mountains ranges of great height. | Compression and Uplift Refers to a set of stresses directed toward the center of a rock mass, and lifts upwards. | The Himalayas, for example, were raised by the compression that accompanied collision of the Indian plate with the Eurasian plate.

11: Transform Boundary | Reverse faults are exactly the opposite of normal faults. If the hanging wall rises relative to the foot wall, you have a reverse fault. | Strike-slip faults, the rupture is nearly vertical and during an earthquake one side slides past the other. | Tension separates rock. Unlike gravity or normal fault, since strata may reappear on other side of gap caused by fall of intervening section to lower level when fissure opened.

14: Part 2 (Chapter 12)

15: Earthquakes | Elastic Rebound theory is an explanation for how energy is spread during earthquakes. Plates on opposite sides of a fault shift slowly. | Seismology is the scientific study of earthquakes and elastic waves. | A Seismograph is a sensitive instrument that detects seismic waves.

16: Focus is the depth at which an earthquake occurs. | Epicenter is the point on the Earth's surface that is directly above the hypocenter or focus, the point where an earthquake or underground explosion originates. | Seismic Waves | Body waves travel through the interior of the Earth. The density and modulus, in turn, vary according to temperature, composition, and phase. This effect is similar to the refraction of light waves.

17: P waves are pressure waves that are the initial set of waves produced by an earthquake. In air, they take the form of sound waves, hence they travel at the speed of sound. | S waves typically follow P waves during an earthquake. They can only travel through solids. Depending on the direction, the wave can take on different surface characteristics. | Surface waves are analogous to water waves and travel along the Earth's surface. They can be the most destructive type of seismic wave.

18: Analysis of the Earth's internal structure is made possible because earthquakes produce vibrations called seismic waves. These waves travel through the interior of the Earth that can be measured. | Almost all earthquakes occur at the edges of the crustal plates. The constant bumping, grinding, and lateral movement along crustal boundaries can create sudden movements that result in earthquakes. Each of the three types of plate boundaries, convergent, divergent, and transform has a distinctive pattern of earthquakes.

19: Magnitude scales used in seismology to describe the size of an earthquake. | Intensity describes the perceived surface ground shaking and damage caused by an earthquake. | Mercalli scale is a seismic scale used for measuring the intensity of an earthquake. It measures the effects of an earthquake, and is distinct from the moment magnitude which is a measure of the energy released.

20: A tsunami is a series of water waves caused by the displacement of a large volume of a body of water, typically an ocean or a large lake. Earthquakes, volcanic eruptions and other underwater explosions, landslides, meteorite impacts and other disturbances above or below water all have the potential to generate a tsunami. | A destroyed town in Sumatra after being hit by a tsunami, caused by the 2004 Indian Ocean earthquake

21: Part 3 (Chapter 13)

22: Volcanoes | Magma is a mixture of molten rock, volatiles and solid that is found beneath the surface of the Earth. | Three conditions under which magma forms: 1. decrease in pressure 2. increase in pressure 3. increase in the amount of water in the asthenosphere

23: Lava is expelled by a volcano during an eruption and the resulting rock after solidification and cooling. | A volcano is an opening in a planet's surface or crust, which allows hot magma, volcanic ash and gases to escape from below the surface.

24: List of common volcanoes and The Ring of Fire: Mediterranean, West Asia, Africa, Red Sea, Middle East, Indian Ocean, New Zealand to Fiji, Melanesia, Australia, Indonesia, Philippines, Southeastern Asia, Japan, Taiwan, Marianas, Kuril Islands, Kamchatka, Mainland Asia, Alaska, Canada, Western USA, Hawaii, Pacific Ocean, Mexico, Central America, South America, West Indies, Iceland, Arctic Ocean, Atlantic Ocean, and Antarctica

25: Pyroclastic materials are fire fragmented materials which are formed during a volcanic eruption. | Viscosity is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. | Magma contains gas dissolved in the liquid, but the gas forms a separate vapor phase when pressure is decreased as magma rises toward the surface of the Earth.

26: Shield Volcanoes are built almost entirely of fluid lava flows. They are named for their large size and low profile, resembling a warrior's shield. This is caused by the highly fluid lava they erupt, which travels farther than lava erupted from more explosive volcanoes. | Cinder Cone Volcanoes are steep conical hills of volcanic fragments that accumulate around and downwind from a volcanic vent. Cinder cones range in size from tens to hundreds of meters tall. Cinder cones are made of pyroclastic material.

27: A Composite Volcano is built up by many layers of hardened lava, tephra, pumice, and volcanic ash. Unlike shield volcanoes, composite volcanoes are characterized by a steep profile and periodic, explosive eruptions. The lava that flows from them typically cools and hardens before spreading far due to high viscosity. | Caldera Volcanoes are cauldron-like features that usually form by the collapse of land following a volcanic eruption, such as the one at Yellowstone National Park.

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  • Title: Plate Tectonics
  • Mixbook : Plate Tectonics by : Noel Hofseth
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