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Chapter 21.1

http:// science.discovery.com/videos/100-greatest-discoveries-shorts-plate-tectonics.html. Chapter 21.1. Earth’s Interior and Plate Tectonics. OBJECTIVES!. By the end of this section you WILL be able to… Explain Earth’s interior structures

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Chapter 21.1

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  1. http://science.discovery.com/videos/100-greatest-discoveries-shorts-plate-tectonics.htmlhttp://science.discovery.com/videos/100-greatest-discoveries-shorts-plate-tectonics.html Chapter 21.1 Earth’s Interior and Plate Tectonics

  2. OBJECTIVES! By the end of this section you WILL be able to… • Explain Earth’s interior structures • Explain how the Earth’s appearance has changed over time • Describe geologic features found near tectonic plate boundaries

  3. IN RECENT NEWS!!!! • Earthquakes and tsunamis off the coast of Indonesia • http://dsc.discovery.com/videos/indian-ocean-plate-shift.html

  4. Earth’s interior has several layers • The topmost layer is known as the crust • This is where we live, continental crust • The crust is thin and makes up less than 1% of the Earth’s mass • Some of the crust is not livable because it is underwater, this is known as oceanic crust • Continental crust is thicker, but less dense than oceanic crust

  5. Beneath the crust is rock that is denser, known as the mantle • Humans have never drilled all the way to the mantle

  6. Earth’s interior gets warmer with depth • So why do caves tend to be cool? • Geologists believe that the mantle is much thicker and hotter than the crust • The mantle, for the most part is believed to be solid and rigid • At the deepest parts of the mantle, it is believed that its texture is “plastic-like” or “gummy”

  7. Earth’s core is nearly the same temperature as the surface of the sun • Earth’s core is probably made of iron and nickel • The inner core is solid metal • The outer core is liquid metal • Metals in the core do not turn to gas because of the immense pressure they are under

  8. Radioactivity contributes to high internal temperatures • Radioactive isotopes (elements with different numbers of neutrons) decay and release energy to become more stable

  9. http://dsc.discovery.com/videos/understanding-volcanoes-plate-tectonics.htmlhttp://dsc.discovery.com/videos/understanding-volcanoes-plate-tectonics.html Plate Tectonics • Did you ever notice anything interesting on the eastern coast of South America and the western coast of Africa? • Alfred Wegener hypothesized that these two continents were once a part of a larger landmass • This larger landmass is known as Pangaea • Fossil evidence supported this theory • The same kinds of animals were found even though they were oceans apart http://science.discovery.com/videos/100-greatest-discoveries-shorts-continental-drift.html

  10. At mid-oceanic ridges molten rock pours into the ocean and creates new rock • Minerals such as magnetite align with the Earth’s magnetic field • Roughly every 200,000 years the Earth’s poles switch, that is the North pole becomes the South pole and vice versa • http://dsc.discovery.com/videos/planet-earth-deep-ocean-sea-vents.html

  11. Earth has plates that move over the mantle • The lithosphere (litho-meaning rock) is made up of the crust and the upper portion of the mantle • The lithosphere is made up of roughly 7 large plates and several smaller ones called tectonic plates • Scientists estimate that these plates move from 1cm to 10cm per year

  12. Scientists do not know exactly what makes tectonic plates move • One hypothesis states that convection in the hot “plastic” portion of the mantle (asthenosphere) is responsible for the movement. See demo. Page 733 • The plates float on the top of the soft rock • Other scientists believe that the plates move due to gravity and the mass of the plates themselves

  13. http://dsc.discovery.com/videos/raging-planet-earthquake-landslide.htmlhttp://dsc.discovery.com/videos/raging-planet-earthquake-landslide.html Plate Boundaries • The theory of plate tectonics helps scientists predict geologic events such as earthquakes and volcanic eruptions • Earthquakes and volcanoes most commonly appear where plates meet • Mountains and rift valleys also occur at these places • Divergent and convergent. Difference?

  14. Oceanic plates dive beneath continental plates at convergent boundaries because of their density • In a subduction zone, oceanic crust dives below continental crust forming an ocean trench • Sometimes islands can form where convergent plates meet. • Magma rises to the surface and forms an island arc • Colliding plates can also crate mountains like the Himalayas (caused by the conversion of the Eurasian and Indian plates)

  15. http://dsc.discovery.com/videos/raging-planet-ring-of-fire.htmlhttp://dsc.discovery.com/videos/raging-planet-ring-of-fire.html The Ring of Fire http://dsc.discovery.com/videos/raging-planet-the-most-active-volcano-on-earth.html

  16. Plate movement can cause breaks in the lithosphere • Adjacent rocks can move past each other along these lines known as faults • When rock moves horizontally along plate boundary, the boundary is called a transform fault boundary • This movement can release a lot of energy and cause earthquakes • This is happening in California between the Pacific plate and the North American plate

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