How do geologic processes change the shape of Earth’s surface? - PowerPoint PPT Presentation

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How do geologic processes change the shape of Earth’s surface?

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How do geologic processes change the shape of Earth’s surface?

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  1. How do geologic processes change the shape of Earth’s surface?

  2. What do Earth’s layers consist of? • Crust • Mantle • Core

  3. Crust • Layer of rock that forms Earth’s “outer skin” • Includes rocks, mountains, soil, water • Thin: 5-40km thick • 870◦C

  4. 2 Types: • Continental: Dry land (granite) • Oceanic: Ocean (basalt)

  5. Mantle • Layer of hot rock • 2,900km thick • 2,200◦C

  6. 2 Sub layers: • Lithosphere • Asthenosphere

  7. Lithosphere • Rigid • Much like the crust • 100km thick • Floats on top of the asthenosphere

  8. Asthenosphere • Plastic like • Material can flow slowly like hot tar • Has both solid & liquid qualities

  9. Core • Consists of iron & nickel • 5,000◦C • Makes up 1/3 of Earth’s mass

  10. 2 sub layers: • Outer Core • Inner Core

  11. Outer Core • Layer of molten material • Covers the inner core • 2,250km thick

  12. Inner Core • Dense solid ball of metal • Extreme pressure does not allow Fe & Ni to spread out to form liquid • 1,200km thick

  13. What are the 3 ways that heat is transferred? • Radiation • Conduction • Convection

  14. Radiation • Heat transferred by EM waves through space • EX: Sitting by the fire!

  15. Conduction • Heat transferred through direct contact • EX: Spoon in hot chocolate

  16. Convection • Heat transferred through a fluid movement of either a gas or liquid • EX: Chicken noodle soup heating on the stove!

  17. Which of these do you think happens in Earth’s mantle? • Convection! • Convection currents flow in the asthenosphere • Heated material rises to the top of the mantle (lithosphere), cools, then sinks back to the bottom

  18. What does the Theory of Continental Drift state? • 1910 • Alfred Wegener hypothesized that all the continents had once been a single landmass • A super continent called “Pangaea”

  19. Scientific Method • Problem/Question • Research • Hypothesis • Experiment • Analyze • Conclude

  20. Supporting Evidence of Wegener’s theory • Landforms • Fossils • Climate

  21. Landforms • South America & Africa have similar mountain ranges • Europe & North America have similar coal fields

  22. Fossils • Fossil-any trace of an ancient organism that has been preserved in rock • Mesoaurus fossils have been found in places now separated by oceans • Glossopteris (fern like plant) fossils have been in rocks in Africa, South America, Australia, India, & Antarctica

  23. Climate • Spitsbergen Island lies in the Arctic Ocean, north of Norway, covered with ice • Fossils of tropical plants have been discovered under the ice! • South Africa-deep scratches in rock indicate glacier movement there!!!

  24. REJECTED!!! • Scientists rejected Wegener’s theory of continental drift • Most scientists in the 1900’s believed the Earth was cooling & shrinking causing the continents to move & mountains to form

  25. Is sea-floor spreading like continental drift? • 1960 • Harry Hess, when studying the mid-ocean ridge, proposed that the ocean floor moved like a “conveyer belt” moving the continents with them • Sea-floor spreading is the continually adding to the ocean floor

  26. Sea-floor Spreading • Molten material rises up from the mantle • It spreads out, cools off, & hardens • It pushes the older rock out on both sides of the ridge • New crust forms!

  27. Wait a minute…! • Hess’ idea of sea floor spreading caused scientists to revisit Wegener’s idea of continental drift!

  28. So where does all of the old crust being pushed out go? • Subduction: It is the process by which the ocean floor sinks beneath a deep ocean trench & back into the mantle

  29. Sea Floor Spreading & Subduction… • Can change the shape of the oceans! • The ocean floor is renewed every 200 million years (That’s the time it takes for new crust to form, move across the ocean floor, & sink into a trench)

  30. What is the Theory of Plate Tectonics? • 1965 • Tuzo Wilson proposed that the cracks in Earth’s surface were broken into section called “plates” • He combined the idea of sea-floor spreading, Earth’s plates, & continental drift into a single theory

  31. Plate Tectonics Theory • A geological theory that states that pieces of Earth’s lithosphere are in constant, slow motion driven by convection currents in the mantle

  32. How does it work? • Lithospheric plates float on top of the asthenosphere • Convection currents rise in the asthenosphere & spread out under the plates • No plate can move without affecting another plate • Plates move extremely slow at 1-10cm per year

  33. As the plates move, collide, or pull apart…it produces GREAT changes on Earth’s surface

  34. Like volcanoes, earthquakes, mountain ranges, & deep sea trenches

  35. 3 types of plate boundaries: • Transform • Divergent • Convergent

  36. Transform • Place where 2 plates slip past each other moving in opposite directions • Earthquakes often occur along these boundaries

  37. Divergent • Place where 2 plates move apart • Most occur at the mid-ocean ridge • Some occur on land creating a “rift valley” which is a deep valley • Great Rift Valley in Africa is 3,000km long

  38. Convergent • Place where 2 plates come together • Collisions of 2 plates can cause: • Oceanic to oceanic • Oceanic to continental • Continental to continental • When 2 plates collide the more dense plate comes out on top!

  39. Continental – Continental: mtns form • Oceanic – Continental: Oceanic dives under the continent • Oceanic – Oceanic: the less dense of the 2 sinks into the trench

  40. What is an earthquake? • Shaking & trembling that results from the movements of rock beneath Earth’s surface • The movement of Earth’s plates creates stress that squeezes/pulls the rock in the crust

  41. Stress • A force that acts on rock to change its shape & volume • 3 types of stress • Shearing • Tension • Compression

  42. Shearing • Stress that pushes a mass of rock in opposite directions

  43. Tension • Stress that pulls on the crust stretching the rock so it becomes thinner in the middle

  44. Compression • Stress that squeezes rock until it folds or breaks

  45. What is a fault? • A break in the crust where slabs of rock slip past each other • Faults usually occur along plate boundaries • 3 types: • Strike-slip • Normal • Reverse