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Introduction to Planet Earth
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- 2. The Layers ofthe Earth Š Copyright 2006. M. J. Krech. All rights reserved.
- 3. The Four Layers The Earth is composed of four different layers. The crust is the layer that you live on, and it is the most widely studied and understood. The mantle is much hotter and has the ability to flow. The outer core and inner core are even hotter with pressures so great you would be squeezed into a ball smaller than a marble if you were able to go to the center of the Earth!
- 4. The Crust TheEarth's Crust is like the skin of an apple. It is very thin in comparison to the other three layers. The crust is only about 5-30 km thick under the oceans (oceanic crust) and about 50-100 km thick under the continents (continental crust).
- 5. The Crust Thecrust is composed of two rocks. The continental crust is mostly granite. The oceanic crust is basalt. Basalt is much denser than the granite. Because of this the less dense continents ride on the denser oceanic plates.
- 6. The Mantle TheMantle is the largest layer of the Earth. The middle mantle is composed of very hot dense rock that flows like asphalt under a heavy weight. The movement of the middle mantle (asthenosphere) is the reason that the crustal plates of the Earth move.
- 7. Convection Currents Themiddle mantle "flows" because of convection currents. Convection currents are caused by the very hot material at the deepest part of the mantle rising, then cooling and sinking again --repeating this cycle over and over.
- 8. Convection Currents Thenext time you heat anything like soup or water in a pan you can watch the convection currents move in the liquid. When the convection currents flow in the asthenosphere they also move the crust. The crust gets a free ride with these currents, like the cork in this illustration. ! ! Safety Caution: Donât get your face too close to the boiling water!
- 9. The Outer Core The core of the Earth is like a ball of very hot metals. The outer core is so hot that the metals in it are all in the liquid state. The outer core is composed of the melted metals of nickel and iron.
- 10. The Inner Core The inner core of the Earth has temperatures and pressures so great that the metals are squeezed together and are not able to move about like a liquid, but are forced to vibrate in place like a solid.
- 11. The Structure ofthe Earth Outer Core Liquid Inner Core Solid Asthenosphere Viscous Liquid Mesosphere Solid Lithosphere Solid
- 12. The Asthenosphere Theasthenosphere is the semi-rigid part of the middle mantle that flows like hot asphalt under a heavy ! weight.
- 13. The Lithosphere Thecrust and the upper layer of the mantle together make up a zone of rigid, brittle rock called the Lithosphere.
- 14. The Lithospheric Plates The crust of the Earth is broken into many pieces called plates. The plates "float" on the soft, semi-rigid asthenosphere.
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- 16. What is PlateTectonics ⢠The Earthâs crust and upper mantle are broken into sections called plates ⢠Plates move around on top of the mantle like rafts
- 18. What is theLithosphere? ⢠The crust and part of the upper mantle = lithosphere â100 km thick âLess dense than the material below it so it âfloatsâ
- 19. What is theAsthenoshere? ⢠The layer below the lithosphere = asthenosphere ⢠The plates of the lithosphere float on the asthenosphere
- 21. 2 Types ofPlates ⢠Ocean plates - plates below the oceans ⢠Continental plates - plates below the continents
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- 23. Alfred Wegener âproposed that in the distant past, the Earthâs continents were all joined as a single landmass. Eav.idSeonucteh f Aorm heirsi ctah aenodry Africa would fit remarkably well, shoreline to shoreline. b. If the Americas were moved next to Africa and Europe, there would be a match of ancient continental rocks and tectonic (fold and fault) structures. c. Pangaea â when Wegener placed all the continents together like a puzzle, it formed a large landmass which he called Pangaea.
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- 27. Divergent Boundaries â˘Boundary between two plates that are moving apart or rifting ! " ⢠RIFTING causes SEAFLOOR SPREADING
- 28. Features of Divergent Boundaries ⢠Mid-ocean ridges ⢠rift valleys ⢠fissure volcanoes
- 32. Convergent Boundaries â˘Boundaries between two plates that are colliding " ! ⢠There are 3 typesâŚ
- 33. Type 1 â˘Ocean plate colliding with a less dense continental plate ⢠Subduction Zone: where the less dense plate slides under the more dense plate ⢠VOLCANOES occur at subduction zones
- 35. Andes Mountains, SouthAmerica
- 36. Type 2 â˘Ocean plate colliding with another ocean plate ⢠The less dense plate slides under the more dense plate creating a subduction zone called a TRENCH
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- 39. Type 3 â˘A continental plate colliding with another continental plate ⢠Have Collision Zones: âa place where folded and thrust faulted mountains form.
- 41. Causes of Plate Tectonics
- 42. Convection Currents â˘Hot magma in the Earth moves toward the surface, cools, then sinks again. ⢠Creates convection currents beneath the plates that cause the plates to move.