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Planet Earth in Profile

Planet Earth in Profile. The Layered Interior. Objectives. Explore evidence that helps explain Earth’s internal structure. Outline Earth’s internal layers and discuss some of the evidence leading to their discovery

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Planet Earth in Profile

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  1. Planet Earth in Profile The Layered Interior

  2. Objectives • Explore evidence that helps explain Earth’s internal structure. • Outline Earth’s internal layers and discuss some of the evidence leading to their discovery • Introduce the salient properties of Earth’s outer layers, its crust and the underlying mantle • Investigate the processes at work to modify Earth’s surface, creating physical landscapes of great diversity

  3. Evidence of Earth’s Internal Structure • Earthquakes • Shaking and trembling of Earth’s surface caused by sudden release of stress within the crust • Seismic waves • Surface waves • Travel along the surface • P-waves (primary waves) • Back-and-forth; Compressional • Travel trough liquids and solids • S-waves (secondary waves • Up-and-down; right angles • Travel through solids only

  4. Evidence of Earth’s Internal Structure • Seismic Waves • 0° to 103° • Find P- and S-waves only • 104°-142° • Shadow zone • No P-waves; bend due to higher density of mantle • No S-waves; cannot pass through liquid • 142°-180° • Find P-waves only • No S-waves; cannot pass through liquid

  5. Earth’s Internal Layers • Core • Inner core • Solid; Iron (Fe) and Nickel (Ni) • 1220 km (760 mi) radius; 5150 km (3200 mi) depth • Outer core • Liquid; Iron (Fe) and Nickel (Ni) • 2250 km (1400 mi) thick; 2900 km (1800 mi) depth • Mantle • Lower mantle • Solid; Iron (Fe), Magnesium (Mg), Silicon (Si) • 2230 km (1385 mi) • Upper mantle • Solid-plastic-solid; Iron (Fe), Magnesium (Mg), Silicon (Si) • 670 km (415 mi) depth [Insert Fig. 27.5 ]

  6. Earth’s Outer Layer • Mohorovicic discontinuity (Moho) • The density has a marked different between the crust and mantle • Earthquake waves speed up when passing from crust to mantle • Indicates mantle is more dense than crust • Made it possible to measure the thickness of the crust • Thickness varies • From 5 km (3 mi) to 40 km (25 mi)

  7. Earth’s Outer Layer • Crust • Continental crust • Felsic • Feldspar rich (granitic) • Light colored • Low density (2.8 g/cm3) • Oceanic crust • Mafic • Magenisum (Mg) and iron (Fe) rich (basaltic) • Dark colored • Higher density (3.0 g/cm3) [Insert Fig. 27.7A - felsic] [Insert Fig. 27.7B - mafic ]

  8. Earth’s Outer Layer • Lithosphere • Rigid layer • Crust and uppermost mantle • Asthenosphere • Plastic layer; flows readily • Lithospheric Plates • Large, rigid fragments • Move over asthenosphere Insert Fig. 27.8

  9. The Crustal Surface • Topographic Relief • Vertical difference between highest and lowest elevation • High relief • Large difference from high to low relief • Low relief • Small difference from high to low relief Insert Fig. 27.10 - low relief

  10. The Crustal Surface • Topographic Relief • Vertical difference between highest and lowest elevation • High relief • Large difference from high to low relief • Low relief • Small difference from high to low relief

  11. The Crustal Surface • Continental Shields • Large, stable, low relief expanse of land • Old metamorphic, igneous rocks • North American Shield • Canadian (Laurentian) shield

  12. The Crustal Surface • Orogenic Belts • Series of linear mountains • Zones of high relief • Weathering • Physical, chemical breakdown of rocks • Erosion • Removal of weathered rocks

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