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How do we know about layers deep within the Earth?

How do we know about layers deep within the Earth?. Key Points. There are many layers of the Earth: Core—inner and outer Mantle Crust—oceanic and continental The uppermost layers are divided into two regions: Lithosphere Asthenosphere. Key Points Continued.

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How do we know about layers deep within the Earth?

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  1. How do we know about layers deep within the Earth?

  2. Key Points • There are many layers of the Earth: • Core—inner and outer • Mantle • Crust—oceanic and continental • The uppermost layers are divided into two regions: • Lithosphere • Asthenosphere

  3. Key Points Continued • Earthquakes generate two types of waves: • P Waves • S Waves

  4. The Structure of the Earth • Earth is composed of several layers. • CORE: • Inner core • Densest • Iron and nickel • Solid- high pressure • Hot • Outer core • Iron and nickel • Liquid-lower pressure • Heat within the core generates convection currents in the mantle

  5. 2. MANTLE: • Dense rocky material near the core • “Squidgy” near the crust • Less dense than the core, more dense than crust • Convection currents take place here • This is where magma heats up, rises, cools and sinks back down again to heat and start the process over again.

  6. 3. CRUST: the outermost and thinnest layer of the Earth. Crust is the thickest at mountain ranges and most thin at the ocean bottoms. • Continental Crust: About 22 miles deep under the continents • Oceanic Crust: About 6 miles deep under the oceans

  7. Lithosphere/Asthenosphere • Lithosphere: Includes oceanic/continental crust and the uppermost layer of the mantle up to 100 km below the surface of the Earth. • Asthenosphere: Includes the area of the mantle below the Lithosphere.

  8. Earth’s Magnetic Field • Currently, the Earth’s magnetic pole is located near Earth’s North Pole. This is a condition called normal polarity. • Periods when the north magnetic pole is located near Earth’s South Pole are called reverse polarity.

  9. When molten lava solidifies at mid-ocean ridges, iron-containing minerals in the lava align themselves with Earth’s active magnetic field. These minerals record the orientation of the magnetic field at the time they solidified. Click here to see a demonstration of Earth’s alternating magnetic polarity.

  10. P and S Waves • Scientists analyze seismic data (information from eirthquakes) to infer processes that occur inside the planet. • Every earthquake generates 2 types of waves: • Primary waves (P waves) • Secondary waves (S waves) • Click here for an example of p and s wave movements.

  11. After watching the demo, what do you notice about the speed of the P waves in the land vs. the speed of the S waves in the land? • P waves travel faster through the land • What do you notice about the speed of the P waves in the water? • P waves slow down • What do you notice about the speed of the S waves in the water? • They can’t travel in liquids

  12. Continental (40%) Composition Granite Sedimentary Metamorphic Less dense “Floats” on top of mantle Thicker 35-40 km Oldest of the rocks Because of low density it is rarely subducted (recycled) back into the mantle Oceanic (60%) Composition Mafic rocks Sima More dense Thinner 7-10 km Age doesn’t exceed 200 million years Always subducts between oceanic and continental plate boundaries. (recycled back into the mantle) Continental Crust vs. Oceanic Crust

  13. Summary The Earth is made up of several layers—inner and outer core, the mantle, and the crust. The crust is made up of oceanic and continental crust. The lithosphere includes the crust and uppermost layer of the mantle. The aesthenosphere includes the mantle below the lithosphere. The Earth’s magnetic north reverses over time.

  14. Summary Continues Scientists study P and S waves to determine the layers of the Earth—s waves travel through solids only, p waves travel through solids and liquids.

  15. Since it is not possible to journey to the center of Earth. What must scientists do to infer processes that occur inside the planet? • Use drills to drill deep into the layers • Study seismic data from earthquakes • Use satellites to view images of the layers 20

  16. What are the two types of waves that earthquakes generate? 20 Seconds Remaining • S waves and P waves • A waves and B waves • R waves and S waves • Y waves and X waves

  17. P waves can… • Travel through solids only • Travel through liquids only • Travel through both solids and liquids 20

  18. S waves can… • Travel through solids only • Travel through liquids only • Travel through both solids and liquids 20

  19. Which statement is true? • P waves travel faster through solids than S waves • S waves travel faster through solids than P waves • P and S waves travel through solids at the same speed 25

  20. How do scientists use P and S waves? • To measure the strength of an earthquake • To see what layers are solid and what layers are liquid • To measure the strength of the core :25

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