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Earth Structure

Earth Structure. The Earth’s Water. Ocean Stats and geography of the basins. Ocean Statistics. 70% of the Earth’s surface is covered by the oceans – hence the “water planet” 2/3 of the Earth’s land masses are in the Northern hemisphere, which is 61% ocean

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Earth Structure

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  1. Earth Structure

  2. The Earth’s Water Ocean Stats and geography of the basins

  3. Ocean Statistics • 70% of the Earth’s surface is covered by the oceans – hence the “water planet” • 2/3 of the Earth’s land masses are in the Northern hemisphere, which is 61% ocean • 80% of the Southern hemisphere is ocean • 97% of all water is in the ocean • 50% (or more) of the Earth’s photosynthesis occurs in the oceans • Average depth of the ocean is 4000 km or 2.5 miles • Maximum depth of around 11,000 meters – Mariana Trench

  4. Geography of Ocean Basins Traditionally classified into four large basins (doesn’t include Southern Ocean, listed in decreasing size). Pacific Ocean – largest and deepest Atlantic Ocean – growing ocean (Mid Atlantic Ridge) Indian Ocean Arctic Ocean – northern hemisphere Southern Ocean - continuous body of water which surrounds the Antarctic continent below 60°S latitude.

  5. The Earth’s Layers The Cross section view

  6. Earth’s Composition

  7. Layers: Cross-Section of the Earth Inner core – solid iron, intense pressure Outer core - molten, rich in iron and magnesium - thought to generate the Earth’s magnetic field Mantle - near the melting point, the mantle slowly swirls and mixes (Upper Mantle is found in both the Asthenosphere & Lithosphere) Crust - outermost layer, solid, floats on the mantle, continental and ocean (Part of Lithosphere)

  8. Proof of Layers • What evidence supports the idea that Earth has layers? • The behavior of seismic waves generated by earthquakes give scientists some of the best evidence about the structure of Earth. Wave speed depends on what is traveled through—if it can travel through that medium. • (above-left) S waves cannot penetrate Earth’s liquid core. • (above-right) P waves are bent as they pass through the liquid outer core.

  9. Layering Terms Density Stratification – Layering of earth based upon the density of the materials which it is made of. Moho discontinuity –Boundary between crust and mantle. Identified due to changes in velocity as seismic waves as they move from one material to another

  10. The Floating Layer Where does the heat within Earth’s layers come from? Heat from within Earth keeps the asthenosphere flowing. This allows the lithosphere to keep moving. The source of this heat is radioactive decay, given off when the nuclei of unstable forms of elements break apart. This heat travels in convection currents in the mantle.

  11. The Top Layer The crust: oceanic and continental Buoyancy and Isostasy

  12. Oceanic versus Continental Crust Oceanic crustal plates have a higher density and they are: • Thinner • Geologically younger than continental crust • Rich in iron and magnesium • Basalt, dark in color • Likely to sink

  13. Oceanic versus Continental Crust Continental crustal plates have a comparatively lower density and they are: • Thicker • Geologically older than oceanic crusts • Rich in sodium, potassium, calcium, and magnesium • Granite, lighter in color

  14. Keeping the Crust Afloat • Buoyancy - The tendency or capacity to remain afloat in a liquid or rise in air or gas • Isostasy (Isostatic Equilibrium) - Gravitational equilibrium between the Earth’s lithosphere and asthenosphere. The ship sinks until it displaces a volume of water equal to the weight of the ship and its contents.

  15. Floating Ships Quiz Question: As a ship moves from salt to fresh water what happens to the ship?

  16. Earth Rocks!!! http://www.classzone.com/books/earth_science/terc/content/investigations/es0602/es0602page02.cfm

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