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The Earth’s Structure

The Earth’s Structure. series of layers or spheres which differ in density, chemistry (or composition) and physical properties. Density. is the relative heaviness of a substance Or how heavy something is for its size defined as the mass per unit volume usually expressed in g/cm 3

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The Earth’s Structure

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  1. The Earth’s Structure • series of layers or spheres which differ in density, chemistry (or composition) and physical properties.

  2. Density • is the relative heaviness of a substance • Or how heavy something is for its size • defined as the mass per unit volume • usually expressed in g/cm3 • EARTH HAS DENSITY STRATIFICATION

  3. Evidence of the Earth’s Interior Composition • Can only drill about 7.5 miles (earth’s radius = 4000 mi) • Vents, volcanoes, variation in pull of gravity, etc. • study of the shocks from distant earthquakes

  4. If Earth were uniform (homogeneous) throughout Seismic Waves reveal that Earth’s Interior Is Layered If Earth were layered inside If the density, or rigidity, of Earth increased evenly with depth

  5. Compositional Layers of the Earth • the Crust • thin outermost layer • the Mantle • thick middle layer • the Core • densest inner layer • composed mainly or iron (90%)

  6. 2-3 Continents and Ocean Basins Differ • Continental crust • is mainly composed of granite, a light colored, lower density (2.7 gm/cm3) rock • thicker • Oceanic crust • is composed of basalt, a dark colored, higher density (2.9 gm/cm3) volcanic rock • thinner

  7. Figure 1.17

  8. Physical Properties of the Layers • Not determined only by chemical composition • The behavior of the rock (brittle or plastic) is determined mainly by temperature and pressure

  9. 2-1 Effects of Pressure and Temperature on Physical State of Layers • Increasing pressure raises the melting point of a material. • Increasing temperature provides additional energy causing material to melt. • Both pressure and temperature increase toward the center of the Earth, but at different rates.

  10. 2-1 Divisions of the Earth Based Upon Physical State • the Lithosphere • cool, rigid outer layer • comprised of continental crust, oceanic crust and the uppermost cool, rigid portion of the mantle • the Asthenosphere • hot, slowly flowing layer of the upper mantle • the Mesosphere (Lower Mantle) • rigid layer, similar chemically to the asthenosphere but very different physically • the Outer core • thick liquid layer • the Inner core • solid layer (due to tremendous pressure)

  11. What Are the Sources of Internal Heat That Keep the Asthenosphere Plastic? • Radioactive decay (atoms of elements give off heat when their nuclei break apart) • Internal heat moves to the surface by conduction – slow migration of heat through a material by collision of atoms • And by convection – movement of heat in a fluid as it expands, becomes less dense and rises.

  12. Fig. 3-11, p. 57

  13. Isostatic Adjustment http://media.pearsoncmg.com/bc/bc_0media_geo/geo_animations/isostatic-adjustment/isostatic-adjustment.html

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