EES 1030 1st Edition Lecture 13 Intro to Earth ScienceThe Earth’s Interior- Crust- Upper Mantle- Lower Mantle- Liquid Outer Core- Inner CoreHow do we know?Baseball analogy: if you cut through the leather outside of a baseball you see wool yarn, but it that all there is inside? If you calculate the density of the whole baseball it is greater than that of just the yarn and leather cover. Therefore there must be something else inside the baseball of greater density than the yarn ~ a rubber ball.Average density of Planet Earth: 5.5 g/cm3Density of granite rock (crust): 2.6 g/cm3Density of peridotite rock (mantle): 3.4 g/cm3Seismology: the study of seismic waves from plate movement and earthquakes.*behavior of seismic waves provide critical information about the interior of the earth*- Seismic waves move at different speeds through rocks with different density, elasticity, composition, pressure, and temperate.- Waves change speed and direction at liquids and solidsP waves- Primary waves that are push-pull. Compressional.- Always travel faster than S waves- Can travel through liquidS waves- Secondary waves that are shaking waves. Shear.- Cannot travel through liquid.Global network of seismic stations was established to monitor international nuclear bomb test ban treaties.The core: an iron rich sphere with a radius of 3486 kmInner sphere 1216 km radiusOuter layer 2270 km thickAverage density- 11 g/cm3Evidence for core composition?- Icon is the only common element in the solar system that has the right density toform the core. Also contains 5-10% nickel.Early differentiation: earth was mixed of all the elements that make up the inside and the icon sank to the middle and each layer separated. Earth’s Magnetic field is from the movement of electrically conducting iron in the outer core.The Mantle:- Solid rocky shell that extends to the depth of 2900 km. - Makes up 84% of earths volume.- Made of ultramafic rock, peridotiteThe crust:- Thin outer skin that ranges in thickness from 2 miles at ocean ridges to 50 miles in some mountains.- Takes 15% of earth’s volume.- There are 2 types: oceanic and continentalOceanic crust: density is 3 g/cm3 and made of mafic igneous rock.Continental crust: density is 2.7 g/cm3 and made of felsic igneous rock.With increasing depth earth’s interior is characterized by increases in temperature, and density. Lithosphere:“rock” sphere. cool outer shell of earth that forms plate tectonics that move. Made of crust and upper mantle. Varies in thickness.Asthenosphere: “weak” sphere. Close to or at the melting point, small percent of melt is present.Geothermal gradient: earth’s temperature gradually increases with depth. Is about 25 Degrees C per KM of depth on average.Plate tectonics are driven by convection inside the