GEO 101N 1st Edition Lecture 3Outline of Last Lecture I. Earth in Contexta. ElementsII. Solar System III. Planets/Planet formationOutline of Current Lecture IV. Earth Compositiona. Planetsb. DifferentiationV. Moon VI. Earths compositionVII. Formation of the Oceans and AtmosphereCurrent LectureI. Planetsa. As they grew they began to heat upb. The hotter they became the more spherical they becamec. Planet composition varies because of what materials were available when and where they formedII.Differentiationa.Differentiation: the settling of layers b.began when the earth was still a molten ballc.heavier materials (those more dense) settle “down” or “in”, for earth that is primarily metallic iron (Fe) and Fe seeking elementsd.silicates stayed at the surface making up the crustIII.Moon Formationa.~4.53Ga a Mars sized protoplanet (“impactor”) smacked into young earthb.The planet and part of the mantle were disintegrated; this started the earth spinning and launched materials around the earth, the moon was born of these materialsc.Earth was completely molten again after impactThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.d.The earth absorbed Fe from the impactore.Within a day of impact gravity had reshaped the earth into a sphereIV.The Earths Layersa.Crusti.Continental: granite, average rock density ~2.7g/km3, quartz richii.Oceanic: basalt; silica poor; Fe & Mg rich; basalt lava flows; gabbro sills; igneous rocks like compositionb.Mantle: thickest; composed of ultra-mafic rockc.Core: Fe-Ni compositionV.Eartha.Our atmosphere is what makes earth uniquei.Its visible from spaceb.Volcanoes produce water and atmospherei.When magma hits the surface gases are released; atmosphere developed/s from this release – atmosphere has and is changingii.The cooling of the earth condensed some of these gases, creating liquid wateriii.Today’s atmosphere is 78% N; 21% O2c.Evidence of this is found in Fe deposits that predate O2 (ie, photosynthesis)VI.Crusta.Outermost “skin” of the earthi.Thickest under mountainsii.Thinnest under mid-ocean ridges (divergent boundaries) b.Mohorovicic discontinuity is the base of the crusti.Separates earths’ crust from mantleii.There is a change in seismic velocity of P-waves (type of seismic wave, causes earthquakes)VII.Seismic waves (brief)a.Motion created by shifts in the earthb.Slower through warmer/less dense regionsc.Faster through cooler/more dense areasVIII.Mantlea.Displays temperature variationsIX.Magnetic Fielda.Protects Earth from solar winds; w/o it our atmosphere would be stripped awayb.Rotation and the molten core created/maintain the magnetic