GEO 101 1st Edition Lecture 2 Outline of Last Lecture 1 What does a geologist do 2 Scientific inquiry or scientific method 3 Cosmology 4 Earth s changing place 5 An evolving image of earth 6 The renaissance 7 The solar system 8 The planets 9 Stars and galaxies 10 The Doppler Effect 11 Theory of the Expanding Universe 12 Big Bang Outline of Current Lecture 1 Stellar Nucleosynthesis 2 Solar System Formation 3 Moon Data 4 Earth 5 The Celestial Neighborhood 6 Magnetic Field 7 The Van Allen Belts 8 Aurorae 9 Surface Features 10 Elemental Composition 11 A layered Earth These 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 12 Earth s Interior Layers 13 Uniformitarianism 14 Geological Time Current Lecture Stellar Nucleosynthesis When fuel dwindles stars head by inward collapse This leads to a cataclysmic explosion a supernova The supernova creates heavier elements o Uranium atomic 92 is the heaviest natural element Solar System Formation The Nebular Theory the way the solar system was formed A 3rd 4th or nth generation nebula forms about 4 56 Ga o Hydrogen and Helium left over from the big bang o Heavier elements produced by stellar nucleosynthesis This material coalesces into an accretion disc The ball at the center grows dense and hot Fusion reactions begin the sun is born Dust in the rings condenses into particles Particles coalesce to form planetesimals Planetesimals accumulate into a larger mass An irregularly shaped proto earth developed 4 54 ga billion The interior heats up and becomes soft o Gravity shapes the earth into a sphere rock tumbler Wasn t like it is today It wasn t as round as it is today It was more like a rocky rock that tumbled No atmosphere Not divided into layers The interior differentiates into a FE core and stony mantle ie layers within the earth begin to form Soon a small planetoid object collides with the earth it was about the size of mars Debris forms a ring around the earth The debris coalesces and forms the moon Moon Data Newer data on the age of the mood Moon age 4 47 ga billion years This age is 60 million years younger than previously estimated Old method of dating is to date moon rocks new method uses weight gain from impact with planetoid Solar System Formation continued Lots of cooling has to occur Atmosphere develops from volcanic gases o Too hot for life o There was no water it was too hot When earth becomes cool enough o Moisture condenses and accumulates o Oceans are born Earth What would solar system visitors notice about earth o Magnetic field Sun gives off so much heat We rely on this If we didn t have this the degree from the sun would burn us o An atmosphere o Surface features Continents Oceans Polar ice caps Evidence of humanity The Celestial neighborhood Interstellar space is a vacuum ith scares matter Matter greatly increases approaching the sun The sun ejects matter into space as the solar wind Solar wind Magnetic Field Like a bar magnet earth has a dipolar magnetic field Magnetic field lines flow from N to S and o Extend into space and weaken with distance from Earth o Create a shield around Earth the magnetosphere The Van Allen belts The solar wind is deflected by magnetosphere Near earth stronger magnetic field forms the Van Allen Belts which arrest deadly cosmic radiation Aurorae Some ions escape Van Allen belts o Pulled to the magnetic poles the ions generate light Spectacular aurora follow solar flares o Aurora borealis northern lights o Aurora australis southern lights The atmosphere ATMOSPHERE NOT ON TEST Earth with an atmosphere I unique among other planets Densest at sea level the atmosphere thins upward Mostly nitrogen Oxygen was absent from the atmosphere before 2 5 ga Surface Features Earth s surface continents are high oceans are low due to the differing buoyancy of each type of crust Dark blue deeper red higher Elemental Composition 90 percent of earth is comprised of 4 elements o Iron 35 heavy metal in core o Oxygen 30 o Silicon 15 o Magnesium 10 The remaining elements o Form 10 of the earth A layered Earth We live on the thin outer skin of Earth Early perceptions about earth s interior were wrong o Open caverns filled with magma water and air o Furnaces and flames We now know that Earth is comprised of layers o The crust o The mantle o The core Outer core Inner core Earth s Interior Layers Crust o Continental o Oceanic Mantle o Upper o Lower Core o Outer liquid o Inner sold Moho separates crust and mantle The Crust Outermost skin of earth with variable thickness o Thickest under mountain range 70km 40 miles o Thinnest under mid ocean ridges 3km 2 miles o Still even with these thickness the crust is as think as a balloon around the rest of the earth Two types of crust Continental crust granitic underlies the continents o Average rock density about 2 7 g cm 3 o Average thickness 35 40 km Oceanic crust basaltic underlines the ocean basins o Density about 3 0 g cm 3 o Average thickness 7 10 km Moho Layer that separates crust from mantle The mohorovicic discontinuity is the base of the crust Earth s Mantle Solid rock layer between crust and fore 2 885 km thick mantle is 82 of earth s volume Composition is ultramafic rock peridotite Below about 100 150km the rock is hot enough to flow In connects hot mantle rises cold mantle sinks Three subdivisions o Upper o Transitional o Lower Earth s Layers based on Physical Properties How deep have we drilled Not even close o We don t have the technology o Its very hot equipment would start burning and melting Use seismic wave interpretation to relay boundaries and relative densities Uniformitarianism principle Present is the key to the past Birth of modern Geology Magnitude of Geologic time Involved vast times millions or billions of years Magnitude of geologic time gradual processes Eons eras periods epochs o Eons biggest time There are 4 eons o We divide eons into eras o Eras get divided into periods o We can divide eras into epochs Age of the earth about 4 5 billions years GA billion MA million KA thousand Today at the top Birth of earth at the bottom