GEO 101 1st Edition Lecture 2Outline of Last Lecture 1. What does a geologist do? 2. Scientific inquiry or scientific method3. Cosmology 4. Earth’s changing place5. An evolving image of earth 6. The renaissance7. The solar system 8. The planets 9. Stars and galaxies 10. The Doppler Effect 11. Theory of the Expanding Universe12. Big Bang Outline of Current Lecture 1. Stellar Nucleosynthesis2. Solar System Formation 3. Moon Data4. Earth5. The Celestial Neighborhood6. Magnetic Field7. The Van Allen Belts8. Aurorae9. Surface Features10. Elemental Composition11. A layered EarthThese 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 Layers13. Uniformitarianism 14. Geological Time Current LectureStellar Nucleosynthesis- When fuel dwindles, stars head by inward collapse- This leads to a cataclysmic explosion (a supernova)- The supernova creates heavier elementso 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 planetoidSolar System Formation (continued…)- Lots of cooling has to occur- Atmosphere develops from volcanic gaseso Too hot for lifeo There was no water, it was too hot - When earth becomes cool enough o Moisture condenses and accumulateso 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 atmosphereo 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 windMagnetic 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 beltso Pulled to the magnetic poles, the ions generate light - Spectacular aurora follow solar flareso Aurora borealis – northern lights o Aurora australis – southern lightsThe 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 gaSurface 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 elementso Iron – 35% heavy metal in coreo Oxygen – 30% o Silicon – 15% o Magnesium – 10%- The remaining elements?o Form 10% of the earthA layered Earth - We live on the thin outer skin of Earth- Early perceptions about earth’s interior were wrongo Open caverns filled with magma, water, and air o Furnaces and flames- We now know that Earth is comprised of layers o The crusto The mantle o The core  Outer core  Inner coreEarth’s Interior Layers - Crusto Continental o Oceanic - Mantle o Upper o Lower - Core o Outer – liquid o Inner – sold - Moho separates crust and mantleThe Crust - Outermost “skin” of earth with variable thicknesso 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 earthTwo types of crust- Continental crust – granitic, underlies the continentso Average rock density about 2.7 g/cm^3o Average thickness 35-40 km- Oceanic crust –basaltic, underlines the ocean basins o Density about 3.0 g/cm^3o Average thickness 7-10 kmMoho- Layer that separates crust from mantle - The mohorovicic discontinuity is the base of the crustEarth’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 LowerEarth’s Layers based on Physical Properties - How deep have we drilled? Not even closeo 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 densitiesUniformitarianism – 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 > epochso Eons – biggest time  There are 4 eonso 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 – thousandToday at