Geology Review What is Geology o The scientific study of the Earth 1 Describe the Earth today a Dynamic Planet 2 Learn how it formed a Origins of Planets 3 How did it evolve a Earth History 4 Earth is a unique place in the Solar System Three Types of Scientific Inquiry a Life o Baconian Sir Francis Bacon what we know is based on our own observations Lets go out to the world TRY SOMETHING explore o Aristotelian make an idea and prove it Wrong make a new idea o Galilean later stages two ideas Hypothesis Theories A good B wrong Figure out what will distinguish between these ideas can t be both o Examples Origins of the Universe Prevailing Theory Aristotelian Origins of the Solar System Alternative Theories Galilean Origins of the Earth Galilean Origins of the Planetary Bodies Baconian Science Math Religion o Questioning is not faith o Questioning is fundamental to scientific method o In Science it s always valid to question principles o One of the most important parts of Science IDEAS Principles Science uses a small smallest set of principles that allow us to describe observations measurements things we know about the Earth Science Logical or Deductive o Logical YEAH o Deductive nope Importance of Geology Guessing then collecting data and self correcting revision of ideas o Everyone will need to make decisions concerning Earth related issues o Gives you a perspective on the planet that no other field can o Puts human achievements and natural disasters in context Prevailing Theory of the Origin of the Universe o Remarkable unbelievable creation idea called the Big Bang o Fundamental to all Theories of Origin Origin of Energy Matter in our Solar System The Earth o Biggest explosion ever Hard to believe because of Scale of event Time Scale Energy and matter involved But it s supported by observations including Early Galaxies seen using the Hubble Telescope Big Bang Theory Big Bang is not the same as Solar System o All matter and energy was packed into a super tiny small point and BANG o History of the Universe expanding in all directions o About 12 15 BY ago o Hubble s Law the velocity of a galaxy away from us is proportional to its distance from Earth Farther away the further it ll go Systematic Red shift of galaxies gives us velocity away from us Spectrum used to see how much carbon there is based on lines All matter of universe formed by the Big Bang and later Nuclear Systematic Red shift o Wavelength gets stretched Or Blue shift o Gets pushed together o Motivation for Hubble Telescope To image earliest formed Galaxies Principle it takes time for light to travel o Other evidence from chemistry of Universe Reactions Large explosion Dense cloud neutrons Neutrons react to form Hydrogen Hydrogen and Neutrons form Helium Later reactions in stars heavier elements o Other evidence from chemistry of Sun and Earth They have a close link based on elements o 4 K Background Radiation Very low wavelength it s everywhere Still get the same radiation Absolute evidence of an explosion We re still seeing or we re in an explosion Solar System o Sun and planets much younger About 4 5 5 BYA o Lots of systematics central most of the mass at center Sun Inner Terrestrial Planets Mercury Venus o Thick CO2 atmosphere o Impact craters o Fractured plains o Volcanic Domes o Volcano o Unique and best studied Earth Mars Jupiter Saturn Outer Planets Gas Giants o Competing theories for origin of Solar system all have one thing in common Single origin event for planets Systematic Observation 1 Common sense of Planetary Orbits around Sun a All orbit around the Sun counter clockwise b No capturing planets 2 Co planar Orbits 3 Orbits of Moon a Define plane for Earth same for others rotate same way a Orbit same way as planets 4 Rotations of Sun Planets except Venus Uranus 5 Planetary Orbital Radii a Titius Bode Law it s really an observation i For both inner and outer planets b Led to the discovery of Asteroids because this led to the search for a missing planet 6 Most of the mass of the Solar System in Sun 99 9 7 Most of the angular momentum of Solar System in Planets 99 8 Chemistry of SS a Yet chemistry of SS b implies common origin of Sun and planets Jupiter and Saturn have a similar elemental composition like the sun c Even though they have the same composition they did not ignite like the Sun because their masses are so SMALL Competing Theories for SS o Collision Hypothesis Count Buffon 1749 Our Sun starts with no planets Planets form when star star collision tears matter out from Sun o Nebular Hypothesis Immanuel Kant 1755 Solar system started as slowly rotating Nebular gas Soon favored because it explains orderly orbits and rotations of planets o Nebular Hypothesis Laplace 1796 Hot nebula Contraction during cooling Cooling leads to condensation of solids from gas Formation of planets by gravitational attraction Preferred for quite a while BOOM James Maxwell James Jeans showed several problems o Condensed dust particles not enough mass to form planets Gravity not strong enough o Sun is rotating too slowly o Bye bye to Nebular Hypothesis Hello again to a modified Collision Hypothesis Proposed a near miss of another star producing planetessimals with enough mass to attract each other to form planets Problem matter ripped out of Sun too hot to form planetessimals instead made hot plasma Problem low chance of two stars colliding and producing this crap o Astronomical Observations of Nebula Favor Nebular Hypothesis Planetessimals bodies whose diameter exceeds about 1 km vacuum cleaners Protoplanets bodies almost the size of today s planets Accretion the process by which smaller pieces of matter clump and bind together to form sand sized grains Difference between Protoplanets and Planetessimals o Protoplanets and large planetessimals developed internal layering early Process in bodies whose temperatures rose sufficiently to cause melting denser iron alloy separated out and sank to the center of the body Early Earth and its Character o What makes the Earth spherical Gravity forces tend to shape planet into a sphere Geoid gravitationally stable shape Why are planets spherical When a protoplanet gets big enough gravity can change its shape Permits gravity to be the same at all points on its surface When it becomes so soft But is Earth really spherical o Density structure of Earth Lightest at surface Heaviest at center Principle of Isostacy o Crust floating on mantle o Highest points are the thickest crust How did it get