Planet Earth Building a Planet Lecture 1 and 2 1 The basic scientific principle the universe is sensible and governed by unchangeable rules 2 The Scientific Method 1 Make an observation 3a Make new experiments 3b Make new observations 2 Develop a hypothesis an explanation that predicts the outcome of other experiments 4 Do results match hypothesis if yes return to step 3 if no return to step 2 Multiple yes s plus hypotheses Scientific Theory Scientific Theory predictions of behavior Georges Cuvier Catastrophism In geology uniformtarinism James Hutton present is key to the past Horizons animals rocks new organisms at every horizon new horizon and everything is wiped out Repopulation has never been seen by human beings but that s what horizons suggest happens at every new horizon All rocks in the world are created by a world encircled by the ocean Rocks dissolved into the ocean 2 Volcanos said to be recent but there is evidence found of old rocks which look the same as ancient findings Abraham Werner Neptunism 5 different types of rocks Problems 1 Where did the water go James Hutton Uniformitarinism Present to Past Siccar Point Scotland Unconformity Werner Cuvier rapid event not seen no time quick event random Hutton Detail look at surroundings process took a long time Hutton came up with the first theory that the world is old 1 Ancient sediments turn to rocks 2 depositing uplifting depositing etc Process 7 Lithify Principle processes we observed today we also observed in the past Charles Lyell Principles of Geology 1830 1833 Responsible for acceptance of Hutton s ideas Eloquent writer How old is the Earth 4 6 Billion years old Ga iridium the flux from outerspace In comparison time it took about 6 seconds for human life to form haven t been around for that long Dinosaurs were extinct by impact because of a meteorite because they found iridium spike in Glubbio Italy between rocks which would have taken much too long to form on the time line of original extinction of the dinosaurs therefore it must have been an impact Iridium brought in by impact or volcanos Found quartz grains shocked quartz very common quartz shattered and volcanos do not do that so it was an impact tested hypothesis Sound has a pitch Pitch depends on frequency which is the number of waves that pass a point in a given period of time Doppler Effect which direction sound is waving distance between adjacent crests High sound high frequency low sound low frequency Color of light is measured by frequency Red Shift color function frequency high frequency blue low frequency red Everything is red shifted so everything is flying apart as created by a gigantic explosion this is a component of the Big Bang theory all matter on the universe was concentrated at a single point and then it expanded Occurred about 14 billion years ago Some data to explain this 1 Planets isolated 2 Orbits circular in same plane Nebular Hypothesis In a room 10 atm in space 107 atm 3 Planets Moons travel along orbits in the same direction same direction as the sun Molecular cloud an area in space where there s an abundance of gas and dust the inward collapse of this is what possibly formed the sun Stars are born from molecular clouds as well they are 80 percent hydrogen and 20 percent helium the1 10 of a percent is other stuff gravity attracts pulls together and this forms density Nuclear fusion pressure density temperature plus rotation create a star Centrifical Force pushes things from center pressure of infall Relative Abundance of Elements crust divisons oxygen is the most common on the crust surface 2 7 is the density of crustal rock The average density of the whole earth is 5 5 Iron is the most common element on earth 35 this is because elements are differentiated as you go deeper inside the earth 46 rock 28 silicon 8 aluminum 6 Iron 4 Magnesium Earth is in layers How earth got warm compression radioactivity heat radiodecay collisions Asteroid the size of mars hit earth approximately 4 6 billion years ago and sterilized the earth melted the earths surface Knocked the earth s axis on a tilt 23 and a half degrees The impact also sped up Earth s rotation and changed orbital plane added energy and caused melting moon formed from the debris of the impact meteor moon rocks from 4 47 billion years ago support this hypothesis Differentiation began after this point and elements moved towards the center of the earth The Crust the crust is the most shallow layer and heterogenous Ocean crust 5 8km thick Continent crust 35 45km thick The boundary is considered the Mohorovic layer at the base of the crust which is a chemical boundary between crust and what s underneath it Mantle flows and begins at the bottom of the crust 2 900 km down Gutenburg discontinuity The Earth has 4 layers 1 crust 2 mantle 3 outer core 4 inner core The uppermost mantle crust to 400 km depth The transition zone 400 700 km depth The mid mantle 700 to 2650 km depth The lowermost mantle 2650 2891 km depth Earth s core is actually freezing as the earth cools due to the pressure the boundary of the liquid homogenous outer core and the solid inner core occurs at about 1220 km Lehman discontinuity the change in density across earth s core is greater than that at the earth s surface Mechanical Layers Lithosphere 100 km thick strong uppermost layer of the earth not a strict boundary b t this layer and the asthenosphere Consists of all crust and uppermost mantle Behaves rigidly like a solid over long periods of time Cold and brittle Asthenosphere plasticy flowy 100km 300km HOT flows weakest part of mantle The asthenosphere decouples the lithosphere tectonic plates from the rest of the mantle Mesosphere Earth s Magnetic Field Region affected by Earth s magnet solar wind interacts with it distorts it to a huge teardrop shape Shields earth from solar wind and cosmic radiation Dipole Magnet inside earth lines of force north and south align with magnetic field It is generated in the outer core Magnetic Dyanmo generates the magnetic field Magnetic Inclination earth s mag field is inclined at vertical poles Earth s magnetic field behaves like a bar magnet Earth has spinning axis so geographic north and south are different from magnetic north and south about 11 degrees off from geo north pole mag declination In 1900 Pierre Curie recognized that permanent magnetism is lost from magnetizable materials at temperatures from 500 to 700 C This is known as the Curie point At the equator the magnetic field