1 2 3 Scales of Earth Science p 9 a Extremely small to unimaginably large b Distances sizes numbers time i Atoms in crystalline arrangement ii Formation of mountain ranges iii Stars in the sky c Earth is 4500 million years old or more 4 5 billion i Geologic time scale divided into meaningful intervals ii Based on changes in fossil record iii Correlated with numeric dates recently Earth Spheres a Hydrosphere i Water planet 71 of surface covered ii Average depth of ocean is over two miles iii Most water is sea water small portion is fresh and liquid b Atmosphere i Consider half of the molecules are within 3 miles of surface Other half are more diffuse with no definite outer boundary ii Gaseous envelope that shields us from cosmic radiation iii Surface layer is homogeneous mixture outer layers differentiated by density iv Has evolved with life on Earth c Biosphere i All of the organisms animals plants bacteria fungi ii Interact with hydrosphere and atmosphere depend on them alter them d Geosphere i 6400 km radius the distance from center to surface ii Dynamic and changing but on a long time frame iii Acted upon by the other three spheres Mobile Geosphere a Oceanic crust is lower than continental crust because it is denser It has ocean because it is lower i Where there are collisions between continental crust and oceanic crust the continent pushes the oceanic crust down into the mantle to be assimilated destructive plate margin ii Consequence is younger oceans older continents b Continents are higher and older because they are less dense i Margin at edge of oceanic crust is below sea level ii Shelf is part of continent just too much water to let it be above sea level c Lithosphere moves around puts continents in different places d Places where crust is torn apart there is a constructive margin with mantle material filling in the rip from below The hotness of this material makes it rise above adjacent ocean floor Page 1 of 5 4 5 Earth System science a Interaction of components integration of biology chemistry physics meteorology geology b System subject to feedback mechanisms parts of the system that increase tendencies or reduce tendencies i Positive feedback mechanism Global climate change 1 warmer summers increase melting of ice 2 less ice less reflection of heat 3 more warming more melting ii Negative feedback mechanism in Global climate change 1 increase in temperature increases evaporation 2 more evaporation more clouds 3 clouds reflect heat moderating temperature c Cycles in Earth s system i hydrologic cycle evaporation condensation precipitation runoff There are interactions with geosphere biosphere and atmosphere in this cycle ii rock cycle come up from mantle as lava or magma solidifies in upper crust Hydrosphere dissolves changes mineral composition erosion removes material deposits of sediments become rock destructive margins may bring material back into crust and upper mantle to be recrystallized or melted d Energy of Earth s systems comes from two sources i Sun provides energy for biosphere atmosphere hydrosphere ii Internal heat from radioactive decay and gravitational compression fuel the movement of the geosphere Earth Structure a Composition varies from center to surface 3 distinct zones i Crust 100 km thick 1 oxygen silicon aluminum iron calcium etc 2 about 100 km thick 3 two types a continental older thicker more silica less dense b oceanic younger thinner more iron Mg more dns ii Mantle 2900 km thick 1 oxygen silicon iron magnesium 2 2900 km thick iii Core 3600 km radius 1 iron nickel 2 3400 km radius Page 2 of 5 6 7 b Properties change also 5 zones only one boundary same as comp i inner core 1 solid due to pressure 2 1200 km radius ii outer core 1 liquid does not transmit shear waves 2 over 2200 km thick iii lower mantle 1 more rigid than asthenosphere 2 over 2200 km thick iv Asthenosphere 1 below lithosphere but part of upper mantle 2 weak zone allows lithosphere to move around 3 about 500 km thick v Lithosphere 1 rigid crust and uppermost mantle 2 250 km thick Evolution of the Solar System Nebular hypothesis p 10 about 5 b y a Cloud of atoms mostly hydrogen and helium b Gravitational collapse contracted it into rotating disc c Heat of conversion of gravitational to thermal energy fired Sun into star in center of nebular cloud d Cooling allowed condensation of rocky particles in inner solar system that collided to become planets accretion i Their accretion created gravitational heat of contraction warm but fairly small ii Unable to attract much lighter elements e Outer nebular cloud stayed cool i Ices of methane carbon dioxide ammonia and water ii Cooler at greater distances from Sun 1 these solid particles collided to become outer planets 2 Large quantities existing there allowed these planets to become enormous and attract and hold lighter elements Big Bang happened before all of this 14 billion years ago a created the universe the early galaxies and the first generation stars b Remember Sun is a second or third generation star the nebular cloud of dust and gases was created by a supernova of a pre existing star Page 3 of 5 8 9 History of Astronomy ch 21 a Most ancient civilizations believed that Earth was at the center of the universe b Age of Reason beginning to recognize Sun is center c Age of Technology exploring wide reaches of the universe Ancient Greeks thought planets rotated around Earth in perfect circles a Anaxagoras 5th century BC reasoned that Moon had phases because it is a sphere and is lighted by Sun b Aristotle tutor of Alexander BC 382 322 i knew Earth was round from shadow of Earth on Moon during lunar eclipse ii helped cement the Geocentric view of the solar system because 1 Earth has no apparent movement 2 Things do not fly off the surface 3 Looks like the stars and Sun are moving 4 No stellar parallax could be observed 5 Earth must be stationary c Aristarchus BC 312 230 i Determined relative sizes of Sun and Moon by shadows during eclipse events ii Greater size of Sun lead him to believe Sun was center Heliocentric iii Believed Earth s axis was tilted to orbit around Sun and this creates seasons iv Hypothesis discounted due to observations of Aristotle etc d Erastosthenes BC 276 194 Librarian in Alexandria i Determined size of Earth 1 Found notes indicating Sun is directly overhead in Syene on summer solstice 2 Sun was about 7o south of overhead in Alexandria 3 this is about 1 50 of a circle so Earth s circumference must be 50x that
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