Chapter 1 Earth s Structure most common mineral is silica The deeper you go in earth the denser it gets metal in center Increase in pressure and temp due to weight of overlaying rock Geothermal gradient rate of change in temp with depth Crust outermost layer with a depth of 7 to 70 km Consists of a variety of rocks Oxygen and sil icon are most abundant elements Oceanic crust 7 10 km thick Made of sediment clay shells then basalt then gabbro Continental crust 35 70 km thick Made of many rocks mafic and felsic in composition less dense than oceanic Mantle 2 885 km thick consists of ultramafic perdotite solid Core consists of iron alloy Outer core 3 000 5 100 km liquid because of heat and flow gen erates magnetic field Inner core 1 200 km hotter than outer core but solid because it is deeper and has higher pressure Lithosphere outer shell of rock uppermost coolest part of mantle Oceanic 100 km Continental 150 km Asthenosphere portion of the mantle in which rock can flow 1280 degrees Terrestrial planets shell of rock surrounding metallic iron ball Mercury Venus Earth Mars Gas Giants Hydrogen and helium gases Jupiter Saturn Nebular theory explanation for origin of planets and moons objects formed from material in flattened outer part of of the disk that did not become part of the star Outer part is called proto planetary disk Earth has lower of volatile elements hydrogen helium methane etc than gas giants Volatile materials can exist as gas at earth s surface At the frost line they turn to ice Refractory materials melt only at high temps forming dust particles Heat energy due to thermal vibrations Doppler Effect change in frequency when wave source moves Red shift Light source moves away from you so light becomes redder as the light shifts to longer wavelength or lower frequency Scientists saw a red shift meaning galaxies must be moving away from the Earth and expanding known as the expanding Universe theory Big Bang Theory 13 7 years ago all matter and energy were packed into a small point which exploded Formation of nuclei produced only light atoms hydrogen and helium few protons Universe cooled and expanded so atoms and molecules slowed down and accumulated into patchy clouds called nebulae Protostar nebula begins to suck in gas growing in density and getting more compact Because of increased rotation nebula evolves into disk shape Gravity collapses inner portion into a dense ball Temp increases central ball of disk glows As protostar grows hydrogen nuclei slam together to fuse and form helium nuclei Produce heat and energy Few million years before star becomes supernova Stardust earth contains elements that could have been produced only during life cycle of stars Formation of moom Protoplanet slammed into Earth then disintegrated and melted along with part of Earth s mantle Ring of debris formed around Earth and coalesced to form the moon Earth now has a metallic iron core versus the mantle and crust that have lower iron contents meteors tracks of light in the sky formed by vaporizing part or all of small we hope solid ob jects from space that intersect our atmosphere heat up and provide a brief we hope flash of light Small meteors that vaporize completely Meteorites larger meteors partly vaporize and what doesn t can impact the surface Some ce lestial objects are mainly large blocks of ice those will generally vaporize completely even if some survives the trip to the surface Only kinds of meteorites that survive on the earth s surface have stony or metallic compositions netic field rotation of the earth s iron core generates electric currents which create the earth s mag field lines go steeply into the earth at the north rotational pole today steeply out of the earth at the earth s south rotational pole today and the lines near the equator are basically hori zontal today Dipole Earth s magnetic field has two poles Atmosphere main gases include nitrogen 78 and oxygen 21 Air pressure decreases with elevation Four classes of igneous silica rocks greatest to least less dense to densest felsic intermediate mafic ultramafic Review Questions p 33 look at these 2 3 4 12 13 14 16 17 and 18