GEOL 101 Earth's Core and Ocean Creation
GEOL 101 Earth's Core and Ocean Creation GEOL 101
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This 0 page Class Notes was uploaded by Victoria Williams on Monday March 14, 2016. The Class Notes belongs to GEOL 101 at George Mason University taught by Mark Uhen in Fall 2016. Since its upload, it has received 28 views. For similar materials see Introductory Geology in Geology at George Mason University.
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Date Created: 03/14/16
Core Mantle Boundary 0 P Waves can go through the earth s core while S waves cannot go through the core because S waves cannot ow through liquid 0 Earth s Core 0 O O The outer core is a liquid as indicated by the S Wave Shadow Zone The core is composed mostly of iron some nickel and about 15 of lighter elements The change in density between the mantle and core is greater than between air and rock at the surface The solid inner core is almost completely iron 0 Inner Core Spin Imagine a marble inside of J ell O the center is completely solid but the outer core is still moveable The core spins 0 Sources of Earth s Heat 0 O The initial source of heat was input by collisions of many planetesimals Kinetic energy of these collisions was converted to heat Heat added by the decay of short lived radioactive elements Collision of a Mars Sized object led to the formation of the moon Earth has cooled since then Additional heat is added from longer term radioactive decay 0 Conduction and Convection Transferring Heat 0 O Conduction is heat traveling through a material like a metal spoke you put in a fire After a while the end of the spoken you are holding will get really hot too Convection happens when uid material liquids gases heat up and rise then fall as it cools then heats up again by the source of the heat and the material will rise again Compare it to boiling water over a fire The hottest places on earth s surface is the mid ocean ridge 0 Earth s Gravity The earth is NOT a perfect circle The spin of the planet causes the edges of the earth to become wider and the planet vertically compresses by a tiny bit So if you are at the North Pole and weigh 200 pounds you will weigh 199 pounds at the equator 0 Levels of gravity change all over the place gtgt 0 Earth s Magnetic Field a 0 As uid rises in the liquid Scale WZQUUUUUUU 250 500 750 1000 1250 1qu core it twists due to the rotation of the earth 0 Because the uid is electrically charged it creates a magnetic field like an electromagnent 0 This is called the geodynomo O Earth s magnetic pole is moving all the time not by much but it s still moving 0 Dip needles a kind of compass needle and levels perpendicularly to the magnetic field facing north Ocean Composition 0 Mapping the Sea Floor 0 Basic Sonar Originates from the shipsubmarine and bounces off the ocean oor then returns to the ship which records it to map the ocean oor 0 Sidescan Sonar A new way of mapping the sea oor by towing a sonar scanner behind a ship that can produced a detailed scan of the sea oor 0 Seismic Profiles 0 Low frequency sound waves penetrate sediments to imagine underlying bedrock 0 Sea Surface Anomalies 0 Variations in the mass of the sea oor create piles of water over more massive features due to differences in the pull of gravity 0 Two Types of Continental Margins 0 Passive Margins are present when there is no break between continental and oceanic crust No active tectonics are going on I There is a continental shelf which is a part of the continental crust that is ooded by the ocean it has a very gentle slope I The oceanic crust is defined where there is a shelf break and a continental slope These slopes are relatively steep and they dip down deep into the ocean I When you finally hit the oceanic crust it s called the abyssal plane Deep Sea fans form here 0 Active Margins form where oceanic lithosphere is being subducted underneath a continent An accretionary wedge forms on the edge of the overriding plate from sediment and tectonic blocks scraped off the subducting plate The scraped material gathers in the wedge 0 Deep Oceanic Basis Trenches 0 Deep ocean trenches are long narrow areas of the ocean oor that are extremely deep They represent the boundary between a subducting plates 0 Abyssal Plains 0 Bottom is composed of fine continental sediments and marine microfossils When an animal dies in the ocean their skeleton slowly oats down to the bottom and settles I Seamounts guyots are submarine volcanoes that rise above the ocean floor but do not rise above sea level These seamounts are basically cooled volcanoes that are sinking into the ocean cool things sink As these sink they form reefs and lagoons But once it sinks below the photic zone it becomes a seamount underwater volcano while heading towards the subduction zone I Oceanic plateaus are large raised areas on the ocean oor composed of thick layers of basalt which come from basaltic magma spilling out of the crust I Oceanic Ridges or mid ocean ridges are elevated linear features that mark the divergence of two areas of oceanic lithosphere The ridge in the Pacific ocean grows the fastest the ridge south of India Australia and Africa grows at an intermediate rate then the Atlantic ridge is very slow at growing 0 Oceanic Ridge Topography 0 Slow forming oceanic crust creates a well developed rift valley 0 Fast forming oceanic crust doesn t have the time to develop well and just makes little bulges in the crust 0 Ophiolite CompleX A cross section adjacent to a mid ocean ridge 0 The deep sea sediments are composed of sediment and skeletons of animals 0 Pillow Basalt is Typical Uphiel ite Suite iteica39 dareiii sens em Dphiullte Suite Deep Sea Sediments chart created When ladiulairians valta nagenic a n u m mmm mummmnnu m mf F llruw Lamas spherulltlc amygElalcuilzl all ea llHlDEChi mlIE l th pyF DKE39HRELDll39lETlC the Dikes Mined Hallie and Lavans dyke swarms Fillew Emits g reensehist and eenlite laties Sheated Byline EDWI EMEJ learn tlyllesv porphynitin separate and El39lrllilll39lrlil llEGlliu39ll Dll l l39leyll KElFlEpll39llf 39icj reel and buegreert weathering diabasie pink weathering W microg abbrIzlilz39 basal and upper contavrts lax gradatlenal er faultedruated iin cumulate eel nplea the laVa ShOOtS 39li l Shutdi Byline implant vertical r M sheets of lined grained gabbre Hf Layered Ea hliraa amphihellte Eagle of anerthasite and FIaglagranlte gladlng dewnwam 3quot lb lmm i Elm ITIEISEWE39 gabbm39 gabbrenet iteminernairnblentledinrlteantl 11p Ollt 0f the 39le write olivine xxx trend hjemlte locally layered basal quot k1 breceiatetl faciee crack and Eggl39i l dlflrgte t 5 fr quot quot a layered Cumulatesnumtilate periclntites N 39 F J at Eller EMIE fr quot39 quotquot l39 all llherznlite hanhurgtlte dunitEII pymxenit s f b 3 1 lorthopyroxeniteclinopwoxenitewebstelitei 011118 a O Unlawmd Eerpen ini d Peridati 9x loading St rlJlCIIVIJFESrE LJl by pyraixenile and gabbm petldmlte with dunlte hamburgite l at dli39k 39 and EMS and olivinewroxenite 51 l it Tallyaeemenrtlnlte Schismaalterad and 39 A Iquot dietarmed peridatites peridotitie conglomerates 39 535 l F Elfld 39tlfll braceletstalemmagnetiteumagnesitem i ankeritemlphid e schists Ii I l 0 Continental Rifts O The best example of this is in East Africa where there are Rift Valleys This is an example of a triple junction East Africa and the Arabian Peninsula are separating and creating a new ocean basin which is currently the Red Sea The other two prongs of the junction are the rift valley and the Gulf of Aden 0 Ocean Basin Evolution Walla va ei f New Ocean Basin End Sui Ridge Mature Ocean Atlantis Sediments 0 Mantle Plume and Gravity Sliding O O O O A mantle plume create a bulge underneath a continent Decompression melting creates a large volume of magma that triggers volcanism This break in the surface initiates rifting An example of this is between South America and Africa A plume of magma formed under the continents when they were together but the plume kept owing and broke the surface into a rift The rift kept producing new oceanic crust and eventually completely separated the two continents 0 Slab Suction O O O O Roll back of the trench creates ow of the asthenosphere This ow pushes the continental plate toward the trench This motion creates tension on the continent which causes rifting It s like tearing off a piece of land which allows magma to rise where the tear is in the continent creating a new rift 0 Death of a Plate 0 Plates subduct at different angles and different speeds O The Farallon plate used to be prominent 5 6 million years ago on the West Coast of the United States The plate was subducting so fast and the West Coast was moving to the west very quickly The Farallon plate cannot keep up with how fast it is being eaten up by North America so now there is only a small fraction left in the northwest called the Juan de Fuca plate