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Lecture 3

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Environmental Science
Nick Eyles

Lec03  250 mill.yrs ago pangea  Earth history is the oceans history  Uniformitarism-how ancient rocks are preserved/detected - geologic phenomena may be explained as the result of existing forces having operated uniformly from the origin of the earth to the present time.  Rifts,are narrow cracks then widen to young oceans - Super volcanoes,in new Zealand,15 metres thick,capable to bury north America to ashes - Plate tectonics-all the plates go around the margins - Vertical tectonics-huge magma come from mantle and erupt nd they are they called igneous rocks,lups…they are very important economic, contains a lot of gold.and have connection with the biological extinction on earth history mantle rapidly built thick piles of hydrously altered mafic to ultramafic volcanics. - Magma-first for volcanoes to be made ..oxygen,salt..sulphur gas all toxic - Uniformifarmitism-It’s a Geological timescale we cant comprehend - Today go to east Africa.,,ancient ocean first opened - Continental slab-plate motion - Rifts(cracks)-widen - Triple junctions and auglacogens (failed rifts) fig.2.4-only two arms grow up and become active rift, nd one will fail will never develop (Russian rifts)…these are the rifts develop during pangea breaking up - East Africa-ocean first opened - Fig.2.4 magma Trapping heat, wants to escape but cant since continental crust on top..process called inflation,tht is why supercontinents are dry(not good for diversity of life forms) - Failed rifts fill up sediment ovr time-first place to discover oil/gas…. - lake Ontario have failed rifts - failed rift can reactivate,its around all the continents…will have intraplate earthquake- in the interior of a tectonic plate faults near plate margins - structurllly controlled by the rocks below the earth (failed rifts) - fig.2.41 reactivated rifts are widening (volcanic activity,mantle plumes- upwelling of abnormally hot rock within the Earth's mantle …when spread out ,flood basalt Vast sheets of basalt that spread from a volcanic vent over an extensive surface of land; they may form where a rift develops above a continental hot spot, and where lava is particularly hot and has l-ocean crust…very fluid..very key process this is how supercontinents breakup -fig.2.19 ;graben,rind robin …have a ocean widening(ocean seafloor spreading) -arabian plate moving away from Africa Fig.2.2; east African rift system,breakup of the African plate and birth of a new ocean -looks torn apart,for birth of a new ocean -basalt magma when come out of volcano gets mixed with silica (thickening)will increase its viscosity. Will form very steep slopes.since the gas can explode in steeper slopes -when volcano explodes…..there will be caldera(rock) nd gets broken up and then turns into ash(dust),pyroplastic(rocks tht are broken by fire) - tuff(hard ash) -east African rift-birthplace of a new ocean and cradle of humans -homo habilis-‘handy man’ creation of tools 650cc;made stone axes -Date those ash layers, can date human evolution -in a rift valley,climate change gets amplified…pluvey..wet and dry period…major influence on human evolution -shield volcano-associated with flood basalt, domed volcano with gently sloping sides, characteristic of the eruption of fluid, basaltic lava -salt comes from evaporation of water -afar triangle-rift widening,Arabian plate moved out,plate filling up with flood basalt…how make thick ocean floor crust -crater;builds up lava and then overflows it’s a continium -transform fault-diverging;red sea rift -big contrast with north Egypt-made up of limestone-the south is made up of granite -cheop’s pyramid-tura limestone(facing limestone);bioclastic limestone-made entire of fossils coin szed-nummulities(ferraminofera) -mokkatam limestone-facing limestone-first -tura can be smooth too  fine-grained micrictic limestone  south-cause of the rifting we got uplift younger rocks get stripped off..has gabbro..igneous rock..same chemistry of basalt but never quite made over surface courser grain of basalt ,nd quartzite,sandstone/pylon,granite,obelisk  rock names having ancient Egyptian source: poryphyry-give to any igneous rock tht crystal is very lrg,basalt,alabaster,syenite,ophiolite-basalt altered by heat and pressure,green color, ancient ocean crust  poryphyry…sum purple rock associated with royalty in Egypt  gold was thought tobe the skin of the gods,orginate from the south  3150 yrs old-geological oldest map;written by ramses ,wadi  Hot water forced into rock,as water cools then have minerals call quartz having (white colored) vines contributing to gold  Dead sea rift(lowest point on the planet)-transform boundary b/w Arabian and African plate  Colliding with Eurasian plate  North anno fault-transform fault  Eastern bold-built right on top of the boundary..  Each successive earth quick moves thru  Seismates:frequency of earthquick nd impact  Look at sediments(deform rocks) will tell how frequent the earthquake are  Lithium comes from salted rock  Dead sea has gone done cause of sediment layer witin them they have seismates..Seismate risk analysis  Wall offset by slip along plate boundary;b/w sini-isereal and Arabian plate  Ancient roman city of hippos;destroyed, AD749-can find out where the earth quake was, how big the earthquake was, eracter scale or,mercalli scale..identifes the damage done by a major earthquake)Seismic wave direction,the whole idea is to predict whens the next ones going to be..the frequency lec.  petra,hidden city,place abandoned quite quickly
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