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Lecture 3

Lecture 3 Notes

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Environmental Science
Nick Eyles

Planet EarthLecture 3 Chapters 34UniformitarianismVery important concept in geologyFrench use the word actualismWhats happening today is a guide to what has happened in the ancient pastWe use clues from modern day to interpret ancient records rocksExceptionsThere are things that have happened in the past that havent happened in our timeExamples of processes meteorite strikes 65 million years ago supernova supervolcanoes Yellow StoneGeological processes are operating on a timescale that we cannot comprehendSo a mix of uniformitarianismcatastrophismPlate TectonicsAssumption that all activity goes on around plate marginsBut you can interpret part of the history in what we call vertical tectonicsHuge amounts of magma arise from mantle and erupt on Earths surfacelarge igneous provincesLipsTheyre very important in Canada economicallycontain a lot of goldWhat else comes up in the magmaWater vapour creating oceansSulphuric gasesMineralsHow Continents Break Up and Ocean FormsModern oceans form narrow cracks called rifts and then they widen to form young oceansEast Africa Where geologists go to understand how ancient oceans opensTriple Junctions and AulacogensFailed riftsA continental slab part of a supercontinent being warmed from below so it rises due to heat inflationAnother reason why interior of supercontinents are dryso supercontinents dont provide a range of environments for lifeusually has one deep oceanOnce supercontinent rises it it splitsyou see a triple junctionthree parts of the riftOnly 2 of the gaps grow up and become active riftsThe other is just a crack that never develops furtherit just fills up with sediment overtimecontain a lot of oilgasinterest in their formation for economic purposesWere not too far away from a failed rift in Toronto St LawrenceFailed rifts are preserved in modern continents from the break up of pangeafailed rifts from a long time ago have left a mark on the world we see todayThese failed rifts are present in all the continentsevery now and then they shiftWhen theyre activated they produce intraplate earthquakesa reason for why we might have earthquakes in the North American plate instead of marginsMost of the worlds large rivers Mississipi all follow these old failed riftsThey are structurally controlled by the rocks that lie at depthEast AfricaRed SeaGulf of Aden are ACTIVE failed riftsMantle plumes also play a roleFlood basalts
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