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Lecture 2

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Environmental Science
Nick Eyles

Planet EarthLecture 2 Formation of Earth4 500 million yrs agoContinental drift and pangaea 1912Alfred WegenerSea floor spreading 1960Harold HessMagnetic Stripes on the ocean floor and wander paths for continents 1965Fred VineMidocean ridges and hot spots 1965Tuzo WilsonPlate tectonicsWilson Cycle 1967Tuzo WilsonPlate tectonics is a hypothesis and its about 20 years oldIts not the continents that are drifting its the larger plates that continents are embedded withinAlfred WegenerMeteorologiststudied craters on the moonAlready early ideas that the continents fit together but noone stated it scientifically until Alfred WegenerPangaea consists of Laurasia Northern AmericaAsia and Gondwana Southern ContinentsHow did Wegner prove that all continents were togetherEvidenceRocksLook at the rocksyoull find out about climate belts and the rocks ageAnd if you reassembled the continents youll be able to see thisPaleobiologyfossil organismsThese were land animals there is no way they could have swam across oceansIce SheetsGlacialsRocksStriations are scrathes that are made by iceThey tell us the direction of ice flowWherever you go in Canada ice flow is from the NorthSo ancient rocks have these scratchesLook at geochemistry of the glacial sedimentslook for dispersed mineral fragments of the metals were interested in and we found anomalies higher concentrations than normal to project back to the pastWegener proposed that continents moved by plowing through the sea floorHis theory gets rejectedHe dies in the 1930sBut then 1960s the ocean floor gets mappedGeophysical techniques were developedapplication of physicals to understanding geologyInstuments are soundbasedaccousticTime it takes tells you something about the density of rocksSound waves reflect off different layersSeismic statrigophySwath bathymetry mapping broad areas of the seafloor to get accurate mapsSidescan Tow Vehicle black and white picture of sea floor based on soundClassic thing that appeared is that ocean floors are NOT FLATMidocean ridge MORsFeature of all oceans occuring along the middle of the oceans There are fracturesbreaks that run across themvolcano beltsWestern Pacific There are deep water trenches depth of up to 9 kmSo 1960s midocean ridges trenches
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