ERS120H5 Lecture Notes - Lecture 3: Isostasy, Mantle Convection, Oceanic Crust
15 Jan 2018
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Winter 2018: wegener"s continental drift hypothesis, proposed in 1912, based on 4 main pieces of evidence: Four kind of main fossils found across the continent (pangea) Same question as above point: matching glaciers, one giant glacier cover a large portion of pangea, as the glacier flowed out, the rocks would have scraped the surface beneath. Is it more logical that there is one giant glacier (antarctica) or they formed separately: wegener"s sea-floor spreading, polar wandering and reversals. Some rocks are magnetic: seafloor spreading, what do magnetic rocks tell us, earth"s magnetic field that magnetizes iron-bearing rocks as they crystalize, harry hess (1960s) conclude magnetic surveys across the atlantic sea floor. Found symmetrical magnetized bands of rocks around a center line that runs down the atlantic: the bands alternated between normal polarity and reversed polarity. Seafloor spreading: driven by convection (example of boiling water in a pot) Seafloor spreading = divergent boundary: constructive - new oceanic crust is made.
