EARTH121 Lecture Notes - Lecture 12: Accretionary Wedge, Alpine Fault, Fracture Zone
21 Dec 2017
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Earth(cid:859)s (cid:373)ag(cid:374)eti(cid:272) field is like a si(cid:373)ple (cid:271)a(cid:396) (cid:373)ag(cid:374)et; e(cid:454)te(cid:374)di(cid:374)g f(cid:396)o(cid:373) o(cid:374)e pole to the othe(cid:396); certain rocks contain minerals that serve as a fossil compasses. Even if rocks are moved, usually magnetism is retained. Paleomagnetism: fossil magnetism contained by rocks that were formed thousands or mya and recorded location of magnetic poles at the time; studied by edward a. irving who provided first evidence of continental drift. Study by k. runcorn & associates showed locations of poles have wandered from the past. 500my until their current position rn known as polar wandering (lava flows moving) aka continents drifting. Polar wandering is explained when separated continents (due to continental drift) are placed next to each other and the curves overlap. During 1950s &60s ocean was mapped and global oceanic ridge was discovered. Harry hess in the 1960s had proposed sea-floor spreading ocean ridges zones location above upwelling; and proposed deep-ocean trenches are where ocean crust is drawn inwards.
