Earth Sciences 2123F/G Lecture 8: Plate Tectonics

• School: Western University
• Department: Earth Sciences
• Course: Earth Sciences 2123F/G
• Professor: Catherine Neish

Document Summary

Alfred wegner father of continental drift theory 1915. Wegner could not suggest a viable mechanism to move plates, so the idea of continental drift died with. But (cid:271)(cid:455) (cid:1005)95(cid:1004)"s it e(cid:374)jo(cid:455)ed a re(cid:448)i(cid:448)al as a result of the (cid:272)olle(cid:272)tio(cid:374) of (cid:374)e(cid:449) data sets (cid:449)ith u(cid:374)e(cid:454)pe(cid:272)ted features: earth"s past (cid:373)ag(cid:374)eti(cid:272) (cid:373)o(cid:448)e(cid:373)e(cid:374)t. Similarity of rock assemblages on different continents. In 1956 re-established viability of the theory of continental drift by construction of the relative motions of europe and america. Igneous: find that earth"s (cid:373)ag(cid:374)eti(cid:272) field re(cid:448)erses dire(cid:272)tio(cid:374) o(cid:448)er hu(cid:374)dred of thousa(cid:374)ds of (cid:455)ears. Last magnetic field reversal 780,000 years. It changes every 5,000 years with unknown effects. Magnetic stripes on the seafloor: oceanographers conducted magnetic surveys of ocean floors, discovered alternating stripes of high and low intensity magnetism, stripes were symmetric about ocean ridges. Width of strips determined by speed of seafloor spreading and timing of magnetic field reversals. The ne(cid:449) glo(cid:271)al te(cid:272)to(cid:374)i(cid:272)s of the (cid:1005)97(cid:1004)"s earth"s ulti(cid:373)ate re(cid:272)(cid:455)(cid:272)li(cid:374)g progra(cid:373)