CEE 1030 1nd Edition Lecture 14 Oceans and Continents Outline of Last Lecture I Calculating the density of Earth II Seismology III Boundaries a Crust mantle boundary b Core mantle boundary IV Seismic Tomography a The core b The mantle c The crust V Earth s internal heat engine Outline of Current Lecture I Mapping the ocean floor II Types of continental margin III Types of plate boundaries IV Isostasy and crustal thickness V Origin and evolution of continents Current Lecture I II III Mapping the ocean floor a We know more about the surface of Mars and the moon than we do about the ocean floor b 5 of ocean floor has been mapped in detail c SONAR Sound Navigation and Ranging d Multibeam sonar map bathymetry over a 10 20 km swath slow e Can use satellites to map features Types of continental margin a Passive continental margin i Include continental shelf continental slope continental rise b Active continental margin i Located primarily around Pacific Ocean where oceanic lithosphere is being subducted beneath leading edge of a continent Types of plate boundaries a Interactions among individual plates occur along their boundaries These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute IV V b Where most of the geological action is c Types i Convergent plates move together 1 Features subduction zones volcanic arcs collision belts 2 Continental collisions result in the development of mountains 3 Fold and thrust belts deformation of thick sequences of shallow marine sedimentary rocks Isotasy and crustal thickness a Isotasy less dense crust floats on denser deformable rocks of the mantle in gravitational balance b Isotasic adjustment when weight is added to the crust it will respond by subsiding c Returns crust to normal thickness d Erosion and uplift happens to mountains so interior of the mountain will be exposed to surface e How high can mountains get i The higher mountains get the more gravitational forces work with erosion and mass wasting ii The higher the mountain the greater the downward force on rocks near base iii Hot deep crust not strong enough to support the weight of the mountain resulting in gravitational collapse Origin and evolution of continents a Some continental crust was formed early in Earth s history old fragments preserved in Canada and Greenland b Silica rich rocks such as granite are less dense than the mantle so they float at the surface c Plate tectonics constantly rearranges continents and adds new material d How continents grow i Accretion of terranes 1 Small crustal fragments collide and merge with continental margins ii Terrane crustal fragments whose geologic history is distinct from that of the adjoining terranes e Oceanic plateaus and islands are too thick to subduct f Island arcs are too buoyant to subduct
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