CEE 1030 1nd Edition Lecture 14: Oceans and ContinentsOutline of Last Lecture I. Calculating the density of EarthII. SeismologyIII. Boundariesa. Crust-mantle boundaryb. Core-mantle boundaryIV. Seismic Tomographya. The coreb. The mantlec. The crustV. Earth’s internal heat engineOutline of Current Lecture I. Mapping the ocean floorII. Types of continental marginIII. Types of plate boundariesIV. Isostasy and crustal thicknessV. Origin and evolution of continentsCurrent LectureI. Mapping the ocean floora. We know more about the surface of Mars and the moon than we do about the ocean floorb. 5% of ocean floor has been mapped in detailc. SONAR: Sound Navigation and Rangingd. Multibeam sonar: map bathymetry over a 10-20 km swath (slow)e. Can use satellites to map featuresII. Types of continental margina. Passive continental margini. Include continental shelf, continental slope, continental riseb. Active continental margini. Located primarily around Pacific Ocean where oceanic lithosphere is being subducted beneath leading edge of a continentIII. Types of plate boundariesa. Interactions among individual plates occur along their boundariesThese 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.b. Where most of the geological action isc. Typesi. Convergent: plates move together1. Features: subduction zones, volcanic arcs, collision belts2. Continental collisions result in the development of mountains3. Fold and thrust belts: deformation of thick sequences of shallow marine sedimentary rocksIV. Isotasy and crustal thicknessa. Isotasy: less dense crust floats on denser deformable rocks of the mantle in gravitational balanceb. Isotasic adjustment: when weight is added to the crust, it will respond by subsidingc. Returns crust to normal thicknessd. Erosion and uplift happens to mountains, so interior of the mountain will be exposed to surfacee. How high can mountains get?i. The higher mountains get, the more gravitational forces work with erosion and mass wastingii. The higher the mountain, the greater the downward force on rocks near baseiii. Hot deep crust not strong enough to support the weight of the mountain,resulting in gravitational collapseV. Origin and evolution of continentsa. Some continental crust was formed early in Earth’s history, old fragments preserved in Canada and Greenlandb. Silica-rich rocks such as granite are less dense than the mantle, so they float at the surfacec. Plate tectonics constantly rearranges continents and adds new materiald. How continents growi. Accretion of terranes1. Small crustal fragments collide and merge with continental marginsii. Terrane: crustal fragments whose geologic history is distinct from that of the adjoining terranese. Oceanic plateaus and islands are too thick to subductf. Island arcs are too buoyant to
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