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EARTH’S INTERNAL STRUCTURE AND MAGMA FORMATION PROCESSES

EARTH’S INTERNAL STRUCTURE AND MAGMA FORMATION PROCESSES. Oceanic crust. Continental crust. Crust-mantle boundary (MOHO). Upper mantle (down to 660-670 km). Mantle is subdivided mainly based on seismic wave velocities. http://www.nature.com/nature/journal/v451/n7176/full/nature06583.html

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EARTH’S INTERNAL STRUCTURE AND MAGMA FORMATION PROCESSES

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  1. EARTH’S INTERNAL STRUCTURE AND MAGMA FORMATION PROCESSES

  2. Oceanic crust Continental crust Crust-mantle boundary (MOHO) Upper mantle (down to 660-670 km)

  3. Mantle is subdivided mainly based on seismic wave velocities

  4. http://www.nature.com/nature/journal/v451/n7176/full/nature06583.htmlhttp://www.nature.com/nature/journal/v451/n7176/full/nature06583.html Nature451, 266-268 (17 January 2008)

  5. Information from seismic waves • “CAT-scan” of the mantle, using SEISMIC TOMOGRAPHY Faster seismic velocity Colder and stronger rocks Slower seismic velocity Warmer and weaker rocks

  6. http://www.nature.com/nature/journal/v451/n7176/full/nature06583.htmlhttp://www.nature.com/nature/journal/v451/n7176/full/nature06583.html Nature451, 266-268 (17 January 2008) Red = Slow seismic velocity Blue = Fast seismic velocity

  7. Seismic tomography shows that some parts of the mantle are hotter than others Would result in heat transfer Conduction in lithosphere Convection in asthenosphere

  8. http://www.es.mq.edu.au/gemoc/Participants/AcademManag/SueResources/4DMapping.htmlhttp://www.es.mq.edu.au/gemoc/Participants/AcademManag/SueResources/4DMapping.html 4D Lithosphere Mapping: a methodology and philosophy for tracing the architecture and composition of the lithosphere through time Fig. 2.13, page 31

  9. CONVECTION • Heat transfer that results when warmer, less dense material rises, and cooler, denser material sinks http://www.columbia.edu/itc/ldeo/mutter/jcm/Topic3/Topic3.html

  10. CONVECTION • Convection within the mantleused to be considered by some to be a major driving mechanism of plate tectonics (“ridge push” mechanism, page 30) http://www.columbia.edu/itc/ldeo/mutter/jcm/Topic3/Topic3.html

  11. http://anquetil.colorado.edu/szhong/

  12. Melting by lowering pressure • Melting temperature of a solid goes UP under high pressure (becomes difficult to melt) • Melting temperature of a solid goes DOWN under low pressure (becomes easier to melt) Is the major process of magma generation at divergent boundaries and hot spots (pages 30-31)

  13. Rocks start to melt Pressure is reduced and hot rocks from asthenosphere move upward (convection) At divergent boundaries and hot spots, lithosphere becomes thinner due to pulling from subducting slabs

  14. Melting caused by decreasing pressure is called DECOMPRESSION MELTING Example: Hawaii (hot spot) Mid-Atlantic Ridge (divergent boundary)

  15. A little note on hot spots … • Hot spot volcanoes are NOT associated with any plate boundary (example: Hawaii, Yellowstone, Galapagos island etc.) • They develop over columns of very hot, plastic rock called MANTLE PLUMES (pages 39-44)

  16. LINK TO: http://karel.troja.mff.cuni.cz/staff/HANKA_CIZKOVA/Anim/animace.htm Dr. Hana Cizkova (Kyvalova)

  17. Adding water under pressure Melting temperature of a solid goes DOWN when water is added (wet rocks melt more easily than dry rocks) Is the major process of magma generation at subductionzones (page 37, figure 2.18)

  18. Increasing temperature: When magma passes through and melts other solid rocks Not a major process of magma formation

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