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1/5/2011 Earth as a system • The Earth system is also powered from the Earth’s interior • Heat remaining from the formation and • Heat that is continuously generated by radioactive decay powers the internal processes that • Produce volcanoes, earthquakes, and mountains • i.e., The rock cycle The rock cycle The rock cycle: part of the Earth system • The loop that involves the processes by which one rock changes to another • Illustrates the various processes and paths as Earth materials change both on the surface and inside the Earth Earth’s internal structure • Earth’s internal layers can be defined by • Chemical composition • Physical properties • Layers defined by composition • Crust • Mantle • Core Earth’s internal structure • Four main layers of Earth are based on physical properties and mechanical strength • Lithosphere: “sphere of rock”, 5 – 250 km. thick. cool, rigid and brittle. The location of all earthquakes. • Asthenosphere: “weak sphere” 660 km. thick plastic region where rock begins to melt • Mesosphere: “middle sphere” 2240 km thick. Pressure strengthens the molten rock, still hot but also brittle • Core: Mostly iron and nickel, Outer core 2270 km thick. Liquid movement generates magnetic field. Inner core 1216 km behaves like a solid and is as hot as the surface of the sun. Created with Print2PDF. To remove this line, buy a license at: http://www.binarynow.com/ 1 1/5/2011 Dynamic Earth Dynamic Earth • The theory of plate tectonics • The theory of plate tectonics • Involves understanding the workings of our dynamic (always changing) planet • It began in the early part of the twentieth century with a proposal called continental drift – the idea that continents moved about the face of the planet • A theory, called plate tectonics, has now emerged that provides geologists with the first comprehensive model of Earth’s internal workings • Plate boundaries • All major interactions among individual plates occurs along their boundaries Dynamic Earth Divergent Boundary • Plate boundaries • Divergent boundary – two plates move apart, resulting in upwelling of material from the mantle to create new seafloor • Convergent boundary – two plates move together with subduction of oceanic plates or collision of two continental plates. • Transform boundaries - located where plates grind past each other without either generating new lithosphere or consuming old lithosphere • • • • • • Mid-Ocean Ridge Motion: Away from one another Process: new seafloor is created Appears like a scar on the map Earthquakes: yes Volcanics: yes Convergent Boundary • • • • • Motion: Towards one another Common name: Subduction zone Ocean plate always subducts. Earthquakes: yes Volcanics: yes Transform Boundaries • • • • • • • Motion: Slide past one another Apparent motion Process: Strike-Slip Appears like offsets in the Mid-Ocean Ridge Most visible for us is the San Andreas Fault Earthquakes: yes Volcanics: no Created with Print2PDF. To remove this line, buy a license at: http://www.binarynow.com/ 2