Earth’s Crust
•The outer layer of the Earth •Similar to the skin on an apple (thinnest layer) •Made up of both continental (land)and oceanic crust(under the ocean) 5-50 km thick Oceanic Crust •A thin layer of crust that overlies the ocean basins •More dense than continental crust •Mostly basalt rock •Thinner that continental crust. (5-10km) •Younger (newer) than continental crust Continental Crust •Layer of rock which forms the continents •Less dense than oceanic crust •Mostly granite •Thicker that oceanic crust •Older than oceanic crust Lithosphere •Solid outer section of the Earth, which includes the crust (rocky layer) Also, includes the cool, dense, rigid upper part of the mantle Asthenosphere •Solid part of the upper mantle •Weaker, less rigid (plasticity - like silly putty) •Crust moves over the plastic-like asthenosphere •These plates crash into each other. Here the oceanic crust is subducting under the continental crust which creates volcanoes. Mantle •Largest layer of the Earth •Under the crust about 2,890km •Composed of silicate rocks rich in magnesium and iron •Intense heat causes the rocks to rise and then cool and sink. •The process is called convection, which causes the crust to move. Average temperature 3000o Outer Core •Liquid layer 2,300 km thick, second largest •Composed of liquid iron and nickel •Lies between inner core and mantle •Because the magma moves around the inner core, Earth’s magnetic field is created. •Average temperature 4000o -5000o Inner Core •A solid ball of metal •1,250 km thick •Made of solid nickel and iron •So hot it melts everything in the outer core •Spins at a speed faster than the Earth rotates •Densest layer of the Earth •Average temperature 5000o -6000o What are seismic waves? •Waves of energy caused by earthquakes and other rock movement •Travel through some layers of the Earth •Recorded with seismographs • Seismic waves are used to determine which layers of the Earth are solid or liquid. •Some seismic waves cannot pass through certain layers giving us a clue to the layers composition. Comments are closed.
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Erik E. Mason
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