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GEOGRAPHY FORM THREE: TOPIC 1: STRUCTURE OF THE EARTH

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GEOGRAPHY FORM THREE: TOPIC 1: STRUCTURE OF THE EARTH Feb 15, 2017 TOPIC 1: STRUCTURE OF THE EARTH  The earth has Internal and External structures INTERNAL STRUCTURE OF THE EARTH The earth is composed of three internal, concentric layers of increasing densities. These layers are the  crust, mantle  and  core.  They are made up of different layers of rocks, with their densities increasing towards the centre of the earth. That is, densities of rocks that make up the earth increase as you move from the surface towards the interior The Crust (Lithosphere) This is the outermost part of the earth. It consists of silica and aluminium (sial). It forms the upper layer of the continent and is mostly composed of granite rocks. The layer below SIAL is called SIMA. This layer is made of silica and manganese. It is a layer of basaltic rocks which are denser and underlies the continental block to form the ocean floor. The Mantle (Mesosphere) This is the layer below the crust. ...