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Why is earth geologically active?

       1- Internal Structure: -

              -Core: The highest density material; consists primarily of metals such as iron and nickel.

              - Mantle: Rocky material that have medium density- mostly minerals such as silicon and oxygen, forms the thick mantle that covers the core.

              - Crust: The lowest density rock, such as granite and basalt (volcanic rock) forms the thin crust that essentially covers the world's outer skin

            - A planet's lithosphere is its outer layer of cool, rigid rocks.

         2- Internal heat is the primary driver of geological activity, because the heat supplies the energy needed to move rock and re-shape the surface. Heat     travels in the mantle through convection.

        3- Magnetic field: is generated by the motions of molten metal in the earth's  liquid outer core