THE STRUCTURE OF THE EARTH (Internal Structure)

Geography
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THE STRUCTURE OF THE EARTH (Internal Structure)

Internal Structure of the Earth

The evidence used to study the earth’s interior are

  1. mining
  2. drilling
  3. quarrying/excavation
  4. Crust/Lithosphere
  • Outermost layer of the earth
  • Made of soils and other loose deposits of sand
  • The dominant rocks are granites.
  • Extends 0-50km
  • Has 2 layers
  1. Sial
  • Also called continental crust
  • Made of light coloured rocks
  • Called sial because it’s made up of silica and aluminium.
  1. Sima
  • Also called oceanic crust
  • Mainly made of basaltic rocks which are brittle.
  • Called sima because it is made of silica magnesium and iron.

Mohorovicic Discontinuity (Moho)

  • A definite zone of discontinuity between the crust and the mantle.
  • Was discovered by Dr. Andrija Mohorovicic in 1909.
  1. The Mantle/Asthenosphere
  • Layer lying between the crust and the core
  • Made of iron and magnesium
  • Has two layers
  1. Upper mantle
  • Rocks are more elastic than those of sima.
  • Temperature is about 1000◦c.
  1. lower mantle
  • Rocks are like very viscous liquid.
  • Temperature ranges between 1000◦c to 3000◦c.

Why the Interior of Earth Is Very Hot

  1. a) Due radio-active decay causing most of the heating.
  2. b) Due to great pressure as a result of overlying crustal materials.
  3. c) The original heat resulting from slow cooling of the materials which were pulled off the sun

Gutenberg Discontinuity

  • A definite zone of discontinuity between mantle and core.
  1. Core/barysphere/Centrosphere
  • The innermost/central layer of the earth.
  • Has 2 layers

Outer Core

  • Composed of very dense rocks
  • Made up of nickel and iron
  • Temperatures are up to 3700◦c.

Inner Core

  • A solid mass of mainly iron
  • Temperatures are estimated to be 4500◦c to 5000◦c.

Author: Ajayi

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