THE STRUCTURE OF THE EARTH (Internal Structure)
Internal Structure of the Earth
The evidence used to study the earth’s interior are
- 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
- Also called continental crust
- Made of light coloured rocks
- Called sial because it’s made up of silica and aluminium.
- 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.
- The Mantle/Asthenosphere
- Layer lying between the crust and the core
- Made of iron and magnesium
- Has two layers
- Upper mantle
- Rocks are more elastic than those of sima.
- Temperature is about 1000◦c.
- lower mantle
- Rocks are like very viscous liquid.
- Temperature ranges between 1000◦c to 3000◦c.
Why the Interior of Earth Is Very Hot
- a) Due radio-active decay causing most of the heating.
- b) Due to great pressure as a result of overlying crustal materials.
- c) The original heat resulting from slow cooling of the materials which were pulled off the sun
- A definite zone of discontinuity between mantle and core.
- The innermost/central layer of the earth.
- Has 2 layers
- Composed of very dense rocks
- Made up of nickel and iron
- Temperatures are up to 3700◦c.
- A solid mass of mainly iron
- Temperatures are estimated to be 4500◦c to 5000◦c.