Internal Structure of the Earth
The evidence used to study the earth’s interior are
- mining
- drilling
- quarrying/excavation
- 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
- Sial
a. Also called continental crust
b. Made of light coloured rocks
c. Called sial because it’s made up of silica and aluminium.
- Sima
a. Also called oceanic crust
b. Mainly made of basaltic rocks which are brittle.
c. Called sima because it is made of silica magnesium and iron.
Mohorovicic Discontinuity (Moho)
a. A definite zone of discontinuity between the crust and the mantle.
b. Was discovered by Dr. Andrija Mohorovicic in 1909.
- The Mantle/Asthenosphere
a. Layer lying between the crust and the core
b. Made of iron and magnesium
c. Has two layers
- Upper mantle
a. Rocks are more elastic than those of sima.
b. Temperature is about 1000◦c.
- lower mantle
a. Rocks are like very viscous liquid.
b. 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
Gutenberg Discontinuity
A definite zone of discontinuity between mantle and core.
- Core/barysphere/Centrosphere
a. The innermost/central layer of the earth.
b. Has 2 layers
Outer Core
a. Composed of very dense rocks
b. Made up of nickel and iron
c. Temperatures are up to 3700◦c.
Inner Core
a. A solid mass of mainly iron
b. Temperatures are estimated to be 4500◦c to 5000◦c.