Form Five Notes Geography Subject-Kidato cha Tano Nukuu Geography|Geography Notes Form Five|Advanced Level Geography Notes|Notes Of Geography for Form Five|Form Five Notes Geography
STRUCTURE OF THE EARTH
PHYSICAL GEOGRAPHY
TOPIC: - STRUCTURE OF THE EARTH
The earth is a system which composed of two zones. These are
1) Outer zone
2) Inner zone
Thus, the structure of the earth consists of external structure and internal structure.
INTERNAL STRUCTURE / CONCENTRIC ZONE OF THE EARTH
The internal structure of the earth consists of three zones. These are
i) Lithosphere/crust
ii) Mesosphere/Mantle
iii) Barysphere / Core.
LITHOSPHERE / CRUST
Is the outermost and thinnest zone of the earth which found between 8 – 50km or 5 – 30 miles.
It is largely composed of igneous rocks.
Other types of rocks also exist as a result of changes on the earth’s surface. When subjected to forces or any stress.
Igneous rocks are hard and brittle.
The crust also consist of two layers are sial and sima layers.
THE SIAL LAYER
Is the outer layer of the crust which rich in silica and Aluminium minerals.
The sial layer consist of granites rocks with density of about 2.65.
The sial for the basis of the continent.
The presence of silica and aluminium minerals collectively form SIAL layer.
THE SIMA
Is the layer which found beneath the sial.
Is the inner layer of the crust which separated from sial layer by the zone called Conrad discontinuity line.
The sima layer is composed by silica and magnesium.
It has the density of about
It forms the basis of ocean floor.
Note: - Sial and sima layer together forms the crust.
MESOSPHERE / MANTLE
Mesosphere or mantle which found between the crust and core.
It lies beneath the crust
It separated from the crust by the zone of separation called Mohorovic discontinuity line has temperature which may reaches to.
It consist of denser rock to about 3.03 –
It consist of pale green minerals called Olivine (Ferromagnesium silicate) in form of ultra basic rock
It consists of lower and upper mantle.
The upper mantle is rigid and crust to form a large layer called lithosphere.
The lower mantle is less rigid and forms the moltern layer within the earth’s interior called asthenosphere.
Asthenosphere is the molten layer layer which responsible for the balancing movement of the earth’s material called isostatic readjustment.
Asthenosphere has been investigated is found between 100 to 200km below the upper surface.
The Form Five Geography notes has the following topics;
- STATISTICS
- PHOTO
- SURVEY
- MAP
- PHOTOGRAPHY
