internal structure of the earth
LESSON 12: THE INTERNAL STRUCTURE OF THE EARTH
Evidence from earth quake volcanic eruption, digging into the earth crust has shown that the earth is composed of many circular layers which are divided into 3
Main layers of the earth surface
There are three main layers of the earth namely; THE CRUST, THE CORE, THE MANTLE
- The earth crust
Another name for the crust is the LITHOSPHERE it is the outer most layer of the earth. It is 6 kilometer beneath the ocean but below the continent it is between 35 to 40 kilometer. It is the thinnest layer of the earth it is subdivided into 2 namely SIAL and SIMA
- SIAL: it is the continental rock. It is made up of igneous, sedimentary and metamorphic rocks. This rocks are made up of mineral such as Silicon(Si) and Alumina(Al) and so it is called sial
- SIMA: It is the oceanic crust. It occurs beneath the ocean floor and extends beneath the continental crust. It is mainly made up of basaltic salts these rocks contain Silica and Magnesium thus it name SIMA
Since the sial is lighter than the sima the continents, therefore are said to be floating on the denser sima
- The mantle
It is also called the mesosphere and is about 2900Km thick. The mantle contains very dense rocks rich in olivine mineral (iron and magnesium silicate). Its density is between3 to 5. The temperature at this level is 5000°c hence rocks re in their molten form .The production of magma is done at this layer
- The core
It is found beneath the mantle its diameter is 6900Km. It is divided into 2 parts namely THE INNER AND OUTER CORE. The outer core is in the molten state and contain mainly Nickel (Ni) and Iron (Fe). The inner core is in a solid state and consists mainly of Fe. It has a temperature of 5500°c and a density of about 5 to 13
The earth layers are separated by boundaries
- Boundary between crust and mantle is called the MOHOROVICIC DICONTINUITY
- Boundary between mantle and the core is called the GUTENBERG DISCONTINUITY
