Sunday, 14 February 2016


Internal structure of earth :

The earth is made up of several concentric layers. Concentric means having a common centre. The earth has one layer inside another.
Broadly, there are three layers of the earth:
a. Crust
b. Mantle
c. Core

The Crust:

·        It is the outermost layer over the earth’s surface.
·        It is the thinnest of all the layers.
·        About 35 km on the continental masses and only 5 km on the ocean floors.
·        The main minerals constituting the continental mass are:
• Silica
• Alumina
·        The continental mass is also called ‘sial’.
·        The name sial is derived from letters ‘si’ of silicon and ‘al’ of alumina.
·        The main mineral constituents of the oceanic crust are:
• Silicon
• Magnesium
·        The oceanic crust is called ‘sima’.
·         The root of the word sima is ‘si’ from silica and ‘ma’ from magnesium.

Mantle :


·        It is the layer just beneath the crust and extends up to a depth of 2900 km below the crust.
·        As Earth began to take shape about 4.5 billion years ago, iron and nickel quickly separated from other rocks and minerals to form the core of the new planet. 
·         The molten material that surrounded the core was the early mantle.
·        Over millions of years, the mantle cooled. Water trapped inside minerals erupted with lava, a process called “outgassing.”
·        As more water was outgassed, the mantle solidified.
·        The transfer of heat and material in the mantle helps determine the landscape of Earth. 
·         Activity in the mantle drives plate tectonics, contributing to volcanoes, seafloor spreading, earthquakes, and orogeny (mountain-building).

Asthenosphere :

·        The asthenosphere is the denser, weaker layer beneath the lithospheric mantle.

Core :

·        It is the innermost layer .
·         The core consists of outer core and inner core.
·        It is mainly made up of:
• Nickel
• Iron
·        The innermost layer is also called ‘nife’.
·        The name nife is derived from the word ‘ni’ from nickel and ‘fe’ from ferrous meaning iron.
·         The temperature and pressure of the central core is very high.

Outer Core :

·        mostly composed of liquid iron and nickel.

Inner Core :


·    The inner core is a hot, dense ball of (mostly) iron.
·        The temperature of the inner core is far above the melting point of iron.
·        However, unlike the outer core, the inner core is not liquid or even molten.
·        The inner core’s intense pressure—the entire rest of the planet and its atmosphere—prevents the iron from melting

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