NCERT Notes: Geography - Inside Our Earth

Inside Our Earth

• The earth, is a dynamic planet.
• It is constantly undergoing changes inside and outside.

Inside Our Earth (UPSC Notes):- Download PDF Here

Interior of the Earth

• The earth is made up of several concentric layers with one inside another.
• Crust – The uppermost layer over the earth’s surface.
• It is the thinnest of all the layers.
• It is about 35 km. on the continental masses and only 5 km. on the ocean floors.
• The main mineral constituents of the continental mass are silica and alumina. It is thus called si-al (si-silica and al-alumina)
• The oceanic crust mainly consists of silica and magnesium; it is therefore called sima (si-silica and ma-magnesium)
• Mantle – Just beneath the crust is the mantle which extends up to a depth of 2900 km.
• Core – The innermost layer is the core with a radius of about 3500 km.
• It is mainly made up of nickel and iron and is called nife (ni – nickel and fe – ferrous, i.e. iron).
• The central core has a very high temperature and pressure.

Rocks and Minerals

• The earth’s crust is made up of various types of rocks.
• Rock- Any natural mass of mineral matter that makes up the earth’s crust.
• There are three major types of rocks-
• Igneous rocks-when the molten magma cools; it solidifies to become igneous rock.
• Sedimentary rocks- igneous rocks are broken down into small particles that are transported and deposited to form sedimentary rocks.
• Metamorphic rocks- When the igneous and sedimentary rocks are subjected to heat and pressure, they change into metamorphic rocks.
• Rocks are made up of different minerals.
• Minerals- are naturally occurring substances which have certain physical properties and definite chemical composition.
• Minerals are very important to humankind. Some are used as fuels. For example, coal, natural gas and petroleum. They are also used in industries – iron, aluminium, gold, uranium, etc., in medicine, in fertilisers, etc.