NCERT Notes: Geography – Inside Our Earth

UPSC Exam Preparation: NCERT Notes: Geography – Inside Our Earth.

Inside Our Earth

Inside Our Earth

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