RBSE Class 11 Geography Notes Chapter 4 Interior of the Earth

Go through these RBSE Class 11 Geography Notes Chapter 4 Interior of the Earth contain important concepts so that students can score better marks in the exam.

Rajasthan Board RBSE Class 11 Geography Notes Chapter 4 Interior of the Earth

→ The interior of the Earth is invisible and unreachable. Due to the rapid increase in temperature with depth, more deep mining and exploration work are not possible.

→ Lava and hot gases coming from volcanic eruptions are the source of information about the internal structure of the earth.

→ Seismology provides more scientific and authentic information about the geological structure of the earth’s interior.

Sources of Information about the Interior Structure of the Earth

  • Information about the interior structure of the earth is obtained from artificial sources, meteorites and natural resources.

Artificial Sources

  • Temperature, pressure and density are artificial sources of information about the internal structure of the Earth.
  • Going from the surface of the Earth to the center, the temperature increases by 1°C every 32 metres.
  • Rocks are plasticum solid because of the high pressure and high temperature in the center.

RBSE Class 11 Geography Notes Chapter 4 Interior of the Earth

Meteorite Shower

  • Meteors are a part of the solar family. They sometimes fall on the ground.
  • Nickel and iron are found in the composition of meteors. Earth also reflects the properties of magnetism. Therefore, it should have the same composition.

Natural Sources

  • Volcanic eruption and earthquake science are the natural means of obtaining information about the interior structure of the earth.
  • Magma, lava and seismic waves coming out of the volcano provide information about the earth.
  • An earthquake is the accidental vibration of the crust. The point at which the vibrations starts it called the earthquake origin.
  • Seismic energy travel in the form of P, S and L waves. The area between the 105° – 145° to the seismic center is the seismic shadow area.

Layers of Interior Earth

  • Three layers of earth are crust, mantle and core.
  • Crust is the outer layer, mantle is the middle layer and core is the innermost layer of the Earth.
  • The average thickness of the crust is 30 km, the mantle layer extends from crust to 2900 km whereas the core extends from 2,900 km to 6371 km.
  • The core is divided into two parts – the outer core (2900 – 5150 km) and the internal core (5150 – 6371 km).

Classification of Suess

  • Based on the chemical classification by Suess, the earth is divided into three layers – Sial, Sima and Nife.
  • Sial is made from silica and aluminum, Sima is made from silica and magnesium and Nife is primarily from nickel and ferrium.
  • The average density of Sial is 2.9 – 4.7 and the density of Nife is 11.

RBSE Class 11 Geography Notes Chapter 4 Interior of the Earth

Classification by Van der Gracht

  • Van der Gracht has divided the earth into four layers – the outer silica crust, internal silicate layer, mixed metals and silicate layer and metallic center.
  • The external silica crust is made of silica, aluminum, potassium and sodium, whose density is 2.75 – 3.1. Its depth varies under the continents and the oceans.
  • Internal silicate layer is 60 – 1200 km, whose density is 3.1 – 4.75. It is made of silica, magnesium and calcium.
  • The internal silicate layer is up to 1200 – 2900 km. Its density is up to 4.75 – 7.8. Metallurgical center extends from 2900 km. to the centre of earth. Its density is greater than 11.

Interior of the Earth Notes Important Terms

→ Earth: A member planet of the Solar System, which is inhabited by humans and which revolves around the sun in a fixed orbit, while rotating on its axis.

→ Volcano: A mountain or hill, typically conical, having a crater or vent through which hot and fluid lava, rock fragments hot vapour, ashes, water, etc. erupt from the earth’s crust.

→ Rock: In simple language, a solid body is called a rock.

→ Meteorite Shower: The small celestial bodies (meteors) present in the solar family, residual part of which fall on the earth. They start to burn when they Earth’s atmosphere.

→ Magma: The molten rock found below the surface of the Earth with which hot gases thick, often found.

→ Seismology: The science in which the earthquake waves are studied based on the vibration recorded by special instruments.

→ Seismic Focus: The point in the crust below the surface of the earth from where the earthquake originates.

→ Epicentre: The point on the earth’s surface which is located right above the seismic focus.

→ Surface Waves: The seismic waves which travel on the earth’s surface. These waves travel along the circumference of the earth.

→ Earthquake Shadow Zone: These are those areas on the ground where no seismic wave is recorded.

→ Crust: The crust forms the topmost part of the Earth. It is mainly the outer layer of the Earth which forms continents and oceans.

→ Mantle: Around 2900 km thick layer, situated between Crust and Core, whose density is found from 3.0 to 3.4.

→ External Core: This is the upper part of the Earth’s core found in the liquid state. It is believed to spread from 2900 km to 5150 km.

→ Internal Core: The Earth’s layer is the lower part of the core which is in solid state. It stretches from 5150 to the center of the earth.

→ Astheno Sphere: Below the crust, there is a weak strip in which the rocks are in liquid plastic form.

→ Sial: Term used for relatively light rocks of the lithosphere.

→ Sima: Term used for relatively heavy rocks of the lithosphere.

→ Nife: The word is used for the central part of the earth made of heavy substances, nickel (ni) and iron (fe).

→ Ocean: Very large open aquatic part of the Earth that is filled with saline water.

→ Zone of Mixed Metals: According to Van der Gracht, the third layer 1200 – 2900 km in the internal structure of the earth.

→ Metallic zone: The earth’s innermost part extending from 2900 km to 6371 km. It is made of nickel and iron.

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