RBSE Class 11 Geography Notes Chapter 2 The Earth as a Planet

Go through these RBSE Class 11 Geography Notes Chapter 2 The Earth as a Planet contain important concepts so that students can score better marks in the exam.

Rajasthan Board RBSE Class 11 Geography Notes Chapter 2 The Earth as a Planet

→ Earth is a living planet that is at the third place from the Sun in the sequence of planets. It is the planet where life the only planet in our solar system.

→ Life on earth has been possible due to the sun, due to its certain distance from the sun and optimum solar insolation, ideal for sustenance of life.

→ Some planets like the Earth have been discovered, which may have the possibility of having.

Origin of the Earth

  • Many philosophers and scientists have presented their concepts in relation to the origin of the Earth.
  • Immanuel Kant had interpreted the Gaseous hypothesis, which was introduced in 1796 by Laplace as the Nebular hypothesis.
  • In 1900, Chamberlain and Moulton gave the Planetesimal hypothesis and James Jeans a Tidal hypothesis.
  • Otto Schmidt rendered Inter-stellar Dust hypothesis in 1950.

Origin of the Universe

  • The modern theory of the origin of the universe in modern times is the ‘Big Bang Theory’. It is also called the ‘Expanding Universe hypothesis’.
  • According to this theory, the distance between the galaxies is increasingly expanding the universe.
  • The incident of Big Bang took place 14 billion years ago, in which several tiny balls explosions occured.
  • A scholar named Hoyle rendered a steady-state concept.

RBSE Class 11 Geography Notes Chapter 2 The Earth as a Planet

Formation of Stars

  • There is a large number of countless stars in a galaxy. These galaxies are formed by the solidification of various substances.
  • The construction of the galaxy begins along with the storage of hydrogen clouds around solidifying heavier matter. These gaseous celestial bodies are called nebula.
  • Huge volumes of gas evolved in the nebula. These gaseous clouds became increasingly dense and this started the formation of the stars.
  • The stars were formed around 5 to 6 billion years ago.

Light Year

  • Light year is a measure of distance. The speed of light is 3 lakh km. per second.
  • The distance which fight covers in its travel in one year is called a light year.
  • The average distance between the Earth and the Sun is 14.96 crore kilometers.

Formation of Planets

  • The stars are lacalised lumps of gas within a nebula. The gravitational force within the lumps leads to the formation of a core to the gas cloud.
  • Planetesimals have been formed due to the condensation of the gas clouds.
  • Large number of small planetesimals accrete to form a fewer large bodies in the form of planets.

RBSE Class 11 Geography Notes Chapter 2 The Earth as a Planet

Solar System

  • Nebula is considered to be the Father of the Solar System. There are eight planets in our solar system.
  • Our solar system consists of the Sun, eight planets, 183 satellites, millions of small bodies like asteroids and comets.
  • Mercury, Venus, Earth and Mars are also known the inner (internal) planets.
  • Jupiter, Saturn, Uranus and Neptune are called as Jovian or outer planets.
  • The terrestrial planets are devoid of the condensation of the gases due to the proximity of the stars.

The Moon

  • The Moon is the only natural satellite of the Earth.
  • The Big Splat incident took place approximately 4.44 billion years ago.

Evolution of The Earth

  • Initially, the Earth was a hot, deserted planet, whose atmosphere was sparse.
  • The structure of the earth is layered. The substances that are present on the outer edge of the atmosphere to the earth’s crust are not the same.
  • There are many concentric layers from the surface of the Earth to its centre.

Geological Time Scale

  • The history of the Earth is divided into etc.
  • The history of the earth is divided into four Eras cenzoic mesozoic paleozoic arid pre Cambrian.

Development of the lithosphere

  • The planets have been formed by the accumulation of many elements. One of these planets is our Earth.
  • The entire outer layer of the Earth on which the continents and oceans were formed is called the lithosphere.
  • The Earth has three layers: Crust, Mantle and Core.


  • Comets are the most attractive celestial bodies of our solar system.
  • These stars that revolve around the Sun are solid and rocky structures.
  • When they come near the Sun, due to heat, the substances and gases found in them extend to the opposite direction of the Sun and form a tail with the effect of radiation and solar winds.


  • When the asteroids come in the Earth’s gravitational perimeter, they burn up due to friction. Some meters bum up completely, while the residud part of bigger meteors strike the earth’s surface. These are called meteorites.
    Meteorites are made up of many minerals. Due to their impact, large creaters are formed on earth’s surface.

RBSE Class 11 Geography Notes Chapter 2 The Earth as a Planet

Development of Atmosphere and Hydrosphere

  • Development of the atmosphere has taken place due to presence of gaseous the chemical combination of indigenous gases, the formation of water vapour due to solar heat and the photosynthesis process of the biosphere.
  • During the cooling and solidification of the Earth, the atmosphere formed from matter in the inner part of the Earth which came Out of the solidifying earth as gas and water vapour.
  • The oceans were formed due to the accumulation of rainwater on the earth’s surface. The hydrosphere developed as a huge water reservoir.

Origin of Life

  • The final stage of the origin of the earth is related to the origin of life.
  • Development of life began almost 3800 million years ago on earth.
  • The summary of evolution of life from unicellular bacteria to the modern man.

The Earth as a Planet Notes Important Terms

→ Earth: A living planet or the solar system on which the living beings reside. It revolvee around the sun and also rotates on its own axis. It orbits the Sun in 365-days.

→ Planetesimal: Before the origin of the planeus, small particulate substances scattered in the universe. Planets hnve been formed by coming together of planetesimals.

→ Planet: Such a celestial body in the universe that revolves around a star. The planets found in our solar system revolve around the Sun.

→ Solar-System: The Solar System (Solar family) is a group or planets, satellites, comets, asteroids and meteors that revolve around the Sun in an elliptical path.

→ Universe: The Universe is the eternal sky in which innumerable stars, planets, alms, earth and other planets, moons, meteors, asteroids, etc. are found. It is also called cosmos.

→ Insolation: The heat from the sun is called insolation. This insolation is in the form of sun rays.

→ Stars: Radiant cosmie mass made of gaseous matter is called star. They contain hydrogen 70%, helium 28%, carbon, nitrogen and neon 1.5%, and 0.05% ferrous elements. The nearest star of the Earth is the Sun.

→ Environment: The surroundings or conditions in which a person, animal or plant lives or operates.

→ Binary Theory: nhe principle related to the origin ot the Earth in which the solar family is believed to have been formed with the help of two or more than two stars.

→ Galaxy: The galaxy is a large agglomeration of innumerable stars. Each star has its own independent planetary family with it. Every galaxy rotates around ite center. There are 1010 galaxies in the universe.

→ Light Year: The distance that light travels in one year is called a light year. This distance is the large unit of measurement.

→ Nebula: Clouds of dust and gases are called nebula. According to the American astronomer GP Tupier, the creator of the Solar System is a rotating cloud made of dust and ice, i.e. the solar nebula.

→ Natural Satellite: Such natural bodies found in the universe that revolve around a planet For example: Moon (The natural satellite of the Earth).

→ Satellite: Any natural or man-made object left in the orbit of a planet, which revolves around the related body.

→ Asteroids: The small celestial rocky bodies found in between the orbits of Mars and Jupiter are called asteroids. Their size is small and shape irregular.

→ Comets: Upon reaching close to the sun, due to heat, the volatile found in them travel in a opposite direction from the Sun and form a tail. Such celestial bodies are called comets or caudal stars.

→ Terrestrial Planets: The planets that are close to the Sun including Mercury, Venus, Earth and Mars.

→ Jovian Planets: The gaseous planets Jupiter, Saturn, Uranus and Neptune, located away from the Sun.

→ Celelestial Objects: Stars, planets, moons, meteors, asteroids and planets found in the universe.

→ Equator: The imaginary line passing midway the two poles on the globe, which divides the globe into two equal parts. It is also called the 0° latitude line.

→ Continent: A continent is one of several very large landmasses of the world. Generally identified by convention rather than any strict criteria upto seven regions are commonly regarded as continents.

→ The Big Splat: The origin of the moon is due to a major collision. This collision is called ‘The Big Splat’.

→ Ocean: Huge amount of water found on the earth’s surface, where saline water is found. Around three-fourths of earth’s surface area is surrounded by them.

→ Core: The central part of the Earth in the internal structure of the Earth which extends from 2900 to 6370 km depth. It is composed of a mixture of solid and molten substances.

→ Era: The largest unit of time used in geographical time scale.

→ Period: A sub-division of the era which consists of many epochs.

→ Epoch: A sub-division of period is called the epoch.

→ Lithosphere: The upper layer of the Earth formed by the solid crust supporting the internal biosphere.

RBSE Class 11 Geography Notes Chapter 2 The Earth as a Planet

→ Crust: The topmost layer in the structure of the earth is believed to be mainly formed by silica and aluminum.

→ Outer Core: The upper part of the central layer of the earth which is present from 2900 km to 5150 km.

→ Differentiation: The process of separation of light and heavy density materials.

→ Inner Core: The lower part of the central layer of the Earth which is present from 5150 km to 6370 km. In this, the highest density of the Earth is found.

→ Comets: A comet is an icy, small celestial body that, when passing close to the sun, warms up and begins to release gases, which produces a visible atmosphere and a tail.

→ Hydrology: The branch of science concerned with the properties of the earth’s water and especially its movement in relation to land.

→ Photosynthesis: The process of building carbohydrates in the presence of water, light, chrolophyll and carbon dioxide in plants is called photosynthesis.

→ Solar wind: A large blast of gases emitted by the Sun, which travels from the Sun in all directions.

→ Volcano: A conical vent in the ground through which liquid lava, gases, water vapour and ash are emitted on the surface.

→ Degassing: The process of gases coming from the inner part of the Earth onto the surface.

→ Rain: Condensation of moisture present in the atmosphere that falls on the earth’s due to the earth’s gravity.

→ Fossil: A fossil is the hard remains of a prehistoric animal or plant that are found inside a rock.

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