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The Origin and Evolution of The Earth Early theories of origin of earthNebular hypothesis by Immanuel KantThe hypothesis considered that the planets were formed out of a cloud of material associated with a youthful sun, which was slowly rotating. Some world ring star oppose the sun as a result, a cigar shaped extension of material was separated from the solar surface. As the passing start moved away, the material separated from the solar surface continued to revolve around the sun and it was slowly condensed into planet.Binary theoriesIt was considered under this theory that the sun was surrounded by a solar nebula containing mostly the hydrogen and helium along with what may be termed as dust. The friction and collision of particles led to formation of disk- shaped cloud and planets were formed through the process of accretion .Modern theories of origin of the UniverseBig bang theoryIt considers the following stages in the development of the Universe.i. In the beginning, all matters forming the universe existed in one place in the form of “tiny ball” (singular atom) with an unimaginable small volume, infinite temperature and infinite density.ii. At the big bang The tiny ball exploded violently. This led to a huge expansion. It is now generally accepted that the event of Big Ben took place around 13 .7 billion years before the present. The expense and continues to the present day. As it gave some energy was converted into matter. There was particularly rapid expansion within fraction of a second after the Big Bang. Therefore, the expense and has slowed down. Within first three minutes from the Big Bang event, the first item begin to form.iii. Within 3 million years from the big bang, temperature dropped to 4500 Kelvin and gave rise to atomic matter. The universe became transparent. The expansion of universe means increase in space between the galaxies. An alternative to this watch holds concept of steady-state. It considered the universe to be roughly the same at any point of time. However, with greater evidence becoming available about the expanding universe, scientific community at present favours arguments of expanding universe.The Star FormationThe distribution of matter and energy was not even in the early universe. These initial density differences gave rise to differences in the gravitational forces and it cost the matter to get drawn together. This form the basis for development of galaxies. A galaxy contain large number of stars. Galaxies spread over voice distances that are measured in thousands of light years. The diameters of individual galaxies range from 80,000 to 150,000 light years. A galaxy starts to form by accumulation of hydrogen gas in the form of a very large cloud called nebula. Eventually, growing nebula develops localised sums of gas. These clumps continue to grow into even denser gaseous bodies, giving rise to formation of stars. The formation of stars is believed to have taken place some 5-6 billion years ago.The formation of planetsThe following are considered to be the stages in the development of planets:a. The stars are localised lumps of gas within a nebula. The gravitational force within the lumps leads to the formation of a core to the gas cloud and the use rotating base of gas and dust develops around the gas core.b. In the next stage, the gas cloud starts getting condensed and the matter around the core develops into a small rounded objects. This is more rounded objects by the process of cohesion develop into what is called planetesimals. Larger bodies start forming by collisions, and gravitational attraction causes the material to sing together. Planetesimals are a large number of smaller bodies.c. In the final stage, a large number of small planetesimals hey Siri led to form or fewer large bodies in the form of Planets. The formation of our solar systemThe nebula from which our solar system is supposed to have formed, started its collapse and the core formation sometime about 5 to 5 .6 billion years ago and the planet were formed about four 4.6 billion years ago.Out of the eight planet, first four are considered to be inner planet because of high the density in the building materials and other four are considered to be outer planet or Jovian or gas giant planet because of lower density like that of Jupiter.Formation of the moonIn 1838, sir George Darwin suggested that initially, the earth and the moon formed a single rapidly rotating body. The whole mass became a dumb bells a body and eventually it broke. It was suggested that material forming the moon was separated from what we have at present the depression occupied by pacific ocean.However, the present sentence do not accept either of the explanations. It is now generally believed that the formation of moon, as a satellite of earth, is an outcome of giant impact or what is described as the big splat. A body of the size of one to 3 times of Mars collided with the earth sometimes shortly after the earth was formed. It blasted a large part of earth into space. This portion of blasted material then continued to orbit the earth and eventually formed into present moon about four 4.4 billion year ago.Evolution of the EarthThe earth has a layered structure. From the outermost end of the atmosphere to the centre of the earth, the material that exist is not uniform. The atmospheric matter has least density. From the surface to the deeper depth, the earths interior has different zones and each of these contains materials with different characteristics.Evolution of lithosphereThe earth was mostly in volatile state during its primordial stage. Due to gradual increase in density the temperature inside has increased. As a result the material inside started getting separated depending on their densities. This allowed heavier material like iron to sing towards the centre of the earth and lighter ones to move towards the surface. With passage of time it cooled further and solidified and condensed into a smaller size. This letter led to the development of the outer surface in the form of a crust. During the formation of the moon, due to the giant impact, the Earth was further heated up. It is through the process of different reason that the earth for the material got separated into different layers. Starting from the surface to the central parts, we have layers like the crust, mantle , outer core and inner core. From the crest to the core, the density of the material increases.Evolution of Atmosphere and HydrosphereThere are three stages in the evolution of present atmosphere.1. Loss of primordial atmosphere.2. The hot interior of earth contributed to the evolution of atmosphere.3. The composition of the atmosphere was modified by living world who the process of photosynthesis.The early atmosphere, with hydrogen and helium, is supposed to have stripped of as a result of solar winds. This happened not only in case of the earth, but also in all the terrestrial planets, which are supposed to have lost their primordial atmosphere through the impact of solar winds.During the cooling of the earth, gases and water vapour were released from the interior solid earth. This started the evolution of the planet atmosphere. The early atmosphere largely content water vapour, nitrogen, carbon dioxide, methane, ammonia and very little free oxygen. The process through which the gases were out food from the interior is called degassing. Continuous volcanic eruption contributed water vapour and gases to the atmosphere. As the earth cooled the water vapour released started getting condensed. The carbon dioxide in the atmosphere got dissolved in the rainwater and temperature for the decreased causing more condensation and more rains. The rainwater falling into the surface got collected in the depression to give rise to oceans. The earth ocean performed within 500 million years from the formation of the earth. Sometime around 3800 million years ago, life begin to evolve. Life has confirmed to the ocean for a long time. Ocean begin to have contribution of oxygen through the process of photosynthesis. Eventually, ocean were saturated with oxygen and 200 millions year ago oxygen begin to flood the atmosphere. Source: NCERT XI The physical geography
Early theories of origin of earth
Nebular hypothesis by Immanuel Kant
The hypothesis considered that the planets were formed out of a cloud of material associated with a youthful sun, which was slowly rotating. Some world ring star oppose the sun as a result, a cigar shaped extension of material was separated from the solar surface. As the passing start moved away, the material separated from the solar surface continued to revolve around the sun and it was slowly condensed into planet.
Binary theories
It was considered under this theory that the sun was surrounded by a solar nebula containing mostly the hydrogen and helium along with what may be termed as dust. The friction and collision of particles led to formation of disk- shaped cloud and planets were formed through the process of accretion .
Modern theories of origin of the Universe
Big bang theory
It considers the following stages in the development of the Universe.
i. In the beginning, all matters forming the universe existed in one place in the form of “tiny ball” (singular atom) with an unimaginable small volume, infinite temperature and infinite density.
ii. At the big bang The tiny ball exploded violently. This led to a huge expansion. It is now generally accepted that the event of Big Ben took place around 13 .7 billion years before the present. The expense and continues to the present day. As it gave some energy was converted into matter. There was particularly rapid expansion within fraction of a second after the Big Bang. Therefore, the expense and has slowed down. Within first three minutes from the Big Bang event, the first item begin to form.
iii. Within 3 million years from the big bang, temperature dropped to 4500 Kelvin and gave rise to atomic matter. The universe became transparent.
The expansion of universe means increase in space between the galaxies. An alternative to this watch holds concept of steady-state. It considered the universe to be roughly the same at any point of time. However, with greater evidence becoming available about the expanding universe, scientific community at present favours arguments of expanding universe.
The Star Formation
The distribution of matter and energy was not even in the early universe. These initial density differences gave rise to differences in the gravitational forces and it cost the matter to get drawn together. This form the basis for development of galaxies. A galaxy contain large number of stars. Galaxies spread over voice distances that are measured in thousands of light years. The diameters of individual galaxies range from 80,000 to 150,000 light years. A galaxy starts to form by accumulation of hydrogen gas in the form of a very large cloud called nebula. Eventually, growing nebula develops localised sums of gas. These clumps continue to grow into even denser gaseous bodies, giving rise to formation of stars. The formation of stars is believed to have taken place some 5-6 billion years ago.
The formation of planets
The following are considered to be the stages in the development of planets:
a. The stars are localised lumps of gas within a nebula. The gravitational force within the lumps leads to the formation of a core to the gas cloud and the use rotating base of gas and dust develops around the gas core.
b. In the next stage, the gas cloud starts getting condensed and the matter around the core develops into a small rounded objects. This is more rounded objects by the process of cohesion develop into what is called planetesimals. Larger bodies start forming by collisions, and gravitational attraction causes the material to sing together. Planetesimals are a large number of smaller bodies.
c. In the final stage, a large number of small planetesimals hey Siri led to form or fewer large bodies in the form of Planets.
The formation of our solar system
The nebula from which our solar system is supposed to have formed, started its collapse and the core formation sometime about 5 to 5 .6 billion years ago and the planet were formed about four 4.6 billion years ago.
Out of the eight planet, first four are considered to be inner planet because of high the density in the building materials and other four are considered to be outer planet or Jovian or gas giant planet because of lower density like that of Jupiter.
Formation of the moon
In 1838, sir George Darwin suggested that initially, the earth and the moon formed a single rapidly rotating body. The whole mass became a dumb bells a body and eventually it broke. It was suggested that material forming the moon was separated from what we have at present the depression occupied by pacific ocean.
However, the present sentence do not accept either of the explanations. It is now generally believed that the formation of moon, as a satellite of earth, is an outcome of giant impact or what is described as the big splat. A body of the size of one to 3 times of Mars collided with the earth sometimes shortly after the earth was formed. It blasted a large part of earth into space. This portion of blasted material then continued to orbit the earth and eventually formed into present moon about four 4.4 billion year ago.
Evolution of the Earth
The earth has a layered structure. From the outermost end of the atmosphere to the centre of the earth, the material that exist is not uniform. The atmospheric matter has least density. From the surface to the deeper depth, the earths interior has different zones and each of these contains materials with different characteristics.
Evolution of lithosphere
The earth was mostly in volatile state during its primordial stage. Due to gradual increase in density the temperature inside has increased. As a result the material inside started getting separated depending on their densities. This allowed heavier material like iron to sing towards the centre of the earth and lighter ones to move towards the surface. With passage of time it cooled further and solidified and condensed into a smaller size. This letter led to the development of the outer surface in the form of a crust. During the formation of the moon, due to the giant impact, the Earth was further heated up. It is through the process of different reason that the earth for the material got separated into different layers. Starting from the surface to the central parts, we have layers like the crust, mantle , outer core and inner core. From the crest to the core, the density of the material increases.
Evolution of Atmosphere and Hydrosphere
There are three stages in the evolution of present atmosphere.
1. Loss of primordial atmosphere.
2. The hot interior of earth contributed to the evolution of atmosphere.
3. The composition of the atmosphere was modified by living world who the process of photosynthesis.
The early atmosphere, with hydrogen and helium, is supposed to have stripped of as a result of solar winds. This happened not only in case of the earth, but also in all the terrestrial planets, which are supposed to have lost their primordial atmosphere through the impact of solar winds.
During the cooling of the earth, gases and water vapour were released from the interior solid earth. This started the evolution of the planet atmosphere. The early atmosphere largely content water vapour, nitrogen, carbon dioxide, methane, ammonia and very little free oxygen. The process through which the gases were out food from the interior is called degassing. Continuous volcanic eruption contributed water vapour and gases to the atmosphere. As the earth cooled the water vapour released started getting condensed. The carbon dioxide in the atmosphere got dissolved in the rainwater and temperature for the decreased causing more condensation and more rains. The rainwater falling into the surface got collected in the depression to give rise to oceans. The earth ocean performed within 500 million years from the formation of the earth. Sometime around 3800 million years ago, life begin to evolve. Life has confirmed to the ocean for a long time. Ocean begin to have contribution of oxygen through the process of photosynthesis. Eventually, ocean were saturated with oxygen and 200 millions year ago oxygen begin to flood the atmosphere.
Source: NCERT XI The physical geography