The Origin And Evolution Of The Earth

The age of the Earth is 4.6 billion years. It represents the time duration of core formation. This age is calculated from the meteorite, terrestrial and lunar materials.

An eon refers to an extremely long or indefinite duration of time. But, in science eon is roughly equal to about a billion years.

Solar winds, Degassing and photosynthesis are all related to the formation or modification of the present atmosphere. But differentiation is not, It refers to the process of differentiating between two or more things or people.

The inner planets are the planets between the sun and the belt of asteroids.

3.8 billion years ago life had appeared on the earth.

(i) Terrestrial planets are the planets that are composed of silicate rocks or metals. It is rocky due to the following reasons:

a. The terrestrial planets were formed in the close vicinity of the parent star where it was warm for the gases to condense to solid particles.

b. The solar winds were most intense near to the sun. So it blew off most of the gas and dust away from the terrestrial planets.

c. Moreover, these planets are small and their lower gravity could not hold the escaping gases.

(ii) a. Kant and Laplace

i. The Nebular hypothesis was firstly given by Kant and later revised by Laplace.

ii. This hypothesis explains the origins and development of the solar system within the framework of naturalism.

iii. According to this hypothesis, the planets were formed out of a cloud of material associated with the sun which was slowly rotating.

iv. It explained that the interior of the earth must be gaseous as the earth had orginated from these gases itself.

b. Chamberlain and Moulton

i. Chamberlain and Moulton's hypothsesis was proposed by Thomas Chamberlian and Forest Moulton.

ii. In 1905, they believed that a wandering star had come closer to the sun.

iii. A cigar shaped extension material was separated from the solar system.

iv. As the passing star moved away. the material separated from the sun and continued to revolve around the sun and eventually formed planets.

(iii) The process of differentiation is explained below:

Differentiation is a process of separating the different elements of a planet due to their physical and chemical behavior.

The body forms different layers. The denser materials sink int the center and the less dense materials rise above.

The different layers of earth, starting from the outside are- crust, mantle, outer core, and inner core.

As we move towards the inner parts of the Earth, the density of the material continues to increase.

(iv) a. The surface of the Earth was barren, rocky and hot.

b. It was covered with a thin atmosphere of hydrogen and helium.

c. It was in the liquid form initially but was late changed to the current state.

(v) The gases which initially formed the earth’s atmosphere were hydrogen and helium.

These gases eventually declined due to the high solar winds.

During the process of Colling of earth, gases and water vapor was released from the interior of the Earth.

This began the process of the current state of the atmosphere.

(i) The Big Bang Theory was given by Edwin Hubble in 1920. This theory was also called the expanding universe hypothesis.

b. According to this theory, the universe is continuously expanding. The galaxies are moving away from each other which makes the universe appears to be growing larger as well.

c. In the beginning, all the matter which formed the universe existed in the form of a tiny ball with extremely small volume, infinite temperature, and infinite density.

d. At the big bang, this tiny ball exploded and lead to a huge expansion.

e. This event is said to be taken place 13.7 years ago.

f. Some of the energy converted into matter and rapid expansion to place within a few seconds. After the three minutes, the first atom began to form.

g. After 300000 years, the temperature fell down to 4500 k and developed the atomic matter.

h. The universe became transparent.

i. Most of the scientists are in favor of this theory. The expansion of the universe indicates the increasing space between the galaxies.

(ii) The stages in the evolution of the earth explained below:

STAGE 1:

a. The earth was in a volatile stage.

b. With the increase in density, the temperature also increased.

c. The material inside the earth started separating on the basis of its density.

d. The materials with a heavy density such as iron sunk towards the center of the earth and the materials to work with lower density begin to rise above.

e. As time passed, it cooled, solidified and condensed into a smaller size. This formed the crust.

f. With the process of differentiation, the material separated into different layers on the basis of their density.

g. Starting from the inside, the four layers of the earth aa our inner core, outer core, mantle and crust.

STAGE 2:

a. The atmosphere of the earth initially consisted of hydrogen and helium.

b. But the intense solar wind had stripped off the atmosphere of these gases.

c. During the cooling of the earth, gases and water vapour be released from the interior surface of the earth. This began the process of the formation of the current atmosphere.

d. The atmosphere consisted of water vapour, nitrogen, carbon dioxide, methane, ammonia, and very little oxygen.

e. With the cooling of the earth, the water vapour released began to get condensed. The carbon dioxide present in the atmosphere dissolved with the rain water.

f. The falling temperature led to more rainfalls.

g. The rainwater got collected into the surface of the earth and oceans were formed.

STAGE 3:

a. The origin of life on the earth was a chemical reaction.

b. Organic molecules which are complex in nature were generated and later assembled.

c. This assembly was in a way that they could duplicate themselves converting inanimate matter into living substance

(i) NASA or the National Aeronautics and Space Administration had launched this project.

(ii) Stardust is a type of cosmic dust which is present in outer space. According to physcis, we all are made up of stardust. All the elements except hydrogen, lithium, and helium consist of stardust. The scientists are interested in it because of the elements present in it. These elements are important to conduct field and research work.

(iii) NASA had launched stardust which was the first U.S mission to explore a comet and to robotically obtain samples from a comet and bring them back to the planet Earth. It was launched on 7th February 1999. It had collected interstellar dust particles between a period of two years from 2000 to 2002.

Inner planets are the planets that are located in the asteroid belt. There are four inner planets- Mercury, Venus, Earth, and Mars. These are also called terrestrial planets.

These planets are rocky due to the following reasons:

a. The terrestrial planets were formed in the close vicinity of the parent star where it was warm for the gases to condense to solid particles.

b. The solar winds were most intense near to the sun. So it blew off most of the gas and dust away from the terrestrial planets.

c. Moreover, these planets are small and their lower gravity could not hold the escaping gases.

The gaseous planets are Jupiter, Saturn, Uranus, and Neptune. They are called gaseous planets because they are located from the sun.

a. The earth was in a volatile stage.

b. With the increase in density, the temperature also increased.

c. The material inside the earth started separating on the basis of its density.

d. The materials with a heavy density such as iron sunk towards the center of the earth and the materials to work with lower density begin to rise above.

e. As time passed, it cooled, solidified and condensed into a smaller size. This formed the crust.

f. With the process of differentiation, the material separated into different layers on the basis of their density.

g. Starting from the inside, the four layers of the earth aa our inner core, outer core, mantle, and crust.