The earth science is the science that tries to understand the earth, its components and its neighbours in the space. It can also be regarded as the study of the function of the earth system as well as the study of the natural interaction between the existing atmosphere, hydrosphere and the lithosphere describing the history of how they have been evolved, how they have been functioned and how they may be expected react and respond to the human activity.
The earth science was developed in the 18th century as a result of the need for a practical knowledge about the rocks and the minerals in the mining industry when the developed countries were running in the pathway of development. On today’s context, it has been the major concern in the field of civil engineering and in the environment science. Obviously, during the survival, the life gets hampered with the components where it has been surviving. Similarly, the living organism and the things surviving on the earth has been affected by the physical parameters of the earth. The parameters such as the temperature, light, moisture, climate affect the living life.
The earth science also includes the geology of the earth. The major aim of the environment geology is to obtain the scientific understanding of the geology and the geomorphological process, engineering geology and the natural man–made hazards, urban geology, environmental regional planning and the management, hydrogeology for the environmental health, impacts of the exploitation of the mines and the quarries.
The environmental geology enables to study the following phenomenon:
The earth is the dynamic body. Every particle stays in its own form on earth because the earth pulls the particles through the gravity. Through time the various interactions have been driven by the energy sources like external energy, solar radiations, internal energy and the geothermal heat of the earth. Every particle stays in its own form on earth because the earth pulls the particles through the gravity. All such types of energies operate a cycle within the earth’s surface which is known as the geological cycle. James Hutton developed the concept “Present is the key to Past” which became the main basis for the study of the dynamic behavior of the earth and has forwarded the concept of the geological cycle as hydrological cycle and the rock cycle.
The water cycle that includes the evaporation, condensation, precipitation and absorption and again repeats the same action is known as the hydrological cycle. The sun evaporates the water from the ocean and seas. The vapour gets condensed over and forms clouds and that when gets heavier falls on the earth in the form of precipitation that may be in the form of the rain or the snow. The rain gets into the soil through infiltration to the groundwater and through run-off to the sea. Again the same process repeats again and again to continue the cycle.
The earth has the huge amount of the rocks. The moisture attacks the bedrock in which the bed rocks break down into the mass of the loose particles called regolith. When the regolith becomes transported, it is known as the sediments. Slowly the sediments changed to the sedimentary rocks. These sedimentary rocks undergo extreme changes into constituents caused by the heat pressure and the chemical action. During the folding, faulting and thrusting it is named after the metamorphic rock when the pressure and the temperature are increased, these rocks are changed into its molten form called magma. This magma during the volcanic eruption comes out to the surface of the earth and gets cooled which finally changes to the igneous rock. By natural soil erosion these sedimentary, igneous and metamorphic rocks are all changed into the sediments and so on.
These cycles (hydrological and the rock cycle ) shows that this cycle occurs within the earth creating and destroying it without loosing anything .
The chronologic measurement system that relates the stratigraphy with the time and is used by the earth scientists, geologist , paleontologists to describe the timing and the relationship between events that have occurred within earth’s history is known as the geological time scale. Evidence have shown that the earth was originated before 4.5 billion years ago. Accordingly, the time scale was divided into eras, periods and epochs.
According to the scientists, there are three eras, (Palaeozoic, Mesozoic, and Cenozoic). In these, there were various periods.
Ordovician Period :
The climate was progressively warmer and the invertebrates were numerous and varied.
The climate was warm and the first indication of the fishes, trilobites were abundant.
The climate was slight cooling and there was the wide expansion of invertebrates and rise of the fishes.
The temperature increased during this period and there was diversification of fishes and evolution of the amphibians.
In this period the climate was uniform and there was the spread of the tropical seas. There was also the rise of the insects and the spread of the ancient sharks.
Pennsylvanian period :
In this period there was uniform climate throughout the world and the amphibians were dominant and appearance of first reptiles.
In this period there were the rise of the continents and the glaciation in the southern hemisphere and the extinction of the ammonites and trilobites appearance of mammals like reptiles.
The continents were exposed and there was sub-tropical climate. The Gymnosperms were dominant and there was transition of the reptiles to the mammals, progressive rise of the reptiles and egg laying mammals whereas the extinction of the primitive amphibian.
There was the cumulation of the worldwide warm climate and there was the dominance of dinosaurs, an appearance of the first toothed birds, spread of the reptiles and the rise of the insectivorous marsupials and also the first appearance of flowering plants.
Birth of modern reptiles and development of climatic diversity, extinction of dinosaurs and toothed birds archaic birds common and the rise of flowering plants.
There were various epochs in this period when there was the development of climatic belts, modernization of gymnosperms, development of grasses and the evolutionary explosion of mammals, the evolution of modern mammals and first ape-like the man.
Quarternary Period :
During this period to the end of various epochs, there were changes in the rise of western North America, periodic continental glacier in the north, warmer climate. There was the increase in herbs, woody plants, and evolution of elephant, horse, extinction of many large mammals and finally the development of human and human culture.
Keller, E.A. Environmental Geology. Columbus, Ohio: Charles E. Miller Publishing Company, Bell, and Howell Company, 1985.
Mahapatra, G.B. Textbook of Physical Geology. Shahadra,Delhi-110032: CBS Publishers and Distributers Pvt.Ltd., 1992.