GEOLOGY - Scope of Geology

The scope of geology is so broad that it has been split into two major division : (1) Physical Geology. (2) Historical Geology. Each of these divisions , have for convenience of specialised study , been further sub-divided into various branches or sub sciences. The term Earth science is commonly used in conjunction with the study of the Earth ; although Earth science includes the study of geology , and also encompasses the science of meteorology (the study of the atmosphere), oceanography (the study of oceans), and astronomy of course.

<b>1. Physical Geology :-</b> Physical geology deals with the Earth's composition , structure , the movement with in and upon the Earth's crust , and the geologic processes by which the Earth's surface is, or has been changed. This division of geology includes in itself , the following branches :-

(A) Mineralogy :- The mineralogy , obviously deals with the study of minerals. Minerals are the basic constituents of rocks , and thus , influence the properties of the rocks. Hence , in order to know the properties of the rocks , one has to study the properties of the minerals. In mineralogy , therefore ,  the mode of formation , composition , occurrence , types , association , properties , uses etc. of the minerals , shall be studied in details. This study will helps the civil engineers to know as to why the rocks like Quartzite and Marble , which though resemble in shine , colour and appearance , yet differ widely in their behavior ; Quartzites being very tough , strong and durable ; while Marbles disintegrate and decompose in a shorter period. This happens so , because of the difference in their mineral composition.

(B) Petrology :- The term Petrology is derived from the Greek word , Petro + logos. Petro means rocks and logos means study. Hence , petrology means the study of the rocks. Since the earth crust, also called lithosphere , is composed of different types of rocks , their study is under this branch , which deals with the study of mode of formation , structure , textures , composition , occurrence , types etc. of the various rocks of the Earth's crust.

(C) Structural Geology :- The rocks which constitute the Earths crust , have undergone and continuous to under go various deformations , dislocations under the influence of tectonic forces ; causing formation of geological structures like folds , faults , joints , unconfirmities etc. in the dark masses .

(D) Geomorphology :- This branch of geology explains and studies the origin of various surface features of the Earth.

(E) Economic Geology :- This is a specialised division of Mineralogy and Petrology , where in the product of the Earths crust having good economic value , are studied. Valuable ores , containing metals, like diamond , gold etc. economical minerals are like coal , petroleum , etc. do come under the domain of this specialised study. It includes the study of their occurrence , search and exploitation for commercial and industrial uses.

<b>2. Historical Geology :-</b> Historical geology deals with the study of origin and evolution of the earth and it's inhabitants. Like physical geology , this division of geology has also been bifurcated into several branches , due to the variety and vastness of this field. Each of these branches is actually a science in its own right , and one may devote a lifetime to study the specialised subject in any one of them. The various sub-division of this branch of geology includes :

(A) Stratigraphy :- These studies help in working out the geologic history of an area , and is concerned with the origin , composition , proper sequence , and correlation of the rock strata. The term Stratigraphy has been derived from the Greek words : strata + graphy. Strata means the sets or beds of sedimentary rocks ; while graphy means the description. Hence , this branch of science deals with the study of the beds of the sedimentary rocks. The study of such rocks gives an indication of the time that has passed since their formation ; thereby indicating the life history of the rocks and of the earth and it's inhabitants. The study of these rocks will also involved extraction of fossils , I.e the remains of plants and animals of the past geological Eras.

(B) Palalentology :- Palalentology deals with the study of the ancient organism , plants and animals etc. as revealed from there remains and remnants. This study helps in providing a background to the development of life on Earth , over the past geological eras.

(C) Palaeogeography :- This branch of science deals with the study of the geographic conditions of the past times. It, thus deals with the reconstruction of the relations of the ancient lands and seas , and the organism that inhabitanted them.

These branches of historical geology are , intact interconnected with each other , and overlap also in various respects ; as in the case with the various branches of physical geology.