GEOLOGY: Definition, Types, Spheres and Structure Of The Earth
What is Geology?
Geology is derived from the Greek words Geo-meaning ‘earth’ and logos-meaning ‘discourse’. It is a science that pursues an understanding of planet earth. In other words, it is a science that seeks to expand our understanding of the natural world and our place in it.
It is basically divided into two:
1. Physical geography: It is the study of the earth minerals and the processes occurring both on the earth and beneath.
2. Historical Geography: It seeks to understand the origin of the earth and its development over time.
Basic primary information sought by geologists are related to:
Petrology: The study of rocks.
Stratigraphy: The study of sedimentary layers.
Structural Geology: The study of position of rock units and their deformation.
The Earth’s Spheres
The earth’s spheres are:
1. Atmosphere
2. Hydrosphere
3. Biosphere
4. Geosphere/Lithosphere
The earth’s structure includes:
(a) Crust: It is sub-divided into the oceanic and continental crust. While the oceanic is 7km in depth, contains gabbro and basalt, the continental crust ranges from 35-40km in depth and contains granodiorite.
(b) Mantle: It forms 82% of the earth’s structure, about 2900km deep and contains about 3.3g/cm^3 peridotite.
(c) Core: It is made up of iron-nickel composition, contains minor Oxygen; Silicon and Sulphur elements and has a density of 11g/cm^3.
