Definition of Geology:

Geology is the study of the Earth, the materials of which it is made, the structure of those materials, and the processes acting upon them. It includes the study of organisms that have inhabited our planet. An important part of geology is the study of how Earths materials, structures, processes and organisms have changed over time.

1. The science which treats: (a)Of the structure and mineral constitution of the globe; structural geology. (b)Of its history as regards rocks, minerals, rivers, valleys, mountains, climates, life, etc.; historical geology. (c)Of the causes and methods by which its structure, features, changes, and conditions have been produced; dynamical geology. See Chart of {The Geological Series}.

2. A treatise on the science.