Geology is the study of the earth (geo means earth, and ology means study of). This is a very simple definition for something so complex. Geology involves studying the materials that make up the earth, the features and structures found on Earth as well as the processes that act upon them. Geology also deals with the study of the history of all life that’s ever lived on or is living on the earth now. Studying how life and our planet have changed over time is an important part of geology.
Two Main Types of Geology

Typically, geology is divided into two categories: physical geology and historical geology. Physical geology deals with the study of the physical features of the earth and the processes acting on them. This includes volcanoes, earthquakes, rocks, mountains and the oceans; just about any feature of the earth.

Historical geology is the study of the history of the earth. Historical geologists focus on what’s happened to Earth since its formation. They also study the changes in life throughout time. In historical geology, you essentially get to travel back in time to the formation of the earth and move forward through time, witnessing the changes in Earth itself and the life on it. (study dot com)