What is geology and How old is the science of geology?

 What is Geology?

Simply put, Geology is the study of the Earth. Like so many scientific words, "geology" is constructed from root words dating back to ancient times: geo comes from the Greek word meaning "the Earth"; it is a prefix used in other related fields, too, such as geography, geodesy, and geophysics. The ology suffix comes from the greek logos, meaning "discussion," and is roughly translated as "the study of."

How old is the science of geology?

• Although the science of geology as we know it today is a relatively young field, insightful observations of Earth processes were made as far back as the ancient Greeks. 
• Some of these early ideas were handed down through the ages. For example, Herodotus (c. 484-425? B.C.E.) had rather modern insights about the formation of the Nile River delta and the important role sediment (deposited by flooding) played in producing the fertile Nile Valley. 
• The Greek historian also applied a primitive form of a principle known as uniformitarianism, the idea that existing processes are sufficient to explain all geological changes that have occurred over time. 

• But many other "geological" observations by the ancient Greeks seem fanciful today. 
• For example, Aristotle (384-322 H.C.E.), the famous philosopher and tutor to Alexander the Great, believed that the heat from volcanic eruptions was produced by underground fires. He also believed that air moving through caverns became heated by friction, causing these fires.