Introduction
Geology (from the Greek γῆ, gē, i.e. "earth" and -λoγία, -logia, i.e. "study of, discourse") is the science comprising the study of solid Earth, the rocks of which it is composed, and the processes by which they change.
A piece of weathered limestone highlights a geological process. image: R.Conan-Davies
Geology can also refer generally to the study of the solid features of any celestial body (such as the geology of the Moon or Mars).
Nature and insights
Geology gives insight into the natural history of the Earth by providing the primary evidence for plate tectonics, the evolutionary history of life, and past climates.
In modern times, geology is commercially important for mineral and hydrocarbon exploration / exploitation as well as for evaluating water resources.
Applications
It is publicly important for the prediction and understanding of natural disasters or hazards, the remediation of environmental problems, and for providing insights into past climate change. Geology also plays a role in geotechnical engineering and is a major academic discipline.
See also Earth Sciences
source: http://en.wikipedia.org/wiki/Geology