What is Geology?
Geology - the basics
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Earth from Space
The Earth from space

Geology is the study of the Earth and how it was formed. It investigates the Earth, its origin, structure, composition and the nature and development of the processes which have given rise to its present state.

Geology IS NOT Archaeology!

Archaeology is the study of past human life and activities as shown by the relics, monuments and artifacts left by ancient peoples.

The main subjects of geology are:

Petrology which is the study of rocks (origin and composition).

Mineralogy - the study of minerals or mineral components within the rocks as well as Crystallography - the study of the crystalline properties of minerals.

Minerals under the microscope
Minerals under the microscope
Close view of Stromboli Volcano erupting incandescent molten
lava fragments, Italy. U. S. Geological Survey/photo by B. Chouet
A specific aspect of petrology is Volcanology - the study of volcanoes.

Geochemistry is the study of the chemical composition of the earth and the elements' chemical behaviour, in rocks especially, but also in water and atmosphere.

Structural Geology - Geophysics is the study of the physical structure and properties of the earth.
Cross section of the Earth
Cross section of the Earth

Marine Geology studies the geology of the deep ocean floor and continental shelves.
Sedimentology studies how rocks are deposited over time and how sedimentary rocks form.

Stratigraphy is the study of the succession of sediments over time.
Sedimentary rock stratas
Succession of sedimentary rocks stratas in the South East of France

Tectonic plates


Image  ©NASA

Tectonics studies how the earth's continents move around...
Palaeontology is the study of fossils - animals and plants as the relics of former life. We talk about micropalaeontology when it concerns very small organisms.
Photo. ©National Museums & Galleries of Northern Ireland
The Burren
The Burren, Ireland - photo: David Drew.

Geomorphology studies the evolution of the landforms on the surface of the earth and the processes that form them.

Hydrogeology is the study of groundwater and the prevention of hazards within the groundwater system. It is also involved in finding new sources of groundwater for towns and villages 


Applied geology considers all the practical applications of geology like mines/mining, petroleum, gas, hydrogeology/groundwater, public works, environmental geology...  See "What geologists do" page.

The Geological Heritage Section of GSI has produced a special exhibition called "What on Earth?" It has been designed especially for the general public and is a visual exploration of what geology is about and what geologists do. Click here to view it.

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