University of Edinburgh

BSL Geography Glossary - Oil - definition

Definition: Oil was formed over millions of years from tiny creatures that lived in the sea. When these creatures died they sank to the bottom of the sea and form layers. Over time these layers were buried by sediment and put under high pressures and temperatures. The extra pressure and temperature caused the creatures to change and become oil. Oil is now collected by drilling down into the earth and bringing it back up to the surface.