Geologists use complex instruments that determine the mineralogy, physical texture, and chemical composition of rocks, soils, and water. Besides locating resources and protecting the environment, geologists advise construction companies and governmental agencies on the suitability of certain locations for constructing buildings, dams, or highways. Some geologists administer and manage research, exploration, and environmental programs. Others teach and work on research projects in colleges and universities. Geologists usually specialize in one or a combination of three general areas - Earth materials, Earth processes, and Earth history.
Economic geologists locate Earth materials such as mineral and solid fuels.
Petroleum geologists locate oil and gas deposits below the Earth's surface. Some petroleum geologists work on specific drilling prospects, while others develop petroleum-related geologic information for entire regions. Marine geologists collect data during scientific ocean cruises. They study formation of ocean basins, pollution, earthquake activity, and petroleum and economic mineral potential. Engineering geologists determine suitable sites for the construction of roads, airfields, tunnels, dams, and other structures.