A large variety of sophisticated laboratory instruments is used, including x-ray diffractometers, which determine the crystal structure of minerals, and petrographic microscopes, for study of rock and sediment samples. The locations and intensities of earthquakes are determined using seismographs, instruments which measure energy waves resulting from movements in the earth's crust. Geologists and geophysicists also apply geological knowledge to engineering problems in constructing large buildings, dams, tunnels, and highways. Some administer and manage research and exploration programs, and others become general managers in petroleum and mining companies. Geology and geophysics are closely related fields, but there are some major differences.
Geologists study the composition, structure, and history of the earth's crust.
They try to find out how rocks were formed and what has happened to them since their formation. Geophysicists use the principles of physics and mathematics to study not only the earth's surface but its internal composition, ground and surface waters, atmosphere, and oceans as well as its magnetic, electrical, and gravitational forces. Both, however, commonly apply their skills to the search for natural resources and to solve environmental problems. Geologists and geophysicists often specialize. Geological oceanographers study and map the ocean floor.