The fields of geology and geophysics are closely related 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 the earth's internal composition, surface, and atmosphere and also various forces such as its magnetic, electrical, and gravitational fields. Geologists and geophysicists usually specialize.
Geological oceanographers study the ocean bottom.
They collect information using remote sensing devices aboard ships or sometimes from underwater research craft. Physical oceanographers study the physical aspects of oceans such as their currents and their interaction with the atmosphere. Geochemical oceanographers study the chemical composition, dissolved elements, and nutrients of oceans. Hydrologists study the distribution, circulation, and physical properties of underground and surface waters. They may study the form and intensity of precipitation, its rate of infiltration into the soil, and its return to the ocean and atmosphere.