They study and map the ocean floor, and collect information using remote sensing devices aboard surface ships or underwater research craft. Geophysicists may specialize in areas such as geodesy, seismology, or marine geophysics, also known as physical oceanography. Geodesists study the size and shape of the Earth, its gravitational field, tides, polar motion, and rotation. Seismologists interpret data from seismographs and other geophysical instruments to detect earthquakes and locate earthquake-related faults. Physical oceanographers study the physical aspects of oceans such as currents and the interaction of the surface of the sea with the atmosphere.
Hydrology is a discipline closely related to geology and geophysics.
Hydrologists study the distribution, circulation, and physical properties of underground and surface waters. They study the form and intensity of precipitation, its rate of infiltration into the soil, movement through the earth, and its return to the ocean and atmosphere. The work they do is particularly important in environmental reservation and remediation. Some geoscientists spend the majority of their time in an office, others divide their time between fieldwork and office or laboratory work. Geologists often travel to remote field sites by helicopter or four-wheel drive vehicles and cover large areas on foot.