Oceanography is the scientific study of the oceans. It is a sub-discipline of Earth science. Seventy percent of the earth's surface is covered by oceans and this area encompasses diverse environments. Research is carried out on scales ranging from microscopic water drops to entire ocean basins. A variety of tools and techniques are employed and modern oceanography is further divided into four sub-disciplines:
- Biological Oceanography (Marine Biology) - The study of biological processes in the ocean. This field encompasses the ecology, taxonomy and physiology of organisms inhabiting the oceans.
- Chemical Oceanography (Marine Chemistry) - The study of the chemical composition of seawater and the processes that control and alter this composition, including marine pollution. This field encompasses the study of biogeochemical cycles in the ocean and exchanges of chemicals between the water and surrounding environments including the sediments, atmosphere and land.
- Geological Oceanography (Marine Geology & Geophysics) - The study of the rocks and sediments found within the ocean basins and the geological processes responsible for their formation. Included also is marine geophysics, the study of the rock structure within the ocean basins, the properties of rocks such as their magnetism, and the occurrence and cause of earthquakes. Topics include paleontology, vulcanology, plate tectonics, seafloor (seabed) morphology and sedimentation processes.
- Physical Oceanography (Marine Physics) - The study of physical processes in the oceans. Topics include currents, tides, large scale ocean circulation and the formation of different water masses, and air-sea interactions such as the generation of surface waves by the wind.
In addition there is the field of ocean engineering, the branch of engineering concerned with the design, construction, and installation of various instruments and vehicle to be used in oceanographic studies. In spite of the above categories, individual oceanographers tend to be broad in their outlooks and may not always be easily placed into one of these "boxes". Oceanographic research tends to be highly interdisciplinary, involving a team of investigators who combine their expertise to better understand the oceans.