ABSTRACT
Oceanography is the study of the oceans, their origin, composition, history and ecology. It examines water movements (via currents, waves and tides) and the chemical and physical properties of seawater. As well as studying ocean dynamics, oceanography also seeks to describe and account for the origin and topography of the ocean floor. This includes the role of plate tectonics in forming ocean trenches and ocean ridges (see p. 149), and the role of sealevel change (see p. 511) in creating coastlines and continental shelves.
