Billions of tonnes of sediment accumulate in the ocean basins every year. The nature of such sediments may be indicative of climate conditions near the ocean surface or on the adjacent continents. Sediments are composed of both organic and inorganic materials.
The organic component of sea sediment includes the remnants of sea-dwelling microscopic plankton, which provide a record of past climate and oceanic circulation. For example, by studying the chemical composition of plankton shells, we can reveal information about past seawater temperatures, salinity (saltiness), and nutrient availability. Indeed, such techniques have been used to reconstruct ocean temperatures over the last 100 million years, and have confirmed continental drift theories of climate change that a long term global cooling has taken place since the extinction of the dinosaurs.
Most inorganic material comes from adjacent landmasses, eroded from rocks and washed down to the coast by river channels, or blown from soils, dusty plains and deserts. The nature and abundance of inorganic materials provides information about how wet or dry the nearby continents were, and the strengths and directions of winds.