By Michael Slezak. About half the carbon emitted into the atmosphere by human activity ends up in the ocean. It dissolves into the surface water, where it is taken up by phytoplankton during photosynthesis.
Alyson Santoro, a postdoctoral researcher at Woods Hole Oceanographic Institutionwrites from off the coast of Chile, where she is studying microbes in the nitrogen cycle. We are interlopers here on the surface of the ocean. Despite having access to the most modern oceanographic sampling equipment on the research vessel Melville, our surface seawater and particle samples represent the briefest slice of time.
Before World War II, most people thought the ocean floor was the oldest and probably most boring place on Earth. After all, nothing happened except dirt and dead organisms piling up, right? The ocean floor actually consists of different kinds of sediments, each with its own special characteristics.
The seabed also known as the seafloorsea flooror ocean floor is the bottom of the ocean. Most of the oceans have a common structure, created by common physical phenomena, mainly from tectonic movement, and sediment from various sources. The structure of the oceans, starting with the continents, begins usually with a continental shelfcontinues to the continental slope — which is a steep descent into the ocean, until reaching the abyssal plain — a topographic plainthe beginning of the seabed, and its main area. The border between the continental slope and the abyssal plain usually has a more gradual descent, and is called the continental risewhich is caused by sediment cascading down the continental slope.
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Sediment on the seafloor originates from a variety of sources, including biota from the overlying ocean water, eroded material from land transported to the ocean by rivers or wind, ash from volcanoes, and chemical precipitates derived directly from sea water. A very small amount of it even originates as interstellar dust. In short, the particles found in sediment on the seafloor vary considerably in composition and record a complex interplay of processes that have acted to form, transport, and preserve them.
The bottom of the ocean is a very important place for marine life. We call this mode of life 'benthic. Some species even live under the surface of the bottom of the ocean called infauna.
Marine sedimentany deposit of insoluble material, primarily rock and soil particles, transported from land areas to the ocean by wind, ice, and rivers, as well as the remains of marine organisms, products of submarine volcanism, chemical precipitates from seawater, and materials from outer space e. Although systematic study of deep-ocean sediments began with the HMS Challenger expeditions between andintensive research was not undertaken until nearly years later. Since American scientists, in collaboration with those from the United Kingdom, the Soviet Unionand various other countries, have recovered numerous sedimentary core samples from the Atlantic and Pacific oceans through the use of a specially instrumented deep-sea drilling vessel called the Glomar Challenger. Marine sediments deposited near continents cover approximately 25 percent of the seafloor, but they probably account for roughly 90 percent by volume of all sediment deposits.
Except within a few kilometres of a ridge crest, where the volcanic rock is still relatively young, most parts of the sea floor are covered in sediments. This material comes from several different sources and is highly variable in composition, depending on proximity to a continent, water depth, ocean currents, biological activity, and climate. Sea-floor sediments and sedimentary rocks can range in thickness from a few millimetres to several tens of kilometres.