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The shells of dead diatoms can reach as much as a half-mile (800 m) deep on the ocean floor, and the entire Amazon basin is fertilized annually by 27 million tons of diatom shell dust transported by transatlantic winds from the African Sahara, much of it from the Bodélé Depression, which was once made up of a system of fresh-water lakes.
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Diatomaceous earth is a soft, siliceous, sedimentary rock made up of the cell walls/shells of single cell diatoms and readily crumbles to a fine powder. Diatom cell walls are bivalve, i.e. made up of two halves, and are made up of biogenic silica; silica synthesised in the diatom cell by the polymerisation of silicic acid.
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Diatomite rock sample from Sisquoc Formation Scanning electron micrograph of diatomaceous earth. Diatomaceous earth (/ ˌ d aɪ. ə t ə ˈ m eɪ ʃ ə s / DY-ə-tə-MAY-shəs), also known as diatomite (/ d aɪ ˈ æ t ə m aɪ t / dy-AT-ə-myte), celite, or kieselguhr, is a naturally occurring, soft, siliceous sedimentary rock that can be crumbled into a fine white to off-white powder.
As new species of diatoms evolved and spread, oceanic silica levels began to decrease. [19] Today, there are an estimated 100,000 species of diatoms, most of which are microscopic (2-200 μm). [19] Some early diatoms were larger, and could be between 0.2 and 22mm in diameter. [17]
Diatoms are enclosed in protective silica (glass) shells called frustules. Each frustule is made from two interlocking parts covered with tiny holes through which the diatom exchanges nutrients and wastes. [156] The frustules of dead diatoms drift to the ocean floor where, over millions of years, they can build up as much as half a mile deep. [160]
Diatoms are enclosed in protective silica (glass) shells called frustules. They are classified by the shape of these glass cages in which they live, and which they build as they grow. Each frustule is made from two interlocking parts covered with tiny holes through which the diatom exchanges nutrients and wastes. [63]