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Oceanography Ch 03
The Sea Floor and its Sediments
Term | Definition |
---|---|
Bathymetry | study and mapping of seafloor elevations and the variations of water depth; the topography of the sea floor. |
Soundings | measurement of the depth of water beneath a vessel |
continental margin | zone separating the continents from the deep-sea bottom, usually subdivided into shelf, slope, and rise. |
continental shelf | zone bordering a continent, extending from the line of permanent immersion to the depth at which there is a marked or rather steep descent to the great depths. |
continental shelf break | zone along which there is a marked increase of slope at the outer margin of a continental shelf. |
continental slope | relatively steep downward slope from the continental shelf break to depth. |
submarine canyon | relatively narrow, V-shaped, deep depression with steep slopes, the bottom of which grades continuously downward across the contineotal slope. |
turbidity current | dense, sediment-laden current flowing downward along an underwater slope. |
turbidite | sediment deposited by a turbidity current, showing a pattern of coarse particles at the bottom, grading gradually upward to fine silt or mud. |
continental rise | gentle slope formed by the deposition of sediments at the base of a continental slope. |
abyssal plains | flat ocean basin floor extending seaward from the base of the continental slope and continental rise. |
seamount | isolated volcanic peak that rises at least 1000 m from the sea floor. |
guyot | submerged, flat-topped seamount. Also known as a tablemount. |
fringing reef | reef attached directly to the shore of an island or a continent and not separated from it by a lagoon. |
barrier reef | coral reef that parallels land but is some distance offshore, with water between reef and land. |
atoll | ring-shaped coral reef that encloses a lagoon in which there is no exposed preexisting land and which is surrounded by the open sea. |
island arc system | chain of volcanic islands formed above the sinking plate at a subduction zone. |
neritic zone | shallow-water marine environment extending from low water to the edge of the continental shelf |
pelagic zone | primary division of the sea, which includes the whole mass of water subdivided into neritic and oceanic zones; also pertaining to the open sea. |
lithogenous sediment | sediment composed of rock particles eroded mainly from the continents by water, wind, and waves. |
biogenous sediment | sediment derived from organisms |
ooze | fine-grained deep-ocean sediment composed of at least 30% calcareous or siliceous remains of small marine organisms, the remainder, being clay-size particles. |
calcareous ooze | fine-grained deep-ocean biogenous sediment containing at least 30% calcareous tests, or the remains of small marine organisms. |
siliceous ooze | fine-grained deep-ocean biogenous sediment containing at least 30% siliceous tests, or the remains of small marine organisms. |
coccolithophorids | microscopic, planktonic alga surrounded by a cell wall with embedded calcareous plates (coccoliths). |
coccolith | microscopic, planktonic alga surrounded by a cell wall with embedded calcareous plates (coccoliths). |
lysocline | depth at which calcareous skeletal material first begins to dissolve. |
carbonate compensation depth (CCD) | depth at which the amount of CaCO3 falls below 20% of the total sediment..the amount of CaCO3 produced by organisms in the water column is equal to the rate at which it is dissolved in the water. No CaCO3 will be deposited below this depth. |
hydrogenous sediment | sediment precipitated from substances dissolved in seawater. |
carbonate | a sediment or rock formed from the accumulation of carbonate minerals (CaCO3) precipitated organically or inorganically. |
manganese nodule | rounded, layered lumps found on the deep-ocean floor that contain, on average, about 18% manganese, 17% iron, with smaller amounts of nickel, cobalt, and copper and traces of two dozen other metals; a hydrogenous sediment. |
sedimentary rock | a rock formed by the cementation of mineral grains accumulated by wind, water, or ice transportation to the site of deposition or by chemical precipitation at the site. |
Exclusive Economic Zone (EEZ) | coastal zone that generally extends 200 nautical miles (370 kilometers) perpendicular from shore- around the coastal boundaries of all countries...each country regulates its own mineral resources, fishing stocks, and pollution controls. |
Sediment thickness | thickness of sediments at the bottom of the ocean, above the crust about 600 meters thick.. |