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Definition
| Very level area of the deep-ocean floor, usually lying at the foot of the continental rise. |
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| Active Continental Margin |
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Definition
| Usually narrow and consisting of highly deformed sediments. They Occur where oceanic lithosphere is being subducted beneath the margin of a continent. |
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Definition
| The measurement of ocean depths and the charting of the shape of topography of the ocean floor. |
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| Seafloor sediments consisting of material of marine-organic origin. |
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| That portion of the seafloor adjacent to the continents. Includes Shelf, Slope, and Rise. |
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| The gently sloping surface at the base of the continental slope. |
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| The gently sloping submerged portion of the margin, extending from the shoreline to the slope. |
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| The steep gradient that leads to the deep-ocean floor and marks the seaward edge of the shelf. |
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| Mountains formed in part by igneous activity associated with the subduction of oceanic lithosphere beneath a continent. |
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| The portion of the seafloor that lies between the continental margin and the oceanic ridge system. |
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| Deep-Ocean Trench (Trench) |
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Definition
| An elongated depression in the seafloor produced by bending of oceanic crust during subduction. |
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Definition
| A cone-shaped deposit at the base of the continental slope. THe sediment is transported to the fan by turbidity currents that follow submarine canyons. |
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Definition
| An instrument used to determine the depth of water by measuring the time interval between emission of a sound signal and the return of its sound from the bottom. |
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Definition
| Unusually compact chemical structures made of water and natural gas. Occur beneath permafrost areas on land and under the ocean floor at depths below 525 meters. |
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| A sediment layer that is characterized by a decrease in sediment size from bottom to top. |
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Definition
| A submerged flat-topped seamount. |
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Definition
| Seafloor sediments consisting of minerals that crystallize from seawater. An important example is maganese nodules. |
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Term
| Mid-Ocean Ridge (Oceanic Ridge) |
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Definition
| A continuous elevated zone on the floor of all the major ocean basins and varying in width from 500 to 5,000km. The rifts at the crests of ridges represent divergent plate boundaries. |
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Definition
| An extensive region on the ocean floor composed of thick accumulations of pillow basalts and other mafic rocks that in some cases exceed 30km in thickness. |
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Definition
| A continuous elevated zone on the floor of all the major ocean basins and varying in width from 500 to 5,000km. The rifts at the crests of ridges represent divergent plate boundaries. |
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Definition
| The scientific study of the oceans and oceanic phenomena. |
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Term
| Passive Continental Margin |
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Definition
| Margins that consist of a continental shelf, slope, and rise. They are NOT associated with plate boundaries and therefore experience little volcanism and few earthquakes. |
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Definition
| A deep downfaulted structure along the axis of some ridge sediments. |
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Definition
| An isolated volcanic peak that rises at least 1,000 meters above the deep-ocean floor. |
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Term
| Seismic Reflection Profile |
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Definition
| A way to let marine geologists view the rock structure beneath the sediments that blanket much of the seafloor. Strong low-frequency sounds are produced by explosions (depth charges) or air guns. These sound waves penetrate beneath the seafloor and reflect off the contacts between rock layers and fault zones. |
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Definition
| An acronym for Sound Navigation And Ranging. The first devices that used sound to measure water depth. |
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Definition
| A seaward extension of a valley that was cut on the continental shelf during a time when sea level was lower, or a canyon carved into the outer continental shelf, slope, and rise by turbidity currents. |
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Definition
| Another name for guyots; submerged, flat-topped seamounts. |
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Definition
| Seafloor sediments derived from terrestrial weathering and erosion. |
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Definition
| A chain of volcanic islands generally located a few hundred kilometers from a trench where active subduction of one oceanic slab beneath another is occuring. |
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Definition
| Turbidity current deposit characterized by gradded bedding. |
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Definition
| A downslope movement of dense, sediment-laden water created when sand and mud on the continental shelf and slope are dislogded and thrown into suspension. |
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Definition
| A subdivision of the benthic zone characterized be extremely high pressures, low temperatures, low oxygen, few nutrients, and no sunlight. |
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| That portion of the ocean where there is no sunlight. |
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| The marine life zone that includes ANY seabottom surface regardless of its distance from shore. |
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| The forms of marine life that live on or in the ocean bottom. |
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| The total mass of a defined organism or group of organisms in a particular area or ecosystem. |
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| Mass per unit volume of a substance, usually expressed as grams per cubic centimeter (g/cm3). |
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Definition
| The portion of the photic zone near the surface, where light is bright enough for photosynthesis to occur. |
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Definition
| A succession of organisms in an ecological community through which food energy is transferred from producers through herbivores and on to one or more carnivores. |
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Definition
| A group of interrelated food chains. |
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Definition
| The area where land and sea meet and overlap; the zone between high and low tides. |
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Definition
| Pelagic organisms that can move indepently of ocean currents by swimming or other means of propulsion. |
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Definition
| The marine-life zone that extends from the low tideline out to the shelf break. |
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Definition
| The marine-life zone beyond the continental shelf. |
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Definition
| Open ocean of ANY depth. Animals in this zone swim or float freely. |
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Definition
| The upper part of the ocean into which any sunlight penetrates. |
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Definition
| The process by which plants and algae produce carbohydrates from carbon dioxide and water in the presence of chlorophyll, using light energy amd releasing oxygen. |
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Definition
| Algal plankton, which are the most important community of primary producers in the ocean. |
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Definition
| Passively drifting or weakly swimming organisms that cannot move independently of ocean currents. Includes microscopic algae, protozoa, jellyfish, and larval forms of many animals. |
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Definition
| The amount of organic matter synthesized by organisms from inorganic substances through photosynthesis or chemosynthesis within a given volume of water or habitat in a unit of time. |
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| A layer of water in which there is a rapid change of density with depth. |
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| The proportion of dissolved salts to pure water, usually expressed in parts per thousand (‰). |
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| A layer of water in which there is a rapid change in temperature in the vertical dimension. |
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| A nourishment level in a food chain. PLant and algae producers constitute the lowest level, followed by herbivores and a series of carnivores at progressively higher levels. |
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