deep-sea fan
88
auspices of JOIDES the project started in 1968 with R.V. Glomar Challenger
and since then over 800 holes have been drilled, some of them up to the
lower portion of the basaltic layer. ~Iayer 1, layer 2, etc.
deep-sea fan terrigenous, core- or fan-shaped deposit located off the shelf in
front of large rivers and submarine canyons, of which it often forms an extension. The sediment is supplied by rivers or by longshore transport over the
shelf, usually over the inner shelf or near-shore. The sediment is funneled to
the fan by way of a canyon; the dominant transport mode is a turbidity current.
Sediment is deposited where the current reaches the lower gradients of the
ocean basin. Deep-sea fans receive sediment from specific hinterland areas
as do alluvial fans on land. The volume of many fans, in relation to sediment
supply, indicates that they are millions of years old. A striking example is the
Ganges cone (2500 km long, terminating at a depth of ca. 5000 m). Smaller
fans occur along most continental slopes. Most, if not all, fans are marked by one
or more deep-sea channels, which are usually the distal extension of a submarine canyon. At the Ganges and Indus cones the fan reaches almost to the
shelf break but the canyons are short, whereas the Congo (Zaire) canyon
begins in the river estuary, crosses the shelf, and extends to the base of the
continental slope where the Congo deep sea begins at ca. 3500 m depth.
deep-sea sediments sediments found on the deep-sea floor. Except for some turbidites, these sediments are often pelagic in origin. Pelagic sediments are those
derived from the precipitation of dissolved or suspended matter in the open
ocean together with the accumulation of the remains of planktonic organisms.
These sediments are generally found at depths greater than 1000 m and
comprise oozes and red clays. Pelagic sediments may be classified as eupelagic
or hemipelagic, according to the abundance of terrigenous or volcanic material. Eupelagic sediments are deposits in which less than 25 % of the fraction
coarser than fine silt is of terrigenous or volcanic origin. Such sediments
usually form far from the continents. Hemipelagic sediments contain more
than 25 % terrigenous or coarse volcanic-derived material. These deep-sea
sediments usually accumulate near the continental margin, so that continentally derived sediment is more abundant than in eupelagic sediments.
deep-water species animals which live in and are confined to the deep sea. Their
mostly stenothermal character, i.e., the absence of an ability to deal with fluctuating temperatures, prevents their existence in the warmer upper water
layers, but in polar regions some can be found at shallow depths.
deep water wave ~short wave.
deformation radius a length scale, also called Rossby radius of deformation, at
which the effects of the rotation of the earth cannot be neglected, compared
88
auspices of JOIDES the project started in 1968 with R.V. Glomar Challenger
and since then over 800 holes have been drilled, some of them up to the
lower portion of the basaltic layer. ~Iayer 1, layer 2, etc.
deep-sea fan terrigenous, core- or fan-shaped deposit located off the shelf in
front of large rivers and submarine canyons, of which it often forms an extension. The sediment is supplied by rivers or by longshore transport over the
shelf, usually over the inner shelf or near-shore. The sediment is funneled to
the fan by way of a canyon; the dominant transport mode is a turbidity current.
Sediment is deposited where the current reaches the lower gradients of the
ocean basin. Deep-sea fans receive sediment from specific hinterland areas
as do alluvial fans on land. The volume of many fans, in relation to sediment
supply, indicates that they are millions of years old. A striking example is the
Ganges cone (2500 km long, terminating at a depth of ca. 5000 m). Smaller
fans occur along most continental slopes. Most, if not all, fans are marked by one
or more deep-sea channels, which are usually the distal extension of a submarine canyon. At the Ganges and Indus cones the fan reaches almost to the
shelf break but the canyons are short, whereas the Congo (Zaire) canyon
begins in the river estuary, crosses the shelf, and extends to the base of the
continental slope where the Congo deep sea begins at ca. 3500 m depth.
deep-sea sediments sediments found on the deep-sea floor. Except for some turbidites, these sediments are often pelagic in origin. Pelagic sediments are those
derived from the precipitation of dissolved or suspended matter in the open
ocean together with the accumulation of the remains of planktonic organisms.
These sediments are generally found at depths greater than 1000 m and
comprise oozes and red clays. Pelagic sediments may be classified as eupelagic
or hemipelagic, according to the abundance of terrigenous or volcanic material. Eupelagic sediments are deposits in which less than 25 % of the fraction
coarser than fine silt is of terrigenous or volcanic origin. Such sediments
usually form far from the continents. Hemipelagic sediments contain more
than 25 % terrigenous or coarse volcanic-derived material. These deep-sea
sediments usually accumulate near the continental margin, so that continentally derived sediment is more abundant than in eupelagic sediments.
deep-water species animals which live in and are confined to the deep sea. Their
mostly stenothermal character, i.e., the absence of an ability to deal with fluctuating temperatures, prevents their existence in the warmer upper water
layers, but in polar regions some can be found at shallow depths.
deep water wave ~short wave.
deformation radius a length scale, also called Rossby radius of deformation, at
which the effects of the rotation of the earth cannot be neglected, compared