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bottom samplers
flood entering over a shallow bottom slope is deformed into a steepening
front that travels upstream at the speed of a long wave. The bore marks the
transition from subcritical flow downstream to supercritical flow upstream
(~Froude number). The Tsing Kiang river in China has a strong bore with a
front up to 4 m high. In England, the Severn estuary has a well-known bore.
boreal areas geographical region with short summer and long cold winters.
~biogeography.
borers, marine organisms that live in holes that they bore in hard substrates.
Borers are found in several taxonomic groups: Fungi, algae, Porifera, Bryozoa,
Phoronida, Bivalvia, Sipuncula, Polychaeta, Crustacea, even in the Echinodermata and
Cirripedia. Borers usually penetrate substrates by mechanical means: wood,
calcareous algae, corals, shells of mollusks or barnacles, sandstone, limestone, chalks, and even bricks, but not granite or concrete. Special measures
have to be taken to protect marine cultures and constructions against damage by borers. Shellboring sponges (Cliona) can be a pest in oyster cultures
and wood-borers can destroy constructions such as ships and sluices. Even
submarine cables need special protection, as some animals bore through
lead casing.
bottom friction ~friction.
bottom nepheloid layer in deep ocean waters containing fine-grained sediment,
resuspension occurs due to near-bottom currents. The turbid layer of several meters is called bottom nepheloid layer.
bottom samplers variety of scientific equipment used for sampling bottom sediments and benthic organisms. Depending on the aim, and the wide variation in local conditions, sediment type, water depth, and size or lifting gear of
the research vessel, bottom samplers range from simple hand-operated
corers in intertidal zones (~zonation) to complicated bottom trawls, sledges,
dredges, grabs, box corers, and deeply penetrating geological corers in subtidal zones (~zonation) and at the ocean bed. In the early days of oceanographic exploration, most bottom sampling was by dredging (~dredge), and the
primary purpose was to collect marine life. At the beginning of the century
the grab sampler was devised and large sediment samples could be obtained.
Such samples, however, are usually somewhat disturbed. If the stratification
of the sea floor is of interest, cores of the sea bottom are preferable to grab
samples. The use of drilling to study the deep ocean bottom was not seriously considered until the 1960s. Ever since, as drilling from an unanchored
ship became feasible, deep-sea drilling has proved to be a powerful tool in
obtaining scientific information on the sea floor. ~Deep-Sea Drilling Project, JOIDES, corer and box corer.
bottom samplers
flood entering over a shallow bottom slope is deformed into a steepening
front that travels upstream at the speed of a long wave. The bore marks the
transition from subcritical flow downstream to supercritical flow upstream
(~Froude number). The Tsing Kiang river in China has a strong bore with a
front up to 4 m high. In England, the Severn estuary has a well-known bore.
boreal areas geographical region with short summer and long cold winters.
~biogeography.
borers, marine organisms that live in holes that they bore in hard substrates.
Borers are found in several taxonomic groups: Fungi, algae, Porifera, Bryozoa,
Phoronida, Bivalvia, Sipuncula, Polychaeta, Crustacea, even in the Echinodermata and
Cirripedia. Borers usually penetrate substrates by mechanical means: wood,
calcareous algae, corals, shells of mollusks or barnacles, sandstone, limestone, chalks, and even bricks, but not granite or concrete. Special measures
have to be taken to protect marine cultures and constructions against damage by borers. Shellboring sponges (Cliona) can be a pest in oyster cultures
and wood-borers can destroy constructions such as ships and sluices. Even
submarine cables need special protection, as some animals bore through
lead casing.
bottom friction ~friction.
bottom nepheloid layer in deep ocean waters containing fine-grained sediment,
resuspension occurs due to near-bottom currents. The turbid layer of several meters is called bottom nepheloid layer.
bottom samplers variety of scientific equipment used for sampling bottom sediments and benthic organisms. Depending on the aim, and the wide variation in local conditions, sediment type, water depth, and size or lifting gear of
the research vessel, bottom samplers range from simple hand-operated
corers in intertidal zones (~zonation) to complicated bottom trawls, sledges,
dredges, grabs, box corers, and deeply penetrating geological corers in subtidal zones (~zonation) and at the ocean bed. In the early days of oceanographic exploration, most bottom sampling was by dredging (~dredge), and the
primary purpose was to collect marine life. At the beginning of the century
the grab sampler was devised and large sediment samples could be obtained.
Such samples, however, are usually somewhat disturbed. If the stratification
of the sea floor is of interest, cores of the sea bottom are preferable to grab
samples. The use of drilling to study the deep ocean bottom was not seriously considered until the 1960s. Ever since, as drilling from an unanchored
ship became feasible, deep-sea drilling has proved to be a powerful tool in
obtaining scientific information on the sea floor. ~Deep-Sea Drilling Project, JOIDES, corer and box corer.