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34-503: Depth-sounding data first revealed existence consistent with a seamount chain in 1972 although some of the seamounts had been assigned as a ridge in 1964 linked to the Eltanin fracture zone system, hence the name. The oldest volcanic rocks of the chain come from Osbourn Seamount at 78.8 ± 1.3  Ma and ages become younger in a non linear fashion towards the south east with a youngest age of 1.1  Ma . Composition studies of

68-493: A strait ; or also a lagoon between a barrier island and the mainland. A sound is often formed by the seas flooding a river valley . This produces a long inlet where the sloping valley hillsides descend to sea-level and continue beneath the water to form a sloping sea floor. These sounds are more appropriately called rias . The Marlborough Sounds in New Zealand are good examples of this type of formation. Sometimes

102-437: A backup to electronic depth sounding in the event of malfunction. GPS has largely replaced the sextant and chronometer to establish one's position at sea, but many mariners still carry a sextant and chronometer as a backup. Many small craft still rely solely on a sounding line. The first practical fathometer (literally "fathom measurer"), which determined water depth by measuring the time required for an echo to return from

136-621: A few million years appeared to exist. The area of subduction of the Louisville chain into the Tonga Trench is associated with a relative seismic gap beneath the Tonga forearc. This implies that the subduction of the volcanoes compared to normal sediment has a significant impact in terms of normal relief of stress but it is unclear if the subducted volcanoes relieve it as suggested by some or say increase potential for sudden release. Further

170-428: A former river pilot , likely took his pen name from this cry. The term lives on in today's world in echo sounding , the technique of using sonar to measure depth. A sounding line or lead line is a length of thin rope with a plummet , generally of lead , at its end. Regardless of the actual composition of the plummet, it is still called a "lead". Leads were swung, or cast, by a leadsman, usually standing in

204-556: A geographical term. Traditional terms for soundings are a source for common expressions in the English language, notably "deep six" (a sounding of 6 fathoms). On the Mississippi River in the 1850s, the leadsmen also used old-fashioned words for some of the numbers; for example instead of "two" they would say "twain". Thus when the depth was two fathoms, they would call "by the mark twain!". The American writer Mark Twain ,

238-471: A half", "and a quarter", or "a quarter less"; thus 4 3/4 fathoms would be called as "a quarter less five", 3 1/2 as "and a half three", and so on. Where the depth was greater than 20 fathoms the line would commonly be marked with a single knot at 25 fathoms, two knots at 30, and so on. Soundings may also be taken to establish the ship's position as an aid in navigation , not merely for safety. Soundings of this type were usually taken using leads that had

272-428: A high-pitched sound sent through the water and reflected from the sea floor, was invented by Herbert Grove Dorsey and patented in 1928. Sound (geography) In geography , a sound is a smaller body of water usually connected to a sea or an ocean. A sound may be an inlet that is deeper than a bight and wider than a fjord ; or a narrow sea channel or an ocean channel between two land masses, such as

306-472: A postulated historic change in trend of the subducted Louisville chain compared to present is backed up by compositional analysis of more recent arc volcanism as the volcanics from the Louisville chain are recycled. A bathymetric high c. 2 km (1.2 mi) north-west of the Osbourn Seamount has been interpreted as the currently subducting portion of the Louisville chain, but this continuation

340-536: A protected anchorage. It can be part of most large islands. In the more general northern European usage, a sound is a strait or the narrowest part of a strait. In Scandinavia and around the Baltic Sea , there are more than a hundred straits named Sund , mostly named for the island they separate from the continent or a larger island. In contrast, the Sound is the common international short name for Øresund,

374-555: A sound is produced by a glacier carving out a valley on a coast then receding, or the sea invading a glacier valley. The glacier produces a sound that often has steep, near vertical sides that extend deep underwater. The sea floor is often flat and deeper at the landward end than the seaward end, due to glacial moraine deposits. This type of sound is more properly termed a fjord (or fiord). The sounds in Fiordland , New Zealand, have been formed this way. A sound generally connotes

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408-480: A wad of tallow in a concavity at the bottom of the plummet. The tallow would bring up part of the bottom sediment (sand, pebbles, clay, shells) and allow the ship's officers to better estimate their position by providing information useful for pilotage and anchoring . If the plummet came up clean, it meant the bottom was rock. Nautical charts provide information about the seabed materials at particular locations. Nautical charts also include depth contour lines. It

442-444: Is not aligned with the existent chain. Some of the seamounts are known coral reef stoney habitats, with typical species including the coral Solenosmilia variabilis , brisingid starfishes (Order Brisingida ), and sea-lilies and feather stars (Class Crinoidea ). They can be a fishery resource for species such as the orange roughy ( Hoplostethus atlanticus ) that can be fished by bottom trawling . The Louisville Ridge includes

476-555: Is thus sometimes possible to navigate in poor visibility by noting which contour line one is closest to. During the nineteenth century, a number of attempts were made to mechanise depth sounding. Designs ranged from complex brass machines to relatively simple pulley systems. Navies around the world, particularly the Royal Navy in Britain, were concerned about the reliability of lead and line sounding. The introduction of new machines

510-654: The English noun sin , German Sünde ("apart from God's law"), and Swedish synd . English has also the adjective "asunder" and the noun "sundry', and Swedish has the adjective sönder ("broken"). In Swedish and in both Norwegian languages , "sund" is the general term for any strait. In Danish, Swedish and Nynorsk , it is even part of names worldwide, such as in Swedish "Berings sund" and "Gibraltar sund", and in Nynorsk "Beringsundet" and "Gibraltarsundet". In German "Sund"

544-649: The Gulf of Mexico from the mainland, along much of the gulf coasts of Alabama and Mississippi . The term sound is derived from the Anglo-Saxon or Old Norse word sund , which also means " swimming ". The word sund is also documented in Old Norse and Old English as meaning "gap" (or "narrow access"). This suggests a relation to verbs meaning "to separate", such as absondern and aussondern ( German ), söndra ( Swedish ), sondre ( Norwegian ), as well as

578-634: The Wishbone scarp and while the seamounts show no compositional change as they cross the scarps, the East Wishbone scarp crossing point is associated with a distinct decrease in the volume of the younger seamount eruptives from that point east into the Pacific Plate. Volcanic hotspot chains are used to suggest the net movements of tectonic plates and so in the case of the large Pacific Plate validation of models of its movement and indeed

612-426: The chains of a ship, up against the shrouds . Measuring the depth of water by lead and line dates back to ancient civilization. It continues in widespread use today in recreational boating and as an alternative to electronic echo sounding devices. Greek and Roman navigators are known to have used sounding leads, some of which have been uncovered by archaeologists. Sounding by lead and line continued throughout

646-700: The medieval and early modern periods and is still commonly used today. The Bible describes lead and line sounding in Acts , whilst the Bayeux Tapestry documents the use of a sounding lead during William the Conqueror 's 1066 landing in England . Lead and line sounding operates alongside sounding poles, and/or echo sounding devices particularly when navigating in shallower waters and on rivers. At sea, in order to avoid repeatedly hauling in and measuring

680-645: The U.S. state of Washington . It was also applied to bodies of open water not fully open to the ocean, such as Caamaño Sound or Queen Charlotte Sound in Canada; or broadenings or mergings at the openings of inlets, like Cross Sound in Alaska and Fitz Hugh Sound in British Columbia. Along the east coast and Gulf Coast of the United States, a number of bodies of water that separate islands from

714-529: The agency responsible for bathymetric data in the United States, still uses fathoms and feet on nautical charts. In other countries, the International System of Units (metres) has become the standard for measuring depth. "Sounding" derives from the Old English sund , meaning "swimming, water, sea"; it is not related to the word sound in the sense of noise or tones, but to sound ,

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748-409: The depth as he read it off the line. If the depth was at a mark he would call "by the mark" followed by the number, while if it was between two marks, he would call "by the deep" followed by the estimated number; thus "by the mark five", since there is a five-fathom mark, but "by the deep six", since there is no six-fathom mark. Fractions would be called out by preceding the number with the phrases "and

782-424: The erupted dominantly alkali basalt are consistent with a single Louisville mantle source distinct from other hotspots and the composition has remained homogeneous over at least the last 70 million years. In the past 25 million years magma upwelling rates may have decreased. There is almost certainly a deep plume origin to the hotspot. The Louisville hotspot chain passes through the western and eastern branches of

816-413: The following: Depth sounding Depth sounding , often simply called sounding , is measuring the depth of a body of water . Data taken from soundings are used in bathymetry to make maps of the floor of a body of water, such as the seabed topography . Soundings were traditionally shown on nautical charts in fathoms and feet. The National Oceanic and Atmospheric Administration (NOAA),

850-511: The hot spot hypothesis itself relies on data from several hot spot chains. As well as the Louisville hotspot there is data over tens of millions of years available from the movements of the Hawaii hotspot and the Arago hotspot . While the model of Pacific Plate movement, including bends in the hotspot track can be made to fit very well there has been long debate on timing of such bends as mismatchs of

884-401: The later nineteenth century, new machines were introduced to measure much greater depths of water. The most widely adopted deep-sea sounding machine in the nineteenth century was Kelvin's sounding machine , designed by William Thomson (Lord Kelvin) and patented in 1876. This operated on the same principle as lead and line sounding. In this case, the line consisted of a drum of piano wire whilst

918-485: The lead was of a much greater weight. Later versions of Kelvin's machine also featured a motorised drum in order to facilitate the winding and unwinding of the line. These devices also featured a dial which recorded the length of line let out. Both lead-and-line technology and sounding machines were used during the twentieth century, but by the twenty-first, echo sounding has increasingly displaced both of those methods. A sounding line can still be found on many vessels as

952-591: The mainland are called "sounds". Long Island Sound separates Long Island from the eastern shores of the Bronx , Westchester County , and southern Connecticut . Similarly, in North Carolina , a number of large lagoons lie between the mainland and its barrier beaches, the Outer Banks . These include Pamlico Sound , Albemarle Sound , Bogue Sound , and several others. The Mississippi Sound separates

986-695: The narrow stretch of water that separates Denmark and Sweden , and is the main waterway between the Baltic Sea and the North Sea . It is also a colloquial short name, among others, for Plymouth Sound , England . In areas explored by the British in the late 18th century, particularly the northwest coast of North America, the term "sound" was applied to inlets containing large islands, such as Howe Sound in British Columbia and Puget Sound in

1020-412: The nineteenth century. The Royal Navy also purchased a number of Peter Burt's buoy and nipper device. This machine was quite different from Massey's. It consisted of an inflatable canvas bag (the buoy ) and a spring-loaded wooden pulley block (the nipper). Again, the device was designed to operate alongside a lead and line. In this case, the buoy would be pulled behind the ship and the line threaded through

1054-417: The pulley. The lead could then be released. The buoy ensured that the lead fell perpendicular to the sea floor even when the ship was moving. The spring-loaded pulley would then catch the rope when the lead hit the sea bed, ensuring an accurate reading of the depth. Both Massey and Burt's machines were designed to operate in relatively shallow waters (up to 150 fathoms). With the growth of seabed telegraphy in

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1088-548: The sea floor, the rotor would lock. Massey's sounding machine could then be hauled in and the depth could be read off the dials in fathoms. By 1811, the Royal Navy had purchased 1,750 of these devices: one for every ship in commission during the Napoleonic Wars . The Board of Longitude was instrumental in convincing the Royal Navy to adopt Massey's machine. Massey's was not the only sounding machine adopted during

1122-431: The wet line by stretching it out with one's arms, it is common practice to tie marks at intervals along the line. These marks are made of leather , calico , serge and other materials, and so shaped and attached that it is possible to "read" them by eye during the day or by feel at night. Traditionally the marks were at every second or third fathom: at 2, 3, 5, 7, 10, 13, 15, 17, and 20 fathoms. The "leadsman" called out

1156-412: Was understood as a way to introduce standardised practices for sounding in a period in which naval discipline was of great concern. One of the most widely adopted sounding machines was developed in 1802 by Edward Massey, a clockmaker from Staffordshire . The machine was designed to be fixed to a sounding lead and line. It featured a rotor which turned a dial as the lead sank to the sea floor. On striking

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