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Deep-sea exploration | HearLore
— Ch. 1 · Tides and the First Depths —
Deep-sea exploration.
~7 min read · Ch. 1 of 7
French scientist Pierre-Simon Laplace investigated the average depth of the Atlantic Ocean by observing tidal motions registered on Brazilian and African coasts circa the late 18th or early 19th century. He calculated the depth to be a value later proven quite accurate by echo-sounding measurement techniques. The exact date of his investigation remains unknown, yet this early work laid the groundwork for future inquiries into ocean depths. Later on, due to increasing demand for the installment of submarine cables, accurate measurements of the sea floor depth were required. The first deep-sea life forms were discovered in 1864 when Norwegian researchers Michael Sars and Georg Ossian Sars obtained a sample of a stalked crinoid at a depth of 2,000 meters. This discovery challenged existing theories about life in extreme environments.
Antoine Risso, an apothecary from Nice published a series of papers that remained long ignored, describing and naming dozens of fish and crustaceans species collected by fishermen at depths between 300 and 500 meters in the Gulf of Genoa. In 1818, British researcher Sir John Ross independently discovered that the deep sea is inhabited by life when catching jellyfish and worms in about 1,000 feet with a special device. Edward Forbes claimed that diversity of life in the deep sea is little and decreases with increasing depth. He stated that there could be no life in waters deeper than 1,000 fathoms, the so-called Abyssus theory. Near Lofoten, Michael Sars found a rich variety of deep sea fauna in a depth of 1,000 fathoms, thereby refuting the Abyssus Theory.
Weights and the First Maps
The first instrument used for deep-sea investigation was the sounding weight, used by British explorer Sir James Clark Ross. With this instrument, he reached a depth of 4,000 fathoms in 1840. The sounding weight was designed as a tube on the base which forced the seabed in when it hit the bottom of the ocean. Baillie sounding machines were slightly more advanced versions used on HMS Challenger to extract samples from the sea bed. These machines utilized wire-line soundings to investigate sea depths and collected hundreds of biological samples from all oceans except the Arctic.
A more advanced version of the sounding weight is the gravity corer. The gravity corer allows researchers to sample and study sediment layers at the bottom of oceans. The corer consists of an open-ended tube with a lead weight and a trigger mechanism that releases the corer from its suspension cable when the corer is lowered over the seabed and a small weight touches the ground. The corer falls into the seabed and penetrates it to a depth of up to 3 meters. By lifting the corer, a long, cylindrical sample is extracted in which the structure of the seabed's layers of sediment is preserved. Recovering sediment cores allows scientists to see the presence or absence of specific fossils in the mud that may indicate climate patterns at times in the past, such as during the ice ages.
When did Pierre-Simon Laplace investigate the average depth of the Atlantic Ocean?
Pierre-Simon Laplace investigated the average depth of the Atlantic Ocean circa the late 18th or early 19th century. He calculated the depth to be a value later proven quite accurate by echo-sounding measurement techniques.
Who discovered the first deep-sea life forms and when was this discovery made?
Norwegian researchers Michael Sars and Georg Ossian Sars discovered the first deep-sea life forms in 1864. They obtained a sample of a stalked crinoid at a depth of 2,000 meters which challenged existing theories about life in extreme environments.
What is the Abyssus theory proposed by Edward Forbes regarding deep sea life?
Edward Forbes claimed that diversity of life in the deep sea decreases with increasing depth and stated there could be no life in waters deeper than 1,000 fathoms. This hypothesis became known as the Abyssus theory until Michael Sars found rich deep sea fauna at that depth near Lofoten.
How deep did William Beebe and Otis Barton dive during their first human deep sea exploration?
William Beebe and Otis Barton reached a depth of 3028 feet in 1930 while diving in the Bathysphere. During this historic dive they observed jellyfish and shrimp through a porthole.
When did Jacques Piccard and Donald Walsh make the deepest dive in history to the Challenger Deep?
Jacques Piccard and United States Navy Lieutenant Donald Walsh descended to the Challenger Deep in the Mariana Trench in 1960. Their dive reached 35,800 feet making it the deepest dive in history.
In 1930 William Beebe and Otis Barton were the first humans to reach the deep sea when diving in the Bathysphere, a spherical steel pressure resistant chamber. They reached a depth of 3028 feet, where they observed jellyfish and shrimp. During the dive, Beebe peered out of a porthole and reported his observations by telephone to Barton who was on the surface. In 1948, Swiss physicist Auguste Piccard tested a much deeper-diving vessel he invented called the bathyscaphe, a navigable deep-sea vessel with its gasoline-filled float and suspended chamber or gondola of spherical steel.
On an experimental dive in the Cape Verde Islands, his bathyscaphe successfully withstood the pressure on it at 1,500 fathoms, but its body was severely damaged by heavy waves after the dive. In 1960, Jacques Piccard and United States Navy Lieutenant Donald Walsh descended in Trieste to the deepest known point on Earth - the Challenger Deep in the Mariana Trench, successfully making the deepest dive in history: 35,800 feet. The potential danger was that if the cable broke, the occupants could not return to the surface.
Robots and Remote Eyes
One of the first unmanned deep sea vehicles was developed by the University of Southern California with a grant from the Allan Hancock Foundation in the early 1950s to develop a more economical method of taking photos miles under the sea with an unmanned steel high-pressure sphere called a benthograph. The original benthograph built by USC was very successful in taking a series of underwater photos until it became wedged between some rocks and could not be retrieved. Remote operated vehicles are also seeing increasing use in underwater exploration. These submersibles are piloted through a cable which connects to the surface ship, and can reach depths of up to 20,000 feet.
New developments in robotics have also led to the creation of AUVs, or autonomous underwater vehicles. The robotic submarines are programmed in advance, and receive no instruction from the surface. A Hybrid ROV combines features of both ROVs and AUV, operating independently or with a cable. Alvin was used in 1985 to locate the wreck of the Titanic; the smaller Jason Jr. was also used to explore the shipwreck. High-resolution video cameras, thermometers, pressure meters, and seismographs are other instruments useful for deep-sea exploration.
Metals Under Pressure
Deep-sea exploration vessels must operate under high external hydrostatic pressure, and most of the deep sea remains at temperatures near freezing, which may cause embrittlement of some materials. Structural geometry, material choices and construction processes are all important design factors. If the vessel is crewed, the compartments housing the occupants is almost always the limiting factor. Other parts of the vehicle such as electronics casings can be filled with lightweight yet pressure resistant syntactic foams or filled with incompressible liquids. The occupied portion, however, must remain hollow and under internal pressures suitable for humans.
The most commonly used metals for constructing the high-pressure vessels of these craft are wrought alloys of aluminum, steel, and titanium. Aluminum is chosen for medium-depth operations where extremely high strength is not necessary. Steel is an extremely well-understood material which can be tuned to have incredible yield strength and yield stress. It is an excellent material for resisting the extreme pressures of the sea but has a very high density that limits the size of steel pressure vessels due to weight concerns. Titanium is nearly as strong as steel and three times as light. It seems like the obvious choice to use but has several issues of its own. Firstly, it is much more costly and difficult to work with titanium, and improper processing can lead to substantial flaws.
Vents and New Life
In 1974, Alvin explored the great rift valley of the Mid-Atlantic Ridge, southwest of the Azores. About 5,200 photographs of the region were taken, and samples of relatively young solidified magma were found on each side of the central fissure of the rift valley, giving additional proof that the seafloor spreads at this site at a rate of about 3 centimeters per year. In a series of dives conducted between 1979, 1980 into the Galápagos rift, off the coast of Ecuador, French, Italian, Mexican, and U.S. scientists found vents, nearly 1,000 feet high and about 100 feet across, discharging a mixture of hot water up to 600 degrees Fahrenheit and dissolved metals in dark, smoke-like plumes.
Numerous biological samples have been collected during deep sea explorations, many of which providing findings and hypotheses new to science. For instance microbiological samples from the deep Tyrrhenian Sea collected in oceanographic campaigns of the Mediterranean Science Commission have confirmed the major contribution of marine bacteria and viruses to bathypelagic productivity. These discoveries highlight the importance of understanding how life thrives in extreme conditions without sunlight.
Mining and Future Horizons
Private companies have also expressed interest in these resources. Various contractors in cooperation with academic institutions have acquired 115,591 square kilometers of high resolution bathymetric data, 10,450 preserved biological samples for study and 3,153 line-kilometers of seabed images helping to gain a deeper understanding of the ocean floor and its ecosystem. Scientists are working to find ways to study this extreme environment from the shipboard. With more sophisticated use of fiber optics, satellites, and remote-control robots, scientists hope to one day explore the deep sea from a computer screen on the deck rather than out of a porthole.