1807 - The United States Coast Survey is founded following President Thomas Jefferson's authorization of a survey of the coast.
1840 - January 3, 1843, Sir James Clark Ross takes the first modern sounding in the deep sea at Latitude 27 S Longitude 17 W.
1842 - Darwin publishes The Structure and Distribution of Coral Reefs, in which he suggests that coral atolls are the final stage in the subsidence and erosion of volcanic islands.
1843 - Edward Forbes declares that life cannot exist below 300 fathoms in the deep sea, thus starting a 20-year debate on the presence of the lifeless (azoic) zone.
1845 - Alexander Dallas Bache, second superintendent of the Survey of the Coast, issues instructions for systematic surveys of the Gulf Stream.
1849 - Coast Survey soundings in support of Gulf Stream investigations result in the discovery of the continental shelf break and the continental slope.
1855 - Matthew Fontaine Maury publishes The Physical Geography of the Sea. Although incorrect in much of the science, Maury's flowing prose leads to popular interest in the oceans and the science of the sea.
1857 - James Alden, commanding officer of the Coast Survey Steamer Active, discovers a deep submarine valley, or "gulch," in the center of Monterey Bay. Alden had discovered the first known sea-floor canyon, now called Monterey Canyon.
1867-1868 - Louis F. de Pourtales conducts dredging operations from the Coast Survey Steamers Corwin and Bibb off southern Florida in water depths to 517 fathoms, and finds prolific life extending below 300 fathoms.
1868-1869 - Wyville Thomson dredges from the HMS Lightning and Porcupine and discovers life as deep as 2,400 fathoms, exploding forever Edward Forbes' theory of a lifeless (azoic) zone below 300 fathoms.
1871 - Spencer Fullerton Baird is appointed the U.S. Commissioner of Fisheries. The following year, he uses the Coast Survey Steamer Bache to dredge along the continental slope of New England. This is the first oceanic research conducted by the U.S. Fisheries Commission, forerunner of today's National Marine Fisheries Service.
1872 - The Coast Survey Steamer Hassler proceeds from the East to the West Coast via the Straits of Magellan and attempts deep-ocean dredging and other deep-sea operations along the way. The expedition is led by the famous naturalist Louis Agassiz, accompanied by Louis F. de Pourtales. Unfortunately, the hemp dredge line is defective and breaks on every deep dredging attempt. Although deep dredging operations fail, the cruise is generally successful; Louis Agassiz collects more than 30,000 specimens of sea life.
1872-1876 - Challenger Expedition circumnavigates the globe in the first great oceanographic expedition. Research is conducted on salinity, density and temperature of sea water as well as ocean currents, sediment and metrology. Hundreds of new species are discovered and underwater mountain chains documented. Modern oceanography is based on this research.
Sir Wyville Thomson leads the British Challenger expedition, the first worldwide oceanographic cruise. Thomson dies before all of the results are compiled. Sir John Murray finishes the great work, publishing 50 volumes of the Challenger's results and discoveries.
1873-1874 - The USS Tuscarora, under Commander George Belknap, uses a Thomson sounding machine on a telegraph cable to survey across the Pacific Ocean between Cape Flattery, Washington, and Japan. Belknap discovers the Juan de Fuca Ridge, indications of seamounts, and indications of the Aleutian Trench and Japan Trench.
1874-1877 - Commander Charles D. Sigsbee commands the Coast Survey Steamer Blake . Sigsbee modifies the Thomson Sounding Machine and designs an instrument termed the Sigsbee Sounding Machine. This becomes the basic model for wireline sounding in the deep sea for the next 50 years.
1872-1878 - Accurate, high-density soundings taken by the Coast Survey Steamer Blake in the Gulf of Mexico and Caribbean Sea lead to the first modern bathymetric map.
1882 - The U.S. Fisheries Commission Steamer Albatross -- the first vessel built by any government from the keel up as an oceanographic research vessel -- begins operations.
1885 - The Coast and Geodetic Survey (as the Coast Survey was renamed in 1878) Steamer Blake, under Commander John Elliott Pillsbury, pioneers deep-ocean anchoring techniques during Gulf Stream studies. The Blake is reported to have anchored in 2,200 fathoms.
1899-1900 - The Fisheries Commission Steamer Albatross, under Alexander Agassiz, makes an extended cruise into the south central Pacific, conducting sounding, dredging, and water temperature observations.
1912 - April 15, the White Star Liner Titanic sinks with horrendous loss of life after striking an iceberg in the North Atlantic Ocean. This leads to a concerted effort to devise an acoustic means of discovering objects in the water forward of the bow of a moving vessel.
1914 - On April 27, Reginald Fessenden, of Submarine Signal Corporation, sails on the U.S. Coast Guard Cutter Miami. He uses a Fessenden Oscillator to reflect a signal off an iceberg and simultaneously reflect an acoustic signal off the sea bottom. This test marks the beginning of the acoustic exploration of the sea.
1917-1919 - World War I accelerates oceanic acoustic research as both the U.S. Navy and the Army Coast Artillery develop research programs to devise means to detect enemy submarines.
1919 - French scientists succeed in running the first line of soundings obtained from an acoustic echo sounder.
1923 - The Coast and Geodetic Survey Ship Guide is equipped with a Hayes sounding instrument. Over the next five years, virtually all Coast Survey ships are equipped with deep-water acoustic sounding instruments.
1924 - The Coast and Geodetic Survey conducts the first RAR (radio acoustic ranging) navigation operations on the West Coast. This is the first navigation system capable of round-the-clock operation in all weather conditions, and does not require a navigator to see either some recognizable landmark or celestial object to position a vessel. It is a major step on the road to modern electronic navigation systems, oceanic seismic refraction and reflection profiling, and the development of telemetering oceanographic instruments.
1925-1927 - The German Meteor expedition systematically surveys the South Atlantic with echo-sounding equipment and other oceanographic instruments, proving beyond a doubt the continuity of the Mid-Atlantic Ridge.
1925-1939 - The Coast and Geodetic Survey conducts systematic tracklines across the Gulf of Alaska, discovering numerous seamounts, including the flat-topped variety that Dr. Harry Hess later terms guyots. Systematic C&GS surveys of the continental shelf and slope lead to the discovery of the Mendocino Escarpment, which H.W. Menard later shows to be part of a great system of Pacific fracture zones; delineation of the basin and range topography of Southern California's continental borderlands; the discovery of California seamounts such as Davidson, Pioneer and Guide; and the discovery of many East Coast canyons, particularly in the Georges Bank and Mid-Atlantic areas.
1934 - Edward Beebe is lowered in a tethered bathyscaph to a depth of 3,028 feet marking the advent of manned exploration of the sea.
1935 - Researchers at the Coast and Geodetic Survey invent an automatic telemetering radio sono-buoy. This instrument eliminates the need for manned station ships during RAR (radio acoustic ranging) navigation operations. This is, perhaps, the first offshore moored telemetering instrument.
1938 - Lieutenant Elliott B. Roberts, of the Coast and Geodetic Survey, develops the Roberts Radio Current Meter. This instrument is possibly the first automatic moored telemetering instrument to measure a physical oceanographic parameter.
1941-1945 - During World War II, electronic navigation systems are developed for precision bombing, including the gee system, which C&GS hydrographers adapt and rename Shoran. In 1945 the C&GS conducts its first hydrographic surveys using Shoran. Other inventions from this period pertinent to ocean exploration include deep-ocean camera systems, early magnetometers, sidescan sonar instruments, and early technology for guiding ROVs (remotely operated vehicles).
1953 - Marie Tharpe notices rift valley in sounding profiles along the Mid-Atlantic Ridge. Later Bruce Heezen and Maurice Ewing interpret this to indicate a continuous rift valley extending over 40,000 nautical miles along all the oceanic ridge segments of the world.
1954 - February 15, 1954, the French research submersible F.N.R.S. 3 dives to 13,257 feet off the coast of Dakar, Africa, piloted by Georges Houot and Pierre Willm. This ushered in the era of manned untethered research submersibles.
1955 - The Coast and Geodetic Survey Ship Pioneer in a joint project with the U.S. Navy and the Scripps Institution of Oceanography tows the first marine magnetometer and discovers magnetic striping on the seafloor off the west coast of the United States. Called the PIONEER Survey, this survey was called one of the most significant geophysical surveys ever conducted as it provided a key element to the Theory of Plate Tectonics.
1960 - Bathyscaph Trieste dives to what was believed to be the deepest point in the Mariana Trench. A depth of 10,915 meters was observed. Since that time a Japanese research vessel measured 10,938 meters in the same area in 1998. The trench was first sounded by H.M.S. Challenger in 1875 again by H.M.S. Challenger II in 1951.
1961 - Scripps Institution of Oceanography begins development of the Deep Tow System which is the forerunner of all remotely-operated and unmanned oceanographic systems.
1963 - The first operational multibeam sounding system was installed on the USNS Compass Island. This system, and other multibeam sounding systems that have evolved since, observe a number of soundings to the left and right of a ship's head as well as vertically allowing the development of a relatively accurate map of the seafloor as the ship proceeds on a survey line.
1977 - Hydrothermal vents discovered and with it an ecosystem that survives without the energy of the sun. These ecosystems rely on biota absorbing chemical energy from venting materials in a process called chemosynthesis.
1982 - Major El Niño event leads to the installation of a Pacific equatorial oceanographic buoy array by NOAA's Pacific Marine Environmental Laboratory. Observations from this array have since predicted the onset of El Niño/La Niña events which has been a major step in understanding the coupling of the ocean/atmosphere system.
1985 - September 1, a team led by Dr. Robert Ballard discovers the Titanic, the most famous shipwreck in modern history.
1995 - Declassification of Geosat satellite radar altimetry data leads to worldwide mapping of seafloor from space by Walter Smith and Dave Sandwell with observed data enhancing accuracy over images of the ocean basin drawn by Heezen and Tharpe in earlier years.