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Some 100 or 150 years ago a sea captain knew but little about what was happening under the keel of his ship - unlike an aeronaut overflying strange lands in a balloon or airship, who could watch the terrain below. Seafarers were mostly concerned with reefs, sand-banks, subwater rocks, anchorages and the like. They were interested in shallow waters by and large. But they thought little of deeper waters. Small wonder that by the end of the 19th century there were only a few hundred benthic spots where reliable measurements had been made. And even when some of the ocean floor relief features were mapped, such maps proved not accurate enough.
Dr. G. Udintsev, Corresponding Member of the Russian Academy of Sciences and an authority on the geomorphology and tectonics of the World Ocean floor, has contributed an article for the journal Zemlya i Vselennaya (Earth and Universe) in which he overviews the stupendous work accomplished during the 20th century in mapping the bottom of seas and oceans.
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Data acquisition progress had been sluggish up until the 1940s when echo sounders (sonic depth finders) came to be adopted for exploring the sea floor relief. The echo sounder works on the principle of measuring the time elapsed between transmission of a sound towards and its return from the sea bottom. Meanwhile a new, geomorphological method was introduced in the 1950s, one based on data processing and interpolation relative to explored benthic areas. These studies were complemented with the conventional techniques of taking samples from the sea floor by using dredges.
Detail of Africa's map. 1631.
The breakthrough came soon after the end of the Second World War in the course of military and strategic rivalry between the two superpowers, the Soviet Union and the United States, who dispatched many research parties to explore the World Ocean and its floor. The Soviet Union built up a fleet of research vessels assigned to the USSR Academy of Sciences and other research bodies. Major discoveries in oceanology came as a sideline of this tug of war. Thus, new underwater mountains, rises, troughs and canyons were detected as well as geological structures like mid-oceanic ridges (forming a single system on the bottom of the World Ocean), deep-sea trenches and so forth. The data thus obtained allowed to survey and map the benthic relief features and expand the available body of knowledge about oceanic areas and their formative processes. Soviet research parties exploring in the Sea of Okhotsk, in the Bering Sea and in the northwestern Pacific discovered a number of oceanic rises (named after the Academy of Sciences, Oceanology Institute, Acad. Obruchev) as well as a deep-sea trench (dubbed Vityaz) stretching for over 6,000 km. Other depth geology studies were carried out. The maximum depths of nearly all trenches of the Pacific Ring were measured.
With the upgrading of research methods and techniques it became possible to map ever larger areas using echo-ranging sonars and multipath echo sounders. The effect of such investigations is up if close geophysical surveys in key areas are combined with sample taking by means of deep-sea drilling and dredging, and space altimetry. So, in these past 30 to 40 years a large body of data on oceanic depth geology has been added.
The work of oceanologists, geologists and geophysicists in many countries is coordinated by UNESCO's International Oceanological Committee, the International Hydrographical Organization and other bodies. They have produced several editions of the General Bathymetric (deep-sea sounding) Map of the Ocean published since 1995 with assigned numerical values. The new approach in condensing a vast array of data allows to turn out updated maps in the form of atlases published under UNESCO's auspices - like those of the Indian (1975), Atlantic (1990) and Pacific (2003) oceans. Here the initiative came from Russia's scientists, in the first place from Dr. G. Udintsev, the author of the article under review. Involved in this project is a large international collective of over 400 researchers from Russia, the United States, Great Britain, Germany, Japan and other countries. The Russian Academy of Sciences, too, has been taking part in financing the project; data processing and mapping has been assisted by the geodetic and cartographic services of the Soviet Union and Russian Federation. The departments of navigation and oceanography of the USSR and RF Defense Ministries have also been participating in the effort. The atlases comprise geophysical and geological maps of different scales - from general to large-scale ones. We are getting a better idea of the suboceanic picture of the earth and coming closer in the geographical and geological level of our knowledge of the World Ocean's floor to what we know about the dry land. Work is on in studying oceans from space orbits. Ocean relief maps help ships to navigate safely in seas where the underworld has been studied in much detail. Today we cannot help but wonder at ancient maps whose makers had to people the mysterious voids of seas and oceans with images of fantastic monsters or funny sailboats dauntless in braving the seas towards terra incognitae.
G. B. Udintsev, "The Face of the Oceanic Earth ", Zemlya i Vselennaya (Earth and Universe) journal, No. 3, 2005
Prepared by Andrey BIRYUKOV
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