File:Elementary physical geography (1907) (14771975085).jpg

Identifier: elementaryphysic00tarr (find matches)
Title: Elementary physical geography
Year: 1907 (1900s)
Authors: Tarr, Ralph S. (Ralph Stockman), 1864-1912
Subjects: Physical geography
Publisher: New York, The Macmillan company
Contributing Library: The Library of Congress
Digitizing Sponsor: The Library of Congress

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ounding of 4655 fathoms wasmade. The deepest place in the Atlantic (4561 fathoms) isnear Porto Rico. It is a noticeable fact that these excessivedepths are found close to the land. While the greatest ele-vations occur on the land, the average oceanic depth is verymuch .in excess of the average land elevation1; and the greatland elevations are at a considerable distance from the sea,so that the elevation of the high mountain peak above itsbase is much less than its elevation above sea level. Thegreatest ocean depths descend almost directly from the land. Topography near the Coast. — While this description ofthe ocean bottom will serve to present the features of thedeep sea, it does not convey any idea concerning the irregu-larities near the coasts. Along all continent margins, andparticularly among archipelagoes, the form of the bottom is 1 The average depth of the ocean is as much as 12,000 feet, while theaverage elevation of the land above sea level is not much more than 2000 feet.
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H o hi crt Ph ■d +3 Ml fl 162 PHYSICAL GEOGBAPHT. exceedingly irregular. Without entering into the subjectin very great detail, these irregularities could not be ade-quately described; and indeed, our knowledge of the largerpart of the ocean floor is so slight, that as yet we know onlythe general features. Temperature of the Ocean Bottom. — In the neighborhoodof continents, where the depths of the sea are relativelyslight, the temperature is more or less irregular, and deter-mined by local conditions. It changes with the season, andis influenced by the oceanic and tidal currents, and even bythe prevailing winds. After passing this shallow and variable zone, very uniformtemperature conditions are encountered. As a general state-ment, it may be said that throughout the ocean, there is adecrease in temperature with the increasing depth. Startingfrom the variable zone of relatively high temperatures, thereis at first a rather rapid descent until the zone of about 40°is reached at a d

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