. The Earth beneath the sea : History. Ocean bottom; Marine geophysics. SECT. 1] THE FLOW OF HEAT THROUGH THE FLOOR OF THE OCEAN 229 ocean trenches, since they have not been found in the Japan Trench (Uyeda et ol., 1962), the Puerto Rico Trench (Gerard et al., 1962) or the Aleutian Trench (Foster, 1962). Exchiding the high vahies on the ridges and in the Gulf of California, the values give a roughly normal distribution, the means and standard deviations of the values available in late 1960 being : Atlantic ± (^cal/cm2 sec = Pacific ± pLcal/cm2 sec =
. The Earth beneath the sea : History. Ocean bottom; Marine geophysics. SECT. 1] THE FLOW OF HEAT THROUGH THE FLOOR OF THE OCEAN 229 ocean trenches, since they have not been found in the Japan Trench (Uyeda et ol., 1962), the Puerto Rico Trench (Gerard et al., 1962) or the Aleutian Trench (Foster, 1962). Exchiding the high vahies on the ridges and in the Gulf of California, the values give a roughly normal distribution, the means and standard deviations of the values available in late 1960 being : Atlantic ± (^cal/cm2 sec = Pacific ± pLcal/cm2 sec = The means agree closely and it seems probable that their mean, ± [acal/cm2 sec, represents the mean oceanic heat flow away from the ridges with an uncertainty of 5 or 10%. This is close to the continental mean, which is less well determined. Fig. 11. Section across the South American trench showing heat flow and generalized topography. but probably lies between and [xcal/cm^ sec. The scatter of the Pacific results is greater than that of those from the Atlantic. This is probably due to the former being drawn from a much wider area. To maintain a. heat flow as large as that observed requires very large amounts of heat if it is to be continued through geological time. In 10'^ years the total heat flowing through 1 cm^ amounts to 3 x 10^ cal, which is the heat generated by the complete combustion of a layer of coal 270 m thick. The contribution to the heat flow from chemical and biological processes in the sediments is negligible compared to this, as also is that from radioactivity in the sediments and from compaction. These and other sources of heat have been discussed by Bullard et al. (1956). The only adequate source of heat that has been suggested is radioactivity within the earth. The observed heat flow is about that which would be expected from the uranium, thorium and potassium contained in an earth built uj) from stony and iron meteorites. If the eart
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