228 



BULLARD 



[chap. 11 



measurements on the Mid-Atlantic Ridge by Gerard et al. and by Nason and 

 Lee. Unpublished work by Von Herzen has shown that the heat flows on the 

 crest of the East Pacific Rise occur in two strips 20 to 40 km wide, and that the 

 curve of Fig. 10 should consist of two peaks and not of a single broad maximum. 

 The high heat flows also seem to be similarly distributed on the Mid-Atlantic 

 Ridge. Nason and Lee foiuid a narrow peak of high values not far from a place 

 where Lister found nothing abnormal. 



Pacific 



Atlantic 



Heat flow (//cal/cm sec) 



Fig. 9. Histogram of heat-flow values in the Atlantic and Pacific Oceans. The black bars 

 are values on the Mid-Atlantic Ridge and the East Pacific Rise. Values in the Gulf 

 of California are excluded from this figure. 



^ 8r 



- e 



s o 



3, 



6- 

 4- 

 '2- 



Fig. 10. Section across East Pacific Rise showing heat flow and generalized topography. 



Heat flows measured in the Gulf of California are high and appear to form an 

 extension of the hne of high values on the crest of the East Pacific Rise. It is 

 possible that the same belt of high heat flow runs out to sea again to the north 

 of California (Menard, 1961). 



Values in the Acaj)ulco and South American trenches tend to be below those 

 elsewhere, as is shown in Fig. 11, which shows a section off the coast of Peru 

 in latitude 14°S. These low values are probably not a general feature of deep 



