274 



University of 



California P ublications. 



[Geology 



TWO PROBLEMS PRESENTED. 



The temperature relations of the surface Avater of the North 

 Pacific represented in PI. 32 present two problems for solution. 

 First, what is the cause of the belt of cold water along the west- 

 ern coast of the United States? We have already seen that it 

 must be due to an upwelling of cold water from the adjacent 

 ocean depths, but what are the causes which produce this up- 

 welling? And secondly, why should the coldest part of this area 

 be in the vicinity of Cape Blanco and Mendocino, instead of 

 farther to the northward? Before attempting to answer these 

 problems, a brief review will be made of the discussions of cold 

 water in other portions of the world and also of the general tem- 

 perature relations of the North Pacific. 



COLD WATER ALONG OTHER COASTS. 



In PI. 34 A is shown the belts of cold coast water as mapped 

 by Andrees.* Berghausf gives practically the same areas omit- 

 ting the southeast coast of Arabia. Both authors make the belt 

 extend along the entire Pacific coast of the United States and 

 of Lower California. Neither of them attempts any differentia- 

 tion of the cold water area into belts or sections of different tem- 

 perature. In the handbook accompanying Andrees't Atlas, these 

 areas of cold water are attributed to a vertical current caused 

 by winds blowing off shore and dividing the surface water to 

 the leeward. The supposition is that the accumulation of water 

 to leeward would cause a return drift at the bottom of the ocean 

 and an upwelling near the shore. 



A discussion and indorsement of this idea is given by Murray§ 

 as a preface to his study of the effect of winds on the lochs of 

 Scotland. With such small bodies of water as the lochs, the 

 entire surface is under the influence of wind blowing in the 

 Mime direction and return surface currents are not possible. 

 With the ocean partial compensation may be made in other ways. 



* Andrees. Allgemeiner Hand Atlas, 1900. 

 t Berghaus. Atlas der Hydrographie, 1891. 

 t Geographisches Handbuch zu Andrees Handatlas, 1899. 

 § Murray, Sir John. Effects of Winds on Distribution of Temperature, 

 etc. Scot. Geog. Mag., 1898, p. 345. 



