SUNSPOTS AND VOLCANIC AND SEISMIC PHENOMENA. 49 



III. Sedimentation. — The importance of sedimentation 

 and rise of isogeotherms in sedimentary rocks as factors 

 in the production of volcanic action is not to be overlooked. 

 We have only to consider the fact that the majority of the 

 earth's active volcanoes at the present time, and several 

 areas of high earthquake frequency are situated on the 

 western shores of the Great Ocean basins, or on strings of 

 islands lying in the western portions of the oceans. 



The most notable exceptions are the Alaskan volcanoes 

 and those of the Andes. Off the Alaskan coast, however, 

 sedimentation is going on at a rapid rate, partly by the 

 deposition of the suspended detritus of the great Alaskan 

 rivers, partly from the destruction of organisms by the 

 meeting of a hot and a cold current, the Japan current 

 flowing northwards along the east coast of Japan, and the 

 Behring current flowing southwards from the Arctic Ocean. 

 Volcanic activity in the Andes is dying out, sedimentation 

 on the west coast of South America having been reduced 

 to a minimum ; the volcanic cones of the Andes are con- 

 nected, probably, with a period of sedimentation of no great 

 geological antiquity, when the elevation of the Andean 

 chain was just commencing, and a kind of ' Sargasso ' sea 

 existed around Galapagos island. 



We have no very definite evidence, as far as I am aware, of 

 great sedimentation having taken place in Tertiary and Post- 

 Tertiary time in the Pacific Ocean around Galapagos Island, yet 

 there are many geological facts pointing that way. In Ball's 

 "Tertiary Mollusca," (Vol. ill., Pt. iv., Transactions of the Wagner 

 Free Institute of Modern Science), an interesting discussion on 

 the " Tertiary Fauna of Florida " is given. In this, on p. 1550, it 

 is stated as probable that the Isthmus of Panama was formed and 

 the two Americas were united at the commencement of the 

 Miocene. . . In " The Palaeontology and Stratigraphy of the 

 Marine Pliocene and Pleistocene of San Pedro, California," by 



D— June 1, 1904. 



