,1909-] 



OUTLOOK OF SEISMIC GEOLOGY. 



277 



period of seventeen years by Professor Thoroddsen of Copenhagen, 

 and the islands of the East Indian Archipelago, surveyed for the 

 Dutch Government by the distinguished geologist, Verbeek. Of the 

 Icelandic volcanic region Thoroddsen says :-" 



Of larger eruption fissures and crater chains I have found 87, all of 

 postglacial origin ; . . . 



. . . The many fissures which are common to several districts can not 

 possibly be entered upon a map of small scale; the terrane is often so 

 divided by clefts that both within the flat country and upon the slopes of 

 mountains it appears to be separated into numerous narrow strips some 

 kilometers in length. . . . 



. . . Between the numerous non-volcanic and the volcanic clefts which 

 have poured out important streams, no difference is to be noticed ; an ordi- 

 nary cleft may suddenly become volcanic. . . . 



. . . Where larger fissure systems cross, there are often found large 



Fig. I. Map showing arrangement of volcanoes in the western part of the 

 Island of Java. (After Verbeek.) 



volcanoes, as for example the largest volcano in Iceland, Askja, with a 

 crater of 55 sq. km. area situated at the intersection of the southland fissure 

 running NE.-SW. and the northland one trending N.-S. 



^ " Die Bruchlinien Islands und ihre Beziehungen zu den Vulkanen," 

 Pet. Mitt., Vol. 51, 1905, pp. i-S, map pi. 5. 



