270 VREDENBURG: SKETCH OF BALtJCHISTAN UESERf. 



Chapter II.— Recent Volcanoes. 



There exist, as pointed out by Mr. Blanford, two separate vol- 

 canic districts in Persia, one in North- Western Persia and one on the 

 south-eastern frontier. 1 The western portion of the region examined 

 by me contains the most eastern cones of the south-eastern district. 

 Two large volcanoes were visited, the K6h-i-Tafd3n and the Koh-i- 

 Sultdn, both of which consist of compound cones of ash-beds and lava- 

 flows. In the neighbourhood of the K6h-i-Sultin there are a number 

 of smaller lava-cones, mostly of andesitic nature like the larger vol- 

 canoes. Lastly, there are a great many deposits of travertine, even 

 in regions distant from the actual volcanic foci. 



Various travellers have asserted the existence of active or dor- 

 mant volcanoes in Eastern Persia, even as early as the beginning of 

 the century. Pottinger gives some very interesting information re- 

 specting the Basman volcano. 2 But up to the present day accurate 

 information has been very scanty. The eruptive products from these 

 volcanoes are both explosive and effusive, giving rise to ash-beds as 

 well as lavas. They nearly all belong to one class of rocks, that of the 

 andesites. They consist very largely of oligoclase felspar and do not 

 contain any free quartz. They are nearly always 



Andesitic eruptions. . . 



very scoriaceous, so that their specific gravity is 

 not readily ascertained. By means of special tests, General McMahon 

 has determined it in a number of specimens. 8 The numbers found 

 are somewhat low, which shows that the rocks are of a comparatively 

 acid type approaching that of the trachyte group, from which they 

 are removed nevertheless by the absence of orthoclase. Some slight- 

 ly more basic types do also occur, but sparingly. A great many of 

 these rocks contain a hornblende of an exceptional type which was 

 described by General McMahon as a rhombic arnphibole and by 

 Mr. Holland as a soda-hornblende. 



1 Eastern Persia, Vol. II, p. 468. 

 5 Travels in Beloochistan and Sinde, p. 179. 

 3 Quart. Jotrn. Geol. Soc, Vol. LIU (1897), p. 295. 



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