VULOANISM, ETC., IN ICELAND. 497 



LOCATION OF THE ACTIVE VOLCANOES. 



The interior of Iceland forms a plateau of about 630 meters in height, 

 which, towards the north, northwest, and east, is cut up into a large 

 number of fjords and valleys; it slopes gently towards the north- 

 northeast (with a rpean inclination of 0° 23' 52" between VatunjokuU 

 apd the promontory of Tjornes); and toward the southwest (with an 

 inclination of 0° 13' 1" between the plateau of Sprengisandr and the 

 mouth of the Thj6rs4) ; while the steepest slopes are on the east and 

 northwest sides, where they form abrupt cliffs facing the sea. The 

 most elevated portions are covered with glaciers, which occupy a 

 superficial surface of 14,000 square kilometers ; the currents of lava 

 covering 7,400, of which 3,400 result from the Odddahraun. Two 

 chains of volcanic mountains, the Reykjanes and the Snaefellsnes, ex- 

 tend on both sides of the Gulf of Faxe easterly across the plateau. 

 The formation of the east and northwest portions of the island is 

 mostly trap, while that of the central portion is soft gravel, with banks 

 of palagonite, a formation in which the volcanic phenomena seem to 

 be prevalent. Volcanic eruptions appear to be confined to two locali- 

 ties, one in the south of the island, running southwest to northeast, 

 and the other in the north, running from south to north. Eruptions 

 of trachyte have occurred in the eastern portion of the ishmd. Glacial 

 and alluvial deposits cover large spaces. There are a large number 

 of extinct volcanoes; but we shall confine ourselves to those which 

 have been active within historic times. 



We may distihguish eight groups of active volcanoes in Iceland : 



(1) Group of Snaefellsnes (Eldhorg). 



(2) Group of the Hecla (Hecla, Randhukambar). 



(3) Group of Beylcjanes (Thurrdrhraun, Trolladyngja, Eldeyjar). 



(4) Group of Katla (Katla, Eyjaijallajokull*). 



(5) Group of Varmdrdalr. 



(G) Group of the volcanoes south of the VatnajoJcull (Oraefajokull, 

 Skeidhardrjokull, Grimsvatn, Sidhujokull). 



(7) Group of the volcanoes of Odddahraun (Kverktjall, D^ngjutjall, 

 Sveinagjd). 



(8) Group of the volcanoes of Myvatn (Krafla, Leirhuukr, Hrossa- 

 dalr, Bjarnarflag, Dalfjall). 



(1) Group of Snaefellsnes. — The only active volcano in this group is 

 the Eldhorg (64° 47' Lat. N., 34° 54' Long. W. of Copenhagen), which 

 at about the year 950 threw out from a crater of 200 meters iu diameter 

 and 53 meters depth a current of lava 11,300 meters long by 3,770 meters 

 wide. 



(2) Group of the Hecla.— Thoi Hecla (63° 59' N . Lat. and 32° 19' Long. 



* Jokull is the Icelandic word for glacier. Eyjafjallajokull, for iu.'tance, signifies 

 the glacier of Eyjafjall, but at the same time serves to designate the volcano or 

 mountain of that name. 



fl. Mis. 15 32 



