VULCANISM, ETC., IN ICELAND. 400 



syssel) from that of IJanjiJ'irvalla, are located two centers of eruption, 

 the Eyjafjallajokull and the Katla. The iieighborliood of this group 

 consists of sandy deserts and bowlders, which have their origin in the 

 glacial movement and in volcanic eruptions. The configuration < f 

 several districts have in this manner been entirely changed within his- 

 toric times. The combined power of the glacial movement and of the 

 volcanoes is plainly seen in many instances. At one i)lace when^ for- 

 merly quite a considerable fjord existed, there is at present a desert, and 

 several small mountains which formerly rose from th6 coast are at 

 present quite a distance away from the sea. The Eyjabjallajokull 

 (630 37' N. Lat. and W. Long. 32° 16' 18"), to the west, is a truncated 

 cone of 1,706 meters in height. The principal crater has tumbled in 

 and is tilled up with ice. The erni>tion of 1821 took place from a crevice 

 of about 50 meters, on the northwest slope of the mountain. The Katla 

 (630 37' is^. Lat., 31° 35' W. Long, is a deep crater, situated in the east- 

 ern portion of the M;^rdal8Jokull, and ordinarily tilled with ice. It has 

 several times been attempted to closely examine this volcano, but always 

 in vain. 



From the Katla, descending to the base of the glacier, extend two 

 valleys, the one in a southeasterly direction, towards the Mj'rdalssandr, 

 beyond the isolated mountain Hafrsey, the other one in a southwesterly 

 direction, towards the Solheimasandr. The greater part of the water- 

 courses issuing from the glaciers at the time of the eruptions descend 

 through the valley to the southeast ; still some few find their way 

 through the southwesterly valley. The eruptions which in the annals 

 have been ascribed to the MA^-rdalsjokull, Midhdalsjokull, Hefdhajokuli, 

 &elheimajokull, and Katla, should all be credited to the Katla, since 

 all these names have been given to the same volcano. Several districts 

 and a large number of farms have been destroyed by the ertiptions of 

 the Katla. Neither the Katla nor the other ice-covered volcanoes in the 

 south of Iceland have ever emitted any lava. This, next to the He(!la, 

 is the most active volcano, twelve or thirteen eruptions having been 

 recorded within historic times. 



(5) Group of Yarmdrdalr. — The most violent eruptions ever recorded 

 in Iceland within historic times occurred in 1783, to the northeast of 

 the glacier of Myrdalr, in the neighborhood of the sources of the 

 Skaptd. These eruptions issued from a large number of craters, situ- 

 ated to the southAvest, north, and east of Mont Laki (64<^ 2' oST. Lat.), and 

 throughout a valley named Varmdrdalr, and not from the Skaptarjo- 

 kull, as mentioned in most geological manuals, although it is not implied 

 that on other occasions eru])tions have not taken i^lace from craters in 

 that region of glaciers. The craters which occupy our attention in the 

 present ca.se are but imperfectly known. Magnus Stephenseu (1784) and 

 Sveinn Pallson (1794) examined several of them superficially. Thovse of 

 the valley of Varmardalr extend throughout a length of about 15 kilom- 

 eters. The currents of lava which were formed are the most extensive 



