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on top, the last lava-flow having filled it up. In Iceland this 

 form is very common, some nineteen " Dyngjen " being known, 

 but owing to the low angle of the cone, the slope varying from 

 6° to 8°, they are easily overlooked, especially in the snow- 

 covered area. One such buckler cone, the Skjaldbreid, is 3,000 ft. 

 high, and seven miles in diameter at the base; it has a small 

 crater on top, but others may have very large ones. In the 

 Kalotta Dyngja, a post-volcanic fissure has cut through the 

 cone, and it is therefore possible to study its internal structure. 

 Mauna Toa, in Hawaii, belongs to this type, although the great 

 spreading base is concealed beneath the ocean. 



Fissure Eruptions. — Iceland has long been known as the 

 typical locality of this type of volcano. The eruption of Laki, 

 or Skapta Jokiill, occurred in 1783. The first eruption took 

 place on June 8, and was accompanied by tremendous detona- 

 tions and earthquake shocks. A great black bank of ash was 

 thrown into the air, in which several up-rushing columns could 

 be seen ; that is to say, the explosions occurred at several places 

 along the fissure. Later on, the explosive stage became confined 

 to the southern half, while the northern half poured out lava, 

 as was evident from the reflection of the glowing mass in 

 the overhanging canopy of cloud. On June 12 a lava stream, 

 200 yards wide, had flowed nine miles down the bed of the 

 Skapta River. The lava in this part is covered with hornitos, 

 little blowing cones, whose origin is ascribed to the escape 

 of water-vapour which the lava had absorbed from the river 

 water. Towards the end of June the eruptions ceased for a 

 time, but in the beginning of August activity was renewed, and 

 stream after stream of lava flowed down the river-beds, destroy- 

 ing all the meadow land adjoining. After a period of rest, 

 the eruptions started again on October 25, when the entire 

 plain in the neighbourhood became a glowing lake of lava, 

 and the molten rock continued to flow during the whole of 

 November. All this time the air was filled with ash and 

 sulphurous vapours, and the vegetation over a large part of 

 the island was killed ; half the animals perished, and 5,000 

 people, out of a total population of 50,000, died of famine or 

 disease. Iceland is full of such fissures, as also in all probability 

 was the whole basaltic plateau of which it is part. The effect 

 of fissure and other eruptions occurring more or less simul- 

 taneously over an area little short of a million square miles 



