To the south of the Island is another volcano, termed the 'Kotlugja,' or 'Cauldron Rift,' lying among glaciers known as the 'Myrdals Jökull,' whose eruptions, thirteen of which have been noted, are considered to have done more mischief than any others in the Island. Between the Myrdals and the 'Orœja Jökla' lies one of the most noted volcanoes of Iceland—the 'Skaptar-Jökull,' whose eruption in 1783 is chronicled in all works on Iceland, as the prodigious floods of lava it poured forth in that year were unparalleled in historic times. The molten streams rushing seaward, down the rivers and valleys, the glowing[p. 151] lava leaping over precipices and rocks, which in after years, when they have cooled down, resemble petrified cataracts, and now form one of the grand scenic attractions of the Island.
In Mrs Somerville's 'Physical Geography,' she vividly describes this eruption, narrating how, commencing in May 1783, it continued pouring forth its fiery streams with unabated fury until the following August. So great was the amount of vapour, that the sun was hidden for months, whilst clouds of ashes were carried hundreds of miles out to sea. The quantity of matter ejected on this occasion was calculated at from fifty to sixty thousand millions of cubic yards. The burning lava flowed in a stream in some places 20 to 30 miles broad, filling up the beds of rivers, and entering the sea at a distance of 50 miles from where the eruption occurred. Some of the rivers were not only heated to boiling point, but were dried up, and the condensed vapour fell as snow and rain. Epidemic disease followed in the wake of this fearful lava flood. It was calculated that no less than 1300 persons, and 150,000 sheep and cattle perished, 20 villages were destroyed. The eruption lasted two years.
Mr Paulson, a geologist, who visited Iceland eleven years later, found smoke still issuing from the rocks in the locality.
The heat of this eruption not only re-melted old lavas, and opened fresh subterranean caverns, but one of its streams was computed to course the plains to an extent of 50 miles, with a depth of 100 feet,[p. 152] and 12 to 15 feet broad. Another stream was calculated at 40 miles long, and 7 wide. Men, their cattle and homesteads, their churches and grazing lands, were burnt up, whilst noxious vapours not only filled the air, but even shrouded the light of the sun.
The terrible convulsions which occurred in Iceland during the year 1783, were greater than those recorded at any other period. About a month previously to the convulsion of 'Skaptar-Jökull,' a submarine volcano burst out at sea, and so much pumice stone was ejected that the sea was covered with it for 150 miles round, ships being stopped in their course, whilst a new island was thrown up, which the King of Denmark claimed, and named Nyöe, or New Island. Before the year had elapsed, however, it as speedily disappeared, leaving only a reef of rocks some 30 fathoms under water to mark its site.
But what of Hecla? which is 5000 feet high, and is situated close to the coast at the Southern end of a low valley, lying between two vast parallel table lands covered with ice.
If the eruptions of Hecla are not considered to have been quite so devastating as those just recorded of the 'Skaptar-Jökull,' their duration has been longer, some of them having lasted six years at a time.
When Sir George Mackenzie visited Hecla, he found its principal crater 100 feet deep, and curiously enough, it contained a quantity of snow at the bottom. There are many smaller craters near its summit, the surrounding rocks, consisting chiefly[p. 153] of lava and basalt, are covered with loose stones, scoria, and ashes.
A record of the eruptions of Hecla has been chronicled since the 10th century, and they number 43. One of its most violent convulsions occurred in the same year as that of the 'Skaptar-Jökull,' viz., in 1783. At a distance of two miles from the crater, the lava flood was one mile wide, and 40 feet deep, whilst its fine dust was scattered as far as the Orkney Islands, 400 miles distant.
The mountain itself is composed of sand, grit, and ashes, several kinds of pumice stone being thrown out of it. It also ejects a quantity of a species of black jaspars, which look as if they had been burned at the extremities, while in form they resemble trees and branches. All the different kinds of lava found in volcanoes are to be met with here, such as agate, pumice stone, and both black and green lapis obsidian. These lavas are not all found near the place of eruption, but at some distance, and on their becoming cold form arches and caverns, the crust of which being hard rock. The smaller of the caverns are now used by the Icelanders for sheltering their cattle. The largest of the caves known is 5034 feet long and from 50 to 54 feet broad and from 34 to 36 feet high.