Our trip to Iceland was, however, unfortunately so limited in duration as to preclude, save in our four days' ride to the Great Geyser tract, any extension of travel in the various volcanic regions. Hence the omission. I have therefore extracted the following data relative to its principal volcanoes and their eruptions from such books of reference[a] as have been available to me.
The annexed compilation will, I think, explain to such of my readers as are not acquainted with the geological strata of Iceland, its sterile nature, the extreme poverty of its inhabitants, and the constant terror under which their existence is[p. 148] passed, lest a fresh outbreak of lava should sweep away both them and their homesteads. It is somewhat singular, that although Iceland may be looked upon as a veritable mass of volcanoes and hot springs—for with the exception of some 4000 square miles of habitable ground, it may be said literally to rest on underground fires, and while the various eruptions of Etna, Vesuvius, and other volcanoes have for centuries been watched and recorded in the public papers with interest—it is only comparatively recently that the awe-inspiring volcanic eruptions of Iceland have been brought into notice. For instance, while full fifty pages in Ree's 'Cyclopædia' are devoted to the subject of volcanoes, those of Iceland are barely touched upon; yet their eruptions are by far the most devastating on record. So limited, indeed, formerly were the researches of science in these ice-clad regions, that for long Hecla was quoted as its only volcano.
[a] Mrs Somerville's 'Physical Geography;' Chambers' 'Encyclopædia;' Ree's 'Cyclopædia;' Lyell's 'Geology;' Mr George Lock's 'Guide to Iceland.'
Now that the Island has attracted the further notice of geologists, it has been shown that there exist no less than twenty volcanic mountains, all of which have been in active eruption within historic times, and nearly one hundred eruptions have been chronicled as having taken place in the Island.
Although Hecla is doubtless the best known of the Iceland volcanoes, it is by no means the largest; that of 'Askja' (a basket), far surpasses it in size. This latter volcano lies in a great central desert termed 'Odaxa-hraun' or 'Misdeed Lava Desert,' covering a space of 1200 square miles, and[p. 149] a most appropriate name it is, for the devastation caused by its last flood of lava is indescribable.
In one of the convulsions of this mountain in 1875, a quantity of lava five miles in circumference was disrupted, sinking into the mountain to a depth of 710 feet, and causing an earthquake which was felt all over the island. In one region, viz., that of the 'Myvatn's Orœfi' or 'Midge Lake Desert,' a fissure was opened which extended over 20 miles in a north-easterly direction, through which molten lava flowed continuously for four months after the earthquake. Although this fissure is at least 30 miles from Askja, so great was the column of fire thrown up by the eruption, that it was visible for four successive days at Reykjavik, 100 miles distant. The study of an Icelandic map will show the numerous volcanic ranges of mountains which intersect the island in almost every direction.
To the north there will be seen a wonderful volcanic tract. So vast, in fact, that Professor Johnstrup has termed it the Fire Focus of the North. To the north-east, again, is found a large lake, called 'Myvata,' or 'Midge Lake,' with a volcanic range of mountains which stretch from north to south; the most famous of these are 'Leivhnukr,' and 'Krafla,' which, after years of quiescence, poured forth such an amount of lava into the adjoining lake that for many days its waters stood at boiling heat. Other volcanoes in this region eject with terrible force a quantity of boiling mineral pitch, throwing up the dark matter completely[p. 150] enveloped in steam, accompanied by horrible rumbling noises.
Sir George Mackenzie, in his travels in Iceland, thus describes one of the deposits:—
'It is impossible,' he says, 'to convey any idea of the wonders of its terrors, or the sensations of a person even of strong nerves standing on a support which but feebly bears him, and below which fire and brimstone are in incessant action, having before his eyes tremendous proof of what is going on beneath him; enveloped in thick vapour, his ears stunned with thundering noises—such a situation can only be conceived by one who has experienced it.'
The extent of the sulphur beds too in this region are beyond calculation: they reproduce themselves every few years. In the vicinity of 'Krafla' is a curious rock, composed of obsidian, a substance which closely resembles black glass.