Ultima Thule; or, A Summer in Iceland. vol. 2/2

by Sir Richard Francis Burton

THE SULPHUR SPRING.

“With little variation the general appearance of the ‘solfataras’ over the space of twenty-five miles along the volcanic diagonal is much alike: an elevation about two feet high and three feet in diameter, which is composed of a dark-bluish-black viscid clay, forms a complete circle round the mouth of a medium-sized spring. The water is sometimes quiescent, and sunk about two feet within the aperture; at other times it is ejected, with great hissing and roaring noise, to the height of from five to eight feet. At all times clouds of steam, strongly impregnated with sulphuretted hydrogen and sulphurous acid gas, issue from the orifice, both of which, during an eruption of the water, are greatly augmented in quantity. From the dark coloured and elevated margin of the fountain the yellow crust of crystallised sulphur extends a great distance in every direction. Columns of steam ascend from numberless points in the whole district, which are thus impregnated; and thus it is that, apparently for ages past, sulphur has been gradually heaped up in this locality till there are actually hills, which, as far as they have yet been pierced, show sulphur earth to be their main constituents. Hence they have acquired the name of the Sulphur Mountains.

“The soil is of different colours, but most generally white. It is, in the vicinity of the springs, a viscid earth, less plastic than clay, and more readily broken.

“When excavations are made into this earth, it is found to be composed of multitudinous layers, of different colours or shades of colour, each layer being quite distinctly divisible from those above and below it, though frequently no more than an inch or two in thickness.

“It is much to be regretted that the good example set by Olafsen and Povelsen of investigating the nature of the earth’s crust round about the solfataras, by piercing the soil, has not been more frequently carried out. In the summer of last year one of the suggestions which I made for the instruction of an expedition to this place, was that boring implements should be taken out and extensively used; but accident prevented the necessary appliances being forthcoming at the right time. I believe, however, that one of the chief features in the expedition which is to set out in March, will be the thorough examination, to as great a depth as practicable, of the strata in various parts of the Sulphur Valley.

“The spring chosen by Olafsen and Povelsen as the subject of their first experiment, was one which had made its appearance since the preceding winter, and which was just beginning to be surrounded by other mud springs and jets of steam. The ground was still covered with lovely verdure, and charming flowers were abundant, even at the very verge of the caldron of hideous hue and odour. A short distance from this opening they established their boring apparatus. The sequence of the layers was as follows:

“1. Three feet of reddish-brown earth, of a fatty consistence—of the ordinary temperature; at the bottom heat was perceptible to the touch.

“2. Two feet of a firmer kind of earth, nearly the same in colour as the first layer, unctuous to the touch.

“3. One foot of a lighter kind of soil.

“4. Five feet of a very fine earth of different colours, the first two feet being veined red and yellow, with streaks of blue, green, red, and white intermingled. The lower portion of this earth was somewhat firmer than that which covered it. The heat of this thick bed was so great that the soil extracted by the auger could not be handled until it had been for some time exposed to the air.