A Girl's Ride in Iceland

by Mrs. Alec-Tweedie

3d. That there are vast internal fires still actively at work in the neighbourhood of geysers; and,

4th. That the smell of the acid vapours and sulphuretted hydrogen, as well as the mineral matters dissolved and suspended in the ejected waters, are proof positive of chemical activity, he will entirely fail to perceive the value of my remarks regarding the cause of a geyser's action being not only spasmodic but periodic.

On the next page is an explanatory diagramatic sketch, in which no attempt has been made at the impossible, namely, to apportion the size, the shape, or the situation of the cavities to each other. As they may in reality be close together, or miles apart. They may all be on the same level, or more likely not. They may be of nearly equal dimensions, or of varying sizes. It matters not one whit, for the purposes of the demonstration of the theory of geyser action now being adduced.[p. 164]

a. A cavernous reservoir, receiving its water supply by streamlet feeders (b) from the hills (a). b. A natural, and, it may be, circuitous syphon conduit, by which the water can only reach chamber (c) after it has filled tube (b) to the level of the syphon's top, consequently the supply of water to chamber (c) is intermittent, and only lasts until the water in chamber (a) has sunk down to the orifice of its syphon connection. c. Is supposed to be the chemical laboratory in which the decomposable minerals are, and it is further supposed to be heated by subterranean fires. In case the reader knows but little of chemistry, I may remark that all chemical changes are greatly accelerated by heat, and that superheated steam is a most powerful agent in expediting the decomposition of earthy and alkaline compounds.

In the case of these subterranean laboratories, it is utterly impossible for even the scientifically trained mind to conceive what the extent of the heat may be. All he knows is that it is probably far greater than suffices to resolve water into its gaseous elements—oxygen and hydrogen—and that even before this point is reached, superheated steam becomes a terrifically formidable explosive agent. Look at what it did at Ban-dai-san in Japan last year. It actually split a mountain three miles in circumference in twain, and blew one half of it right away into a valley as if it had been the mere outside wall of a house. And such[p. 165] was the force of the wind-shock it occasioned that all the trees growing on the opposite mountain's side were knocked down by it as if they had been mere nine-pins. (In 'Nature,' of the 17th January 1889, at p. 279, will be found an account of the scene of devastation when it was visited (in the month of October 1888) by my son Vaughan; the same who visited the geysers of the Yellowstone with me in 1884, and those of Iceland with his sister in 1887.)

In the case of the geyser, superadded to the superheated steam's explosive power, there will be in addition that of the gases liberated by the decomposition of the carbonates, sulphates, and chlorides (under the combined influence of heat and water) in chamber (c), which I call for the nonce the chemical laboratory. Not alone will all earthy and alkaline, but even metallic compounds, like iron pyrites, therein contained, be rapidly decomposed on the advent of the superheated water. And from their gaseous elements being held in a confined space, they will acquire an enormous explosive power. Consequently, there is no difficulty in understanding how that on obtaining entrance into chamber (e) by means of conduit (d), they will instantly proceed to expel from it all its water. And from the water finding no other outlet except by vent (f), it will rush through it, and, by virtue of the propelling force of the gases, be thrown up into the air in the form of a geyser. Whose activity will only last so long as the supply of water in chamber (f) remains unexhausted.[p. 166]

The above being a rough outline of the salient points of what I consider to be a rational, though, it may be, incomplete, theory of the geyser action I saw in the Yellowstone Park, I shall now add a concluding word on the probable mode of action of the so-called 'earth-sod emetic' that my daughter describes as having been given to the 'Stroker' geyser in Iceland in order to make it eject its water.

The mode of action of the sods, I think, is easily enough explained on the supposition that the geyser has a constriction at some point or another in its vent, and that the sods plug it up sufficiently to hold back the steam and water until they have accumulated sufficient power to blow out the obstructing body, and escape after it with a rush into the air. Precisely in the same way as a fermenting barrel of beer blows out its bung, and its fluid contents gush out, when its vent-hole accidentally becomes plugged up.

George Harley, M.D., F.R.S.