Cave Regions of the Ozarks and Black Hills

by Luella Agnes Owen

(2) At no point does the water in the tube attain the temperature of ebullition which it should have under the pressure to which it is subjected, but the temperature depends on the time that has elapsed since the last eruption. As a great eruption comes near it approaches the boiling point.

(3) At the depth of about forty-five feet the difference between the temperature of the water and the calculated boiling point for that pressure is the least.

The main point of his theory appears to be that an eruption takes place when the water in the tube reaches the boiling point, and to account for it, "He supposes that the column in the central tube communicates by a long and sinuous channel with some space, be it what it may, which is subjected to the action of the direct source of subterranean heat. The temperature gets raised above the boiling point, due to the pressure, and a sudden generation of steam is the result. This steam rises in the column of water, which, being cooler, causes it to condense. Gradually the heat of the water is raised until the water of the channel must boil, and the steam therefore cannot condense, but must accumulate and acquire a gradually increasing tension. The condensation of the bubbles possesses a periodic character, and to this is due the uplifting of the water in what Bunsen calls conical water hills, which are accompanied by the subterranean explosions."

Prof. Comstock is quoted as thinking "Bunsen's theory has not yet been proved adequate to explain the more prominent features of geyser eruptions. Nor does it, in his opinion, account for all the differences between geysers and hot springs, and he proposes a structural hypothesis which combines Bischof's and Bunsen's theories."

This hypothesis is illustrated by a figure in which a reservoir partly filled with water is connected with the surface by a tube having a double curve, and he explains that the water collecting in the depressed curve should confine the steam, rising from the reservoir in the other curve until the pressure is sufficient to cause an eruption. His theory of action being that the water in the reservoir remains in equilibrium at a certain level, and the constant heat fills the space above with vapor, which heats the water held in the downward bend of the tube, and that also evolves vapor which fills the balance of the tube to the vent. When the combined pressure of this vapor and water are overcome by the expansion of vapor accumulated above the reservoir, they are forced out, and followed by a portion of the water of the reservoir. This theory is in the report of Captain Jones on Northwestern Wyoming.

The last theory cited by Dr. Peal is that of S. Baring-Gould, "Who visited the Iceland geysers in 1863, and thinks that a bent tube is sufficient to explain the action of the Great Geyser. He took an iron tube and bent it in an angle of 110°, keeping one arm half the length of the other. He filled the tube with water and placed the short arm in the fire. For a moment the surface of the liquid remained quiet, and then the pipe began to quiver; a slight overflow took place, without any sign of ebullition, and then suddenly, with a throb, the whole column was forced high into the air. With a tube, the long arm of which measured two feet and the bore of which was three-eighths of an inch, he sent a jet to the height of eighteen feet. Steam is generated in the short arm and presses down the water, causing an overflow until the steam bubble turns the angle, when it forces out the column in the long arm with incredible violence."

Dr. Peal now goes on to say:

"Of the theories that we have just enumerated, perhaps no one is adequate to explain all the phenomena of geyser action. Bunsen's theory comes nearest to it, and in the simplest kinds of geysers is a sufficient explanation. The variations and modifications in the geyser tubes and subterranean water passages must undoubtedly be important factors entering into any complete explanation of geyser action. Now, of course, we can see what the conditions are at the surface, but in our experiments we can penetrate to a very inconsiderable distance. We have, therefore, no data to present on these points, and investigations of this branch of the subject will have to be carried on in an artificial manner; that is artificial geysers will have to be constructed, and various modifications made in the tubes until results are reached analogous to those seen in natural geysers. If water in a glass tube be heated with rapidity from the bottom, it will be expelled from the tube violently, and if boiled in a kettle which has a lid and a spout, either the lid will be blown off or the water will be forced out through the spout. The first case is an illustration, in part at least, of Bunsen's theory, and the second exemplifies the theories which presuppose the existence of subterranean cavities with tubes at or near the surface. According to the former we must suppose that the layer of rock, extending seventy-five to seventy-seven feet below the surface, contains sufficient heat to account for geyseric phenomena; or else that the geyser tube has some opening, either at the bottom or on the sides, by which steam and superheated water have access to it from a considerably greater depth where the temperature is very high. At these depths caverns probably exist." * * * *

"That such cavities exist is more than probable. On page 405 I have indicated my belief, that all geysers are originally due to a violent outburst of steam and water, and under such conditions, irregular cavities and passages are more likely to be formed than regular tubes." * *

"In view of what we have just written, Bunsen's conclusion (No. 2) would have to be modified somewhat. His conclusion was that at no point in the tube did the water attain the temperature of ebullition which it should have under the pressure to which it is subjected. As far as this relates to the straight tube in which his temperatures were taken, it may be so; but if he could have taken temperatures in the side conduit, I have little doubt he would soon have reached a point where the temperature would not only be at the boiling point for that depth but even exceed it. In the Yellowstone Park we obtained a number of surface temperatures which were above the boiling point. In the Great Geyser of Iceland, the mass of water in the tube prevents this condition at the surface, and when it takes place opposite the aperture an eruption is caused. In the main, however, I am inclined to accept Bunsen's theory, especially as it seems to me to require subterranean cavities in which the water must be heated. Whether these are caverns, enlargements of tubes, or sinus channels, appears to me to be of no consequence, except as the interval or period of the geyser might be affected by the form of the reservoir holding the water."