Wonders of the Yellowstone

by James Richardson

The history of this great, but no longer the greatest geyser, begins in the early part of the fifteenth century, when its eruptions are mentioned in Icelandic records. In the middle of the seventeenth century the Bishop of Skalholt noticed its daily discharges. A hundred years later Olafsen and Povelsen described it as having three or four eruptions a day, some of them attaining the height of 300 feet, including, doubtless, the uprush of vapor. The depth of its tube was then 72 feet; now it is commonly given as 74, though Commander Forbes, R. N., claims that it is not so deep by ten feet. In 1774 Von Troil estimated the height of the ejected column at 92 feet. Seventeen years later, Stanley gave 96 feet as its greatest height. Forty yards west of the Geyser this traveller found a rival, called the Strokr, (in English, the Churn,) playing to the height of 130 feet. The same year, 1789, an earthquake destroyed the mechanism of the Strokr, converting it into a quiet reservoir of boiling water, whereupon its name was transferred to the present Strokr, which then became especially active and noisy. In 1804 the Geyser had regained somewhat of its ancient power, erupting every six hours to the height of 200 feet; and the original Strokr had repaired its tube so that it could lift a column to nearly the same height and sustain it for a much longer period. During the next five years the power of the Geyser fell off a half, and its paroxysms became much less frequent—Hooker estimating its column, in 1809, at 100 feet, and Mackenzie, a year later, at 90 feet, its eruptions taking place every thirty hours. At the same time the Strokr played every ten or twelve hours, sixty feet high, for the space of thirty minutes. In 1815 the periods had changed again, the Geyser erupting every six hours, to an average height of 80 feet,—the jets occasionally reaching 150 feet, while the Strokr had prolonged its quiet intervals to twenty-four hours. Of late years the Geyser's violent eruptions seldom occur oftener than once in thirty hours, and do not exceed 100 feet in altitude, and generally averaging 70 or 80 feet. Between these eruptions are usually two minor spirts, attaining from 30 to 50 feet. The Strokr is exceedingly irregular in its operation, and generally requires a dose of turf to bring on an exhibition.

A grand eruption of the Geyser has been admirably described by Commander Forbes.

"Twice during the night," he says, "I was aroused by the unearthly complaints of The Geyser; but beyond the vast clouds of vapor which invariably follow each detonation, and a gentle overflowing of the basin, they were false alarms. As morning was breaking it sounded an unmistakable 'reveille,' which would have roused the dead: and I had barely time to take up my position at the brink of the old 'Strokr' before full power was turned on. Jet succeeded jet with fearful rapidity, earth trembled and the very cone itself seemed to stagger under the ordeal. Portions of its sides, rent with the uncontrollable fury it had suddenly generated, were ripped off and flew up in volleys, soaring high above water and steam, whilst the latter rolled away in fleecy clouds before the light north wind, and catching the rays of the morning sun just glistening over the Jökul tops in the East, was lustrous white as the purest snow. Discharge succeeded discharge in rapid succession for upwards of four minutes, when, apparently exhausted and its basin empty, I scrambled up to the margin, intending to have a good look down the tube, which I imagined must also be empty; but the water was still within a few feet of the brink, and boiling furiously. Hastening back to my former position, the basin filled rapidly, and I was just in time to witness the most magnificent explosion of all. Everything seemed to depend on this superhuman effort, and a solid, unbroken column of water twenty-five feet in circumference, was hurled upwards, attaining an altitude very near 100 feet. Here the column paused for a moment before reversing its motion, then fell listless and exhausted through the volumes which followed it into its throbbing cup, again to undergo its fiery ordeal at the threshold of the infernal regions."

Grand as this display must have been, it was but a momentary spasm, a feeble effort compared with the terrific force which sustains the Giant's river-volume, with a steady uprush two hundred feet high, for the space of three hours and a half. There are many, perhaps scores, of geysers in the Firehole Basin, which—even in midsummer, when their action is weakest—far surpass the glory of Iceland.

But what is the origin of the power that sustains these wonderful eruptions? And what is the cause of its intermittent action? Fortunately these questions are not only answerable, but the answers are susceptible of demonstration, as Professor Tyndall has shown in his admirable lectures on heat considered as a mode of motion, wherein he gives the following lucid description of the mechanism and development of the Great Geyser of Iceland: in principle the description applies equally to the geysers of Firehole Basin, and all other springs of the kind.

"It consists of a tube seventy-four feet deep and ten feet in diameter. The tube is surmounted by a basin which measures from north to south fifty-two feet across, and from east to west sixty feet. The interior of the tube and basin is coated with a beautiful smooth silicious plaster, so hard as to resist the blows of a hammer; and the first question is, how was this wonderful tube constructed—how was this perfect plaster laid on? Chemical analysis shows that the water holds silica in solution, and the conjecture might therefore arise that the water had deposited the silica against the sides of the tube and basin. But this is not the case: the water deposits no sediment; no matter how long it may be kept, no solid substance is separated from it. It may be bottled up and preserved for years as clear as crystal, without showing the slightest tendency to form a precipitate. To answer the question in this way would moreover assume that the shaft was formed by some foreign agency, and that the water merely lined it. The geyser basin, however, rests upon the summit of a mound about forty feet high, and it is evident from mere inspection that the mound has been deposited by the geyser. But in building up this mound the spring must have formed the tube which perforates the mound, and hence the conclusion that the geyser is the architect of its own tube.

If we place a quantity of geyser water in an evaporating basin the following takes place: in the centre of the basin the liquid deposits nothing, but at the sides where it is drawn up by capillary attraction, and thus subjected to speedy evaporation, we find silica deposited. Round the edge a ring of silica is laid on, and not until the evaporation has continued a considerable time do we find the slightest turbidity in the middle of the water. This experiment is the microscopic representative of what occurs in Iceland. Imagine the case of a simple thermal silicious spring, whose waters trickle down a gentle inclosure; the water thus exposed evaporates speedily, and silica is deposited. This deposit gradually elevates the side over which the water passes until finally the latter has to take another course. The same takes place here, the ground is elevated as before, and the spring has to move forward. Thus it is compelled to travel round and round, discharging its silica and deepening the shaft in which it dwells, until finally, in the course of ages, the simple spring has produced this wonderful apparatus which has so long puzzled and astonished both the traveller and the philosopher."

The time required for the construction of the Great Geyser tube has been estimated by Commander Forbes as ten or eleven centuries, on the following grounds: a bunch of grass, placed under a little fall made by the ejected water, receives, in twenty-four hours, a coating of silica the thickness of a thin sheet of paper, or about one five-hundredth part of an inch. At this rate it would take 1036 years to build up the 762 inches, which, according to his measurement, is the depth of the tube. In evidence of the probable truth of this estimate he makes note of the following facts: first, there is no notice of this fountain in the early history of the colonization of the island 986 years ago, at which time the tube would have been only three feet deep, and its eruptions too slight to attract attention; second, 436 years afterwards, when the tube would have been twenty-six feet deep, and the eruptions proportionately important, the Geyser is mentioned; third, accurate records of all occurrences were kept by the early inhabitants, and if so remarkable a phenomenon had existed at the time, it could not have been left unnoticed.

The phenomena attending a geyser-eruption—the filling of the basin with water, the agitation of the water, with deafening detonations, the escape of steam, and so on—have been sufficiently described in the preceding chapters. Their causes have been ingeniously explained by Professor Bunsen, who succeeded in determining the temperature of the geyser-tube, throughout its entire length, a few minutes before an eruption. The annexed diagram shows on the left the observed temperatures of the water at different depths, and on the right the temperatures at which water would boil, taking into account the pressure of the atmosphere increased by the presence of the superincumbent column of water. The degrees have been changed from Centigrade to our familiar Fahrenheit standard, disregarding fractions.