The Yellowstone National Park Part 13

That Bunsen's theory really explains the phenomena of geyser action there can be little doubt. It is true that in no single geyser does one find a perfect example of the theory. But it must be remembered that typical conditions probably never exist. The point of application of heat; the mode of application, whether from the heated surface of rocks or from superheated steam issuing into the tube; the diameter and regularity of the tube; the point of inflow of the cold water; are all matters which influence the eruption and determine its character.

In the endless variety of conditions in nature one need not wonder at the varying results. He should rather wonder that in a single instance nature has produced a combination of such perfection as is found in Old Faithful, which, for thousands of years has performed its duty with the regularity of clock work.

There are various other theories, each with some particular merit, which may be briefly referred to. Sir George Mackenzie, who visited Iceland in 1810-11, thought the geyser tube at some point beneath the surface curved to one side and then upward, communicating with a chamber in the immediate vicinity of the source of heat. The water in this chamber becomes heated above the boiling point, and, expanding, forces the water from the chamber into the tube until the chamber is finally emptied to the level of the mouth of the tube. Any further expulsion of water lessens the weight of the column of water above.

Bunsen's theory comes into play, and with the acc.u.mulated pressure of the steam in the chamber, produces a violent eruption.

Prof. Comstock, who visited the Park in 1873, thought that there were two chambers, the lower being in contact with the source of heat, and the upper acting as a sort of trap in the geyser tube. After a sufficient force of steam has acc.u.mulated in the lower chamber, it ejects the contents of the chamber above.

S. Baring-Gould, who visited Iceland in 1863, observed that if a tube be bent into two arms of unequal length, the shorter of which is closed, and if the tube be filled with water and the shorter arm then heated, all the characteristic phenomena of geyser action result, the water being finally ejected, with explosive violence from the longer tube.

Now, it is probable that in nature each of these theories may find ill.u.s.tration, but it must still be acknowledged that in all cases Bunsen's theory is the partial explanation, and in many the only adequate one.

The most superficial examination of the geysers in the Park will disclose two widely different characteristics as regards their external appearance and mode of eruption. On this basis they may be divided into two cla.s.ses--the fountain geysers and the cone geysers.

In the fountain geyser there is no cone or mound, but in its place a considerable pool which in intervals of rest bears perfect resemblance to the larger quiescent springs. The eruption generally consists of a succession of prodigious impulses by which vast quant.i.ties of water are thrown up one after another. There is ordinarily no continuous jet. To geysers of this cla.s.s, Mackenzie's and Comstock's theories would seem to find closer application than to any others. Noted examples are the Fountain, the Great Fountain, the Grand and the Giantess Geysers.

The cone geysers, on the other hand, have no pool about the crater, and water is not generally visible in the tube. There is always a self-built cone or mound of greater or less prominence, ranging from a broad gently-sloping mound, like that of Old Faithful, to a huge cone like that of the Castle. The eruptions from these geysers usually take the form of a continuous jet, and are more in accordance with the theory of Bunsen. Prominent examples are the Giant, the Castle, Old Faithful, the Lone Star, and the Union.

[Ill.u.s.tration: _Terry Engr. Co._

_U. S. Geological Survey of the Territories._

Cone of the Giant Geyser.]

[Ill.u.s.tration: _Terry Engr. Co._

_First sketch ever made._[AU]--_Trumbull._

Cone of Giant Geyser.]

[AU] This sketch and a similar one of the Castle Geyser cone and two of the Yellowstone Falls are the _very first_ ever made of these objects. They were made in 1870 by Walter Trumbull, a member of the Washburn Party, and by Private Charles Moore, one of the escort under Lieutenant Doane. Moore was a man of excellent education and considerable culture, and it was a matter of comment among the members of the Expedition that he should be content with the condition of a private soldier. His quaint sketches of the Falls forcibly remind one of the original picture of Niagara made by Father Hennepin in 1697.

An interesting and singular fact pertaining to this region is that in most cases the springs and geysers have no underground connection with each other. Water in contiguous pools stands at different levels, and powerful geysers play with no apparent effect upon others near by.

It is another interesting question to know whence comes the water for these geysers and hot springs. Into the hidden caverns of "Old Faithful" flow nearly a million of gallons per hour. This is a large stream, but it is a mere trifle compared with the entire outflow of hot water throughout the Park. The subterranean pa.s.sages by which the necessary supply is furnished to all these thousands of springs, certainly const.i.tute the most intricate and extensive system of water-works of which there is any knowledge.

Not least wonderful of the features of the great geysers are the marvelous formations which surround them, more exquisitely beautiful than any production of art. They are really much handsomer than those to be found around the ordinary quiescent springs. The falling or the das.h.i.+ng of the hot water seems to be in some way essential to the finest results. To say that these rocky projections simulate cauliflower, sponge, fleeces of wool, flowers or bead-work, conveys but a feeble hint of their marvelous beauty. It is indeed a most interesting fact that nature here produces in stone, by the almost mechanical process of deposition from cooling water, the identical forms elsewhere produced by the very different processes of animal and vegetable life.

[Ill.u.s.tration:

_Terry Engr. Co._ _U. S. Geological Survey of the Territories._

Specimens of Geyserite.]

These formations are all silica and are of flinty hardness. Bunsen, and Prof. Le Conte following him, a.s.sert it to be a rule that the presence of silica in the water is essential to the development of a geyser. In one sense this is true, and in another it is not. Should the heated waters find a ready-made tube, like a fissure in solid rock, this would serve for a geyser tube as well as any other. The Monarch Geyser, in Norris Geyser Basin, seems to have originated in this way. But in the general case, geyser tubes are built up, not found ready made. In such cases silica is an indispensable ingredient of the water. A calcareous deposit, like that at Mammoth Hot Springs, would lack strength to resist the violent strain of an eruption. So it is found to be a fact that silica is the chief mineral ingredient in the water of all important geysers.

CHAPTER IV.

HOT SPRINGS.

Under this general head will be included all thermal phenomena of the Park, except the geysers. The term will cover the quiescent springs, the boiling springs, the mud springs, or "paint pots," and the steam vents and fumaroles.

The quiescent spring seems to stand at the opposite pole from the geyser. The conditions are such that the water nowhere reaches a temperature sensibly above the boiling point. The surface therefore steams quietly away, unruffled except by the pa.s.sing breeze.

The great attraction of these springs is in the inimitable coloring of the water. It is not simply the beautiful green or blue of great depths of clear water. In no ordinary pool can one find all the colors of the spectrum, flitting about, as though seen through a revolving prism. Sometimes there is an iridescent effect similar to that of a film of oil upon water; but there is no oil here. There are doubtless many contributing causes that produce these remarkable effects. There is first a great depth of clear water which always presents a beautiful appearance. Then there are the mineral deposits on the sides of the crater, producing indefinite reflection, the effects of which are multiplied by the refractive power of the water. The mineral ingredients dissolved or suspended in the water doubtless add to the effect.

The hot springs on the Gardiner River are wholly different in character from those in any other part of the Park. The water of these springs holds carbonate of lime in solution while most of the others contain silica. To this fact must be attributed the peculiar character of the formations at Mammoth Hot Springs. Wherever the deposits of springs are calcareous, the character of the formations is the same, and generally different from those produced by the deposit of silica.

They rise in terraces one above another, and mold for themselves overhanging bowls of transcendent beauty in form and color. In the tints displayed by the water, however, these springs are not unlike others in the Park.

[Ill.u.s.tration:

_Terry Engr. Co._ _Haynes, Photo., St. Paul._

Cleopatra Terrace.]

The rims about the quiescent springs are often very beautiful, and the observer is astonished to see how they stand up above the general surface of the ground so evenly built that the water has hardly a choice of route in flowing away. Tyndall, however, makes this puzzling phenomenon clear. He says:

"Imagine the case of a simple thermal siliceous spring, whose waters trickle down a gentle incline; the water thus exposed evaporates speedily, and silica is deposited. This deposit gradually elevates the side over which the water pa.s.ses, 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 that wonderful apparatus which has so long puzzled and astonished both the traveler and the philosopher."

The boiling spring is intermediate between the quiescent spring and the geyser. The circulation is sufficiently free to prevent a great rise of temperature in the lower depths of the tube, and nothing more than a surface ebullition, often extremely violent, results. These springs are generally objects of secondary interest. They are simply enormous caldrons; any kettle placed over a brisk fire simulates their action on a small scale.

The mud springs, or Paint Pots, as they are now always called, are extremely curious phenomena. They are caused by the rising of steam through considerable depths of earthy material. The water is just sufficient in quant.i.ty to keep the material in a plastic condition, and the steam operates upon it precisely as it does upon a kettle of thick mush. Generally there are various mineral ingredients, mostly oxides of iron, which impart different colors to different parts of the group. As the steam puffs up here and there from the thick ma.s.s, it forms the mud into a variety of imitative figures, prominent among which is that of the lily. These figures immediately sink back into the general ma.s.s, only to be formed anew by other puffs of steam. The material is so fine as to be almost impalpable between the fingers.

Lieutenant Doane, however, justly observes that "mortar might well be good after being constantly worked for perhaps ten thousand years."

Other phenomena very common throughout the Park are steam vents or fumaroles in which there is no water or only a very small quant.i.ty.

They are not ordinarily of much popular interest, although there are a few remarkable examples. Among these may be mentioned the Black Growler in the Norris Geyser Basin, and Steamboat Spring on the east sh.o.r.e of the Yellowstone Lake.

The hot spring areas of the Park are both numerous and extensive. They abound throughout the valleys of the Yellowstone, the Madison, and the Snake Rivers, and the number of individual springs is several thousand.

CHAPTER V.

FOSSIL FORESTS OF THE YELLOWSTONE.

A region of great popular and scientific interest in the Yellowstone Park, although as yet hardly known to the tourist, owing to the incomplete condition of the road system, is that of the Fossil Forests in the north-east corner of the Park. The facts which have been brought to light concerning the origin of these forests are worthy of particular consideration.

The trees are found to occur in different planes or horizons of growth, one above another, until the whole series represents a thickness of many hundreds, and possibly thousands, of feet. Going back to the first of these growths, it is found to have been destroyed by an outpouring of volcanic material, which partially or wholly submerged it. After the flow had ceased, the ordinary atmospheric and aqueous agencies began work, eroding the surface in some places and depositing the products of erosion in others, while vegetation rapidly covered the newly-formed soil. A subsequent flow destroyed this second growth and gave a new horizon, on which the same process was repeated.

This continued until there were at least nine, and probably twelve, of these consecutive growths.

[Ill.u.s.tration:

_Terry Engr. Co._ _U. S. Geological Survey of the Territories._