Formation of the Caves.
Mr. Ayres thinks that the Caves have been formed entirely by water erosion, but Mr. Wheeler differs from him in this respect. Mr. Ayres says:—
“The rocks in which the Cave occurs are of very hard crystalline limestone, dipping about 30 degrees to the east. In ‘Entrance No. 1’ these beds are very thick and are made up of alternate bands of white, mottled and grey marble. Some of the bands are very highly impregnated with fine sharp sand, so much so, in fact, that excellent whetstones can be made from them.
On the road 3½ miles from Glacier.
White Pine may be observed along the route—a very unusual spectacle in the Selkirk range of mountains.
“The Cave has, undoubtedly, been formed entirely by water erosion. The stream which formed it, Cougar creek, is entirely made up of glacier and snow water, and above the cave is free from any lime salts. Its capacity, therefore, to dissolve lime rock when brought in contact with it, is at its maximum. The fine grains of sharp sand, loosened from the lime rock and caught in the swift current of the small stream that at first found its way through a shrinkage crack of some particular bed of limestone, have undoubtedly given the water an uncommon erosive power, which, through the countless years of the cave’s history, has enabled that mountain torrent to carve out a mammoth channel in solid marble.
“The absence of all stalactites and stalagmites, such as are usually found in caves, and the presence of curiously carved marble walls, wonderfully carved in fantastic shapes and sombre colouring, suddenly make one realize that he is far removed from things familiar.”
The Indian word “Nakimu,” by which the Caves are generally known, has the Anglo-Saxon equivalent of “grumbling.”
This might imply that in some distant past a seismic disturbance in the interior of the mountain resulted in its Indian appellation, or, on the other hand, it may be due solely to the rumbling sound of the subterranean torrent.
Mr. Wheeler, in differing from Mr. Ayres as to the factors mainly instrumental in forming the underground channels and caverns as seen to-day, states his conviction that an agency, more potent and far-reaching than mere erosion and disintegration by the ordinary processes of nature, has been at work.
In his arguments in this connection he says:—
“From the point where Cougar creek first drops beneath Gopher bridge, the old surface channel may be traced, though dammed and nearly obliterated in places. If the natural dam shown at the first point of entrance were removed, the stream would again revert to the old entrance. Southwest of the old entrance is a still older natural dam, whose removal would allow the stream to proceed to the Mill bridge; thence, following the ravine between the two camp grounds, it would pass directly across the Gorge, supposing that great rift not yet to exist, and flowing past ‘Entrance No. 3,’ would descend in a cataract beyond Lookout point.
“There is no doubt that these particular beds of limestone are badly shattered in the mass. It is shown by the fact that the surrounding streams, the Gopher falls, the periodical stream flowing to Entrance No. 3, and that of the Goat falls all join the main stream by underground ways. There are several other instances where the present bed of the creek could hardly be due to shrinkage and erosion, as in the case of the deep rift of the Gorge lying directly across the dip of the strata (the strata dip a little south of east, at an angle between 35 degrees and 40 degrees). The same thing is noticed in the subterranean bed of the creek from the east end of the Witches Ball-room to where it crosses the main corridor near the Art Gallery.
“From October 16 to 21, last, during the survey made of the Gorge series by the writer, though it was well below zero at the camp in the woods, there was no frost found in the cave interiors at a short distance from the entrance. Thus, two of the highest factors of disintegration, sun and frost, are lacking, when accounting for the wholesale cleavage that has taken place within the old waterways. The enormous size of the blocks, moreover, and the indication that the largest of them had been displaced a very long time ago would point to the agency of a severe shock or series of shocks such as would be caused by an earthquake or some similar seismic disturbance. That such disturbances have taken place and acted in this particular locality is borne out by other curious phenomena for which it is difficult to find a different explanation.
“In 1904, Prof. W. H. Sherzer, on behalf of the Smithsonian Institution of Washington, D.C., visited the Canadian Rockies for the purpose of studying their glaciers. Among a series of five, he made a special study of the Illecillewaet glacier situated about seven and a half miles from the Caves. At some distance from the present ice-tongue of the glacier, were found two moraines about a third of a mile apart, composed of enormous blocks of quartzite, weighing in some single instances as much as 1,250 tons, and retaining the original shape in which they were cast from the peaks above to the snow-field and glacier transporting them to the place where they are now found. Prof. Sherzer has named these ‘Block Moraines’ in distinction to ordinary moraines composed of ice-worn, rounded boulders imbedded in a species of cement, commonly known as boulder clay.
“The question is: How and at what time were these block moraines formed. At the present day the glaciers are wholly incapable of transporting such a load, and no such quantities of material are to be found upon the snow-field, below the peaks, as would be necessary to form a similar moraine, even during a protracted period of rest on the part of the glacier.
“In the endeavor to ascertain a date for their formation, Prof. Sherzer cut down trees growing between the two moraines and counted the rings of growth. The oldest was found to have an age of 550 years. Trees, also, growing on the inner or younger moraine were measured and the age of the oldest ascertained to be 447 years. Allowing for the time required for the collection of sufficient soil to permit of growth taking place, the moraine, therefore, would be between 500 and 600 years old.
“Professor Sherzer points to the probability of seismic disturbances being the cause of these block moraines and that the material of which they are formed had been shaken from the peaks to the snow-field below. Making due allowance for the period of transportation of the material forming the inner moraine, the earthquake would thus have occurred during the thirteenth century. (See ‘Glacial Studies in the Canadian Rockies and Selkirks, Smithsonian Expedition of 1904,’ by William Hittell Sherzer, Ph. D.)
“That disturbances of this nature have taken place in Canada at a much more recent date is pointed out in the above report by the following quotation from the ‘Jesuite Relations,’ Thwaites translations, vol. xlvii, pp. 37-57; 183-223: ‘On the fifth of February, 1663, towards half-past five in the evening, a loud roaring was heard at the same time throughout the length and breadth of Canadas. . . . On level ground, hills have arisen; mountains, on the other hand, have been depressed and flattened. Chasms of wonderful depth, exhaling a foul stench, have been hollowed out in many places, plains lie open, far and wide, where there were formerly very dense and lofty forests. Cliffs, although not quite levelled with the soil, have been shattered and overturned.’
Government building at the Caves for the use of visitors.
“If the origin of block moraines can be accounted for by seismic disturbances, it is not improbable to assume that at some remote date a similar occurrence has shattered this bed of crystalline limestone and precipitated Cougar creek from its surface course into subterranean channels, which, through the course of ages, it has enlarged to their present size, and that subsequent shocks have been mainly responsible for the large quantities of fallen debris that litter the interiors. Under such a condition of affairs, the crack of the Gorge, and similar chasms found below the surface, would be accounted for.”
The gist of Mr. Ayres’ arguments concerning the probable age of the cave is contained in the following paragraphs:—
“The marble rocks in which the cave is formed belong most probably to the Devonian age. No fossils were found, however, to positively verify this conclusion. The limestone rocks have not been completely changed into marble at all points as was observed under ‘Gopher Bridge’ and in ‘The Terror.’ Notwithstanding the fact that the rocks belong to a comparatively old series, yet the beginning of the cave undoubtedly dates from a very recent geological time.
“Assuming the rate of erosion to be one thirty-second of an inch in a year, then to cut down one hundred feet of rock, which is about the average amount eroded in the main cave, would require 38,400 years. Any actual rate greater or less than this assumption would increase or diminish the age of the cave. In several places along Cougar creek in the bottom of the cave an excellent opportunity is afforded to determine actually the present annual rate of erosion. A micrometer measuring apparatus should be used and the area of cross-section of the rock eroded per year thus accurately computed. Also the ratio between the area of the cross-section of the average stream and the area of the rock eroded should be determined. And finally, the quantity of water passing the given section in one year, and its velocity, should be accurately measured.
“In contemplating the foregoing suggestion as to the probable age of the cave, it should be borne in mind that where gravel and sand lodge in the bed of the stream the rate of erosion is many times less than where the bed is continually swept clean by a more rapid current.”