Active Glaciers Within the United States

“How and why these glaciers should have perished while the climate is yet cold enough for their existence has become one of the most interesting questions of the finishing-up period of Western geology.”

Among the great number of explorers who have found their way through the mountainous region of the Western United States, either in search of new lands, or mines, or railway passes, only a few of the bolder sort have left the dust of Indian trails and pushed up into that dark cool zone of pine-land which lies like the shadow of a cloud upon all the high ranges; and still fewer have made their camps among the natural gardens at the foot of the perpetual snow, or have climbed the high white summits. These solitudes have as yet been entered only by some curious hunter whom pluck and the fresh traces of mountain sheep have allured from his more congenial altitude; or men of science, who, like Dr. Parry, botanized with the barometer upon their backs up to the limit of flowers, and on among the snow and lichens, till they gradually found themselves upon the very peaks.

Ten years ago Professor J. D. Whitney began the Geological Survey of California, and, from the earliest days of that work up to the present time, he has kept some of his parties among the heights of the Sierras. I was for several years a member of his corps and shared in this interesting alpine service.

During the last four years, under the orders of Major-General Humphreys, Chief of the United States Engineers, I have been engaged in “The United States Geological Exploration of the Fortieth Parallel,” and have conducted a constant alpine study along the summits of the elevated ranges of the Great Basin, the bounding chain of the Wasatch, the Uintas, and Wind River chain. In 1869 Professor Whitney, with several of his old California staff, explored the region of the parks in Colorado, and collected highly interesting material upon the more lofty portions. These difficult and often dangerous labors have given us the general outlines of the alpine portions of Western America. Summits of lava and granite and wave-like ridges of up-turned sedimentary strata, here and there, over the whole wide extent of the elevated Cordillera, reach the region of perpetual snow. From peak to peak the climber may almost never be out of sight of some whitened summit.

Where, over a comparatively low level, a single mountain towers into the sky, bearing upon its summit a cap of white, it is no wonder that the dry interior air slakes its thirst from the melting snow, and that the mountain gets rid of its burden rather by evaporation than by the crowding downward of glaciers; but where immense, elevated ridges, like the long serrated crest of the Sierra Nevada, stretch for many hundreds of miles with a hardly broken cover of white, it has seemed very remarkable that no active moving glaciers have been found.

Professor Whitney has communicated to the public most interesting accounts of the high Sierras, and among the more important phenomena were the evidences of a vast system of glaciers which once covered the rocky heights and flowed downward through the lateral cañons, and whose sole relics are now the architectural remains—if I may so speak—of the moraines, the wonderfully brilliant polishings of porphyritic granite, and the fields of perpetual icy snow which represent to-day the névé portion of the ancient ice-rivers. From the summit of one of those grand towers which leap upward from the thin crest of the granite Sierras one looks northward and south over a region of lofty needles; thin, blade-like ridges separated from each other by profound gulfs; amphitheatres, flanked by splintered walls of stone which open downward into deeper and broader gorges, until they connect with the immense system of lateral cañons which traverses the Sierra from east to west, carrying its entire drainage. These gorges and cañons are all sculptured by glaciers. Around the curves of their courses the surfaces of granite are burnished, and high upon the mountain walls are seen embankments of débris rock, the old moraines often nearly two thousand feet above the bottom of the cañon. Around the heads of the amphitheatres, and clinging here and there upon the more shadowed slopes of rock, broad fields of white are all that remain of the névé. The same set of phenomena may be observed in the heights of the Rocky Mountains, on a less grand scale, but with a certain added force, for the snows, as one travels eastward, become less and less, until on the front rank of the Rocky Mountains in Colorado and Wyoming the summits are remarkably bare, or dappled with shrunken snow-banks. Over the entire elevated portion of the West the same phenomena may be observed, and the magnitude and extent of the ancient glacier system was directly proportioned to the height and mass of the mountain chain. It is true that forests of great magnitude grow everywhere in the glacier courses, but the life of a forest is of course momentary, in a geological sense.

A comparison of the ranges of temperature over the Cordillera prove very satisfactorily that the climate is quite cold enough for glacier formation. How and why these glaciers should have perished while the climate is yet cold enough for their existence has become one of the most interesting questions of the finishing-up period of Western geology. The solution is probably near at hand, and may be given briefly in the one word, dryness. To the question, Why the dryness? we are unable at present to offer a thoroughly satisfactory answer. Observations made by my associates during the past summer will throw some light upon this, and put a different aspect upon the ice question by the unexpected discovery of a considerable system of living, moving glaciers.

In Northern California the Sierra, after lifting for four hundred miles a continuous wave, breaks down into a broad, confused, hilly region, descending in places to low, flat plains. From these depressions ridges and cones of volcanic origin are lifted. Shasta, the colossal cone of a burned-out volcano, springs upward from a plain about three thousand feet in elevation, bearing upon its summit a cap of solid white. With the varying seasons this snow crest changes very greatly. In 1862 Professor Whitney and his party climbed to the summit peak, measured its altitude (14,441 feet), and determined the general character of its lavas. Before and since then it has been frequently climbed, but, until recently, the only known way to the top was up the southern flank.

In early September of the past autumn, accompanied by Messrs. S. F. Emmons, F. A. Clark, and A. B. Clark, of my corps, and Mr. Sisson, the well-known Shasta guide, I ascended Mount Shasta, making the climb from the west. We rode our mules to the upper limits of vegetation, at a point about nine thousand feet above sea level, on the western slope of a secondary cone which juts from the west side of the main peak. Starting early from the base, we reached the rim of the secondary mountain about one o’clock, and found ourselves upon the edge of a very perfect, circular crater, in whose middle rose a smaller volcanic cone, sheltering upon its northern side a frozen lake. Perhaps a third of the interior slope was covered with snow, which was of an exceedingly compact texture, turning into solid ice toward the bottom. We made our way around the rim of this volcano, part of the time following ridges of rock, and then, walking over sharp knifeblades of ice where the whole crater edge was covered. Reaching the north slope we looked down into a profound cation lying between our peak and the main cone of Shasta, and were thrilled to see a true moving glacier. From the uppermost limits of the névé, which reached quite to the summits of Shasta, we could overlook its whole course as it came down the cone in a series of cascades, curved round the base of the mountain directly at our feet, and flowed down the gorge toward the west. The entire length can hardly be less than three miles and a half, with a breadth varying from three to six thousand feet. All the phenomena of glacier cascades, with the true flame-like sérac, and shattered chaos of blue blocks, lay beneath us. There are but slight lateral moraines, but the terminal one is quite disproportionately large, the whole surface of the glacier being strewn with blocks which have rolled down the slopes of the two cones and bounded far out upon the ice. A small tributary glacier from the saddle-like divide between the two cones joins the main mass.

Mount Shasta is formed of an interior mass of andesite—which was the original volcano—and an overflowing cap of a variety of trachyte rocks. From general examination, it seems probable that a considerable erosion of the surface of andesite took place before a general outpouring of trachyte, and, wherever a glacier has worn its way through the covering of trachyte, the harder knobs and spurs of underlying andesite, resisting the movement of the glacier, probably caused the sudden descents and crevassed portions. Directly in front of our point of view one of the finest ice cascades occurs. The whole surface of the glacier is riven with transverse crevasses which have a general tendency to curve downward, while the breaks above this point recurve upward. After descending, probably a thousand or fifteen hundred feet, the ice is again welded into a comparatively smooth surface, and the chasms are more or less obliterated. Numerous brooks flow over its surface and pour into the crevasses. On examination the glacier proved to possess the well-known stratified structure and the blue veins. From a point about midway out upon its surface, and directly above the main cascade, I looked down over all the lower flow, broken with billowy upheavals, and bright with bristling spires of sunlit ice. Upon the right rose the great cone of Shasta, formed of chocolate-colored lavas, its sky-line a single curved sweep of snow cut sharply against a deep blue sky. To the left the precipices of the lesser cone rose to the altitude of twelve thousand feet, their surfaces half jagged ledges of lava and half irregular sheets of ice. From our feet the glacier sank rapidly between the two volcanic walls, and the shadow of the lesser cone fell in a dark band across the brilliantly lighted surface. Looking down the course of the glacier, the eye ranged over the sunny and shadowed zones of ice, over the gray, boulder region of the terminal moraine, still lower along the former course of the ancient and grander glacier, and down upon the undulating pine-clad foot-hills, descending in green steps, reaching out like promontories into the sea of plain, which lay outspread nine thousand feet below, basking in the half-tropical sunshine, its checkered green fields and orchards ripening their wheat and figs.

The night was spent under the lee of a ledge of rocks upon the crater rim, the clouds eddying around us until after midnight. On the following day we climbed to the summit of the main Shasta, traversing, near the end of our climb, the névé of the glacier. We were very fortunate in the weather; the sky was quite cloudless, and through the intensely pure air we could discern the form and details of range after range, over an immense area. The old moraines radiated from the base of the mountain in all directions; those upon the north and east defined themselves as conspicuous topographical objects. From the very highest peak of Shasta we looked down to the east upon a second considerable glacier, crowded out from the foot of an immensely steep névé: it flows to the southeast, and then turns due east, ending in a deep cañon. Its course is shorter than the other, and its surface is marked by an almost continual succession of sérac.

From the northernmost point of the ridge-like summit of Mount Shasta a good view was afforded of the ice-slopes to the north. They may really be considered as one immense glacier, covering almost completely the broad, convex surface of the cone. The angle of descent is thirty-five degrees, and having flowed down to about eight thousand five hundred or nine thousand feet, the mass divides into several lesser forks, which occupy the bottoms of the cañons, and continue to varying depths, flanked always by the straight embankments of former medial moraines. From the immense height of the cap of Shasta only a faint idea is received of the structure and dimensions of these rivers of ice. In the ordinary hazy atmosphere of summer they will be quite indistinguishable; and, indeed, were it not that we had been prepared to recognize them by finding the first, it may be doubted whether we should have detected their existence from the summit view.

On the following day we descended on the south slope of the mountain, our pathway being alternately over fragmentary fields of névé ice and slopes of lava débris. Glacier tables were of very common occurrence, the stems or platforms on which they rested never rising over three or four feet. In the descent we followed very closely the track of Professor Whitney’s party, and that of all the earlier climbers of the mountain, and upon that pathway were unable to see any glacier masses. That they cannot possibly be seen on this flank, and that there is nothing whatever to indicate their existence, are the reasons Professor Whitney’s party made the ascent without finding them.

Subsequently the whole week was devoted to the study of the southern half of the great cone, and not a single active glacier exists there. The proportion of the snow-covered surface is exceedingly small, and it is quite evident that for a very long period of time no ice-stream has moved upon that side.

The exploration of the northern half of the mountain proved, of course, by far the more interesting. The glaciers descend to an altitude of about eight thousand feet, or nearly a thousand feet below the uppermost line of vegetation. The old moraines, which everywhere flank the present glaciers, are ordinarily covered with a growth of Pinus flexilis, and on the more sheltered portions are groups of Abies Williamsonii. What seemed to me the most unusual feature of these glaciers is the vast amount of terminal moraine, and its mode of arrangement. In some instances a mile and a half of the lower end of the glacier will be buried under deep accumulations of débris, varying from a few feet to sixty or seventy in thickness. Near the lower margin of these moraines young trees are found, and I observed several cases where the advancing ice had crowded the boulders over the trees, bending and crushing them. This is the only fact which indicates a present lengthening movement of the glacier. All the other observations tend to the belief that they are still shrinking, and what we now see are only the wasted relics of the great original system. In general, the surface of the large northern glaciers is quite smooth, but here and there, where they pass over underlying knobs, or formations which create an unusual strain, the face is deeply gashed with crevasses of extraordinary size. I examined several that could not be less than two thousand feet long and thirty to forty feet wide. From the lower or steeper side, I was able to approach the very edge and look down into these blue gulfs. Immense icicles hung from the overreaching eaves, and from a great depth came up the muffled gurgle of sub-glacial streams. The middle part of the northern glacier is fully three and a half or four miles wide, and partakes of the convexity of the cone. It is quite unlike the glaciers of the Alps, which lie deeply hidden between abrupt, precipitous walls. A smooth, rounded field of blue ice bounds the view on either side. Above the névé slope together, uniting at the small bunch of pinnacles which forms the summit. Descending at a very abrupt angle, they crowd before them vast fields of débris, and at the last, dividing, the rapidly shrinking forks push onward for a few thousand feet and end.

There are five distinct glaciers upon Shasta, — the one first described lying between the main and secondary cones; the McCloud glacier, as I call it, upon the east side of the mountain; and three large bodies into which the great northern ice is divided. The greatest length is perhaps not far from four and a half miles; the steepest slope is upon the northern side, and for at least four thousand feet is thirty-five degrees.

The extension of the ancient glacier was of course far greater than this, and, judging by the medial and terminal moraines which stand out very distinctly upon the lowland country, the average length must have been about twelve miles. The configuration of this old system was much more like the bodies at present upon the north side; it was, in fact, a conical capping of ice which buried the whole volcano, except where a few isolated peaks or elevated ridges outcropped above the general surface. Our just discovered system is but the feeble relic of the past, and of course has not been observed long enough to determine whether it is increasing or diminishing. All that may be learned from a single season’s observations points, as I before remarked, to a period of gradual extinction. With the periodical climatic changes which recur upon the west coast, they must certainly shrink and lengthen as the snow-fall increases or diminishes. But a very few years must determine their tendency. We have carefully located the termini of all the ice-masses, and these will be laid down upon our map, and will serve as the basis for a future comparison of their extent. They possess all, or nearly all, the well-known features of the Swiss glaciers, — the immense crevasse, the spires of sérac, the lateral, medial, and terminal moraines, the perched boulders, and the milkiness of the streams which flow from their bases. The dirt-bands, however, are rarely apparent, and when observed are irregular and shadowy. It is not a little remarkable that the many parties who have camped upon these glacier streams should not have even suspected the origin of the turbid waters.

During the progress of these observations assistant geologist Mr. Arnold Hague, accompanied by Topographical Engineer Mr. A. D. Wilson, was engaged in carrying on the same series of observations upon Mount Hood. This peak, so conspicuous from the lowlands of Oregon and the Columbia River, is even more deeply snow-capped than Mount Shasta, and from its greater northern latitude is covered to a lower level, probably averaging sixty-five hundred feet. Mr. Hague’s labors resulted in the discovery of a group of important glaciers, corresponding closely with those of Shasta in dimensions and interest. They were also mapped, and the data gathered for a thorough discussion of their nature. In proportion to the height of the mountain and the mass of snow, they are similar to those of Shasta; the superior height of the latter being fully balanced by the difference in latitude.

Upon the discovery of the Shasta glaciers, Mr. S. F. Emmons left me and proceeded to Mount Rainier (Tachoma), a peak situated near the middle of Washington Territory, and in some respects the greatest of all this family of volcanoes within the boundaries of the United States. Its snow-line descends to about five thousand feet, while the summit is not far from fourteen thousand; its immense bulk, standing next to Mount Shasta and receiving the moist wind of the Pacific in such a high latitude, develops a system of glaciers far grander than those of more southern peaks. That of White River is described by Mr. Emmons as varying from two to four miles in width, and about ten miles in length, descending for two thousand feet into the heart of the forest, the dark alpine pines overhanging its white surface. The climbing and examination of Mount Rainier proved one of the most difficult mountaineering feats within our knowledge, and Messrs. Emmons and Wilson deserve the highest praise for their determination and courage. We have now finished a series of surveys of isolated volcanic peaks of the Northwestern United States, beginning on the south with Lassen’s Peak, which has no glacier at all, and ending for the present with Mount Rainier, which is so greatly burdened with fields and streams of ice. Besides the remarkable interest of discovering active glaciers within our limits, this opens up a field for investigation of the power and character of glacial erosion, since the moraines have written a very legible story of the old extent of the glaciers, and the denuded portions of the mountains are open to careful study as to resultant forms and amount of ice sculpture.

It is a great general fact that the northern halves of these volcanoes are carved away to a much greater extent than the southern. As a rule, the profile angle is ten degrees greater at the north than at the south. Besides this great general condition of form, the ravines and gorges upon the northern sides are worn much more deeply. The actual result, as it will appear upon our grade-curve maps, will, I am inclined to think, astonish certain geologists, disbelievers in the carving force of glaciers. Mount Adams and Mount St. Helens were constantly in view of Messrs. Emmons and Hague, and were often examined through their glasses. The northern slopes of each of these mountains appear to be covered by icy snow. There are then but four more peaks of importance south of the “Northwest Boundary,” upon which glaciers may be found: they are Mount Baker, an unknown high summit between that peak and Mount Rainier, Mount Jefferson and the Three Sisters. The existence of glaciers in our Russian purchase has been long and well known, but their nature and extent, their laws of flow and distribution, must for a long time remain unknown. A very few observations upon one or two Alaskan peaks would throw much light upon the rate of glacial increase with latitude. I hope to be able in the coming summer to complete the series of surveys already begun, including St. Helens, Adams, Rainier, Baker, and perhaps St. Elias, and to finish the series by surveying San Francisco Mountain in Arizona.

Let it be remembered that the glaciers discovered in our summer’s work were not the objects of our study, but were merely one of the interesting episodes of the survey. We were engaged in investigating the extinct volcanoes, and that interesting geological field was not neglected for the ice.