Read Ebook: Man and the Glacial Period by Wright G Frederick George Frederick Haynes Henry W Henry Williamson Contributor

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Ebook has 651 lines and 122522 words, and 14 pages

Appendix on the Tertiary Man 365-374

Index 375-385

FIG. PAGE

MAPS.

TO FACE PAGE

Map showing the glacial geology of the United States 66

Map of glacial movements in France and Switzerland 132

MAN AND THE GLACIAL PERIOD.

INTRODUCTORY.

That glaciers now exist in the Alps, in the Scandinavian range, in Iceland, in the Himalayas, in New Zealand, in Patagonia, and in the mountains of Washington, British Columbia, and southeastern Alaska, and that a vast ice-sheet envelops Greenland and the Antarctic Continent, are statements which can be verified by any one who will take the trouble to visit those regions. That, at a comparatively recent date, these glaciers extended far beyond their present limits, and that others existed upon the highlands of Scotland and British America, and at one time covered a large part of the British Isles, the whole of British America, and a considerable area in the northern part of the United States, are inferences drawn from phenomena which are open to every one's observations. That man was in existence and occupied both Europe and America during this great expansion of the northern glaciers is proved by evidence which is now beyond dispute. It is the object of the present volume to make a concise presentation of the facts which have been rapidly accumulating during the past few years relating to the Glacial period and to its connection with human history.

Before speaking of the number and present extent of existing glaciers, it will be profitable, however, to devote a little attention to the definition of terms.

With this preliminary description of glacial phenomena, we will proceed to give, first, a brief enumeration and description of the ice-fields which are still existing in the world; second, the evidences of the former existence of far more extensive ice-fields; and, third, the relation of the Glacial period to some of the vicissitudes which have attended the life of man in the world.

According to Professor Heim, of Z?rich, the total area covered by the glaciers and ice-fields of the Alps is upwards of three thousand square kilometres . The Swiss Alps alone contain nearly two-thirds of this area. Professor Heim enumerates 1,155 distinct glaciers in the region. Of these, 144 are in France, 78 in Italy, 471 in Switzerland, and 462 in Austria.

These glaciers adjust themselves to the width of the valleys down which they flow, in some places being a mile or more in width, and at others contracting into much narrower compass. The greatest depth which Agassiz was able directly to measure in the Aar Glacier was two hundred and sixty metres , but at another point the depth was estimated by him to be four hundred and sixty metres .

The glaciers of the Alps are mostly confined to the northern side and to the higher portions of the mountain-chain, none of them descending below the level of four thousand feet, and all of them varying slightly in extent, from year to year, according as there are changes in the temperature and in the amount of snow-fall.

In Scandinavia the height of the mountains is also much less than that of the Alps, but the moister climate and the more northern latitude favours the growth of glaciers at a much lower level North of the sixty-second degree of latitude, the plateaus over five thousand feet above the sea pretty generally are gathering-places for glaciers. From the Justedal a snow-field, covering five hundred and eighty square miles, in latitude 62?, twenty-four glaciers push outwards towards the German Sea, the largest of which is five miles long and three-quarters of a mile wide. The Fondalen snow-field, between latitudes 66? and 67?, covers an area about equal to that of the Justedal; but, on account of its more northern position, its glaciers descend through the valleys quite to the ocean-level. The Folgofon snow-field is still farther south, but, though occupying an area of only one hundred square miles, it sends down as many as three glaciers to the sea-level. The total area of the Scandinavian snow-fields is about five thousand square miles.

In Sweden Dr. Svenonius estimates that there are, between latitudes 67? and 68-1/2?, twenty distinct groups of glaciers, covering an area of four hundred square kilometres , and he numbers upwards of one hundred distinct glaciers of small size.

The island of Spitzbergen, in latitude 76? to 81?, is favourably situated for the production of glaciers, by reason both of its high northern latitude, and of its relation to the Gulf Stream, which conveys around to it an excessive amount of moisture, thus ensuring an exceptionally large snow-fall over the island. The mountainous character of the island also favours the concentration of the ice-movement into glaciers of vast size and power. Still, even here, much of the land is free from snow and ice in summer. But upon the northern portion of the island there is an extensive table-land, upwards of two thousand feet above the sea, over which the ice-field is continuous. Four great glaciers here descend to tide-water in Magdalena Bay. The largest of these presents at the front a wall of ice seven thousand feet across and three hundred feet high; but, as the depth of the water is not great, few icebergs of large size break off and float away from it.

Nova Zembla, though not in quite so high latitude, has a lower mean temperature upon the coasts than Spitzbergen. Owing to the absence of high lands and mountains, however, it is not covered with perpetual snow, much less with glacial ice, but its level portions are "carpeted with grasses and flowers," and sustain extensive forests of stunted trees.

Iceland seems to have been properly named, since a single one of the snow-fields--that of Vatnajok?ll, with an extreme elevation of only six thousand feet--is estimated by Helland to cover one hundred and fifty Norwegian square miles , while five other ice-fields have a combined area of ninety-two Norwegian or about four thousand five hundred English square miles. The glaciers are supposed by Whitney to have been rapidly advancing for some time past.

The Caucasus Mountains present more favourable conditions, and for a distance of one hundred and twenty miles near their central portion have an average height of 12,000 feet, with individual peaks rising to a height of 16,000 feet or more; but, owing to their low latitude, the line of perpetual snow scarcely reaches down to the 11,000-foot level. So great are the snow-fields, however, above this height that many glaciers push their way down through the narrow mountain-gorges as far as the 6,000-foot level.

The Himalaya Mountains present many favourable conditions for the development of glaciers of large size. The range is of great extent and height, thus affording ample gathering-places for the snows, while the relation of the mountains to the moisture-laden winds from the Indian Ocean is such that they enjoy the first harvest of the clouds where the interior of Asia gets only the gleanings. As is to be expected, therefore, all the great rivers which course through the plains of Hindustan have their rise in large glaciers far up towards the summits of the northern mountains. The Indus and the Ganges are both glacial streams in their origin, as are their larger tributary branches--the Basha, the Shigar, and the Sutlej. Many of the glaciers in the higher levels of the Himalaya Mountains where these streams rise have a length of from twenty-five to forty miles, and some of them are as much as a mile and a half in width and extend for a long distance, with an inclination as small as one degree and a half or one hundred and thirty-eight feet to a mile.

In the Mustagh range of the western Himalayas there are two adjoining glaciers whose united length is sixty-five miles, and another not far away which is twenty-one miles long and from one to two miles wide in its upper portion. Its lower portion terminates at an altitude of 16,000 feet above tide, where it is three miles wide and two hundred and fifty feet thick.

In South America, however, the high mountains of Ecuador sustain a few glaciers above the twelve-thousand-foot level. The largest of these are upon the eastern slope of the mountains, giving rise to some of the branches of the Amazon--indeed, on the flanks of Cotopaxi, Chimborazo, and Illinissa there are some glaciers in close proximity to the equator which are fairly comparable in size to those of the Alps.

In Tierra del Fuego, where the mountains are only from three thousand to four thousand feet in height and in latitude less than 55?, Darwin reports that "every valley is filled with streams of ice descending to the sea-coast," and that the inlets penetrated by his party presented miniature likenesses of the polar sea.

Again, speaking of the region in the vicinity of the lofty volcanoes Terror and Erebus, between ten thousand and twelve thousand feet high, the same navigator says:

"We perceived a low, white line extending from its extreme eastern point, as far as the eye could discern, to the eastward. It presented an extraordinary appearance, gradually increasing in height as we got nearer to it, and proving at length to be a perpendicular cliff of ice, between one hundred and fifty and two hundred feet above the level of the sea, perfectly flat and level at the top, and without any fissures or promontories on its even, seaward face. What was beyond it we could not imagine; for, being much higher than our mast-head, we could not see anything except the summit of a lofty range of mountains extending to the southward as far as the seventy-ninth degree of latitude. These mountains, being the southernmost land hitherto discovered, I felt great satisfaction in naming after Sir Edward Parry.... Whether Parry Mountains again take an easterly trending and form the base to which this extraordinary mass of ice is attached, must be left for future navigators to determine. If there be land to the southward it must be very remote, or of much less elevation than any other part of the coast we have seen, or it would have appeared above the barrier."

This ice-cliff or barrier was followed by Captain Ross as far as 198? west longitude, and found to preserve very much the same character during the whole of that distance. On the lithographic view of this great ice-sheet given in Ross's work it is described as "part of the South Polar Barrier, one hundred and eighty feet above the sea-level, one thousand feet thick, and four hundred and fifty miles in length."

A similar vertical wall of ice was seen by D'Urville, off the coast of Adelie Land. He thus describes it: "Its appearance was astonishing. We perceived a cliff having a uniform elevation of from one hundred to one hundred and fifty feet, forming a long line extending off to the west.... Thus for more than twelve hours we had followed this wall of ice, and found its sides everywhere perfectly vertical and its summit horizontal. Not the smallest irregularity, not the most inconsiderable elevation, broke its uniformity for the twenty leagues of distance which we followed it during the day, although we passed it occasionally at a distance of only two or three miles, so that we could make out with ease its smallest irregularities. Some large pieces of ice were lying along the side of this frozen coast; but, on the whole, there was open sea in the offing."

Owing to the comparatively low elevation of the Sierra Nevada north of Tuolumne County, California, no other living glaciers are found until reaching Mount Shasta, in the extreme northern part of the State. This is a volcanic peak, rising fourteen thousand five hundred feet above the sea, and having no peaks within forty miles of it as high as ten thousand feet; yet so abundant is the snow-fall that as many as five glaciers are found upon its northern side, some of them being as much as three miles long and extending as low down as the eight-thousand-foot level. Upon the southern side glaciers are so completely absent that Professor Whitney ascended the mountain and remained in perfect ignorance of its glacial system. In 1870 Mr. Clarence King first discovered and described them on the northern side.

North of California glaciers characterise the Cascade Range in increasing numbers all the way to the Alaskan Peninsula. They are to be found upon Diamond Peak, the Three Sisters, Mount Jefferson, and Mount Hood, in Oregon, and appear in still larger proportions upon the flanks of Mount Rainier and Mount Baker, in the State of Washington. The glacier at the head of the White River Valley is upon the north side of Rainier, and is the largest one upon that mountain, reaching down to within five thousand feet of the sea-level, and being ten miles or more in length. All the streams which descend the valleys upon this mountain are charged with the milky-coloured water which betrays their glacial origin.

In British Columbia, Glacier Station, upon the Canadian Pacific Railroad, in the Selkirk Mountains, is within half a mile of the handsome Illicilliwaet Glacier, while others of larger size are found at no great distance. The interior farther north is unexplored to so great an extent that little can be definitely said concerning its glacial phenomena. The coast of British Columbia is penetrated by numerous fiords, each of which receives the drainage of a decaying glacier; but none are in sight of the tourist-steamers which thread their way through the intricate network of channels characterising this coast, until the Alaskan boundary is crossed and the mouth of the Stickeen River is passed.

A few miles up from the mouth of the Stickeen, however, glaciers of large size come down to the vicinity of the river, both from the north and from the south, and the attention of tourists is always attracted by the abundant glacial sediment borne into the tide-water by the river itself and discolouring the surface for a long distance beyond the outlet. Northward from this point the tourist is rarely out of sight of ice-fields. The Auk and Patterson Glaciers are the first to come into view, but they do not descend to the water-level. On nearing Holcomb Bay, however, small icebergs begin to appear, heralding the first of the glaciers which descend beyond the water's edge. Taku Inlet, a little farther north, presents glaciers of great size coming down to the sea-level, while the whole length of Lynn Canal, from Juneau to Chilkat, a distance of eighty miles, is dotted on both sides by conspicuous glaciers and ice-fields.

About forty miles west of Lynn Canal, and separated from it by a range of mountains of moderate height, is Glacier Bay, at the head of one of whose inlets is the Muir Glacier, which forms the chief attraction for the great number of tourists that now visit the coast of southeastern Alaska during the summer season. This glacier meets tide-water in latitude 58? 50', and longitude 136? 40' west of Greenwich. It received its name from Mr. John Muir, who, in company with Rev. Mr. Young, made a tour of the bay and discovered the glacier in 1879. It was soon found that the bay could be safely navigated by vessels of large size, and from that time on tourists in increasing number have been attracted to the region. Commodious steamers now regularly run close up to the ice-front, and lie-to for several hours, so that the passengers may witness the "calving" of icebergs, and may climb upon the sides of the icy stream and look into its deep crevasses and out upon its corrugated and broken surface.

The first persons who found it in their way to pay more than a tourist's visit to this interesting object were Rev. J. L. Patton, Mr. Prentiss Baldwin, and myself, who spent the entire month of August, 1886, encamped at the foot of the glacier, conducting such observations upon it as weather and equipment permitted. From that time till the summer of 1890 no one else stopped off from the tourist steamers to bestow any special study upon it. But during this latter season Mr. Muir returned to the scene of his discovered wonder, and spent some weeks in exploring the interior of the great ice-field. During the same season, also, Professors H. F. Reid and H. Cushing, with a well-equipped party of young men, spent two months or more in the same field, conducting observations and experiments, of various kinds, relating to the extent, the motion, and the general behaviour of the vast mass of moving ice.

The mountains forming the periphery of this amphitheatre rise to a height of several thousand feet; Mount Fairweather, upon the northwest, from whose flanks probably a portion of the ice comes, being, in fact, more than fifteen thousand feet high. The mouth of the amphitheatre is three miles wide, in a line extending from shoulder to shoulder of the low mountains which guard it. The actual water-front where the ice meets tide-water is one mile and a half. Here the depth of the inlet is so great that the front of the ice breaks off in icebergs of large size, which float away to be dissolved at their leisure. At the water's edge the ice presents a perpendicular front of from two hundred and fifty to four hundred feet in height, and the depth of the water in the middle of the inlet immediately in front of the ice is upwards of seven hundred feet; thus giving a total height to the precipitous front of a thousand feet.

The formation of icebergs can here be studied to admirable advantage. During the month in which we encamped in the vicinity the process was going on continuously. There was scarcely an interval of fifteen minutes during the whole time in which the air was not rent with the significant boom connected with the "calving" of a berg. Sometimes this was occasioned by the separation of a comparatively small mass of ice from near the top of the precipitous wall, which would fall into the water below with a loud splash. At other times I have seen a column of ice from top to bottom of the precipice split off and fall over into the water, giving rise to great waves, which would lash the shore with foam two miles below.

This manner of the production of icebergs differs from that which has been ordinarily represented in the text-books, but it conforms to the law of glacial motion, which we will describe a little later, namely, that the upper strata of ice move faster than the lower. Hence the tendency is constantly to push the upper strata forwards, so as to produce a perpendicular or even projecting front, after the analogy of the formation of breakers on the shelving shore of a large body of water.

Evidently, however, these masses of ice which break off from above the water do not reach the whole distance to the bottom of the glacier below the water; so that a projecting foot of ice remains extending to an indefinite distance underneath the surface. But at occasional intervals, as the superincumbent masses of ice above the surface fall off and relieve the strata below of their weight, these submerged masses suddenly rise, often shooting up considerably higher than they ultimately remain when coming to rest. The bergs formed by this latter process often bear much earthy material upon them, which is carried away with the floating ice, to be deposited finally wherever the melting chances to take place.

In other places I have witnessed the formation of a long ridge of gravel by the gradual falling in of the roof of a tunnel which had been occupied by a subglacial stream, and over which there was deposited a great amount of morainic material. As the roof gave way, this was constantly falling to the bottom, where, being exempt from further erosive agencies, it must remain as a gravel ridge or kame.

Beyond Cross Sound the Pacific coast is bounded for several hundred miles by the magnificent semicircle of mountains known as the St. Elias Alps, with Mount Crillon at the south, having an elevation of nearly sixteen thousand feet, and St. Elias in the centre, rising to a greater height. Everywhere along this coast, as far as the Alaskan Peninsula, vast glaciers come down from the mountain-sides, and in many cases their precipitous fronts form the shore-line for many miles at a time. Icy Bay, just to the south of Mount St, Elias, is fitly named, on account of the extent of the glaciers emptying into it and the number of icebergs cumbering its waters.

Leaving Yakutat Bay, and following the route indicated upon the accompanying map, they travelled on glacial ice almost the entire distance to the foot of Mount St. Elias. The numerous glaciers coming down from the summit of the mountain-ridge become confluent nearer the shore, and spread out over an area of about a thousand square miles. This is fitly named the Malaspina Glacier, after the Spanish explorer who discovered it in 1792.

For a long time it was the belief of many that a large region in the interior of Greenland was free from ice, and was perhaps inhabited. It was in part to solve this problem that Baron Nordenski?ld set out upon his expedition of 1883. Ascending the ice-sheet from Disco Bay, in latitude 69?, he proceeded eastward for eighteen days across a continuous ice-field. Rivers were flowing in channels upon the surface like those cut on land in horizontal strata of shale or sandstone, only that the pure deep blue of the ice-walls was, by comparison, infinitely more beautiful. These rivers were not, however, perfectly continuous. After flowing for a distance in channels on the surface, they, one and all, plunged with deafening roar into some yawning crevasse, to find their way to the sea through subglacial channels. Numerous lakes with shores of ice were also encountered.

"On bending down the ear to the ice," says this explorer, "we could hear on every side a peculiar subterranean hum, proceeding from rivers flowing within the ice; and occasionally a loud, single report, like that of a cannon, gave notice of the formation of a new glacier-cleft.... In the afternoon we saw at some distance from us a well-defined pillar of mist, which, when we approached it, appeared to rise from a bottomless abyss, into which a mighty glacier-river fell. The vast, roaring water-mass had bored for itself a vertical hole, probably down to the rock, certainly more than two thousand feet beneath, on which the glacier rested."

A summary of the results of Greenland exploration was given by Dr. Kink in 1886, from which it appears that since 1876 one thousand miles of the coast-line have been carefully explored by entering every fiord and attempting to reach the inland ice. According to this authority--

We are now able to demonstrate that a movement of ice from the central regions of Greenland to the coast continually goes on, and must be supposed to act upon the ground over which it is pushed so as to detach and transport fragments of it for such a distance.... The plainest idea of the ice-formation here in question is given by comparing it with an inundation.... Only the marginal parts show irregularity; towards the interior the surface grows more and more level and passes into a plain very slightly rising in the same direction. It has been proved that, ascending its extreme verge, where it has spread like a lava-stream over the lower ground in front of it, the irregularities are chiefly met with up to a height of 2,000 feet, but the distance from the margin in which the height is reached varies much. While under 68-1/2? north latitude it took twenty-four miles before this elevation was attained, in 72-1/2? the same height was arrived at in half the distance....

A general movement of the whole mass from the central regions towards the sea is still continued, but it concentrates its force to comparatively few points in the most extraordinary degree. These points are represented by the ice-fiords, through which the annual surplus ice is carried off in the shape of bergs.... In Danish Greenland are found five of the first, four of the second, and eight of the third class, besides a number of inlets which only receive insignificant fragments. Direct measurements of the velocity have now been applied on three first-rate and one second-rate fiords, all situated between 69? and 71? north latitude. The measurements have been repeated during the coldest and the warmest season, and connected with surveying and other investigations of the inlets and their environs. It is now proved that the glacier branches which produce the bergs proceed incessantly at a rate of thirty to fifty feet per diem, this movement being not at all influenced by the seasons. . . .

In the ice-fiord of Jakobshavn, which spreads its enormous bergs over Disco Bay and probably far into the Atlantic, the productive part of the glacier is 4,500 metres broad. The movement along its middle line, which is quicker than on the sides nearer the shores, can be rated at fifty feet per diem. The bulk of ice here annually forced into the sea would, if taken on the shore, make a mountain two miles long, two miles broad, and 1,000 feet high. The ice-fiord of Torsukatak receives four or five branches of the glacier; the most productive of them is about 9,000 metres broad , and moves between sixteen and thirty-two feet per diem. The large Karajak Glacier, about 7,000 metres broad, proceeds at a rate of from twenty-two to thirty-eight feet per diem. Finally, a glacier branch dipping into the fiord of Jtivdliarsuk, 5,800 metres broad , moved between twenty-four and forty-six feet per diem.

The principal part of our information concerning the glaciers of Greenland north of Melville Bay was obtained by Drs. Kane and Hayes, in 1853 and 1854, while conducting an expedition in search of Sir John Franklin and his unfortunate crew. Dr. Hayes conducted another expedition to the same desolate region in 1860, while other explorers have to some extent supplemented their observations. The largest glacier which they saw enters the sea between latitude 79? and 80?, where it presents a precipitous discharging front more than sixty miles in width and hundreds of feet in perpendicular height.

Dr. Kane gives his first impressions of this grand glacier in the following vivid description:

"It was in full sight--the mighty crystal bridge which connects the two continents of America and Greenland. I say continents, for Greenland, however insulated it may ultimately prove to be, is in mass strictly continental. Its least possible axis, measured from Cape Farewell to the line of this glacier, in the neighbourhood of the eightieth parallel, gives a length of more than 1,200 miles, not materially less than that of Australia from its northern to its southern cape.

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