Popular Science Monthly/Volume 76/March 1910/The Hubbard Glacier, Alaska

From Wikisource
Jump to navigation Jump to search

THE HUBBARD GLACIER, ALASKA[1]
By Professor LAWRENCE MARTIN

UNIVERSITY OF WISCONSIN

SOUTHEAST of Mt. St. Elias and the Malaspina Glacier, Alaska, in the fiorded upper part of Yakutat Bay, known as Disenchantment Bay, is the Hubbard Glacier. It is the largest ice tongue in this region, except certain tributaries of the great Malaspina glacier. It has a total known length of twenty-eight miles along the trunk glacier, exclusive of one broad tributary whose lower twelve and one half miles is all that man has ever seen, two other much narrower tributaries each twelve miles long, five other branches each over five miles in length and scores of smaller tributaries. This system of ice tongues (Fig. 1) has, therefore, nearly one hundred miles of valley glaciers larger than

PSM V76 D297 Hubbard glacier and its known tributaries.png
Fig. 1. Map of Hubbard Glacier and its known tributaries. The main glacier may rise at least twelve miles farther north, or over forty miles from the sea, while the northwest tributaries may be even longer.
 
PSM V76 D298 Hubbard glacier and disenchantment bay.png
Fig. 2. The Hubbard Glacier descending from its snow-fields to Disenchantment Bay. Mt. Hubbard, on the right, rises to 16,400 feet within twenty-five miles of sea level, its slopes supplying large tributaries of the upper Hubbard Glacier.
 

the best-known glaciers in Switzerland, and the length of the upper parts of the three longest tongues is entirely unknown and the longest may exceed forty miles. No one of the tributaries as yet bears a name.

 

The Upper Glacier

The main glacier flows southward from the unexplored central part of the St. Elias Range past Mount Hubbard (Fig. 2), a beautiful 16,400-foot peak named, like the glacier, for Gardiner G. Hubbard, former president of the National Geographic Society of Washington. North of Mount Seattle the Hubbard Glacier has a width of three and one half miles and receives a tributary nearly two miles wide which rises twelve miles back on the slopes of Mt. Hubbard.

Another great tributary from the east, as wide as the main glacier, has its confluence just to the southward. These three ice tongues form the main upper glacier. It is near this confluence that civilized man has made his farthermost traverse upon the Hubbard Glacier. Several intrepid prospectors advanced this far up an adjacent glacier highway and over a snow divide to the Upper Hubbard Glacier during the gold rushes of 1898 and 1899.

 

The Lower Glacier

Below this confluence, the Hubbard Glacier is crevassed and entirely impassable, and moves down its valley imperceptibly, like the hour hand of a watch, in its irresistible progress to the sea. It descends southwestward over a broad step near the steeply-cascading glacier, shown on the map and in the photographs (Figs. 3 and 4), where it is joined by its longest tributary, the northwest arm. This tributary, two miles wide and at least twelve and one half and probably over twenty miles in length, rises on the slopes of Mt. Vancouver and joins the main glacier at right angles. The combined glacier, with a width of over four miles, advances into Disenchantment Bay in a sinuous cliff four and one half to five miles long and 250 to 300 feet high, one of the most magnificent in the world. Upon this lower glacier surface the Aletsch Glacier, the Rhone Glacier and the Mer de Glace of Switzerland might be placed without covering over two thirds of the lower Hubbard ice tongue.

The surface of the Hubbard Glacier is traversed by several prominent medial moraines. One of these comes from the northwest tributary and sweeps in a broad curve to the ice front. Another comes from near the west side of the main glacier. The east side of the Hubbard ice cliff is dark and debris-laden (Fig. 5) because this side of the glacier is covered with lateral moraine. The basal layers are filled with dirt and stones (Fig. 6) which perform the work of ice erosion. To the eastward this nearly stagnant border almost joins the entirely

PSM V76 D300 Hubbard glacier discharging icebergs into disenchantment bay.png

Fig. 3. West half of Hubbard Glacier, discharging icebergs into Disenchantment Bay. Mt. Hubbard in right background. Panorama with Fig. 4.

stagnant ice of the detached bulb of an adjacent glacier whose parti-colored crescentic moraines have led us to call it the Variegated Glacier. Ice underlies all this dark-colored area, however, where moraine mantles the quiescent and melting ice tongue in which there are numerous lakelets. The Hubbard Glacier is exceptional in having a small proportion of medial and lateral moraines, perhaps partly because it is so crevassed. Its surface is clear and attractive and its sea cliffs almost entirely snowy white.

 

The Ice Cliffs and Icebergs

The foreground of berg-dotted fiord, the silvery ice cliff (Fig. 7), the sea of serac and crevasse behind, and the mountain background rising to 8,000 and 10,000 feet within ten miles of sea-level, form a scene never to be forgotten. One might not presume to too great familiarity with this lordly glacier, however, for an approach to within a half mile of the ice cliff, even in a seaworthy dory, means danger of capsizing in the iceberg-generated waves from the cliff or from overturning bergs. The formation of icebergs from the glacier as seen at safer distances is of fascinating interest. The dazzling white cliff (Fig. 8) with its tints of blue and green in the crevasses suddenly crumbles as if the foundation of one of the castellated ice towers were suddenly removed. Liquid silver seems to slip for minutes from the cliff, then a pinnacle falls with a crash. Instantly the water in front of the glacier, even if clear of bergs a moment before, is filled with white ice fragments, while blue and green and dirty-black icebergs, released from the submerged part of the cliff, rise through the pack of small bergs, casting

PSM V76 D301 Eastern half of hubbard glacier.png

Fig. 4. East half of Hubbard Glacier, discharging icebergs into Russell Fiord. Mt. Seattle (10,000 feet) on right. Panorama with Fig. 3.

many of them into the air and overturning others. This causes a wave that splashes with lightning rapidity against the ice cliff and crunches in the ice caves there, while other waves spread ring-like across the fiord, overturning great icebergs on the way and causing the surf to splash spitefully on shores two and a half miles away for ten minutes or more. The accompanying noises were never absent at our camp facing the Hubbard Glacier. The stream of icebergs thus produced (Fig. 9) moves endless out toward the sea.

 

Retreat of the Hubbard Glacier

This glacier, long known to the natives, was seen from a distance of about six miles by the searchers for the Northwest Passage, Malaspina and Vancouver, in 1793 and 1794. The former gave the undescriptive name of Desangano to this bay because of his disappointment at once again failing to find the passage. Before historic times the Hubbard Glacier extended southward more than thirty miles to the Pacific Ocean, receiving large tributaries on its way. In 1792 and 1794 it had probably retreated nearly to its present position, not being five miles down the bay as several have inferred.[2] When seen by the late Professor I. C. Russell, in 1890 and 1891, it was no doubt slightly farther back than in 1792 and 1794.[3] By 1899, when studied and

PSM V76 D302 East margin of hubbard glacier with moraines.png

Fig. 5. East margin of Hubbard Glacier, showing medial and lateral moraines and marginal lakes.

mapped by Messrs. G. K. Gilbert, Henry Gannett and the Harriman Expedition, it had retreated one or two hundred feet more.[4] Between 1899 and 1905, when the Hubbard Glacier was studied by Professor E. S. Tarr and the writer, the northwest side seemed to have advanced slightly and the southeast to have retreated.[5] That is, although continually advancing strongly, the glacier had extended its ice cliff farther into the fiord only about a quarter mile between 1891 and 1905, because ice was continually being discharged from the end in icebergs. Professor Tarr found very little change between 1905 and 1906, the west half having possibly advanced slightly.[6] It was about the same on this west side in 1909 (Fig. 10).

 

Effects of an Earthquake

In September, 1899, however, this glacier, with the others in the region, was involved in an abnormal sort of experience which has notably affected its later history. This was a series of severe earthquakes.

Just east of the cliff of dirty ice shown in the photographs at the right of Hubbard Glacier (Fig. 11) there is a stagnant ice area which looks black in the pictures and which forms the terminus of Variegated Glacier. Where the streams emerge from this area, eight men were washing the gravels for gold and platinum, their tents being near the base of the moraine-veneered gravel hills. Several earthquakes were felt by them upon September 3, 1899, and on the intervening days till September 10, when there was so severe a shock that seismographs recorded it throughout the world. Other earthquakes followed until September 29.

These prospectors tell us that on September 10 the ground shook and cracked and undulated, that waves washed up on the shore, small glacial ponds broke and caused floods, that the Hubbard Glacier crashed and roared, and that its front was broken instantly. The hundreds of ice towers shaken down at once and the great quantities of enormous icebergs released from beneath the sea by the shaking of the submerged part of the ice cliff so filled the bay that it seemed to them as if the glacier itself advanced half a mile into the fiord.

The men subsequently escaped with their lives and the glacier seemed in 1905 to have recovered from its loss. Its better-known neighbor, the Muir Glacier, 150 miles southeast in Glacier Bay, and other ice tongues there, however, have had a period of retreat initiated by this earthquake shaking in 1899 which has destroyed much of their scenic interest and removed nearly a mile of ice a year from their cliffs for the past eight years.

In Yakutat Bay, however, these earthquakes of 1899, which were

PSM V76 D303 Black ice of the hubbard glacier.png

Fig. 6. Black ice of Hubbard Glacier margin laden with dirt and stones of basal ice. Such ice as this performs work of glacial erosion.

accompanied by faulting and by a 471/3 foot uplift of the coast six miles southwest of Hubbard Glacier, a 171/2 foot uplift 41/2 miles south of it, a 71/2 foot uplift four miles east of it, and a depression of the coast in some other places resulted in another sort of change. The prospectors encamped beside the Hubbard Glacier tell us of the great roar of avalanches during and after the shocks in 1899. In 1906 Professor Tarr found that several glaciers in this region had advanced a mile or more since we visited them the autumn before (Fig. 13). Only one had so advanced between 1899 and 1905. He has

PSM V76 D304 An ice cliff of hubbard glacier.png

Fig. 7. The ice cliff of Hubbard Glacier, between 250 and 300 feet high.

shown this advance to be due to great avalanches which supplied abnormal quantities of snow to the heads of the glaciers during the earthquakes, resulting, after a delay of several years, in a spasmodic advance. The glacier shown on the map on the right and that on the left of Hubbard Glacier, advanced thus between 1905 and 1906 (Fig. 13). The Hubbard Glacier was unchanged in 1906. It may yet respond to a similar impulse imparted by this glacier flood and advance far into
 
PSM V76 D305 Hubbard glacier viewed from osler island.png

Fig. 8. A view of Hubbard Glacier from above Osier Island in 1905. Severely crevassed, with few medial moraines. Icebergs are continually floating away from this cliff and are swirled by the tide into fantastic streamers.

 
PSM V76 D305 Hubbard glacier iceberg in disenchantment bay.png
Fig. 9. An iceberg from Hubbard Glacier floating in front of our camp in Disenchantment Bay in 1905.
 
 
PSM V76 D306 Hubbard glacier from osler island showing advance.png

Fig. 10. The Hubbard Glacier from Osier Island in 1909, and essentially as in 1905 for the western portion of the front. It has had a net advance of at least a quarter mile since photographed from the same site by Professor Russell twenty years before.

 
PSM V76 D306 Glacier advance is visible by the dark cliff.png
Fig. 11. East margin of Hubbard Glacier where ice advance was beginning in dark cliff in 1909.
 

Disenchantment Bay. If avalanches were not abundant enough, however, along its tributaries it ma}' not feel this impulse at all. In any event it will continue to be, as it now is, one of the grand spectacles of nature, and worthy of the visits of appreciative men.

 

Beginning of Advance

The last paragraph was written in December, 1908. During the summer of 1909 the National Geographic Society's Alaskan Expedition, in charge of Professor E. S. Tarr and the writer, observed what seems to be the beginning of the advance predicted above, which has been

PSM V76 D307 Dark cliff marks the beginning of the hubbard glacier advance.png

Fig. 12. Dark cliff of eastern Hubbard Glacier pushed up through ablation moraine between 1905 and 1909, and marking the beginning of the advance.

more fully described elsewhere.[7] The stagnant, dark-colored ice shown on the extreme right in Fig. 11 was resuming activity. Breaking had commenced, ice blocks were being pushed up through the morainic cover, as is shown in detail in Fig. 12. Stones were sliding down the surface and revived streams were burying willows growing near the ice front. A renewal of activity was in progress, but how great an advance there may be will not be known till studies can be made in the summer of 1910.

An adjacent ice tongue, the Hidden Glacier, advanced over two miles between 1906 and 1909. If the south side of the Hubbard Glacier advances a mile and half, however, it will override Osier Island once more (Fig. 13). This would change Russell Fiord southeast of the Hubbard Glacier from an arm of the sea to a fresh-water lake
 
PSM V76 D308 Model of hubbard glacier and disenchantment bay.png

Fig. 14. Model showing the relation of Hubbard Glacier to bifurcation of Disenchantment Bay and Russell Fiord, branches of Yakutat Bay. A slight advance will convert Russell Fiord into a long, narrow lake, draining southward across Yakutat Foreland and probably receiving icebergs from Nunatak, Hidden, Variegated, Hubbard, and other Glaciers.

 

PSM V76 D309 Map of comparison of hubbard glacier and the swiss rhone glacier.png

Fig. 13. Map of the lower fifth of Hubbard Glacier and adjacent ice tongues (after Gannett, Harriman Expedition, and Rich, U. S. Geol. Survey). The whole Rhone Glacier in Switzerland is drawn in black on exactly the same scale for comparison. The hitherto stagnant Variegated Glacier (on the right) and the Haenke Glacier (on the left) became crevassed and advanced between 1905 and 1906, the front of the latter moving nearly a mile in less than nine months and becoming tidal. In 1909 it once more ended on the land. A slight continuation of the advance of Hubbard Glacier would separate Russell Fiord from Disenchantment Bay and the Pacific Ocean.

(Fig. 14) which would be 33 miles long and 100 square miles in area. Its surface would be higher than the present fiord and would receive icebergs from four or more great glaciers, only one of which is now tidal. What would happen to the stagnant, moraine-veneered terminus of Variegated Glacier is a problem. The glacial lake would drain to the Pacific independently until future retreat of Hubbard Glacier resulted in the restoration of the lake to the fiord.

This renewal of activity by Hubbard Glacier is, therefore, of more than ordinary interest, especially as the advance is one of the type now well proved to be due, not to climatic variation, but to excessive avalanching during earthquakes.

  1. Published by permission of the Director of the U. S. Geological Survey. These observations are based upon (1) a U. S. Geological Survey expedition in 1905 under Professor R. S. Tarr, to which the writer was attached, his expenses being met by a grant of the American Geographical Society of New York, and (2) upon the National Geographic Society's Alaskan expedition of 1909, in charge of Professor Tarr and the writer. The illustrations are from photographs by A. J. Brabazon, of the Canadian Boundary Survey, Oscar von Engeln and the author.
  2. See Tarr, R. S., and Martin, Lawrence, "Position of Hubbard Glacier Front in 1792 and 1794," Bull. Amer. Geog. Soc, Vol. XXXIX., 1907, pp. 129-136.
  3. Russell, I. C, "An Expedition to Mount St. Elias, Alaska," Nat. Geog. Mag., Vol. 3, 1891, pp. 90-100; see also "Second Expedition to Mount St. Elias," Thirteenth Ann. Rept. U. S. Geol. Survey, pt. 2, 1892, p. 85.
  4. Gilbert, G. K., "Glaciers and Glaciation," Harriman Alaska Expedition, Vol. 3, 1904, pp. 63-66.
  5. Tarr, R. S., and Martin, Lawrence, "Glaciers and Glaciation of Yakutat Bay, Alaska," Bull. Amer. Geog. Soc, Vol. XXXVIII., 1906, pp. 146-147.
  6. Tarr, R. S., Professional Paper 64. U. S. Geol. Survey, 1909, pp. 45-46.
  7. National Geographic Magazine. Vol. XXI., January, 1910.