Man and the Glacial Period 9

Man and the Glacial Period 9

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 (about 2-1/2 miles) 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 (five miles), and moves between sixteen

and thirty-two feet per diem. The large Karajak Glacier, about 7,000

metres (four miles) 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 (three miles), moved between

twenty-four and forty-six feet per diem.[AK]

 

[Footnote AK: See Transactions of the Edinburgh Geological Society for

February 18, 1886, vol. v, part ii, pp. 286-293.]

 

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:

 

"I will not attempt to do better by florid description. Men only

rhapsodize about Niagara and the ocean. My notes speak simply of the

'long, ever-shining line of cliff diminished to a well-pointed wedge in

the perspective'; and, again, of 'the face of glistening ice, sweeping

in a long curve from the low interior, the facets in front intensely

illuminated by the sun.' But this line of cliff rose in a solid,

glassy wall three hundred feet above the water-level, with an unknown,

unfathomable depth below it; and its curved face, sixty miles in length

from Cape Agassiz to Cape Forbes, vanished into unknown space at not more

than a single day's railroad-travel from the pole. The interior, with

which it communicated and from which it issued, was an unsurveyed _mer de

glace_--an ice-ocean to the eye, of boundless dimensions.

 

"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.

 

"Imagine, now, the centre of such a continent, occupied through nearly

its whole extent by a deep, unbroken sea of ice that gathers perennial

increase from the water-shed of vast snow-covered mountains and all the

precipitations of its atmosphere upon its own surface. Imagine this,

moving onwards like a great glacial river, seeking outlets at every fiord

and valley, rolling icy cataracts into the Atlantic and Greenland seas;

and, having at last reached the northern limit of the land that has borne

it up, pouring out a mighty frozen torrent into unknown arctic space!

 

"It is thus, and only thus, that we must form a just conception of a

phenomenon like this great glacier. I had looked in my own mind for such

an appearance, should I ever be fortunate enough to reach the northern

coast of Greenland; but, now that it was before me, I could hardly

realize it. I had recognized, in my quiet library at home, the beautiful

analogies which Forbes and Studer have developed between the glacier and

the river. But I could not comprehend at first this complete substitution

of ice for water.

 

"It was slowly that the conviction dawned on me that I was looking upon

the counterpart of the great river-system of Arctic Asia and America. Yet

here were no water-feeders from the south. Every particle of moisture had

its origin within the polar circle and had been converted into ice. There

were no vast alluvions, no forest or animal traces borne down by liquid

torrents. Here was a plastic, moving, semi-solid mass, obliterating life,

swallowing rocks and islands, and ploughing its way with irresistible

march through the crust of an investing sea."[AL]

 

[Footnote AL: Arctic Explorations in the Years 1853, 1854, and 1855, vol.

i, pp. 225-228.]

 

Much less is known concerning the eastern coast of Greenland than

about the western coast. For a long time it was supposed that there

might be a considerable population in the lower latitudes along the

eastern side. But that is now proved to be a mistake. The whole coast

is very inhospitable and difficult of approach. From latitude 65° to

latitude 69° little or nothing is known of it. In 1822-'23 Scoresby,

Cleavering, and Sabine hastily explored the coast from latitude 69° to

76°, and reported numerous glaciers descending to the sea-level through

extensive fiords, from which immense icebergs float out and render

navigation dangerous. In 1869 and 1870 the second North-German Expedition

partly explored the coast between latitude 73° and 77°. Mr. Payer, an

experienced Alpine explorer, who accompanied the expedition, reports the

country as much broken, and the glaciers as "subordinated in position to

the higher peaks, and having their moraines, both lateral and terminal,

like those of the Alpine ranges, and on a still grander scale." Petermann

Peak, in latitude 73°, is reported as 13,000 feet high. Captain Koldewey,

chief of the expedition, found extensive plateaus on the mainland, in

latitude 75°, to be "entirely clear of snow, although only sparsely

covered with vegetation." The mountains in this vicinity, also, rising to

a height of more than 2,000 feet, were free from snow in the summer. Some

of the fiords in this vicinity penetrate the continent through several

degrees of longitude.

 

An interesting episode of this expedition was the experience of the crew

of the ship Hansa, which was caught in the ice and destroyed. The crew,

however, escaped by encamping on the ice-floe which had crushed the ship.

From this, as it slowly floated towards the south through several degrees

of latitude, they had opportunity to make many important observations

upon the continent itself. As viewed from this unique position the coast

had the appearance everywhere of being precipitous, with mountains of

considerable height rising in the background, from which numerous small

glaciers descended to the sea-level.

 

In 1888 Dr. F. Nansen, with Lieutenant Sverdrup and four others, was

left by a whaler on the ice-pack bordering the east of Greenland about

latitude 65°, and in sight of the coast. For twelve days the party was

on the ice-pack floating south, and so actually reached the coast only

about latitude 64°. From this point they attempted to cross the inland

ice in a northwesterly direction towards Christianshaab. They soon

reached a height of 7,000 feet, and were compelled by severe northerly

storms to diverge from their course, taking a direction more to the west.

The greatest height attained was 9,500 feet, and the party arrived on the

western coast at Ameralik Fiord, a little south of Godhaab, about the

same latitude at which they entered.

 

It thus appears that subsequent investigations have confirmed in a

remarkable manner the sagacious conclusions made by the eminent Scotch

geologist and glacialist Robert Brown in 1875, soon after his own

expedition to the country. "I look upon Greenland and its interior

ice-field," he writes, "in the light of a broad-lipped, shallow vessel,

but with chinks in the lips here and there, and the glacier like viscous

matter in it. As more is poured in, the viscous matter will run over the

edges, naturally taking the line of the chinks as its line of outflow.

The broad lips of the vessel are the outlying islands or 'outskirts';

the viscous matter in the vessel the inland ice, the additional matter

continually being poured in in the form of the enormous snow covering,

which, winter after winter, for seven or eight months in the year, falls

almost continuously on it; the chinks are the fiords or valleys down

which the glaciers, representing the outflowing viscous matter, empty the

surplus of the vessel--in other words, the ice floats out in glaciers,

overflows the land in fact, down the valleys and fiords of Greenland

by force of the superincumbent weight of snow, just as does the grain

on the floor of a barn (as admirably described by Mr. Jamieson) when

another sackful is emptied on the top of the mound already on the floor.

'The floor is flat, and therefore does not conduct the grain in any

direction; the outward motion is due to the pressure of the particles

of grain on one another; and, given a floor of infinite extension and a

pile of sufficient amount, the mass would move outward to any distance,

and with a very slight pitch or slope it would slide forward along the

incline.' To this let me add that if the floor on the margin of the heap

of grain was undulating the stream of grain would take the course of

such undulations. The want, therefore, of much slope in a country and

the absence of any great mountain-range are of very little moment to the

movement of land-ice, _provided we have snow enough_" On another page Dr.

Brown had well said that "the country seems only a circlet of islands

separated from one another by deep fiords or straits, and bound together

on the landward side by the great ice covering which overlies the whole

interior.... No doubt under this ice there lies land, just as it lies

under the sea; but nowadays none can be seen, and as an insulating medium

it might as well be water."

 

In his recently published volumes descriptive of the journey across

the Greenland ice-sheet, alluded to on page 39, Dr. Nansen sums up his

inferences in very much the same way: "The ice-sheet rises comparatively

abruptly from the sea on both sides, but more especially on the east

coast, while its central portion is tolerably flat. On the whole, the

gradient decreases the farther one gets into the interior, and the mass

thus presents the form of a shield with a surface corrugated by gentle,

almost imperceptible, undulations lying more or less north and south,

and with its highest point not placed symmetrically, but very decidedly

nearer the east coast than the west."

 

From this rapid glance at the existing glaciers of the world we see that

a great ice age is not altogether a strange thing in the world. The lands

about the south pole and Greenland are each continental in dimensions,

and present at the present time accumulations of land-ice so extensive,

so deep, and so alive with motion as to prepare our minds for almost

anything that may be suggested concerning the glaciated condition of

other portions of the earth's surface. The _vera causa_ is sufficient

to accomplish anything of which glacialists have ever dreamed. It only

remains to enquire what the facts really are and over how great an extent

of territory the actual results of glacial action may be found. But we

will first direct more particular attention to some of the facts and

theories concerning glacial motion.

 

 

 

 

CHAPTER III.

 

GLACIAL MOTION.

 

 

That glacial ice actually moves after the analogy of a semi-fluid has

been abundantly demonstrated by observation. In the year 1827 Professor

Hugi, of Soleure, built a hut far up upon the Aar Glacier in Switzerland,

in order to determine the rate of its motion. After three years he found

that it had moved 330 feet; after nine years, 2,354 feet; and after

fourteen years Louis Agassiz found that its motion had been 4,712 feet.

In 1841 Agassiz began a more accurate series of observation upon the same

glacier. Boring holes in the ice, he set across it a row of stakes which,

on visiting in 1842, he found to be no longer in a straight line. All had

moved downwards with varying velocity, those near the centre having moved

farther than the others. The displacements of the stakes were in order,

from side to side, as follows: 160 feet, 225 feet, 269 feet, 245 feet,

210 feet, and 125 feet. Agassiz followed up his observations for six

years, and in 1847 published the results in his celebrated work System Glacière