Exploration of the Antarctic - Part7
See also Chronology of Antarctic Exploration.
In 1911, the Heroic Age of Antarctic Exploration was in full stride and the world's understanding of the nature of Antarctica was being shaped by many new facts. An interesting snapshot of Antarctica at this time, after the Nimrod Expedition, but before the expeditions to the South Pole was the entry on Polar Regions in the 1911 Edition of the Encyclopaedia Britannica which summarized the view of Antarctica at that time:
Physiography of Antarctic Region
In contrast to the Arctic region, the Antarctic is essentially a land area. It is almost certain that the South Pole lies on a great plateau, part of a land that must be larger and loftier than Greenland, and may probably be as large as Australia. This land area may be composed of two main masses, or of one continent and a great archipelago, but it can no longer be doubted that the whole is of continental character as regards its rocks, and that it is permanently massed into one surface with ice and snow, which in some parts at least unites lands separated by hundreds of miles of sea. But all round the land-mass there is a ring of deep ocean cutting off the Antarctic region from all other land of the earth and setting it apart as a region by itself, more unlike the rest of the world than any continent or island. The expedition of the "Scotia " showed the great depth of the Weddell Sea area, and the attention paid to soundings surroundings? on other expeditions - notably that of the "Belgica" - has defined the beginning of a continental shelf which it cannot be doubted slopes up to land not yet sighted. In the Arctic region large areas within the Polar Circle belong to climatically temperate Europe, and to habitable lands of Asia and America; but in the Antarctic region extensive lands - Graham Land, Louis Philippe Land, Joinville Island, and the Palmer archipelago outside the Antarctic Circle|Polar Circle - partake of the typically polar character of the higher latitudes, and even the islands on the warmer side of the sixtieth parallel are of a sub-Antarctic nature, akin rather to lands of the frigid than to those of the temperate zone.
Definite information as to the geology of Antarctic land is available from three areas – Graham Land and the archipelago to the north of it, Kaiser Wilhelm Land and Victoria Land. In the Graham Land region there seems to be a fundamental rock closely resembling the Archaean. Palaeozoic rocks have not been discovered so far in this region, although a graptolite fossil, probably of Ordovician age, shows that they occur in the South Orkneys. Mesozoic rocks have been found in various parts of the archipelago, a very rich Jurassic fossil flora of ferns, conifers and cycads having been studied by Nordenskjold, some of the genera found being represented also in the rocks of South America, South Africa, India and Australia. Cretaceous ammonites have also been found, and Tertiary fossils, both of land and of marine forms, bring the geological record down probably to Miocene times, the fauna including five genera of extinct penguins. Raised beaches show an emergence of the land in Quaternary times, and there is evidence of a recent glacial period when the inland ice on Graham Land was a thousand feet higher than it is now. The most prominent features of the scenery are due to eruptive rocks, which have been identified as belonging to the eruptive system of the Andes, suggesting a geologically recent connection between South America and the Antarctic lands. Volcanic activity is not yet extinct in the region.
As regards Kaiser Wilhelm Land, the Gaussberg is a volcanic cone mainly composed of leucite-basalt, but its slopes are strewn with erratics presumably transported from the south and these include gneiss, mica-schist and quartzite, apparently Archaean.
Much more is known as to the geology of Victoria Land, and the results are well summarized by Professor David and Mr. Priestley of Sir Ernest Shackleton's expedition, whom we follow. From Cape North (71° S.) to 86° S, a grand mountain range runs south curving to south-eastward, where it vanishes into the unknown; it is built up of gneiss and granite, and of horizontal beds of sandstone and limestone capped with eruptive rock, the peaks rising to heights of 8,000, 10,000 and even 15,000 feet, the total length of the range so far as known being at least 1,100 miles. This range rises abruptly from the sea, or from the ice of the Great Barrier, and forms a slightly higher edge to a vast snow plateau which has been traversed for several hundred miles in various directions, and may for aught we know extend farther for a thousand miles or more. The accumulated snows of this plateau discharge by the hugest glaciers in the world down the valleys between the mountains. About 78° S. a group of volcanic islands, of which Ross Island, with the active Mt Erebus is the largest, rise from the sea in front of the range, and at the northern extremity the volcanic peaks of the Balleny Islands match them in height. The composition of the volcanic rocks is similar to that of the volcanic rocks of the southern part of New Zealand. The oldest rocks of Victoria Land are apparently banded gneiss and gneissic granite, which may be taken as Archaean. Older Palaeozoic rocks are represented by greenish grey slates from the sides of the Beardmore glacier and by radiolarian cherts; but the most widespread of the sedimentary rocks occurring in vast beds in the mountain faces is that named by Ferrar the Beacon sandstones, which in the far south Shackleton found to be banded with seams of shale and coal amongst which a fossil occurred which has been identified as coniferous wood and suggests that the place of the formation is Lower Carboniferous or perhaps Upper Devonian. No Mesozoic strata have been discovered, but deposits of peat derived from fungi and moss are now being accumulated in the fresh-water lakes of Ross Island, and raised beaches show a recent change of level. The coast-line appears to be of the Atlantic, not the Pacific type, and may owe its position and trend to a great fault, or series of faults, in the line of which the range of volcanoes, Mt Melbourne, Mt Erebus, and Mt Discovery, stand. Boulders of gneiss, quartzite, and sandstone have been dredged at so many points between the Balleny Islands and the Weddell Sea that there can be no doubt of the existence of similar continental land along the whole of that side, at least within the Antarctic Circle
It is difficult to decide whether the ice of the polar regions should be dealt with as a geological formation or a meteorological phenomenon, but in the Antarctic the ice is so characteristic a feature that it may well be considered by itself. So far as can be judged, the total annual precipitation in the Antarctic region is very slight, probably not mere than the equivalent of 10 in. of rain, and perhaps less. It was formerly supposed that the immense accumulation of snow near the South Pole produced an ice-cap several miles in thickness which, creeping outward all round, terminated in the sea in vast ice-cliffs, such as those of Ross's Great Barrier, whence the huge flat-topped ice-islands broke off and floated away. Evidence, both in the Graham Land and in the Victoria Land areas, points to a former much greater extent of the ice-cap. Thus Shackleton found that the summit of Mt Hope, in 83° 30' S., which stands 2000 feet above the ice of the surrounding glaciers, was strewn with erratics which must have been transported by ice from the higher mountains to the south and west. In McMurdo Sound, as in Graham Land, evidence was found that the surface of the ice-sheet was once at least a thousand feet above its present level. These facts appear to indicate a period of greater snowfall in the geologically recent past—i.e. a period of more genial climate allowing the air to carry more water vapour to the southern mountains. Whatever may have been the case in the past the Antarctic glaciers are now greatly shrunken and many of them no longer reach the sea. Others project into the sea a tongue of hard ice, which in the case of the Drygalski glacier tongue is 30 m. long, and afloat probably for a considerable distance. Some of these glacier tongues of smaller size appear now to be cut off at their shoreward end from the parent glacier. At one time the Victoria Land glacier tongues may have been confluent, forming a great ice barrier along the coast similar to the small ice-barriers which clothe the lower slopes of some of the islands in Gerlache Strait. The Great Ice Barrier is in many ways different from these. Captain Scott showed that it was afloat for at least 400 m. of its extent from west to east. Sir Ernest Shackleton followed it for 400 m. from north to south, finding its surface in part thrown into long gentle undulations, but with no evidence of the surface being otherwise than level on the average. The all-but- forgotten experiments and cogitations of Biscoe convinced that shrewd observer that all Antarctic icebergs were sea-ice thickened with snow "accumulated with time." The recent expeditions seem to confirm this view to a great extent in the case of the Barrier, which, so far as the scientific men on the "Nimrod" could see, was formed everywhere of compressed neve, not of true glacier ice. Instances have been seen of tabular bergs floating with half their bulk above water, showing that they are of very much less density than solid ice. The thrust of the glaciers which descend from the western mountains upon the Barrier throws it into sharp crevassed folds near the point of contact, the disturbance extending 10 miles from the tip of the Beardmore glacier, and the seaward creep of the whole surface of the Barrier is possibly due to this impulse, the rate of movement at the eastern side of the Barrier was found to be at the rate of 500 yds. per annum for the seven years between Scott's and Shackleton's expeditions.
Pack ice composed of broken-up sea-ice and fragments of icebergs appears to form a floating breakwater round the Antarctic area. It is penetrated by powerful steamers with ease or with difficulty according to the action of the wind which loosens the pack when it drives it towards the open sea, and closes it up when it drives it against a coast or a barrier of fast ice. At every point but one around the circumpolar area the pack, be it light or dense, appears to extend up to the southern permanent ice or land, though, as in the Weddell Sea, the pack seems at times to be driven bodily away. The exceptional region is the opening of the Ross Sea east of Cape Adare, where a comparatively narrow band of pack ice has always been penetrated by the resolute advance even of sailing ships and led to an extensive open sea to the south. No doubt the set of the ocean currents accounts for this, but how they act is still obscure. The great flat-topped ice-islands which in some years drift out from the Antarctic area in great numbers are usually met with in all parts of the Southern Ocean south of 50° S . and worn-down icebergs have been sighted in the Atlantic even as far north as 26° 30' S. The greater frequency of icebergs in the Southern Ocean in some years is attributed to earthquakes in the Antarctic breaking off masses of the floating edge of the Barrier.
Although a vast mass of observations has recently been accumulated, it is not yet possible to treat the climate of the South Polar region in the same broad way as in the case of the North Polar region. The following table shows the mean temperatures of each month and of the year at all the stations at which, the Antarctic winter has been passed. The result is to show that while the winter is on the whole less severe at high latitudes that at equal latitudes in the north, the summer is very much colder, and has little relation to latitude. Even in the South Orkneys, in latitude 60°, in the three warmest months the air scarcely rises above the freezing point as an average, while in Shetland (60° N.) the temperature of the three summer months averages 54° F. But on the other hand, the warmest month of the year even in 77° S. has had a mean temperature as high as 30°. A study of the figures quoted in the accompanying table shows that until longer records become available it is impossible to speak definitely as to the normal distribution of monthly temperature throughout the year, for even at the same station in consecutive years the months vary greatly. Thus at Snow Hill (65° S.) the mean temperature of August 1903 was 13.5° higher than that of August 1902, though June had been 7° colder; and at the "Discovery's" winter quarters July 1903 was 13° colder than July 1902 though June was 2° warmer, August having exactly the same mean temperature in each year. The mean temperature of the year is evidently higher in the position of the "Belgica's" drift than in Victoria Land at the same latitude; but it is noticeable that on the west side of Graham Land, where Charcot wintered, the average mean temperature was (taking the average of his two winterings) 15° higher than on the east side, where Nordenskjold wintered in nearly the same latitude. The observations, however, were not synchronous, and it may not be right to compare them. We may perhaps say that along the whole of the known Antarctic coasts the temperature in the two midsummer months is within a degree or two of 32° F., and varies little from place to place or from year to year; but in the winter months the temperature is lower as the latitude increases and is subject to great variations from place to place and from year to year. It seems quite possible that at no place in the Antarctic region do the mean monthly sea-level winter temperatures fall so low as in the Arctic poles of cold, but data regarding winter temperatures in the interior are lacking. All the complete yearly series of temperature show that the winter six months from April to September have a low and nearly equal temperature, there being a very abrupt fall in February and March, and an equally abrupt rise in October and November. The warmest day experienced at the "Discovery's" winter-quarters had a mean temperature of 34.7°, and the coldest -45.7°, the extreme range of daily temperature being thus 80.4°.
+ 11 7
|Mar. 1 to|
|Feb 19 to |
|Feb. 9 to |
|Feb. 1 to |
The absolutely lowest temperature recorded in the Antarctic region was -66.8°on a journey southward from the "Discovery's" winter-quarters by Lieut. Barne on the 15th of September 1903; the lowest temperature at the winter-quarters was -58.5° on the 28th of September 1903. On Sir Ernest Shackleton's expedition the lowest temperature was -57°; but no other expedition met temperatures lower than -45.6° on the "Belgica," -43.1" at Cape Adare, and -41.4° on the "Gauss." Sudden rises of temperature during storms arc common in the Antarctic region, from whichever quarter the wind blows.
During the ascent of Mt Erebus the temperature was found to fall as the height increased, from 0°F. at sea-level to -34° at 5,000 ft.; it remained stationary to 8,600 ft., fell to -28° at 10,650 ft., and then rose to -22° at 11,500 ft., and fell a few degrees at the summit. It might appear as if the ‘isothermal layer" of the upper atmosphere had been reached at a remarkably low elevation; but the temperature variations may also be explained by differences in the temperature of the strong ail currents which were passed through.
Pressure and Winds
The normal fall of pressure southward, which gives rise to the strong westerly winds of the roaring forties, appears to be arrested about 65° S., and to be succeeded by a rise of pressure farther south. This view is supported by the frequency of south-easterly winds in the neighbourhood of the Antarctic Circle reported by all explorers, and the hypothesis of a south polar anticyclone or area of high pressure over the Antarctic continent has gained currency in advance of any observations to establish it. The complete data of Sir Ernest Shackleton's expedition are not available at the time of writing, but the yearly mean pressure as recorded at the "Discovery's" winter-quarters was 29.35 inches for 1902, and 29-23 inches for 1903. At Cape Adare it was 29-13 inches for 1890, in the "Belgica" 29-31 inches for 1898, and in the "Gauss" 29-13 inches for 1902. These figures, so far as they are comparable, show distinctly higher pressures in the higher latitudes, and the wind observations bear out the inference of a south-polar high pressure area, as at the "Discovery's" winter-quarters 80% of the winds had an easterly component, and only 3% a westerly component. It is bewildering, however, to find that on the sledge journeys there was an equally marked preponderance of wind with a westerly component, and in discussing the result in the published records of the expedition Mr. R. H. Curtis, of the Meteorological Office, felt compelled to ask whether the correction for variation of the compass (in that region about 145°) was possibly omitted in the case of the sledge journeys. The "Gauss" observations and those at Cape Adare bore out the frequency of easterly winds, and on the "Scotia " it was observed that practically all of the easterly winds met with were to the south of the Antarctic Circle. The "Belgica" found rather more westerly than easterly winds in her drift; easterly winds predominating in summer, westerly winds in winter. At Cape Royds, Shackleton found easterly winds to predominate, the most frequent direction being south-east; but on the great southern journey, south-south-east winds prevailed, occasionally swinging round to south-south-west, and even at the farthest south (88°S.) the ridges into which the snow was blown, 10,000 ft. above the sea, showed that south-southeasterly winds predominated. On the journey to the Magnetic Pole Professor David found that along the coast the prevailing winds were south-westerly, with occasional blizzards from the south-east, but he noticed that the westerly winds were of the nature of a land breeze, springing up soon after midnight and continuing to blow fresh until about 10 a.m. Thus, the balance of probability inclines towards the hypothesis of a south-polar high-pressure area. An upper current of air blowing from a north-westerly direction was usually indicated by the clouds and smoke on Mt Erebus, and on the occasion of a great eruption, when the steam column reached more than 20,000 ft. above the sea it entered a still higher stratum of wind blowing from the south-east.
The intensity of the blizzards is worthy of remark, for the velocity of the wind often reached 40 or even 60 miles an hour, and they were usually accompanied by a rapid rise of temperature.
Observations of sunshine made at the "Discovery's" winter-quarters yielded many records of continuous sunshine extending throughout 24 consecutive hours, and in the summer months about 50% of the possible sunshine was often recorded, the maximum being 400 hours, or 66% of the total possible for December 1903. Thus, although the sun was above the horizon only for 246 days, it shone sufficiently to yield more than 1,725 hours of bright sunshine for the year, an amount exceeded in few parts of England, where the sun may shine on 365 days. The intensity of solar radiation in the clear weather of the Antarctic makes it feel exceedingly hot even when the air temperature is far below the freezing point. There is a great difference between the clear skies of 78° S. and the extremely frequent fogs which shroud the coast near the Antarctic Circle and render navigation and surveying exceedingly difficult. Heavy snowstorms are frequent on the coast, but inland during the snow blizzards it is impossible to say whether the whirling snow-dust is falling from the air or being swept from the ground. Professor David is inclined to believe that the surface of the snow-plains is being lowered more by the action of the wind sweeping the snow out to sea than it is raised by precipitation, the total amount of which appears to be very small.
Flora and Fauna
Recent expeditions have discovered that, despite the low temperature of the summer, in which no month has a mean temperature appreciably above the freezing point, there are on the exposed Antarctic land patches of ground with a sparse growth of cryptogamic vegetation consisting of mosses, lichens, fungi and fresh-water algae. The richest vegetation discovered on the "Nimrod" expedition consisted of sheets of a lichen or fungoid growth, covering the bottom of the freshwater lakes near Cape Royds, and visible through the clear ice throughout the many months when the water is frozen. No flowering plants occur within the Antarctic Circle or in the immediately adjacent lands.
The marine fauna is very rich and abundant. All the expeditions obtained many new species, and the resemblance which occurs between many of the forms and those which inhabit the Arctic seas has given rise to the hypothesis that certain species have been able to pass from one frigid zone to the other. It is argued on the other hand that all the forms which resemble each other in the two polar areas are cosmopolitan, and occur also in the intermediate seas; but the so-called "problem of bipolarity" is still unsettled. Bird life on sea and land is fairly abundant, the most common forms being the skua gull, snow petrels, and the various species of penguins. The penguins are specially adapted for an aquatic-life, and depend for their food entirely on marine animals. The largest species, the emperor penguin, inhabits the most southerly coast known on the edge of the Great Barrier, and there it breeds at mid-winter, very interesting specializations of structure and habit making this apparently impossible feat practicable. The social organization and habits of the various species of penguins have been carefully studied, and show that these birds have arrived at a stage of what might almost be called civilization worthy of the most intelligent beings native to their continent. The only mammalian life in the Antarctic is marine, in the form of various species of whales, but not the "right whale," and a few species of seals which live through the winter by keeping open blow-holes in the sea-ice. There is no trace of any land animal except a few species of minute wingless insects of a degenerate type. The fresh-water ponds teem with microscopic life, the lardigrada, or "water bears" and rotifers showing a remarkable power of resistance to low temperature, being thawed out alive after being frozen solid for months and perhaps for years.