The good conditions on the 15th lasted only a few hours, and back came the enemy as bad as ever. On the 18th the wind was only thirty miles per hour, giving us an opportunity of continuing the buildings outside. It was only by making the most of every odd hour when the weather was tolerable that our outdoor enterprises made any headway. Sometimes when it was too windy for building we were able to improve our knowledge of the neighbourhood.
A glance at Stillwell's map is instruct*e as to the extent and character of the rocky area. It is devoid of any forms of vegetation sufficiently prominent to meet the casual eye. Soil is lacking, for all light materials and even gravel are carried away by the winds. The bare rock rises up into miniature ridges, separated by valleys largely occupied by ice-slabs and lakelets. Snow fills all the crevices and tails away in sloping ramps on the lee side of every obstacle. In midsummer a good deal thaws, and, re-freezing, is converted into ice. The highest point of the rock is one hundred and forty feet. The seaward margin is deeply indented, and the islets off shore tell of a continuation of the rugged, rocky surface below the sea. On the northern faces of the ridges, fronting the ice-foot, large, yellowish patches mark the sites of penguin rookeries. These are formed by a superficial deposit of guano which never becomes thick, for it blows away as fast as it accumulates. Standing on the shore, one can see kelp growing amongst the rocks even in the shallowest spots, below low-water level.
To the south, the rocks are overridden by the inland ice which bears down upon and overwhelms them. The ice-sheet shows a definite basal moraine, which means that the lowest stratum, about forty feet in thickness, is charged with stones and earthy matter. Above this stratum the ice is free from foreign matter and rises steeply to several hundred feet, after which the ascending gradient is reduced.
The continental glacier moves down to the sea, regularly but slowly; the rate of movement of some portions of the adjacent coastal ice cliffs was found to be one hundred feet per annum. The rocky promontory at Winter Quarters, acting as an obstacle, reduces the motion of the ice to an annual rate measured in inches only. Perhaps the conditions now prevailing are those of a comparative "drought," for there is clear evidence that our small promontory was at one time completely enveloped. In a broad way this is illustrated by the topography, but the final proof came when Stillwell and others discovered rock-faces polished and grooved by the ice.
Whatever "ice-floods" there may have been in the past, the position of the margin of the glacier must have remained for a long period in its present situation. The evidence for this is found in the presence of a continuous, terminal moraine, at or just in advance of the present ice-front. This moraine, an accumulation of stones of all kinds brought to their present resting-place by the ice-sheet, was in itself a veritable museum. Rocks, showing every variety in colour and form, were assembled, transported from far and wide over the great expanse of the continent.
[TEXT ILLUSTRATION]
A section of the coastal slope of the Continental Ice Sheet inland from Winter Quarters, Adelie Land
Stillwell found these moraines a "happy hunting-ground" for the geologist. His plane-table survey and rock collections are practical evidence of work carried out in weather which made it seldom short of an ordeal.
The story of the buried land to the south is in large measure revealed in the samples brought by the ice and so conveniently dumped. Let us swiftly review the operations leading to the deposition of this natural museum.
As the ice of the hinterland moves forward, it plucks fragments from the rocky floor. Secure in its grip, these are used as graving-tools to erode its bed. Throwing its whole weight upon them it grinds and scratches, pulverizes and grooves. The rocky basement is gradually reduced in level, especially the softer regions. The tools are faceted, polished and furrowed, for ever moving onwards. Finally, the rock-powder or "rock-flour," as it is termed, and the boulders, thenceforth known as "erratics," arrive at the terminal ice-face. Here, the melting due to the sun's heat keeps pace with the "on-thrust" and some of the erratics may remain stationary, or else, floating in the sea, a berg laden with boulders breaks off and deposits its load in the depths of the ocean. Each summer the ice-face above the rocks at Winter Quarters thawed back a short distance and the water ran away in rivulets, milky-white on account of the "rock-flour" in suspension. The pebbles and boulders too heavy to be washed away remained behind to form the moraine.