AUSTRALIA AND NEW ZEALAND
The continent of Australia has a relatively low relief, only rising
above the snow-line in Mount Kosciusko, and glacial traces have a
relatively unimportant development. The history of the region appears
to be as follows:
In late Tertiary times the shore-line lay some distance to the
east towards New Zealand, this being a relic of a much earlier
connexion between the two lands. Towards the close of the Tertiary
earth-movements set in, which elevated the mountain belt of eastern
Australia and formed a land connexion with Tasmania and the Antarctic
continent. At the same time the land to the east and the closed
basins of central Australia were also probably developed about this
time. The climate was then somewhat warmer than the present, at least
on the east coast, for the Australian barrier reef extended further
south. Probably at this time the Antarctic ice-sheet did not reach
the sea, and there was none of the floating ice which is such an
important factor in cooling the Southern Ocean.
The next stage was the lowering snow-line on Kosciusko to about 3000
feet below the present and the development of extensive glaciers,
which descended to 5500 feet above the sea, and attained an area
of 80 to 100 square miles and a thickness of at least 1000 feet.
Tasmania was also extensively ice-covered, probably by glaciers
which coalesced at low levels, forming what is known as a “piedmont”
ice-sheet, which possibly reached the sea. The lowering of the
snow-line in Tasmania is estimated as 6000 feet, corresponding to
a fall in temperature of 18° F. Probably a large part of this fall
is accounted for by the increased elevation, which may have been
several thousand feet in Tasmania and more than a thousand feet even
in New South Wales. This glaciation, which was probably dependent on
the growth of the Antarctic ice-sheet, was followed by a very long
interglacial, the duration of which has been estimated by Professor
David as 100,000 to 200,000 years. The old moraines are much
weathered and denuded, resembling in this respect the older moraines
of Europe. No information is available as to the climate of this
interglacial period. Possibly some of the Quaternary raised beaches
with warmth-loving mollusca found in unglaciated parts of Australia
belong to this period, and if so the climate was warmer than the
present for at least part of the time.
The interglacial was followed by uplift and a second much less severe
Glacial period, characterized by valley glaciers on Kosciusko and in
Tasmania, reaching the sea in places on the latter island. It was
at the close of this Glacial period that man reached Tasmania; its
conclusion is dated by Prof. David at about 10,000 years ago. It was
terminated by a period of depression below the present level with a
warm climate.
In the dry interior of Australia there is evidence that at one time,
probably during the maximum glaciation, the rainfall was heavier than
the present, and numerous lakes were developed which have now been
dry for a very long time. It is possible that the artesian water
supply of Australia, which Gregory considers to be “fossil water”
accumulated under different conditions from the present, is a vestige
of the rainfall of this period. Further north, in Java, the beds in
which the famous _Pithecanthropus_ skeleton was found, believed to be
lower glacial, contain also plant remains similar to those now found
in the Khassian mountains of Assam, one of the rainiest climates in
the world. The climate of Java during the maximum glaciation was
thus decidedly rainier, and probably somewhat cooler than the present.
An extraordinary find which may be referred to here is that of
Professor Neuhauss, who discovered giant erratics, scratched and
polished, and moraines at _sea-level_ at the western end of Huon
Gulf, New Guinea. The region is very unstable, and is known to have
stood at a very much higher level, perhaps 10,000 feet or more, in
Quaternary times, and if the moraines indicate glaciers terminating
at 10,000 feet above the sea they are explicable by a slight fall of
temperature and increase of snowfall.
Turning now to New Zealand, we find extensive glacial remains on
South Island, though not on North Island. As in so many other
countries, the Quaternary opened with great elevation, which reached
at least 1500 feet over the whole group. North and South Islands
were united with each other, with Stewart Island and probably also
the outlying islands, even including the Chatham Islands, forming a
great land-mass several times the present area of New Zealand. On the
southern part of this land-mass extensive glaciers were formed; on
the east these did not reach the present sea-level, but on the snowy
south-west they extended far below it, so that the terminal moraines
are now completely submerged; possibly they were never formed, but
the debris was floated away seaward on icebergs. Further north
moraines are found near the present shore-line at many places between
Milford Sound and Hokitika, and morainic mounds cover a large part of
the low ground. Still further north they retreat inland, and in the
Nelson Province are not found below a level of 2000 feet at the foot
of Lake Rotoiti.
In the south-east a great moraine has been described at the south end
of Lake Wakatipu and others at the north-east ends of Lakes Manapouri
and Te Anau, but none are found nearer the sea-coast. The glaciated
area of New Zealand was at least ten times the present ice-covered
area, and the Tasman, the longest glacier in New Zealand, was
expanded from its present length of 16 miles to at least 30 miles.
Much of the apparent fall of temperature shown by this glaciation
was probably due to the great elevation, but apart from this the ice
had a marked influence on climate. Outside the limits of glaciation
on the east is a thick deposit of typical loess, which extends up
to a level of 1000 feet on the flanks of the hills. The occurrence
of this loess points to a steppe climate with dry, cold, southerly
winds on the lee side of the glaciated mountains, and is probably
also connected with the increase of land area. Further north, north
of Auckland in North Island, the present treeless plains were covered
by forests; for Kauri gum, apparently very old, has been found. The
sub-antarctic islands—Campbell, Antipodes, etc.—were not covered by
either New Zealand or Antarctic ice, but were the centres of local
severe glaciations of their own.
The next stage was a great subsidence, during which the glaciers
retreated. The land sank below its present level, raised beaches
probably of interglacial age being found at various heights ranging
from 10 feet above the sea at Manukau in the centre of North Island
to 150 feet at Taranaki, 200 feet at Cape Palliser, 400 feet on
the west coast of South Island, 500 feet at Amuri Bluff, and even
800 feet in the entrances to the south-western sounds. This great
submergence was associated with the deposition of extensive gravel
deposits by the rivers.
The interglacial was followed by a second period of elevation. It is
not certain how far this went. Submerged peat-bogs have been found at
a depth of nearly 600 feet below sea-level near Canterbury, but these
may belong to the early stages of the interglacial and not to the
post-Glacial period. On the other hand, the submerged forests which
are found at many points on the coast of New Zealand are evidently
post-glacial and indicate a slight rise above present level. At the
same time there was a renewal of the glacial conditions, but the ice
was confined to the valleys and had a much less extent than in the
first glaciation. This period seems to have been followed by a slight
submergence and a temporary warm period.
BIBLIOGRAPHY
David, T. W. E. “Australasie. Les conditions du climat aux époques
géologiques.” _Rep. Congr. Geol. Internat._, 10, 1906, pp. 275-98.
Süssmilch, C. A. “An introduction to the geology of New South
Wales.” Sydney, 1914.
Gagel, C. “Beiträge zur Geologie von Kaiser-Wilhelms Land.” _Beitr.
geol. Erforsch. deutsch. Schutzgebieten_, Berlin, 1913, H. 4.
Marshall, P. “The glaciation of New Zealand.” _Trans. New Zealand
Inst._, 42, 1909, p. 334.
Salenka, M. L. et al. “Die Pithecanthropusschichten auf Java.”
_Geol. und Palæol. Ergebnisse der Trinilexpedition (1907 und
1908)._ Leipzig, 1911.