The Ice Ages: Their Nature and
Significance, By L.M. Young F.R.A.I.
(a brief summary)
Pleistocene age of the Quaternary Period was very active in
glaciations, the intervening periods were followed by inter-glacials in which
the climate was more temperate then recent times. The region of the severe
glaciations were found in Northern Europe and North
America and having enormous thickness of ice sheets. Predominance
of the paleoclimatic phenomena exercised in Quaternary period or geology has
had much voluminous literature written on the subject. The formulation of a
glacial theory in 1937 and theories were formed during the last and a
half-century i.e. 19th century. Researchers such as Louis Agassiz
along with de Carpentier and Venetz on their theories on the Alpine Drift and
till as being resultant of the expansions of glaciers and who were the ones who
discovered that they related to different ages. Due to classification they
divided into a number of sequences distinguished as older, intermediate, and
younger drifts whose nomenclature Mindel, Riss, and Wurm have achieved world
wide renown. It must be stated that various stages are not as clear as the
foregoing would suggest and there are numerous complications that cloud this
overall picture. "However it was noticed that similar drift deposits were
prevalent in other parts of Europe, particularly north Germany and it was
inferred from the distribution of till and erratics that there existed at one
time a large ice sheet which not only spread once but retreated and returned
over a long period of time and one occasion covered the entire region. In 1839,
Agassiz visited England
where in the North and parts of Scotland,
the same drift had been discerned though other reasons were attributed of its
presence. This was at a time when the controversy between the two major
doctrines that divided British geologists, namely catastrophism and
uniformitarianism was subsiding in favor of the later. Both ascribed the drift,
which had been recognized to fluvial processes, but for different reasons.
William Buckland the eminent Oxford geologist conceiving the drift and erratics
to the result of universal equated with the Noahian one, which it was
considered, submerged completely the Earth’s continents. Further studies and
discoveries revealed flaws in this reasoning and that the stratigraphy of drift
was extremely complex. In Europe alone two
distinctive types were recognized, one comprising of Scandinavian debris and
the other composing of Alpine material. To reconcile these variations a
multiplicity of deluges were resorted to, but the lack of an adequate
geophysical hypothesis to account for this phenomena that was also proposed by
Cuvier caused Buckland to finally abandon his position in favor of the glacial
theory. It cannot be affirmed as it is has been frequently stated that
catastrophism completely ceased. Prestwich was adhering to the contention that
the drift resulted from marine causes at the end of the 19th century
and in America Ignatius Donnelly, a politician not a geologist elaborated a
theory that drift was a product of cosmological impact, possibly first to do
so. It was Buckland as his conviction in catastrophism waned, who had discerned
the processes in the Alps a year or so earlier and introduced Agassiz
accompanying him on a tour of Scotland.
What the Swiss saw was seen to be the same phenomena as in Switzerland and he
seems to have not only convinced Buckland but also his major opponent Charles
Lyell who however was much more reluctant to accept the premises. Once the
uniform nature of the deposit was realized by geologists the knowledge became
quickly applied to other regions where the topography exhibited similar
manifestations, though again as in previous areas the ice had long
disappeared."
"America,
to where the glacial doctrine eventually spread must be particularly mentioned
in regard to this, where peculiarities of a similar nature soon became
discernable in a territory of continental dimensions. Though noticed by James
Geikie in his volume published in 1874, the first comprehensive work on the
glacial epochs, American glaciology like the British and European counterparts
developed in semi-isolation. This is perhaps to be regretted for the appellations
in the various regions are now so firmly entrenched in th huge literature that
it would be impossible to confine or establish a terminology adaptable to the
whole sequences that are envisaged in the New and Old Worlds. Both in Europe, America and British Isles,
the fluctuation in the various regions were studied by geologists and gradually
a pattern began to emerge."
Terrains began to be distinguished in nomenclatures:
Kames and tills
Boulder
clay and moraines
Rock detritus and small rounded hillocks called drumlins-kind found in
New York.
Eskers ridges of gravel marking the course of meltwater streams all
deposits of former
Ice sheet.
"As stated previously relating to local districts that evolved
into standard appellations given to the various glacial and interglacials.
Though the European and American periods are broadly the same these are still
not altogether correlated and the intervals vary in length."
AmericaEurope N. Europe
Nebraskan (glacial) Mindel Elster
Aftonian (integlacial) Mindel Riss Holsterian
Illinoisian (glacial) Riss Saale
Sangamon (interglacial)
Riss Wurm Eemian
Wisconsin (glacial)
Wurm Weichel
"These are numerous subdivisions and both in Europe and in North America there are a large number of local
appellations applying to small advances and retreats of the ice in one
particular region. Others are merely extensions or alterations for the standard
chronological divisions. Nevertheless the characteristics are the same whenever
they may be discerned and are to be observed in all places. The morphology of a
glacier may be defined as a conglomeration of ice and firn consisting of
re-crystallized snow and refrozen meltwater, principally landward based and
showing evidence of flow. The existing glaciers provide though on a much
smaller scale analogies with the vaster ones of the Pleistocene." The size
depends on the degree of precipitation of snow.
"Furthermore it should be stressed a glacial environment can only
be created given the proper climate and temperature conditions in an area of
high elevation." The eroding effects of ice thrusts itself forward leaving
unusual glacial topography as above mentioned. " There are also cirques,
the semi-circular depressions scooped out by the ice, erratics or large
boulders transported by the glacier ice, sometimes from great distances. Till
or boulder clays are frequently compacted particularly in the instance of
former geological strata in which glacial traces have been discerned and completely
transformed into stone known as tillite. Eskers indicate the periglacial zones
or regions outside the proximity of the glacial periphery situated at a lower
altitude but subjected to the same climatic environment. From the outwash
deposits of the former, aeolian sediments were blown by the dry frost winds
arising in the high atmospheric pressure areas covering large stretches of
territory with loess. The ice sheet even at its maximum was never perfectly
constant and fluctuated considerably through meteorological conditions and when
the seasonal thaw exceeded the winter snowfall, it gradually shrank and finally
provided the temperature remained equable disappeared entirely."
Sediments grew under such conditions subjected to seasonal rates of
flow, layered bottom of glacial lakes arising from great quantities of
meltwater in alternate bands were clearly distinguishable. "The
geochronological import of these varves to the Quaternary is obvious and a
Swedish scientist De Geer devoted a large portion of his time in attempting to
correlate the chronology and the duration of the period which has elapsed since
the withdrawal of the Wurm or Weichel ice sheet. These laminations, light and
dark are considered to represent summer and winter seasons, two therefore
constituting an annual period which in Sweden were assiduously measured by
De Geer at intervals extending northwards for a distance of a 1000 kilometers.
The result of this varve chronology which has been extended backwards in time
to 12,000 years before the present appear to indicate that the Scandinavian ice
sheet was rapidly retreating and had probably been doing so for at least 5,000
years though Alpine evidence suggests there had been some re-advance stages.
Varve chronology has also been extended to the States by Antevs with some
success. De Geer subdivided the varve stratigraphy into four units called
Daniglacial, Gotiglacial, Finiglacial and Postglacial. Varve counts are
important for the establishment of the divisions between the postglacial and the
Wurm III glacial though in spite of corroboration from other sources the
accuracy of the former has been called into question. Scandinavian and Finnish
Geologists with the exception of the Danes appear to support De Geer’s
findings. One circumstance does however clearly stand out prominently for the
formation of these laminations to have taken place in such a orderly
progression, it shows that the retreat of the ice was gradual and did not melt
with excessive suddenness though the rates appeared to have varied. Large
quantities of meltwater also filled the river valleys which had to respond by
excavating their prior aggraded beds deeper and caused the rivers to enlarge
their dimensions which resulted in the formation of river terraces that are
still discernable. These for an important physical feature of the glacial
period and also have an archaeological significance since as it is well known.
Implements can often be correlated with the height of terraces containing these
and the phase of faunal remains. As this process was repeated every time the
climatic conditions altered, a sequence of terraces was built up, the highest
being the oldest and the lowest the most recent, each representing a
periglacial or glacial interval and the erosional stages interstadials.
Meltwater ponded in valleys that had been excavated deeper by the ice also cut
terraces or beaches at alternate stages and two examples of this process are
the famous Parallel Roads of Glen Roy Scotland which many early geologists
considered to have been marine beaches and the terraces of the former lake
Bonnerville in the United States. A falling sea level as occurred during a
glacial period when the water abstracted by precipitation remained immobilized
on the land in the form of ice had the effect of increasing river gradients at
the mouth whose erosive power excavated the former bed until temperate
conditions returned. The point at where the recession ceased shows older and
newer profiles and if there are several, then these are to be attributed to a
period of lower sea level and therefore a glacial environment. At the maximum
glaciation, during the Pleistocene climatic cold interglacials, ice covered
Europe down to the 50th and North America near enough to the same
parallel. In Scandinavia considered the principle center of ice accumulation,
the ice was thousands of meters in depth and both in this area and in Scotland
only the highest peaks were visible above the ice sheet. The longer the
interglacial or glacial lasted and the length of these periods of temperature
climate and intense cold are not uniform and vary considerably, the more the
stands of sea level etched wave cut beach terraces on the continental coastal
margins throughout the world."
Webmaster Note –It would be significant for the reader to read Otto
Muck ‘The Secret of Atlantis’ on Isotherms in the Atlantic in regards to the 50th
parallel in contrast to what occurred at the 30th to 40th
parallel or its influence on the Gulf Stream warming creating a ancient bulge
that reveals a lost continent in the bulge location of current said varied
temperatures? The glaciers and land forms effected the isotherms throughout
time of glacial and interglacial periods in changing current temperatures. I
wanted the reader also to have a chance of seeing the connection of glacial
periods from America to Europe as well since the periods of influence fall
under a glacial period kingdom of this lost continent.
