Geoscience Reference
In-Depth Information
8
Overview of the various models for ice ages in
the recent past (3
MYBP
to present)
More than 100 years ago, G. Frederick Wright (1896) said:
''What were the causes of the accumulation of the ice sheets of the Glacial
period? Upon their areas, warm or at least temperate climates had prevailed
during long foregoing geologic ages, and again at the present time they have
mostly mild and temperate conditions. The Pleistocene continental glaciers of
North America, Europe, and Patagonia have disappeared; and the later and
principal part of their melting was very rapid, as is known by various features
of the contemporaneous glacial and modified drift deposits, and by the beaches
and deltas of temporary lakes that were formed by the barrier of the receding ice
sheets. Can the conditions and causes be found which first amassed the thick and
vastly extended sheets of land ice, and whose cessation suddenly permitted the ice
to be quickly melted away?
Two classes of theories have been presented in answer to these questions.
In one class,
are the explanations of the climate of the Ice Age through
astronomic or cosmic causes, comprising all changes in the Earth's astronomic
relationship to the heat of space and of the sun. The second class embraces
terrestrial or geologic causes, as changes of areas of land and sea, of oceanic
currents, and altitudes of continents, while otherwise the Earth's relations to
external sources of heat are supposed to have been practically as now, or not to
have entered as important factors in the problem.''
...
Wright also described how the astronomical theory ''has been alternately
defended and denied.'' He also pointed out that it was likely that there were ''two,
three or more epochs of glaciation, divided by long interglacial epochs
when
the ice sheets were entirely or mainly melted away.'' He mentions that James
Geike ''distinguished no less than eleven epochs, glacial and interglacial
...
...
.''
Search WWH ::
Custom Search