Theories of the Ice Age
Although the mid-twentieth century accepts the Great Ice Age as a proven fact, in the early 1900's there were still some who rejected it. ... In North America, the new ideas caught men's minds very early. In 1846, Agassiz came to Harvard. His advocacy stimulated tremendous interest, but made few converts for two decades. Today the debate is over. We know as surely as we know anything about the earth's past that repeated cold periods have buried the northern continents in ice during the last million years.Perhaps this level of confidence about the Ice Age is temporary. At any rate, the problem of a cause has been a vexing one, and on this page some of the failed theories are briefly described.
(1) Increased eccentricity of the earth's orbitJames Croll proposed that changes in eccentricity of the earth's orbit caused ice ages. Flint summarized Croll's theory follows [Flint, 1972, p. 798]:
Disturbances of the Earth as a planet by the Moon and the Sun cause a periodic shift in the position of perihelion. The shift has a period, the precessional period, of a little more than 21,000 years. The shift affects the distribution of solar heat received by the Earth, though it does not affect the total amount received. The result will be that any given point at a high latitude in the northern hemisphere will be affected accordingly.Flint stated Croll's theory is not confirmed by geologic evidence, since there is no indication of alternation of glacial activity between the hemispheres. Besides, the calculated variations in temperature are far too small to bring about the results needed for ice ages.
Croll's theory was modified by Milutin Milankovitch in 1938, so that it avoided some serious objections to the original theory. Milankovitch found evidence for 17 major cycles including four groups of summer temperature minima, which he correlated with four principal glacial ages in the past 600,000 years. Discussing the Milankovitch theory, Flint noted that the temperature changes involved would be too small for the effects needed. Several other defects in the theory were mentioned [Flint, 1972, p. 799].
Arthur Holmes pointed out that if the variations in climate were sufficient to cause the glaciations of the Pleistocene, they should have also caused hundreds of similar ice ages since the Cambrian period, but the only comparable example occurs at the close of the Carboniferous [Holmes, 1944, p. 250].
The astronomical theory was further updated by Broecker. [Broecker, 1966].
Changes in the intensity of the sun's radiation were proposed as a cause of ice ages by Huntington et al. [Huntington, 1922]. Homes pointed out this speculation could never be tested, and so cannot be proved or disproved. Veils of cosmic dust have also been postulated.
A theory of an ice dump directly from space, producing a build-up of continental ice was advanced by D.W. Patten. [Patten, 1966]. His idea was that this also caused the Biblical Flood, and he cited frozen mammoths as evidence for a sudden catastrophe. Kinetic energy considerations throttle this theory. Most of the ice falling from space would probably vaporize during its fall through the atmosphere. And there seems to be no evidence for impact near the proposed ice centers.
A change in the axis of the earth's rotation was one of the early theories proposed to explain the ice ages. Arthur Holmes wrote [Holmes, 1944, p. 250]:
It is generally agreed that movements of the poles on a scale sufficient to bring about important climatic changes are highly improbable. The earth behaves like a gyroscope and only very slight changes in the position of the axis are dynamically possible. It is much less improbable that the outer crust may have moved over the interior, or that the continents may have changed their positions relatively to one another. Continental drift might account for the distribution of certain glaciated areas, particularly in the late Carboniferous, when India and central Africa were amongst the glaciated lands; but neither continental drift nor polar wandering begins to explain how these areas came to be glaciated at all. Polar ice caps are exceptional features in the earth's history, and a region does not automatically receive a shroud of ice merely because it happens to lie over or near on of the poles.Following up on the idea that only the outer shell of the earth changed its position, while the main mass of the earth remained unchanged, Charles H. Hapgood argued that the whole crust of the earth slid over its interior, repositioning the poles. [Hapgood, 1970].
Continental Drift TheoryThe theory of Continental Drift was proposed by A. Wegener in 1922 and it suggested that continents sliding around on the globe could bring them into regions of cold climate and so ice sheets could develop.
Change in Elevation TheoryColeman claimed change in elevation of continents was the most natural cause for an ice age, but mentioned many objections. He wrote, "The theory requires that all the land of the word was elevated 3,000 feet and was lowered again three times." High elevation would also mean less moisture in the air. [Coleman, 1941, p. 204].
Plate Tectonics, changes in atmosphere/ocean circulation, mountain building, changes in planetary albedo, Heinrich events, and a Greenhouse Effect have all been invoked for explaining the ice age.
Another theory, called the "White Hole Effect" involves an increase in albedo from thickening and grounding of sea ice on broad Arctic continental shelves and from expansions of snow on Arctic plateaus. The theory says that the accumulation zones were traps for moisture; it invokes rivers running north, that became dammed by ice, and ice floes stranded on Arctic shores, and increased snowfall as the cause of ice sheets.
In 1863 Escher von der Linth and E. Desor proposed a diluvial "Sahara Sea" as the cause of the ice age in the northern hemisphere. Most geologists consider pluvial lakes to be effects, not the cause of ice sheets. Fairbridge proposed that much of tropical Africa became a desert during the periods of mid-latitude glaciation [Fairbridge, 1968, p 479].
J.W. Humphreys suggested fine dust suspended in the atmosphere, from volcanic activity could explain ice ages [Humphreys, 1929]. The temperature effects of eruptions were later found to last a maximum of 15 years so the effect would be limited. No correlation exists between times of volcanic activity and times of glaciation [Holmes, 1944, p. 251].
The Genesis flood was proposed as the solution to the problem of the cause of an ice age by Reginald Daly. [Daly, 1972]. He thought elevation of mountains, and the greater moisture in the atmosphere after the flood combined to cause the growth of ice sheets.
A similar theory has been developed by Michael J. Oard, who proposes only one ice age. His explanation for the ice age is presented in The Ice Age And The Genesis Flood from ICR. A problem with this post-flood ice age theory is that it implies huge populations of Pleistocene animals survived the flood, only to become extinct afterwards during a brief ice age of only a few centuries. The drastically shortened glaciation is probably too short a period to account for all the geologic effects it is supposed to explain.
Bird, J.B. 1972. The Natural Landscapes of Canada. Wiley Publishers, Toronto.
Astronomical Theory Offers New Explanation For Ice AgeReturn to Contents
Copyright © 1999 by Douglas E. Cox
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