Mysteries of glaciation
(1) Elevation of land areas to higher altitudes above sea level
(2) Changes in relative proportions of land and sea areas
(3) Changes in locations of land areas by the floating of continents on a fluid terrestrial interior
(4) Changes in locations of the poles
(5) Increase of obliquity of Earth’s axis
(6) Increased eccentricity of Earth’s orbit
(7) Passage of the solar system through colder or nebulous regions of space
(8) Decrease in the amount of solar heat radiated
(9) Changes in air and ocean currents caused by topographic alterations
(10) Amount of carbon dioxide, volcanic and cosmic dust in the atmosphere
(11) Decrease of internal terrestrial heat
Fate of Theories
Now what has been the fate of these various theories? Every one has been analyzed and thoroughly studied by leading scientists throughout the world; and every single one has been rejected as untenable. The truth of this statement cannot be successfully challenged. Admittedly, the author of any particular theory refuses to reject his own, although in some instances he does admit that it is open to doubt. However, for each proponent of any hypothesis there are dozen critics who find flaws and reject it. The consensus unquestionably is that not one of the theories constitutes an acceptable solution of the mystery.
Perhaps the verdict of Mr. W. B. Wright can be taken as typical. Nobody will question that Mr. Wright is one of the more distinguished students of the subject. His exhaustive, erudite book, The Quaternary Ice Age, embraces 464 pages. On page 463, next to the last, he summarizes his studies with this conclusion:
It must be admitted that among the theories which have been brought forward to account for the phenomena of the Ice Ages, there is not a single one which meets the facts of the case in such a manner as to inspire confidence.
Another distinguished scientist, Dr. A. P. Coleman, in closing his exhaustive study, Ice Ages, Recent and Ancient, laments:
It may be expected that the present writer, after pointing out defects in all the previous attempts to solve the tangled problems of glacial periods, should propose something which he considers more satisfactory. This I do not feel competent to undertake. During many years of study of glaciations I have hoped to find a solution of the difficulties in several theories at different times but have always encountered some point where they failed.
Other geologists also have reached the conclusion that the mystery remains unsolved. For instance, John H. Bradley, Jr., in The Earth and Its History, says: “Although many explanations have been offered, no universally acceptable hypothesis for the causes of glaciation has yet been produced.”
A Recent Theory
The criticism may be made that the above opinions are old and out of date; yet the fact is that every theory in existence today had been previously expounded and was studied by the above critics before their conclusions were reached. Many recent investigators have arrived at the same conclusions which have been cited. The inference that no new theory has lately been advanced may be challenged by citing the recent one propounded by Richard Foster Flint. He first rejects separately every other theory listed herein before; then advances one of his own, which he calls the “Solar-Topographic Hypothesis” (p. 512). It has two essential elements, namely, “fluctuation of solar radiation” and “presence of highlands” as the prime factors determining the accumulation of snow. It can readily be seen that his hypothesis is merely a combination of the old theories numbered (1) and (8), listed above; and as stated before, he had previously discounted both separately. Mr. Flint admits that there is nothing new in his theory, and he can, by his own words, scarcely be considered very enthusiastic about it. He says that
the evidence in support of the first part (fluctuation of solar radiation) is limited to the fact of short-term fluctuation through a small range, beyond which, fluctuations have to be assumed. (Italics added.)
As to the second part (topographical uplifts) he says:
Only when uplifts were unusually high and widely distributed, especially in the regions traversed by the belts of westerly winds, could extra-terrestrial heat fluctuations succeed in reducing temperatures enough to bring about the building of great glaciers.
He fails to establish that “unusually high” uplifts have ever occurred sufficiently “widely distributed” to have caused the known world-wide distribution and recurrence of ice sheets. Neither does he offer evidence to sustain the assumption that long-term, wide-range fluctuation of solar heat radiation has occurred. He says that “all we can say at present is that larger fluctuation is at least possible.” A theory whose merits depend so largely upon mere assumptions would seem to fall short of conclusiveness.
In his later book, Glacial and Pleistocene Geology, Mr. Flint says of his hypothesis (p. 503):
Whether it will stand up under analysis . . . remains to be seen. At best it is only a very general framework. Undoubtedly the true explanation of the Pleistocene climatic changes is much more complex than the concept as stated.
It is generally conceded that as late as the closing centuries of the Pleistocene period continental land platforms were essentially the same as they are now. The question is, can the solar-topographic theory explain how, not more than a very few thousand years ago, an unbroken ice sheet hundreds or thousands of feet thick could accumulate to cover an area 1,500 miles wide, extending south to within forty degrees of the equator—a flat plains region with an average altitude above sea level of less than 1,000 feet; a region centering 1,500 miles from ocean waters; an area where average summer temperatures reach well up toward the nineties. Such an ice sheet existed in what is now the north central United States and perhaps not more than 25,000 years ago. It cannot be doubted that topography of the area at such a recent time was essentially identical with that of today. It seems probable that the solar-topographic hypothesis may in time meet the same fate as have all the other theories.