Palæozoic Glaciation.
“Glacial Periods.”
It is probable and may be regarded as a fact that upon certain of the oldest and highest mountains, glaciation was inaugurated during the Palæozoic Era, to slowly disappear by the gradual setting free of earth heat by vast fractures of the crust or to remain as local glaciation until the Ice Age. Isolated glacial deposits of this nature which were independent of solar exposure readily account for the early “Glacial Periods,” which were evidently local phenomena antedating the Ice Age. It is neither logical nor reasonable to interpret the finding of evidences of early local glaciation into a Glacial Period, for local glaciations are found now in the Alps and upon certain peaks of the Sierra Nevada, and even in the torrid zone, but they by no means establish the present existence of a Glacial Period.
Evidences of glaciations antedating the Ice Age are wholly of a mechanical nature—namely, the transportation of boulders, striæ, etc. No corroborative evidence of fossil life of Arctic habits has been found. This is particularly the case of marine fauna and flora, which may be held as the only indisputable evidence of an Ice Age.
Granting that the evidences found be sufficient to establish Palæozoic glaciations, the absence of fossils of an Arctic type proves such glaciations to have been local and possibly of short duration, for had such glaciation been general and of long duration both plant and animal life would have been modified into temperate and Arctic types, as occurred later when general glaciation ensued.
It is apparent that the isotherm 32° Far. could have shrunk for a short period to the tops of mountains and that glaciers could have formed and coursed their way into a sub-tropical growth below; and that these conditions would be removed by the setting free of earth heat with the consequent rise in temperatures.
These changes followed too closely or were too limited in area to permit the evolution of forms of continental life adapted to temperate and Arctic conditions.
Palæozoic glaciations in no way conflict with the demonstration herein given—they are really corroborative of the other facts advanced to prove that prior to the Ice Age solar heat was shut out from the surface. For the evidences of Palæozoic glaciation occur in temperate and tropical latitudes adjacent to fossil life indicative of high temperatures. Early glaciations were dependent only upon elevation, and latitude did not influence their occurrence in any way whatever, and whether in Norway or India these glacial conditions were coexistent with tropical life at a lower elevation and equally independent of latitude.
When the crust became too thick and non-conducting to yield a sufficient supply of heat to hold mean temperatures at a higher degree of heat than 32° Far. this isotherm shrunk to the surface only to be removed by solar heat. Since the position of this isotherm was independent of latitude its intersections with the surface depended only upon elevation, and as the continents lost their heat more rapidly than oceans, the latter were the last to fall to 32° Far.
As in previous eras torrid, tropical and temperate life had existed in Spitzbergen, France and Brazil independent of the latitudes of these countries, so too were glacial conditions equally independent of latitudes. But in the removal of glacial conditions the isotherms of solar climates were necessarily followed.
Thus the Ice Age marks the date at which the climates of the globe passed from the control of earth heat to that of solar heat. The great specific heat of water retained in the oceans, the energy necessary to maintain the cloud shield shutting out solar heat until both land and ocean areas could be equally cooled and contracted, thus ensuring the maximum degree of thickness and stability to the crust. The mysteries of geological climates, interpreted by known laws, applicable alike to all members of the solar system, develop thus into a system beautiful in its simplicity.
Once realize that the surface temperatures of the globe were at one era in the past too high, by reason of internal heat, to permit water to remain upon the surface, and the peculiar properties possessed by the various forms of water and their relations to heat and cold, and follow out these facts to their natural and logical conclusion, and the whole mystery of geological climates clears up and becomes simple.