The World Before the Deluge

by Louis Figuier

The first drop of water, which fell upon the still heated terrestrial sphere, marked a new period in its evolution—a period the mechanical and chemical effects of which it is important to analyse. The contact of the condensed water with the consolidated surface of the globe opens up a series of modifications of which science may undertake the examination with a degree of confidence, or at least with more positive elements of appreciation than any we possess for the period of chaos; some of the features of which we have attempted to represent, leaving of necessity much to the imagination, and for the reader to interpret after his own fashion.

The first water which fell, in the liquid state, upon the slightly cooled surface of the earth would be rapidly converted into steam by the elevation of its temperature. Thus, rendered much lighter than the surrounding atmosphere, these vapours would rise to the utmost limits of the atmosphere, where they would become condensed afresh, in consequence of their radiation towards the glacial regions of space; condensing again, they would re-descend to the earth in a liquid state, to re-ascend as vapour and fall in a state of condensation. But all these changes, in the physical condition of the water, could only be maintained by withdrawing a very considerable amount of heat from the surface of the globe, whose cooling would be greatly hastened by these continual alternations of heat and cold; its heat would thus become gradually dissipated and lost in the regions of celestial space.

This phenomenon extending itself by degrees to the whole mass of watery vapour existing in the atmosphere, the waters covered the earth in increasing quantities; and as the conversion of all liquids into vapour is provocative of a notable disengagement of electricity, a vast quantity of electric fluid necessarily resulted from the conversion of such large masses of water into vapour. Bursts of thunder, and bright flashes of lightning were the necessary accompaniments of this extraordinary struggle of the elements—a state of things which M. Maurando has attempted to represent on the opposite page ([Plate VII.]).

How long did this struggle for supremacy between fire and water, with the incessant noise of thunder, continue? All that can be said in reply is, that a time came when water was triumphant. After having covered vast areas on the surface of the earth, it finally occupied and entirely covered the whole surface; for there is good reason to believe that at a certain epoch, at the commencement, so to speak, of its evolution; the earth was covered by water over its whole extent. The ocean was universal. From this moment our globe entered on a regular series of revolutions, interrupted only by the outbreaks of the internal fires which were concealed beneath its still imperfectly consolidated crust.

“At the early periods in which the materials of the ancient crystalline schists were accumulated, it cannot be doubted that the chemical processes which generated silicates were much more active than in more recent times. The heat of the earth’s crust was probably then far greater than at present, while a high temperature prevailed at comparatively small depths, and thermal waters abounded. A denser atmosphere, charged with carbonic acid gas, must also have contributed to maintain, at the earth’s surface, a greater degree of heat, though one not incompatible with the existence of organic life.

“These conditions must have favoured many chemical processes, which in later times have nearly ceased to operate. Hence we find that subsequently to the eozoic times, silicated rocks of clearly marked chemical origin are comparatively rare.”[32]

In order to comprehend the complex action, now mechanical, now chemical, which the waters, still in a heated state, exercised on the solid crust, let us consider what were the components of this crust. The rocks which formed its first stratum—the framework of the earth, the foundation upon which all others repose—may be presumed to have been a compound which, in varying proportions, forms granite and gneiss, and has latterly been designated by geologists Laurentian.

What is this gneiss, this granite, speaking of it with reference to its mineralogical character? It is a combination of silicates, with a base of alumina, potash, soda, and sometimes lime—quartz, felspar, and mica form, by their simple aggregation, granite—it is thus a ternary combination, or composed of three minerals.

Quartz, the most abundant of all minerals, is silica more or less pure and often crystallised. Felspar is a crystalline or crystallised mineral, composed of silicate of alumina, potash, soda, or lime; potash-felspar is called orthoclase, soda-felspar albite, lime-felspar anorthite. Mica is a silicate of alumina and potash, containing magnesia and oxide of iron; it takes its name from the Latin micare, to shine or glitter.

Granite (from the Italian grano, being granular in its structure) is, then, a compound rock, formed of felspar, quartz, and mica, and the three constituent minerals are more or less crystalline. Gneiss is a schistose variety of granite, and composed of the same minerals; the only difference between the two rocks (whatever may be their difference of origin) being that the constituent minerals, instead of being confusedly aggregated, as in granite, assume a foliated texture in gneiss. This foliated structure leads sometimes to gneiss being called stratified granite. “The term gneiss originated with the Freiberg miners, who from ancient times have used it to designate the rock in which their veins of silver-ore were found.”[33]