Mesozoic

“ The Triassic, Jurassic, and Cretaceous systems are grouped together as the Secondary or Mesozoic formations (Gr. mesos, intermediate; zoe, life) ; the organic remains of this "Middle-Life" period being, on the whole, intermediate in their characters between those of the palæozoic epoch and those of more modern strata. Lastly, the Eocene, Miocene, and Pliocene formations are grouped together as the Tertiary or Kainozoic rocks (Gr. kainos, new; zoe, life) ; because they constitute a "New-Life" period, in which the organic remains approximate in character to those now existing upon the globe. ”

“ North America was now well-nigh completed. The mediterranean seas which so often had occupied the heart of the land were done away with, and the continent stretched unbroken from the foot of the Sierras on the west to the Fall Line of the Atlantic coastal plain on the east.
The Mesozoic peneplain. The immense thickness of the Mesozoic formations conveys to our minds some idea of the vast length of time involved in the slow progress of its successive ages. The same lesson is taught as plainly by the amount of denudation which the lands suffered during the era. ”

“ The three broad divisions—Palaeozoic, Mesozoic, Cainozoic—which are employed by geologists to mark three stages in the development of life on the earth, are based primarily upon the fossil contents of the strata which, at one time or another, have been continuously forming since the earliest times. ”

“ Looking backwards, we may perhaps sum up what is most essential in the Mesozoic era in Professor Schuchert's sentence: "The Mesozoic is the Age of Reptiles, and yet the little mammals and the toothed birds are storing up intelligence and strength to replace the reptiles when the cycads and conifers shall give way to the higher flowering plants." ”

“ Of the other great land-masses of the globe our knowledge is too limited to allow us to trace their geographical evolution with any confidence. But from the very wide distribution of Mesozoic strata in South America, Africa, Asia, and Australia, there can be no doubt that, at the time of their accumulation, enormous tracts in those regions were then under water. ”

“ The Palæozoic series is more than five times as thick as the Mesozoic, and these two taken together are twenty times the thickness of the Tertiary. Each series is divided by geologists into a series of systems, distinguished by the fossils they contain, which, on the whole, indicate animals of a higher degree of evolution as we ascend the series. ”

“ Summing up what we know of the principal geographical changes that took place during the Mesozoic era, we are impressed with the fact that, all through those changes, a wide land-surface persisted in the north and north-west of the European area, just as was the case in Palæozoic times. The highest grounds were the Urals and the uplands of Scandinavia — 341 — and Britain. In middle Europe the Pyrenees and the Alps were as yet inconsiderable heights, the loftiest lands being those of the Harz, the Riesen Gebirge, and other regions of Palæozoic and Archæan rocks. ”

“ If we take the second class of rocks, the limestones, and suppose these to have been accumulated by the slow growth of corals, shells, etc., in the sea, we might, at first sight, suppose that Palæozoic animals would not grow or accumulate limestone faster than their Mesozoic successors. ”

“ There must have existed great masses of the crude material, stored up in the rocks and in the waters of the sea, to provide with coverings all the testacea of every age, and to furnish the thousands of feet thickness of the Eozoic, Paleozoic, and Mesozoic limestones. ”

“ Again, the student of geology, who forgets the order of his great epochs or eras, might recall them by formulating a sentence that presents the initial letters of the names of these epochs. Thus, “Careful men pay easily,” suggests Cenozoic, Mesozoic, Paleozoic, Eozoic. Of course no one of common sense presumes to assert that these constructive thought-links are any other than crutches, footbridges over streams too wide to stride or jump unaided. ”

“ This further accords with the fact that the Cretaceous subsidence ended in another great crumpling of the crust, like that which distinguished the Permian. By this the Mesozoic time was terminated and the Cainozoic inaugurated; while the Rocky Mountains, the Andes, the Alps, and the Himalayas, rose to importance as great mountain ranges, and the continents were again braced up to retain a condition of comparative equilibrium during that later period of the earth’s chronology to which we ourselves belong. ”

“ It is a remarkable circumstance, that in all parts of the globs in which fossiliferous rocks have yet been examined, tho successive terms of the series of living forms which have thus succeeded one another are analogous. The life of the Mesozoic epoch is everywhere characterized by the abundance of some groups of species of which no trace is to be found in either earlier or later formations ”

“ We saw that during the Mesozoic the Arctic continent was very largely submerged, and, while Europe and America rise again at the end of the Cretaceous, we find no rise of the land further north. A difference of elevation would, in such a world, make a great difference in temperature and moisture. ”

“ And thus ends a long era of world evolution, extending from the early appearance of land life down to the more recent times of the immediate ancestors of the human species and its collateral branches. This, the Cretaceous age, covers fifty million years and brings to a close the premammalian era of land life, which extends over a period of one hundred million years and is known as the Mesozoic. ”

“ If, as most geologists believe, the climate of the Mesozoic was distinctly warm, this habit of the parent of forsaking the egg was not a serious matter. However the creatures arose, it is certain that in this Mesozoic age reptiles roamed the forests, swam the seas, and even flew in the air. Probably at no other time in the earth's history has any one class of animals so completely dominated the situation as did the reptiles of this age. ”

“ The earth’s crust is believed to be at least 31⁄4 billion years old. In order to deal with this vast stretch of time, geologists have divided the billions of years into various time units and have given each unit a name. The great divisions of geologic time, called eras, are Early Precambrian, Late Precambrian, Paleozoic, Mesozoic, and Cenozoic. ”

“ Toward the close of the Mesozoic we find birds approaching to those of our own day, and almost at the beginning of the time there were small mammals, remains of which are found both in the earlier and later formations of the Mesozoic, but which never seem to have thriven; at least so far as the introduction of large and important species is concerned. Traversing the Mesozoic woods, we might see here and there little hairy creatures, which would strike a naturalist as allies of the modern bandicoots, kangaroo rats, and myrmecobius of Australia ”

“ To the south of the primitive back-bone of central Europe succeeds a region composed superficially of Mesozoic and Cainozoic strata for the most part, — 405 — which, along with underlying Palæozoic and Archæan rocks, are often highly-flexed and ridged up, as in the chains of the Jura, the Alps, the Carpathians, etc. One may say, in general terms, that throughout the whole Mediterranean area Archæan and Palæozoic rocks appear at the surface only when they form the nuclei of mountains of elevation, into the composition of which rocks of younger age largely enter. ”

“ Patiently and steadily the geologists gather fresh evidence and reason out completer conclusions. At any time some new deposit may reveal fossils that will illuminate this question. Certainly either mammals, or the ancestors of the mammals, must have lived throughout the Mesozoic period. In the very opening chapter of the Mesozoic volume of the Record there were those Theriomorphous Reptiles to which we have already alluded, and in the later Mesozoic a number of small jaw-bones are found, entirely mammalian in character. ”

“ Where the lost or unknown parts belong, the largest divisions may be made, and possibly such may have been epochs of unusual activity, of diastrophic changes which greatly accelerated organic evolution. No one can say just where the dividing line should be drawn between the rocks of Paleozoic and Mesozoic age, or between the Mesozoic and Cenozoic, for there is none; the most that we can hope for is to make the divisions everywhere in the world conform to those first made for local reasons. ”

“ There is little evidence of volcanic action throughout the long lapse of time extending backwards from the Cretaceous to the Triassic epochs, that is to say, throughout the Mesozoic or Secondary period, and it is not till we reach the Palæozoic strata that evidence of volcanic action unmistakably presents itself. ”

“ Was any form cut off in the world-wide crustal disturbances of the earth at the end of palaeozoic and mesozoic time, when so many forms of animal life appear to have been wiped out, that might in time have given birth to a kind unlike or superior to any now upon the earth? ”

“ The Mesozoic rocks, those of the Age of Reptiles, are exposed with their contained fossils in many places in this broad earth of ours, but nowhere to a greater advantage than in the west, and this is particularly true of the states of Wyoming, Colorado and Montana. ”

“ In the Laurentian Highlands the metamorphosed rocks are of pre-Cambrian age; in New England and the Appalachian region they are, in part at least, of Paleozoic age; and in the Sierra Nevada and Cascade Mountains metamorphosed Mesozoic and Cenozoic rocks occur. As movements in the outer portion of the earth's crust may produce fractures in any class of rocks, and as such fractures favour the intrusion of igneous material, the metamorphic rocks may contain igneous intrusions similar to those noted above in connection with sedimentary rocks. ”

“ The divisions in the fossil record having been thus established, they must for convenience remain, but their artificially cannot be too strongly emphasized, for the broad stratigraphical gaps and lithological groups which made the divisions sharp and clear to the earlier geologists are proved to be absent in other regions, and fossils which were formerly deemed characteristic of the Palaeozoic era are found in some places to commingle with forms of strongly marked Mesozoic type. ”

“ The earth's crust was less stable than now, the upheavals and subsidences and earthquakes more frequent, the warring of the elements more fierce and incessant, deluge and inundation in more rapid succession, and the riot and excesses of animal life far beyond anything we know of. And our line of descent was taking its chances amid it all. The widespread blotting out of life at the end of Palaeozoic time, and again at the end of Mesozoic times, when myriads of forms were cut off, probably from some convulsion of nature or some cosmic catastrophe ”

“ In the older tertiaries, the places of existing animals and plants are taken by other forms, as numerous and diversified as those which live now in the same localities, but more or less different from them; in the mesozoic rocks, these are replaced by others yet more divergent from modern types; and, in the palæozoic formations the contrast is still more marked. ”

“ Toward the close of the Paleozoic era, changing climatic conditions caused the death of many forms of life upon the earth, and the development of new and hardier types. With these, in the Mesozoic era, came the new lords of the earth, the reptiles. ”

“ The more resistant rocks, even though dissected by Tertiary erosion, retain in their summit uplands an indication of the widespread peneplain of Cretaceous time, now standing at the altitude given to it by the Tertiary upwarping and post-Tertiary uplift; and the most resistant rocks surmount the Cretaceous peneplain as unconsumed monadnocks of the Mesozoic cycle. On the other hand, the weaker rocks are more or less completely reduced to lowlands by Tertiary erosion, and are now trenched by the narrow and shallow valleys of the short post-Tertiary cycle. ”

“ Unlike the more rapidly changing higher animals these ancient Mesozoic groups of plants have not wholly disappeared, but still survive, mostly in tropical and southern regions or as a scanty remnant in contrast with their once varied and dominant role. ”

“ After the sediments became rock and the bones had probably been replaced by stone (fossilized) , this part of the world, which lay near or below sea level for millions of years, began to rise. Great forces acted upon the earth’s crust. These forces created faults, or fractures, in the rock crust along which movement occurred. And what had once been sea bottom was moved upward and became lofty mountains. This titanic change has been called the Laramide Revolution; it closed the Mesozoic Era with the formation of the Rocky Mountains. ”

“ According to the present chronological arrangement of the rocks, very many genera, often whole tribes of animals, are found as fossils only in the oldest rocks, and have skipped all the others, though found in comparative abundance in our modern world. Very many others have skipped from the Mesozoic down, while still others skip large parts of the series of successive ages. ”

“ Yet the whole of the Tertiary period, during which all the great groups of the higher animals were developed from a comparatively few generalised ancestral forms, is yet the shortest by far of the three great geological periods—the Mesozoic or Secondary, having been much longer, with still vaster changes both in the earth's crust and in the forms of life; while the Palæozoic or Primary, which carries us back to the earliest forms of life as represented by fossilised remains, is always estimated by geologists to be at least as long as the other two combined, and probably very much longer. ”