A LONELY SCENE, SIERRA DE LA VENTANA.
The real Argentina is the Pampa; it is that vast and fertile champaign which makes the great Republic what she is, and to which she owes all her wealth and prosperity. Erroneous as is the popular idea that Argentina is merely a land of grassy steppes and rich cornfields, this is due to the fact that all except specialists have confined their travels to the Pampa. It extends from Cordoba to the Rios Negro or Colorado. In it are contained the great and growing towns, and from it these towns draw their prosperity. It is a country to delight the heart of the agriculturist. In many countries of South America the traveller passes through interminable jungles sparingly scattered with patches of cultivation where a few bony cattle scour for a livelihood. In the Pampa there is rich tilth and fine pasture; magnificent red and white beasts graze and fatten, standing knee-deep in the fresh grass, and sheep innumerable are raised. The dead level of the land is not quite unbroken, for south of the Plate estuary there are two small mountain ranges, the Tandil and Ventana. They never exceed 2,800 feet. In the east the rainfall is generally satisfactory, but it becomes scanty in the western districts. The winter is cold, the summer decidedly hot, but the climate is not intemperate, and might be called pleasant but for the fierce hot and cold winds which disturb enjoyment and are in some cases prejudicial to health. This brief summary must, for the present, suffice for the four regions; as we survey the country more in detail, we shall have opportunities of describing their characteristics more fully. It remains, however, to take a brief survey of several features which can better be described while we look at the country as a whole. The geology of Argentina greatly interested Darwin. He says:[4] "The geology of Patagonia is interesting. Differently from Europe, where the Tertiary formations appear to have accumulated in bays, here along hundreds of miles of coast we have one great deposit, including many Tertiary shells, all apparently extinct. The most common shell is a massive, gigantic oyster, sometimes even a foot in diameter. These beds are covered by others of a peculiar soft, white stone, including much gypsum, and resembling chalk, but really of a pumiceous nature. It is highly remarkable, from being composed, to at least one-tenth part of its bulk, of infusoria: Professor Ehrenberg has already ascertained in it thirty oceanic forms. This bed extends for 500 miles along the coast, and probably for a considerably greater distance. At Port St. Julian its thickness is more than 800 feet! These white beds are everywhere capped by a mass of gravel, forming probably one of the largest beds of shingle in the world: it certainly extends from near the Rio Colorado to between 600 and 700 nautical miles southward; at Santa Cruz (a river a little south of St. Julian) it reaches to the foot of the Cordillera; half-way up the river its thickness is more than 200 feet; it probably everywhere extends to this great chain, whence the well-rounded pebbles of porphyry have been derived: we may consider its average breadth as 200 miles, and its average thickness as about 50 feet. If this great bed of pebbles, without including the mud necessarily derived from their attrition, was piled into a mound, it would form a great mountain chain! When we consider that all these pebbles, countless as the grains of sand in the desert, have been derived from the slow-falling masses of rock on the old coast-lines and banks of rivers, and that these fragments have been dashed into smaller pieces, and that each of them has since been slowly rolled, rounded, and far transported, the mind is stupefied in thinking over the long, absolutely necessary lapse of years. Yet all this gravel has been transported, and probably rounded, subsequently to the deposition of the white beds, and long subsequently to the underlying beds with their Tertiary shells." His observations upon the Cordillera are equally noteworthy. He says:[5] "No one fact in the geology of South America interested me more than these terraces of rudely stratified shingle. They precisely resemble in composition the matter which the torrents in each valley would deposit if they were checked in their course by any cause, such as entering a lake or arm of the sea; but the torrents, instead of depositing matter, are now steadily at work wearing away both the solid rock and these alluvial deposits, along the whole line of every main valley and side valley. It is impossible here to give the reasons, but I am convinced that the shingle terraces were accumulated during the gradual elevation of the Cordillera by the torrents delivering, at successive levels, their detritus on the beach-heads of long, narrow arms of the sea, first high up the valleys, then lower and lower down as the land slowly rose. If this be so, and I cannot doubt it, the grand and broken chain of the Cordillera, instead of having been suddenly thrown up, as was till lately the universal, and still is the common opinion of geologists, has been slowly upheaved in mass, in the same gradual manner as the coasts of the Atlantic and Pacific have risen within the recent period. A multitude of facts in the structure of the Cordillera, on this view, receive a simple explanation." His conclusion is: "Daily it is forced home on the mind of the geologist that nothing, not even the wind that blows, is so unstable as the level of the crust of this earth."
LA VENTANA.
The geological character of Argentina is tolerably uniform. The surface is a coating of sandy soil, not usually more than 2 feet thick, which is alluvial and, from a geological point of view, quite modern. In the western districts it is usually bare of vegetation, but in the east it is covered with green herbage more or less thick. Underneath this superficial covering, however, lies the true geological formation, and this consists of argillaceous earth or mud of a reddish colour and interspersed with marly rock called by the inhabitants Tosca rock. It extends to latitude 38° or thereabouts, and is the famous Pampean formation, which Darwin calls Pampean mud. The thickness of this stratum varies considerably; it may average about 40 feet, and geologically it belongs to the Quaternary epoch, otherwise called Diluvian or Post-Pliocene. Its most remarkable feature is the enormous number of mammiferous remains which are to be found embedded in this Pampean mud, and naturalists believe that it would be impossible to dig a deep trench in any direction without disinterring some of these extinct giants. Frequently perfect skeletons are discovered. These ossiferous remains are richest in the province of Buenos Aires and become somewhat less frequent in the north and west. Some observers have marvelled that such huge creatures in such vast numbers were ever able to find nourishment, but that question is not a serious difficulty, for the largest animals are by no means the most voracious, and doubtless, like elephants of to-day, their struggle for existence was not so much against hunger as against the depredations of other animals or natural catastrophes. A much greater puzzle is their disappearance. It has been suggested that they were killed off by the Glacial cold, but it is not obvious, as has been pointed out, why this visitation carried off the mastodons and spared the parrots and hummingbirds. Another theory, put forward by a savant named M. Bravard, opines that a vast simoon overwhelmed them, but such a belief, inadequate and full of difficulties, is refuted by the fact that most of the skeletons are mutilated. Had they been overwhelmed by sand storms, they would have been preserved in almost perfect condition. The notion of drought is also inadequate. Darwin remarks that it is absurd to suppose that the most terrible calamity of this sort could destroy every species from Patagonia to Behring Straits. It is impossible to suppose that prehistoric man hunted down and slew these great creatures. The simplest hypothesis and the one which surmounts the greatest number of difficulties is that a mighty deluge overwhelmed man and beast in common ruin. A great geologist"[6] says: "I argue that this destruction was caused by an invasion of the continent by water—a view which is completely en rapport with the facts presented by the great Pampean deposit, which was clearly laid down by water. How otherwise can we account for this complete destruction and the homogeneousness of the Pampas deposits containing bones? I find an evident proof of this in the immense number of bones and of entire animals whose numbers are greatest at the outlets of the valleys, as Mr. Darwin shows. He found the greatest number of the remains at Bahia Blanca, at Bajada, also on the coast, and on the affluents of the Rio Negro, also at the outlet of the valley. This proves that the animals were floated, and hence were chiefly carried to the coast."
But D'Orbigny seems to have erred in attempting to push his theory too far, for he insists that the great deluge not only destroyed the mammoths but at the same time created the Pampean plain. Nothing, however, can be more certain than that the lapse of countless ages was necessary to accumulate "the dust of continents to be." It is incredible that a great fragment of a continent was created per saltum. Darwin believes (and, it appears, rightly), "that the Pampean formation was slowly accumulated at the mouth of the former estuary of the Plata and in the sea adjoining it."[7] As we shall see, when we come to deal with Patagonia, the country was once a lake or sea, and the water system of South America was very different from what it now is, nor is there any difficulty in believing that the stupendous volume of the Parana waters (then even mightier than now) was able to wash down an accumulation of mud capable of making the sea into dry land.
So much, then, for the Quaternary Pampean mud interlaced with the bones of giant animals.