Mexico / Its Ancient and Modern Civilisation, History, Political Conditions, Topography, Natural Resources, Industries and General Development

by C. Reginald Enock

The Mexican mountains are mainly of underlying granite formation. The Jurassic, Cretaceous, and Tertiary Ages rocks are much in evidence throughout the country, whilst the highest ranges, as we have seen, are of volcanic origin. The singular plains of Yucatan are largely of calcareous formation, probably a Tertiary limestone. One of the most plentiful rocks over vast areas of Mexico, and that which forms the striking variation of scenery, is the mountain limestone, the excessively hard stratified crystalline rock of the Lower Cretaceous period. This rock formation extends right across Mexico—although isolated in places—from sea to sea, and its existence possibly goes to show that the Pacific and the Gulf were one, in earlier geological times. The predominating shades of these extensive strata are blue and grey; occasionally there are black bands alternating, and they lie upheaved at such angles as remind the traveller of the still more pronounced strata of the high summits of the Peruvian Andes.[25] The mountain limestone is of very hard texture; white and crystalline, it wears away but slowly under the action of the elements, although on the steep mountain tracks over which we are journeying we shall observe it broken into cubes like sugar, beneath the incessant trampling of hoofs, or worn away to silver-sand and borne down by the streamlets into the river valleys.

25 See my book, "The Andes and the Amazon."

The rock-formations of the tablelands are those to which Mexico owes her fame as a silver-producing country, and it is in the high region, from 5,000 to 9,500 feet above sea-level, that her historical mines are encountered; and the zone of territory embraced by these well-known centres, from Pachuca to Guanajuato and onwards to Chihuahua, may be described without exaggeration as the richest argentiferous region on the surface of the globe. It is to the metamorphic formation that the abundance of mineral ores is due, and the igneous rocks which have given rise thereto—the granites, basalts, diorites, porphyries, and others. This metalliferous zone is more than 1,500 miles long, extending from the State of Chihuahua and Sonora in the north to Oaxaca and Chiapas in the south.

As we cross the coast-zone from Vera Cruz we are enabled to observe something of the orographical structure of the country and the agencies that have been at work. The coastal plains are sedimentaries of Tertiary formation. The médanos, or sand-dunes, of the coast, blown into singular forms by the prevailing norte from the Gulf, give place, as we proceed inland, to the foothills of the Eastern Sierra. Here the Cretaceous formation is shown—the hard crystalline limestone—and this, from its durable nature, has furnished material for the new breakwater at Vera Cruz. Again, as we proceed, the lower rocks are sheeted with the lava of former eruptions of volcanoes, worn away at times by the ravines, and showing the points of Cretaceous rocks protruding; and volcanic dust from the same source drifts hither and thither, and at times has been compressed by the elements into a soft tufa. The great sheets of lava, as in certain places in the Valley of Mexico, are of remarkable appearance on the face of the country, the scorified aspect seemingly little changed since the moment when the fiery sheet must have poured devastatingly down the countryside.

The rock-formation of Mexican landscape gives rise to exceedingly picturesque and romantic scenery in places, and to diverse configurations of striking beauty, among which we shall often draw rein as we journey, or which will attract us continually to the observation-point of our Pullman car as the train winds along. Upon the Gulf of Mexico or the Pacific slopes the territory is grand and broken in the extreme, and presents curious and beautiful examples of rock-scenery. The natural monoliths of the barrancas of the State of Hidalgo are strange examples of scenic geology; monumental caprice of Nature in megalithic structure, as shown by the remarkable basalt columns of the profound Gorge of Itzala. Vari-coloured lichens cover these basalt pillars, affording singular contrast of light and shade. Through the gorge a torrential stream flows, and the floor of the valley is covered with fragments of obsidian, or volcanic glass, gleaming black and brilliant, which has been brought down by the waters from the Cerro de Navajas. This obsidian, or Itzli, was the material from which the Aztecs made their knives and weapons, and this was their prehistoric quarry. The red lava deserts of Sonora are weird and remarkable.

Mexico is divided hydrographically into three systems: the Atlantic, or Gulf of Mexico watershed; that of the Pacific; and the hydrographic entities of the great plateau. In the first of these is the vast region of the northern part of Mexico, which, with Texas and New Mexico, drains into the Rio Grande and thence into the Gulf; the long littoral of the Gulf Coast, whose divortia aquarum, or water-parting, is formed by the Eastern Sierra Madre; and the peninsula of Yucatan. In the second is the vast stretch of the Pacific slope, whose divortia aquarum is the Western Sierra Madre; the peninsula of Lower California, and the southern side of the region south of the Isthmus of Tehuantepec. In the third are the intra-montane portions of the great plateau, whose waters have no outlet or natural source of exhaustion except that by evaporation, such as the great plains known as the Bolson of Mapimi; and the Valley of Mexico. Topographically, however—apart from the three climatic zones of hot, temperate, and cold lands—the country is divided orographically into two portions by the Isthmus of Tehuantepec, the former consisting of the characteristic mountain-chains and great plateau, and the latter of the immense plains of Yucatan, with a low elevation of not more than 300 feet above sea-level.

The formation of Mexico has not given rise to the existence of great or navigable rivers nor, indeed, of harbours. With few exceptions rivers are torrential in character, although some are of considerable length. The Rio Grande, which forms the northern boundary of the United States, and is therefore international in character, is 1,500 miles in length; rising in Colorado and passing through New Mexico in the United States, and thence entering between Texas and Chihuahua, it is joined by two large tributaries—the Pecos on the American and the Conchos river on the Mexican side. Thence it flows south-eastwardly to the Gulf of Mexico. The waters which enter Mexican territory are scarce, as they have been taken out for irrigation purposes in American territory. The Lerma, or Santiago, river is the next in point of length, and is a stream of considerable importance, dividing the main portion of Mexico topographically into two subdivisions. It flows for 540 miles from its source in the mountains near Toluca, passing through the beautiful Lake Chapala—the largest in Mexico—and forms the great cascade of Juanacatlan, the Niagara of Mexico; traverses the State of Jalisco, where it is joined by numerous affluents, and discharges into the Pacific Ocean near San Blas.

FALLS OF JUANACATLAN: THE NIAGARA OF MEXICO.

Southwardly from the above, beyond the intervening Cordillera, is the River Balsas, or Mescala, 430 miles in length. This important stream has its rise in the watershed of the central plateau, or rather the extensive slopes of the Valley of Mexico, and running with a general westerly direction between the Sierras, empties into the Pacific at Zacatula. It is navigable for a short distance. The Yaqui, discharging into Pacific waters, is 390 miles long, flowing through the Sierras of Sonora to the Gulf of California. On the littoral of the Mexican Gulf is the Panuco, which rises to the north of the Valley of Mexico, flowing thence in a great curve; and being joined by various affluents from the eastern watershed of the Sierra Madres, it discharges at the port of Tampico. The Papaloapam, also draining part of the State of Vera Cruz, empties into the Gulf near the port of the same name. From the region of the peninsula of Yucatan flow two main streams—the Usamacinta and the Grijalva—which are partly navigable. All these rivers are further described in the chapter treating of the various States to which they correspond. Another characteristic stream of Mexico is the River Nazas, whose waters, nearly all absorbed by the irrigation canals of the Laguna region, where the famous cotton plantations are, fall in times of flood into the Lagoon of Parras, where they evaporate, the system forming a hydrographic entity, without outlet either to the Pacific or Atlantic watershed. Thus it is seen that most Mexican rivers simply rise in and descend on one or the other slopes of the country; and as the fall is rapid their courses are interrupted by numerous cascades. Except in few cases, these rivers are of no service for navigation, but the elements of water-power and irrigation facilities which they possess are more than compensating circumstances. In addition, their scenic value is very marked in many cases.