nently a region of active volcanism, for hardly a single one of the numerous islands in the various groups of which this belt is made up is entirely destitute of active vents, while on some of them they are crowded together by the hundred. In the groups of the Formosa, Philippine, Molucca, and Sunda Islands, there is perhaps the greatest concentration of volcanic energy which our planet exhibits. Nor is the east side of the Pacific less bountifully supplied with indications of igneous activity. Along the whole coast, from Patagonia to Alaska, the eruptive formations are displayed on the grandest possible scale, although the regions of present activity are sometimes widely separated from each other, and the volcanic belt, taken as a whole, presents evidences of a very considerable slackening of its energy since the close of the Tertiary period.

In the South American Andes the active volcanoes are chiefly limited to three great systems, - those of Chili, Bolivia, and Quito. Each of these has its grand cones, among which are the highest points in the world, with the exception of a few in the Himalaya. Aconcagua, the monarch of the Chilian group, lacking not much of twenty-three thousand feet in height, has been generally supposed to be a volcano, and was even reported by Darwin as having been in eruption in 1835. Some doubts have been thrown on this statement, however, by M. Pissis, a topographical engineer, who has been employed for years by the government of Chili in making a map of that country, and who maintains that Aconcagua consists of rocks of the Cretaceous series. It is curiously indicative of the feebleness of the spark of scientific inquiry which is kept alive even in the most enlightened of all the South American states, that so interesting a question should not have been definitely settled a long time ago. Still higher than Aconcagua is Sahama, chief of the Bolivian group, and only surpassed in elevation, on the American continent, by Illimani and Illampu. It is twenty-four thousand feet high, or one thousand feet higher than Chimborazo, which was long supposed to be the most elevated mountain mass of the New World, but which, although the loftiest of the magnificent group which surrounds the plain of Quito, is only 21,420 feet in height. Off the coast of Central and South America, at a considerable distance, however, are groups of volcanic islands, with long intervals between them, which may be compared with the similar, but far more closely crowded ones on the opposite side of the Pacific. Along the line of these groups, within the intervals between them, frequent volcanic submarine eruptions have been observed, which have given rise to islands; these, however, have since been mostly washed away.

If we may judge of the future by what has occurred in the past, it would be safe to predict that, as volcanic action dies out on the present coast line, a new belt will be gradually added to the continent on the west side. We might, without being considered as indulging in a fanciful speculation, say that the process of adding such a belt on the Asiatic side was already far advanced, while on the American it is just beginning. The most remarkable instance of insular voicanism on the east side of the Pacific is the group of the Galapagos, five hundred miles off shore, in the latitude of Quito. This group consists of five principal islands and several smaller ones, all volcanic. Craters have been seen in eruption on two of these, and on several of the others the streams of lava have quite a fresh appearance. The number of craters on the group is very great, having been estimated by Darwin at as high a number as two thousand.

The volcanic phenomena of the west coast of North America are on a still grander scale than those of the southern half of the continent, as far as the extent of the area covered by igneous products is concerned. There are not, however, as many very lofty cones, and not, in general, as much present activity. The highest development of volcanism on that coast seems to have occurred just at the close of the Tertiary epoch, and at that time the activity of the internal forces must have been prodigious. In spite of the immense erosion which has taken place since that time, the proofs of this activity are everywhere visible along the whole line of the coast from Central America to Alaska. The regions of active volcanic excitement on the Pacific coast of our continent are at present but two in number, and these are placed at the two extremities of the line, one in Central America and Southern Mexico, the other in Alaska and the Aleutian Islands. The southern region is divided into two groups, the Central American and the Mexican; the former begins with the volcano of Chiriqui and extends to that of Soconusco, on the Isthmus of Tehuantepec, a distance of full eleven hundred miles. This group is remarkable, .not only on account of its parallelism with and close proximity to the coast, but for the number and size of the cones of which it is made up; of these there are more than fifty, almost all on the summit or else on the western flank of the Cordilleras. Perhaps, with the exception of Java, there is no region in the world where the volcanic vents are so crowded together. Of all the eruptions which have taken place here during the historical period, that of Coseguina, in 1835, already mentioned, was the most astonishing. The ashes thrown out at that time produced darkness for two days over a great extent of country, and covered an area as large as that of New England to the depth of several feet, the noise being heard in Jamaica and at Bogota.

Four hundred miles north of Soconusco, and exactly in a line with the prolonged axis of the Central American volcanic belt, rises the cone of Popocatapetl, generally considered the loftiest point of North America, and certainly the highest which has been accurately measured. Its only possible rival is its near neighbor, Orizaba, which has been made by some late, but not very trustworthy, measurements a little the higher of the two. Popocatapetl has been repeatedly measured with closely coincident results, so that we probably know its height within twentyfive feet; it is about 17,750 feet. Both these great cones belong to the chain of lofty volcanic vents which traverses the continent, in the direction of east and west, nearly in the latitude of the city of Mexico. Beyond this belt to the north, within the limits of Mexico, there are no active volcanoes ; nor are there any on the peninsula of Lower California, as is uniformly reported in all the books; there are but few volcanic cones even, although rocks of this character in the form of dikes and sheets of lava are abundant in some parts of the peninsula. The volcanic formations on the mainland opposite are extensive and wonderfully varied in character; but they all belong to a past epoch of activity.

Crossing the Mexican boundary, and entering our own

territory, we find eruptive rocks abundant; and, on reaching the parallel of 35o, a little to the north of the centre of Arizona, another great volcanic belt may be traced across the Cordilleras, in a line transverse to their general trend. The most prominent cones of this belt are Mount Taylor, San Francisco Mountain, and Bill Williams's Peak, all magnificent mountains, probably between twelve and fourteen thousand feet high, but none of them has been ascended or accurately measured. They rise grandly from the plateau of horizontally stratified rocks, and are surrounded by vast lava fields bearing all the marks of having been erupted at no very remote period, although there are no indications of present activity.

Passing up through California and Nevada, we find all along both slopes of the Sierra Nevada, and on the parallel ranges east, entirely through to Salt Lake, abundant evidences of former volcanic action, on the grandest possible scale. On the east side of the mountains, this condition of activity seems to have ceased at the commencement of the present geological epoch, or at least to have diminished greatly in violence. The only indications of present volcanic activity along the Sierra Nevada, south of the north line of California, - aside from the numerous hot-springs, -are some comparatively faint remains of solfataric action on a few of the highest points. Thus Lassen's Peak, for instance, has several quite large areas where sulphurous gases escape from pools of hot water and boiling mud, while near the summit of Mount Shasta, amid the eternal snow, there is a hot-spring from which sulphurous vapors are constantly issuing. Between these two lofty volcanoes, one nearly 11,000 and the other 14,440 feet high, there are many others, some with wonderfully well-preserved craters, looking as if of very recent formation, yet entirely destitute of any traces of present activity. On the eastern slope of the Sierra, near Mono Lake, are a number of lofty and beautifully regular cones with well-defined terminal craters, yet apparently quite extinct. All through the State of Nevada, indeed, the mountain ranges are extensively flanked by vast accumulations of lava, and when we cross the Humboldt River, and traverse the region north of the parallel of 41°, we find a continuous covering of volcanic materials extending over all the northern portion of Nevada and California, as well as Southern Idaho, Eastern Oregon, and Washington Territory. This region, which is covered almost exclusively with basaltic lava, is but little, if any, less than six hundred miles square, and occupies an area considerably larger than France and Great Britain combined. It is by erosion of rocks of this character that the many beautiful waterfalls of the Snake, Pelouse, and other rivers have been formed. Those of the Snake River are described by the few who have seen them as of surpassing grandeur. They must be among the very finest in the world, taking into account height, volume of water, and attractiveness of the surrounding scenery.

North of the California line the belt of nearly extinct volcanic activity is continued in the Cascade Range, -- the prominent peaks and cones of that chain, which is in fact a continuation of the Sierra Nevada, being all of volcanic origin. The best known ones south of the Columbia River are — naming them from south to north — Mount Pitt, the Diamond Peaks, the Three Sisters, Mount Jefferson, and Mount Hood. The latter is a magnificent cone, very conspicuous over a great extent of country, and much looked up to and respected by the Oregonians, who were very wroth at having its boasted 17,000 or 18,000 feet cut down by the ruthless hand of science to 11,225. North of the Columbia are Mount Adams and Mount St. Helens, which are in nearly the same parallel; then, Mount Rainier, standing in solitary grandeur about seventy miles east-southeast of Olympia; and finally, Mount Baker, near the line of British Columbia. Of these great cones, Mount Rainier is the noblest : as seen from Puget's Sound, covered with snow nearly down to its base even late in the summer, it is truly a magnificent object. Its summit has never been reached, so far as we can ascertain, while all the other important cones of this region have been repeatedly ascended. That any of these volcanoes have emitted streams of lava since the country became known to the whites is not probable; but that ashes have been thrown out from two of them, Mount St. Helens and Mount Baker, seems to be well authenticated. The newspapers have frequent accounts of columns of vapor being seen to issue

« VorigeDoorgaan »