OCR Text |
Show 316 GEOGRAPHICAL BOUNDARIES canos in the province of Pasto, and three others in that of Popayan. In the provinces of Guatimala and Nicaragua, which lie between the Isthmus of Panama and Mexico, there are no less than twenty-one active volcanos, all of them contained between the tenth and fifteenth degrees of north latitude. 'l'he great volcanic chain, after having pursued its course for several thousand miles from south to north, turns off in a side direction in Mexico, and is prolonged in a great plateau, between the eighteenth and twenty-second degrees of north latitude. This high table-land owes its present form to the circumstance of an ancient system of valleys, in a chain of primary mountains, having been filled up, to the depth of many thousand feet, with various volcanic products. Five active volcanos traverse Mexico from west to east-Tuxtla, Orizaba, Popocatepetl, Jorullo, and Colima. Jorullo, which is in the centre of the great plateau, is no less than forty leagues from the nearest ocean-an important circumstance, as showing that the proximity of the sea is not a necessary condition, although certainly a very general characteristic, of the position of active volcanos. The extraordinary eruption of this mountain, in 1759, will be described in the sequel. If the same parallel line which connects these five vents be prolonged, in a westerly direction, it cuts the volcanic group of islands, called the Isles of Revillagigedo. To the north of Mexico there are three, or according to some, five volcanos, in the peninsula of California, but of these we have at present no detailed account. We have before mentioned the violent earthquakes which, in 181~, convulsed the valley of the Mississippi at New Madrid, for the space of three hundred miles in length. As this happened exactly at the same time as the great earthquake of C~raccas, it is probable that these two points are parts of one contl· nuous volcanic region; for the whole circumference of the inter· vening Caribbean Sea must be considered as a theatre of eat:thquakes and volcanos. On the north lies the island of Ja~a1ca, which, with a tract of the contiguous sea, has often ~xper1enced tremendous shocks; and these are frequent along a hne extending from Jamaica to St. Domingo, and Porto Rico. On tl~e south of the same basin the shore.s and mountains of Colombia are perpetually convulsed. On the west, is the volcanic chain of Guatimala and Mexico, before traced out; and on the east OF VOLCANIC REGIONS, 317 the We. st Indian isles ' where , in St. v·m cen t' s an d G ua d a1 o upe are active vents. ' ;rhus it will be seen tl~~t volcanos and earthquakes occur umnterruptedly, from Cluh to the north f M . d . 0 eXICO; an It seems probable, th~t th:y will hereafter be found to extend from Cape :a:orn to Cahforma, or even perhaps to New Madrid, in the U mted States-a distance as great as from the pole to the equator. In regard to the eastern limits of the region, they lie deep beneath the waves of the Pacific, and must continue unknowt~ to us. On the west they do not appear, except where they mclude the 'Vest Indian islands to be prolonO'ed t d . ' 0 o a great Istance, for there seem to be no indications of volca · d. b . G . me tstur ances 111. mana, ~razil, and Buenos Ayres. . On an equal: If not a sttll grander scale, is another continuous ]me of volcamc action, which commences on the north 'th h AI . . . ' , Wl t e eutian Isles m Russian America, and extends first · 1 d . . , m an easter y 1rect10n for nearly two hundred geog1·aphical miles, and then soutl~wards, without interruption, throughout a space of between s1xty and seventy degrees of latitude to the Moluccas and there branches off in different directions both towards th; eas~ an.d north-w~st. The northern extremity of this volcanic regw~ 1s the Pemnsula of Alaska, in about the fifty-fifth degree of latttude. Fmm thence the line is continued throuO'h the Aleu~ian or Fox Islands, to Kamtschatka. In that archi~elago erup.tiOns are frequent; and a new isle rose in 1814, which, acco. rdmg to s~me reports, is three thousand feet high and four miles round . Earthquakes of the most terrific description aO"itate a~d alter the bed of the sea and surface of the land througllout th1s tract. The line is continued in the southern extremity of the peninsula of Kamtschatka, where there are seven active volcano~, which, in some eruptions, have scattered ashes to immense. dtstances. 'l'he Kurile chain of isles constitutes the prol~ ngation of the range, where a train of volcanic mountains nm e of wh '1 c h are k nown to have been in eruption trends i'n' ~southerly direction. In these, and in the bed of ~he adjoin- 1?g sea, alterations of level have resulted from earthquakes s~nce the middle of the last century. The line is then contmued to the so.uth-west in the great Island of J esso, where • Ilo:ff, vol. ii., p. 414. |