Personal Narrative of Travels to the Equinoctial Regions of America Volume I Part 24

To explain these great effects of volcanic reactions, and to prove that the group or system of the volcanoes of the West India Islands may sometimes shake the continent, I have cited the Cordillera of the Andes. Geological reasoning can be supported only by the a.n.a.logy of facts which are recent, and consequently well authenticated: and in what other region of the globe could we find greater and more varied volcanic phenomena than in that double chain of mountains heaved up by fire? in that land where nature has covered every mountain and every valley with her marvels? If we consider a burning crater only as an isolated phenomenon, if we be satisfied with merely examining the ma.s.s of stony substances which it has thrown up, the volcanic action at the surface of the globe will appear neither very powerful nor very extensive. But the image of this action becomes enlarged in the mind when we study the relations which link together volcanoes of the same group; for instance, those of Naples and Sicily, of the Canary Islands,* of the Azores, of the Caribbee islands of Mexico, of Guatimala, and of the table-land of Quito; when we examine either the reactions of these different systems of volcanoes on one another, or the distance at which, by subterranean communication, they simultaneously convulse the earth. (I have already observed (Chapter 1.2) that the whole group of the Canary Islands rises, as we may say, above one and the same submarine volcano. Since the sixteenth century, the fire of this volcano has burst forth alternately in Palma, Teneriffe, and Lancerote. Auvergne presents a whole system of volcanoes, the action of which has now ceased; but in the middle of a system of active volcanoes, for instance, in that of Quito, we must not consider as an extinguished volcano a mountain, the crater of which is obstructed, and through which the subterraneous fire has not issued for ages. Etna, the Aeolian Isles, Vesuvius, and Epomeo; the peak of Teyde, Palma, and Lancerote; St. Michael, La Caldiera of Fayal, and Pico; St.

Vincent, St. Lucia, and Guadaloupe; Orizava, Popocatepetl, Jorullo, and La Colima; Bombacho, the volcano of Grenada, Telica, Momotombo, Isalco, and the volcano of Guatimala; Cotopaxi, Tunguragua, Pichincha, Antisana, and Sangai, belong to the same system of burning volcanoes; they are generally ranged in rows, as if they had issued from a crevice, or vein not filled up; and, it is very remarkable, that their position is in some parts in the general direction of the Cordilleras, and in others in a contrary direction.)

The study of volcanoes may be divided into two distinct branches; one, simply mineralogical, is directed to the examination of the stony strata, altered or produced by the action of fire; from the formation of the trachytes or trap-porphyries, of basalts, phonolites, and dolerites, to the most recent lavas: the other branch, less accessible and more neglected, comprehends the physical relations which link volcanoes together, the influence of one volcanic system on another, the connection existing between the action of burning mountains and the commotions which agitate the earth at great distances, and during long intervals, in the same direction. This study cannot progress till the various epochs of simultaneous action, the direction, the extent, and the force of the convulsions are carefully noted; till we have attentively observed their progressive advance to regions which they had not previously reached; and the coincidence between distant volcanic eruptions and those noises which the inhabitants of the Andes very expressively term subterraneous thunders, or roarings.* (* Bramidos y truenos subterraneos.) All these objects are comprehended in the domain of the history of nature.

Though the narrow circle within which all certain traditions are confined, does not present any of those general revolutions which have heaved up the Cordilleras and buried myriads of pelagian animals; yet Nature, acting under our eyes, nevertheless exhibits violent though partial changes, the study of which may throw light on the most remote epochs. In the interior of the earth those mysterious powers exist, the effects of which are manifested at the surface by the production of vapours, of incandescent scoriae, of new volcanic rocks and thermal springs, by the appearance of new islands and mountains, by commotions propagated with the rapidity of an electric shock, finally by those subterranean thunders,*

heard during whole months, without shaking the earth, in regions far distant from active volcanoes. (* In the town of Guanaxuato, in Mexico, these thunders lasted from the 9th of January till the 12th of February, 1784. Guanaxuato is situated forty leagues north of the volcano of Jorullo, and sixty leagues north west of the volcano of Popocatepetl. In places nearer these two volcanoes, three leagues distant from Guanaxuato, the subterranean thunders were not heard. The noise was circ.u.mscribed within a very narrow s.p.a.ce, in the region of a primitive schist, which approaches a transition-schist, containing the richest silver mines of the known world, and on which rest trap-porphyries, slates, and diabasis (grunstein.))

In proportion as equinoctial America shall increase in culture and population, and the system of volcanoes of the central table-land of Mexico, of the Caribbee Islands, of Popayan, of los Pastos, and Quito, shall be more attentively observed, the connection of eruptions and of earthquakes, which precede and sometimes accompany those eruptions, will be more generally recognized. The volcanoes just mentioned, particularly those of the Andes, which rise above the enormous height of two thousand five hundred toises, present great advantages for observation. The periods of their eruptions are singularly regular. They remain thirty or forty years without emitting scoriae, ashes, or even vapours. I could not perceive the smallest trace of smoke on the summit of Tunguragua or Cotopaxi. A gust of vapour issuing from the crater of Mount Vesuvius scarcely attracts the attention of the inhabitants of Naples, accustomed to the movements of that little volcano, which throws out scoriae sometimes during two or three years successively. Thence it becomes difficult to judge whether the emission of scoriae may have been more frequent at the time when an earthquake has been felt in the Apennines. On the ridge of the Cordilleras everything a.s.sumes a more decided character. An eruption of ashes, which lasts only a few minutes, is often followed by a calm of ten years. In such circ.u.mstances it is easy to mark the periods, and to observe the coincidence of phenomena.

If, as there appears to be little reason to doubt, that the destruction of c.u.mana in 1797, and of Caracas in 1812, indicate the influence of the volcanoes of the West India Islands* on the commotions felt on the coasts of Terra Firma, it may be desirable, before we close this chapter, to take a cursory view of this Mediterranean archipelago.

(* The following is the series of the phenomena:--

27th of September, 1796. Eruption in the West India Islands.

(Volcano of Guadaloupe).

November, 1796. The volcano of Pas...o...b..gan to emit smoke.

14th of December, 1796. Destruction of c.u.mana.

4th of February, 1797. Destruction of Riobamba.

30th of January, 1811. Appearance of Sabrina Island, in the Azores.

The island enlarged very considerably on the 15th of June, 1811.

May, 1811. Commencement of the earthquakes in the island of St.

Vincent, which lasted till May 1812.

16th of December, 1811. Commencement of the commotions in the valley of the Mississippi and the Ohio, which lasted till 1813.

December, 1811. Earthquake at Caracas.

26th of March, 1811. Destruction of Caracas. Earthquakes, which continued till 1813.

30th of April, 1811. Eruption of the volcano in St. Vincent; and the same day subterranean noises at Caracas, and on the banks of the Apure.)

The volcanic islands form one-fifth of that great arc extending from the coast of Paria to the peninsula of Florida. Running from south to north, they close the Caribbean Sea on the eastern side, while the greater West India Islands appear like the remains of a group of primitive mountains, the summit of which seems to have been between Cape Abacou, Point Morant, and the Copper Mountains, in that part where the islands of St. Domingo, Cuba, and Jamaica, are nearest to each other. Considering the basin of the Atlantic as an immense valley* which separates the two continents, and where, from 20 degrees south to 30 degrees north, the salient angles (Brazil and Senegambia) correspond to the receding angles (the gulf of Guinea and the Caribbean Sea), we are led to think that the latter sea owes its formation to the action of currents, which, like the current of rotation now existing, have flowed from east to west; and have given the southern coast of Porto Rico, St. Domingo, and the island of Cuba their uniform configuration. (* The valley is narrowest (300 leagues) between Cape St. Roque and Sierra Leone.

Proceeding toward the north along the Coasts of the New Continent, from its pyramidal extremity, or the Straits of Magellan, we imagine we recognise the effects of a repulsion directed first toward the north-east, then toward the north-west, and finally again to the north-east.) This supposition of an oceanic irruption has been the source of two other hypotheses on the origin of the smaller West India Islands. Some geologists admit that the uninterrupted chain of islands from Trinidad to Florida exhibits the remains of an ancient chain of mountains. They connect this chain sometimes with the granite of French Guiana, sometimes with the calcareous mountains of Pari. Others, struck with the difference of geological const.i.tution between the primitive mountains of the Greater and the volcanic cones of the Lesser Antilles, consider the latter as having risen from the bottom of the sea.

If we recollect that volcanic upheavings, when they take place through elongated crevices, usually take a straight direction, we shall find it difficult to judge from the disposition of the craters alone, whether the volcanoes have belonged to the same chain, or have always been isolated. Supposing an irruption of the ocean to take place either into the eastern part of the island of Java* (* Raffles, History of Java, 1817, pages 23-28. The princ.i.p.al line of the volcanoes of Java, on a distance of 160 leagues, runs from west to east, through the mountains of Gagak, Gede, Tankuban-Prahu, Ungarang Merapi, Lawu, Wilis, Arjuna, Dasar, and Tashem.) or into the Cordilleras of Guatimala and Nicaragua, where so many burning mountains form but one chain, that chain would be divided into several islands, and would perfectly resemble the Caribbean Archipelago. The union of primitive formations and volcanic rocks in the same range of mountain is not extraordinary; it is very distinctly seen in my geological sections of the Cordillera of the Andes. The trachytes and basalts of Popayan are separated from the system of the volcanoes of Quito by the mica-slates of Almaguer; the volcanoes of Quito from the trachytes of a.s.suay by the gneiss of Condorasta and Guasunto. There does not exist a real chain of mountains running south-east and north-west from Oyapoc to the mouths of the Orinoco, and of which the smaller West India Islands might be a northern prolongation. The granites of Guiana, as well as the hornblende-slates, which I saw near Angostura, on the banks of the Lower Orinoco, belong to the mountains of Pacaraimo and of Parime, stretching from west to east, * (From the cataracts of Atures towards the Essequibo River. This chain of Pacaraimo divides the waters of the Carony from those of the Rio Parime, or Rio de Aguas Blancas.) in the interior of the continent, and not in a direction parallel with the coast, between the mouths of the river Amazon and the Orinoco. But though we find no chain of mountains at the north-east extremity of Terra Firma, having the same direction as the archipelago of the smaller West India Islands, it does not therefore follow that the volcanic mountains of the archipelago may not have belonged originally to the continent, and formed a part of the littoral chain of Caracas and c.u.mana.* (* Among many such examples which the structure of the globe displays, we shall mention only the inflexion at a right angle formed by the Higher Alps towards the maritime Alps, in Europe; and the Belour-Tagh, which joins transversely the Mouz-Tagh and the Himalaya, in Asia. Amid the prejudices which impede the progress of mineralogical geography, we may reckon, 1st, the supposition of a perfect uniformity of direction in the chains of mountains; 2nd, the hypothesis of the continuity of all chains; 3rd, the supposition that the highest summits determine the direction of a central chain; 4th, the idea that, in all places where great rivers take rise, we may suppose the existence of great tablelands, or very high mountains.)

In opposing the objections of some celebrated naturalists, I am far from maintaining the ancient contiguity of all the smaller West India Islands. I am rather inclined to consider them as islands heaved up by fire, and ranged in that regular line, of which we find striking examples in so many volcanic hills in Auvergne, in Mexico, and in Peru. The geological const.i.tution of the Archipelago appears, from the little we know respecting it, to be very similar to that of the Azores and the Canary Islands. Primitive formations are nowhere seen above ground; we find only what belongs unquestionably to volcanoes: feldspar-lava, dolerite, basalt, conglomerated scoriae, tufa, and pumice-stone. Among the limestone formations we must distinguish those which are essentially subordinate to volcanic tufas* from those which appear to be the work of madrepores and other zoophytes. (* We have noticed some of the above, following Von Buch, at Lancerote, and at Fortaventura, in the system of the Canary Islands. Among the smaller islands of the West Indies, the following islets are entirely calcareous, according to M. Cortes: Mariegalante, La Desirade, the Grande Terre of Guadaloupe, and the Grenadillas. According to the observations of that naturalist, Curacoa and Buenos Ayres present only calcareous formations. M. Cortes divides the West India Islands into, 1st, those containing at once primitive, secondary, and volcanic formations, like the greater islands; 2nd, those entirely calcareous, (or at least so considered) as Mariegalante and Curacoa; 3rd, those at once volcanic and calcareous, as Antigua, St. Bartholomew, St. Martin, and St. Thomas; 4th, those which have volcanic rocks only, as St. Vincent, St. Lucia, and St. Eustache.) The latter, according to M. Moreau de Jonnes, seem to lie on shoals of a volcanic nature. Those mountains, which present traces of the action of fire more or less recent, and some of which reach nearly nine hundred toises of elevation, are all situated on the western skirt of the smaller West India Islands.* (* Journal des Mines, tome 3 page 59. In order to exhibit in one point of view the whole system of the volcanoes of the smaller West India Islands, I will here trace the direction of the islands from south to north.--Grenada, an ancient crater, filled with water; boiling springs; basalts between St. George and Goave.--St. Vincent, a burning volcano.--St. Lucia, a very active solfatara, named Oualibou, two or three hundred toises high; jets of hot water, by which small basins are periodically filled.--Martinique, three great extinguished volcanoes; Vauclin, the Paps of Carbet, which are perhaps the most elevated summits of the smaller islands, and Montagne Pelee. (The height of this last mountain is probably 800 toises; according to Leblond it is 670 toises; according to Dupuget, 736 toises. Between Vauclin and the feldspar-lavas of the Paps of Carbet is found, as M. Moreau de Jonnes a.s.serts, in a neck of land, a region of early basalt called La Roche Carree). Thermal waters of Precheur and Lameutin.--Dominica, completely volcanic.--Guadaloupe, an active volcano, the height of which, according to Leboucher, is 799 toises; according to Amie, 850 toises.--Montserrat, a solfatara; fine porphyritic lavas with large crystals of feldspar and hornblende near Galloway, according to Mr.

Nugent.--Nevis, a solfatara.--St. Christopher's, a solfatara at Mount Misery.--St. Eustache, a crater of an extinguished volcano, surrounded by pumice-stone. (Trinidad, which is traversed by a chain of primitive slate, appears to have anciently formed a part of the littoral chain of c.u.mana, and not of the system of the mountains of the Caribbee Islands.)) Each island is not the effect of one single heaving-up: most of them appear to consist of isolated ma.s.ses which have been progressively united together. The matter has not been emitted from one crater, but from several; so that a single island of small extent contains a whole system of volcanoes, regions purely basaltic, and others covered with recent lavas. The volcanoes still burning are those of St. Vincent, St.

Lucia, and Guadaloupe. The first threw out lava in 1718 and 1812; in the second there is a continual formation of sulphur by the condensation of vapours, which issue from the crevices of an ancient crater. The last eruption of the volcano of Guadaloupe took place in 1797. The Solfatara of St. Christopher's was still burning in 1692. At Martinique, Vauclin, Montagne Pelee, and the crater surrounded by the five Paps of Carbet, must be considered as three extinguished volcanoes. The effects of thunder have been often confounded in that place with subterranean fire. No good observation has confirmed the supposed eruption of the 22nd of January, 1792. The group of volcanoes in the Caribbee Islands resembles that of the volcanoes of Quito and Los Pastos; craters with which the subterranean fire does not appear to communicate are ranged on the same line with burning craters, and alternate with them.

Notwithstanding the intimate connection manifested in the action of the volcanoes of the smaller West India Islands and the earthquakes of Terra Firma, it often happens that shocks felt in the volcanic archipelago are not propagated to the island of Trinidad, or to the coasts of Caracas and c.u.mana. This phenomenon is in no way surprising: even in the Caribbees the commotions are often confined to one place. The great eruption of the volcano in St. Vincent's did not occasion an earthquake at Martinique or Guadaloupe. Loud explosions were heard there as well as at Venezuela, but the ground was not convulsed.

These explosions must not be confounded with the rolling noise which everywhere precedes the slightest commotions; they are often heard on the banks of the Orinoco, and (as we were a.s.sured by persons living on the spot) between the Rio Arauca and Cuchivero.

Father Morello relates that at the Mission of Cabruta the subterranean noise so much resembles discharges of small cannon (pedreros) that it has seemed as if a battle were being fought at a distance. On the 21st of October, 1766, the day of the terrible earthquake which desolated the province of New Andalusia, the ground was simultaneously shaken at c.u.mana, at Caracas, at Maracaybo, and on the banks of the Casanare, the Meta, the Orinoco, and the Ventuario. Father Gili has described these commotions at the Mission of Encaramada, a country entirely granitic, where they were accompanied by loud explosions. Great fallings-in of the earth took place in the mountain Paurari, and near the rock Aravacoto a small island disappeared in the Orinoco. The undulatory motion continued during a whole hour. This seemed the first signal of those violent commotions which shook the coasts of c.u.mana and Cariaco for more than ten months. It might be supposed that men living in woods, with no other shelter than huts of reeds and palm-leaves, could have little to dread from earthquakes. But at Erevato and Caura, where these phenomena are of rare occurrence, they terrify the Indians, frighten the beasts of the forests, and impel the crocodiles to quit the waters for the sh.o.r.e. Nearer the sea, where shocks are frequent, far from being dreaded by the inhabitants, they are regarded with satisfaction as the prognostics of a wet and fertile year.

In this dissertation on the earthquakes of Terra Firma and on the volcanoes of the neighbouring archipelago of the West India Islands, I have pursued the plan of first relating a number of particular facts, and then considering them in one general point of view. Everything announces in the interior of the globe the operation of active powers, which, by mutual reaction, balance and modify one another. The greater our ignorance of the causes of these undulatory movements, these evolutions of heat, these formations of elastic fluids, the more it becomes the duty of persons who apply themselves to the study of physical science to examine the relations which these phenomena so uniformly present at great distances apart. It is only by considering these various relations under a general point of view, and tracing them over a great extent of the surface of the globe, through formations of rocks the most different, that we are led to abandon the supposition of trifling local causes, strata of pyrites, or of ignited coal.* (* See "Views of Nature"--On the structure and action of volcanoes in different parts of the world, page 353 (Bohn's edition); also "Cosmos" pages 199-225 (Bohn's edition).)

The following is the series of phenomena remarked on the northern coasts of c.u.mana, Nueva Barcelona, and Caracas; and presumed to be connected with the causes which produce earthquakes and eruptions of lava. We shall begin with the most eastern extremity, the island of Trinidad; which seems rather to belong to the sh.o.r.e of the continent than to the system of the mountains of the West India Islands.

1. The pit which throws up asphaltum in the bay of Mayaro, on the eastern coast of the island of Trinidad, southward of Point Guataro. This is the mine of chapapote or mineral tar of the country. I was a.s.sured that in the months of March and June the eruptions are often attended with violent explosions, smoke, and flames. Almost on the same parallel, and also in the sea, but westward of the island (near Punta de la Brea, and to the south of the port of Naparaimo), we find a similar vent. On the neighbouring coast, in a clayey ground, appears the celebrated lake of asphaltum (Laguna de la Brea), a marsh, the waters of which have the same temperature as the atmosphere. The small cones situated at the south-western extremity of the island, between Point Icacos and the Rio Erin, appear to have some a.n.a.logy with the volcanoes of air and mud which I met with at Turbaco in the kingdom of New Grenada. I mention these situations of asphaltum on account of the remarkable circ.u.mstances peculiar to them in these regions; for I am not unaware that naphtha, petroleum, and asphaltum are found equally in volcanic and secondary regions,* and even more frequently in the latter. (* The inflammable emanations of Pietra Mala, (consisting of hydrogen gas containing naphtha in a state of suspension) issue from the Alpine limestone, which may be traced from Covigliano to Raticofa, and which lies on ancient sandstone near Scarica l'Asino.

Under this sandstone (old red sandstone) we find black transition limestone and the grauwack (quartzose psammite) of Florence.) Petroleum is found floating on the sea thirty leagues north of Trinidad, around the island of Grenada, which contains an extinguished crater and basalts.

2. Hot Springs of Irapa, at the north-eastern extremity of New Andalusia, between Rio Caribe, Soro, and Yaguarapayo.

3. Air-volcano, or Salce, of c.u.macatar, to the south of San Jose and Carupano, near the northern coast of the continent, between La Montana de Paria and the town of Cariaco. Almost constant explosions are felt in a clayey soil, which is affirmed to be impregnated with sulphur. Hot sulphureous waters gush out with such violence that the ground is agitated by very sensible shocks. It is said that flames have been frequently seen issuing out since the great earthquake of 1797. These facts are well worthy of being examined.

4. Petroleum-spring of the Buen Pastor, near Rio Areo. Large ma.s.ses of sulphur have been found in clayey soils at Guayuta, as in the valley of San Bonifacio, and near the junction of the Rio Pao with the Orinoco.

5. The Hot Waters (Aguas Calientes) south of the Rio Azul, and the Hollow Ground of Cariaco, which, at the time of the great earthquake of c.u.mana, threw up sulphuretted water and viscous petroleum.

6. Hot waters of the gulf of Cariaco.

7. Petroleum-spring in the same gulf, near Maniquarez. It issues from mica-slate.

8. Flames issuing from the earth, near c.u.mana, on the banks of the Manzanares, and at Mariguitar, on the southern coast of the gulf of Cariaco, at the time of the great earthquake of 1797.

9. Igneous phenomena of the mountain of Cuchivano, near c.u.manacoa.

10. Petroleum-spring gus.h.i.+ng from a shoal to the north of the Caracas Islands. The smell of this spring warns s.h.i.+ps of the danger of this shoal, on which there is only one fathom of water.

11. Thermal springs of the mountain of the Brigantine, near Nueva Barcelona. Temperature 43.2 degrees (centigrade).

12. Thermal springs of Provisor, near San Diego, in the province of New Barcelona.

13. Thermal springs of Onoto, between Turmero and Maracay, in the valleys of Aragua, west of Caracas.

14. Thermal springs of Mariara, in the same valleys. Temperature 58.9 degrees.

15. Thermal springs of Las Trincheras, between Porto Cabello and Valencia, issuing from granite like those of Mariara, and forming a river of warm water (Rio de Aguas Calientes). Temperature 90.4 degrees.

16. Boiling springs of the Sierra Nevada of Merida.

17. Aperture of Mena, on the borders of Lake Maracaybo. It throws up asphaltum, and is said to emit gaseous emanations, which ignite spontaneously, and are seen at a great distance.

These are the springs of petroleum and of thermal waters, the igneous meteors, and the ejections of muddy substances attended with explosions, of which I acquired a knowledge in the vast provinces of Venezuela, whilst travelling over a s.p.a.ce of two hundred leagues from east to west. These various phenomena have occasioned great excitement among the inhabitants since the catastrophes of 1797 and 1812: yet they present nothing which const.i.tutes a volcano, in the sense hitherto attributed to that word. If the apertures, which throw up vapours and water with violent noise, be sometimes called volcancitos, it is only by such of the inhabitants as persuade themselves that volcanoes must necessarily exist in countries so frequently exposed to earthquakes. Advancing from the burning crater of St. Vincent in the directions of south, west and south-west, first by the chain of the Caribbee Islands, then by the littoral chain of c.u.mana and Venezuela, and finally by the Cordilleras of New Grenada, along a distance of three hundred and eighty leagues, we find no active volcano before we arrive at Purace, near Popayan. The total absence of apertures, through which melted substances can issue, in that part of the continent, which stretches eastward of the Cordillera of the Andes, and eastward of the Rocky Mountains, is a most remarkable geological fact.

In this chapter we have examined the great commotions which from time to time convulse the stony crust of the globe, and scatter desolation in regions favoured by the most precious gifts of nature. An uninterrupted calm prevails in the upper atmosphere; but, to use an expression of Franklin, more ingenious than accurate, thunder often rolls in the subterranean atmosphere, amidst that mixture of elastic fluids, the impetuous movements of which are frequently felt at the surface of the earth. The destruction of so many populous cities presents a picture of the greatest calamities which afflict mankind. A people struggling for independence are suddenly exposed to the want of subsistence, and of all the necessaries of life. Famished and without shelter, the inhabitants are dispersed through the country, and numbers who have escaped from the ruin of their dwellings are swept away by disease.

Far from strengthening mutual confidence among the citizens, the feeling of misfortune destroys it; physical calamities augment civil discord; nor does the aspect of a country bathed in tears and blood appease the fury of the victorious party.

After the recital of so many calamities, the mind is soothed by turning to consolatory remembrances. When the great catastrophe of Caracas was known in the United States, the Congress, a.s.sembled at Was.h.i.+ngton, unanimously decreed that five s.h.i.+ps laden with flour should be sent to the coast of Venezuela; their cargoes to be distributed among the most needy of the inhabitants. The generous contribution was received with the warmest grat.i.tude; and this solemn act of a free people, this mark of national interest, of which the advanced civilization of the Old World affords but few examples, seemed to be a valuable pledge of the mutual sympathy which ought for ever to unite the nations of North and South America.

CHAPTER 1.15.