EARTHQUAKES.
I do not propose to weary my readers with a list of the three hundred earthquakes that have been thought severe enough to be recorded; but a picture of Central America would be unrecognizable without some color of the natural disturbances that are inseparably connected in the popular mind with this part of the continent.
In 1541 the capital of the kingdom of Guatemala, now Ciudad Vieja, was a young and flourishing city. Founded in July, 1524, between the mountains Agua and Fuego, in the place called Almolonga (“water-fountain”), with the proud title of “City of Saint James of the Knights of Guatemala,” it had grown to a respectable size, in spite of numerous misfortunes, to which Juarros devotes an entire chapter of his “Compendio.” An earthquake in 1526, so severe, says Bernal Diaz del Castillo, that men could not stand, seems to have frightened the population less than did an enormous lion (puma?) which descended the forest-clad slopes of Agua in 1532 and made great havoc, until a reward of twenty-five gold dollars and a hundred fanegas of wheat induced a peasant to kill the monster. Politics had, as is usually the case, made more disturbance than the forces of Nature. The Conquistador Alvarado was recently dead, his widow, Doña Beatriz de la Cueva, had claimed the government, and the obsequies of the dead and the ceremonials of the new ruler were agitating the city when the sudden and terrible destruction of both ruler and her capital came. Accounts of the catastrophe vary, as is usual with all history,—which some one has wisely called “probabilities and possibilities extracted from lies;” but from nine extant descriptions and an examination of the physical marks which three centuries have not wholly effaced, I believe the following to be a fair story of the event:—
September is always a rainy month in Guatemala, and on Thursday, the 8th, a storm began which was violent even for that place and season. Rain fell in torrents, and continued to fall all that day and Friday and Saturday. Two hours after dark on the last day a severe earthquake shock was felt, and from Hunapu, since called the Volcan de Agua, came an avalanche of water, carrying with it immense rocks and entire forests. The terror of the earthquake and the roar of the unseen torrent wrought the excitement of the inhabitants to the utmost. Soon the deluge reached the city; the streets were filled to overflowing, and the houses were beaten by the waves and battered by the great trees brought by the torrent. Among the houses most exposed was that of Doña Beatriz, the widow of the Adelantado. She was preparing for bed; but startled by the earthquake and the terrible noise, endeavored to obtain safety in a small chapel near by, and while clinging to the crucifix was killed by the fall of the chapel wall. Her house was uninjured. All through the city the loss of life was very great; six hundred Spaniards perished, and the loss of Indios and Negroes was far greater. In the morning the remains of the city hardly appeared above the trees, rocks, and mud of the avalanche. It was then that the disheartened survivors decided to remove a league eastward, to the present Antigua.
The earthquake did not destroy the city, still less was there an eruption of water from the volcano; but the crater of the long-extinct cone had been filled with the rains, and the tremor shattered the loose dam of the crater-lip and let the great body of water down the steep side of the mountain. There was water in the crater long before, and the crater to-day shows marks of the broken wall and emptied lake. The destruction of the city was considered a judgment of Heaven upon Doña Beatriz for certain impious remarks made in her bereavement, and it was with difficulty that her family were able to bury her remains in consecrated ground.
On May 23, 1575, San Salvador (Cuscatlan) was destroyed by an earthquake which also greatly damaged Antigua. Afterwards the latter city had an experience that would have discouraged the people of any Northern town, for in 1576 and 1577 it was badly shaken, and on Dec. 23, 1586, destroyed. Then it was rebuilt enough to be again shattered on Feb. 18, 1651, and again on Feb. 12, 1689, and Sept. 29, 1717. The day after this last shock Antigua was destroyed completely; but for all that, on March 4, 1751, the chronicler writes “many ruins,” and then the centre of disturbance goes southward for a while. In April, 1765, several towns were destroyed in San Salvador, and the next month many in the Department of Chiquimula in Guatemala; while during the following October the “earthquake of San Rafael” shook many Guatemaltecan towns to pieces.
On July 29, 1773, Antigua was again destroyed,—if such a thing was possible; and although her inhabitants yielded to the momentary discouragement and permitted the Government to be removed to the Valley of the Hermitage, they have never allowed the ruins to become desolate, and to-day the traveller gazes in astonishment at the shattered walls of nearly eighty churches still the ornament of the town. The Antigua that once sheltered eighty thousand inhabitants, beautiful in its situation and distinguished by its architectural display, is still attractive in its ruins; its forty thousand inhabitants go in and out under the shadow of the volcano and await the next destruction, which may come to-morrow or years hence: the lesson that is past is all forgotten. I confess myself that the ruined churches, so fresh after the sun and rains of a century have penetrated their shattered walls, inspired no apprehension of danger; they were objects of great interest rather than warning; and it was no strange thing that those born in that charming place should cling to it still.
In 1774 nearly all the towns on the Balsam Coast of San Salvador were ruined. I hope my readers understand the delicate gradation in the terms used in speaking of the misfortunes of earthquake countries. A place is “shaken,” then “shattered,” then “ruined,” and finally “destroyed” by the visit of a temblor; and it is a very nice matter to decide exactly where one term is appropriate and another not.
In February, 1798, San Salvador was badly shaken and after a rather long rest, broken by “no great shakes,” two very destructive earthquakes were felt in March and October, 1839. On Sept. 2, 1841, Cartago, in Costa Rica, was destroyed; in June, 1847, the Balsam Coast was greatly ruined; on May 16, 1852, the disturbances occurred northward, in the vicinity of Quezaltenango; on April 16, 1854, San Salvador was destroyed,—not, however, for the last time. On Nov. 6, 1857, Cojutepeque was badly shaken, and the same misfortune came upon La Union Aug. 25, 1859. The following December houses were shattered in Escuintla and Amatitlan; Dec. 19, 1862, Antigua, Amatitlan, Escuintla, Tecpan Guatemala, and the neighboring towns were severely shaken; June 12, 1870, Chiquimulilla was destroyed, and much damage done in Cuajinicuilapa; a month later a severe earthquake was felt in the Departments of Santa Rosa and Jutiapa; March 4, 1873, San Salvador and the neighboring towns were destroyed,—a process they must have become quite accustomed to by this time,—and eighteen months later it was the turn of Patzicia to be destroyed, while Chimaltenango, Antigua and the vicinity were only ruined. The year 1878 was marked by the destruction of several towns in Usulutan, San Salvador, and on Dec. 27 and 30, 1879, most of the small towns in the neighborhood of the Lago de Ilopango were overturned.
Hardly a month passes without some slight tremor in western Guatemala. In recent years so much more attention has been paid to seismology, or the observation and record of the time, duration, and direction of earthquake shocks, that the longer lists seem to indicate the increase of slight tremors; but this is not probable, and certainly the volcanic eruptions have diminished in force and frequency. Fuego, the most important, lays claim to twenty-one of the fifty recorded eruptions of the Central American volcanoes; but during the present century it has cast out merely sand, and no lava streams.
VOLCAN DE FUEGO.
I have never had the experience of a very severe earthquake, although I have had the pictures swing on the walls and the plastering crack and fall; therefore I must borrow the description of an earthquake, that the list just given may seem more real. The following account is considered very truthful:—
“The night of the 16th of April, 1854, will ever be one of sad and bitter memory for the people of Salvador. On that unfortunate night our happy and beautiful capital was made a heap of ruins. Movements of the earth were felt on Holy Thursday, preceded by sounds like the rolling of heavy artillery over pavements and like distant thunder. The people were a little alarmed in consequence of this phenomenon, but it did not prevent them from meeting in the churches to celebrate the solemnities of the day. On Saturday all was quiet, and confidence was restored. The people of the neighborhood assembled as usual to celebrate the Passover. The night of Saturday was tranquil, as was also the whole of Sunday. The heat, it is true, was considerable, but the atmosphere was calm and serene. For the first three hours of the evening nothing unusual occurred; but at half-past nine a severe shock of an earthquake, occurring without the preliminary noises, alarmed the whole city. Many families left their houses and made encampments in the public squares, while others prepared to pass the night in their respective courtyards.
“Finally, at ten minutes to eleven, without premonition of any kind, the earth began to heave and tremble with such fearful force that in ten seconds the entire city was prostrated. The crashing of houses and churches stunned the ears of the terrified inhabitants, while a cloud of dust from the falling ruins enveloped them in a pall of impenetrable darkness. Not a drop of water could be got to relieve the half-choking and suffocating, for the wells and fountains were filled up or made dry. The clock-tower of the cathedral carried a great part of that edifice with it in its fall. The towers of the church of San Francisco crushed the episcopal oratory and part of the palace. The church of Santo Domingo was buried beneath its towers, and the college of the Assumption was entirely ruined. The new and beautiful edifice of the university was demolished, the church of the Merced separated in the centre, and its walls fell outward to the ground. Of the private houses a few were left standing, but all were rendered uninhabitable. It is worthy of remark that the walls left standing are old ones; all those of modern construction have fallen. The public edifices of the Government and city shared the common destruction.
“The devastation was effected, as we have said, in the first ten seconds; for although the succeeding shocks were tremendous, and accompanied by fearful rumblings beneath our feet, they had comparatively trifling results for the reason that the first had left but little for their ravages. Solemn and terrible was the picture presented on the dark funereal night of a whole people clustering in the plazas and on their knees crying with loud voices to Heaven for mercy, or in agonizing accents calling for their children and friends whom they believed to be buried beneath the ruins. A heaven opaque and ominous; a movement of the earth rapid and unequal, causing a terror indescribable; an intense sulphurous odor filling the atmosphere, and indicating an approaching eruption of the volcano; streets filled with ruins, or overhung by threatening walls; a suffocating cloud of dust almost rendering respiration impossible,—such was the spectacle presented by the unhappy city on that memorable and awful night.
“A hundred boys were shut up in the college, many invalids crowded the hospitals, and the barracks were full of soldiers. The sense of the catastrophe which must have befallen them gave poignancy to the first moment of reflection after the earthquake was over. It was believed that at least a fourth part of the inhabitants had been buried beneath the ruins. The members of the Government, however, hastened to ascertain, so far as practicable, the extent of the catastrophe, and to quiet the public mind. It was found that the loss of life was much less than was supposed; and it now appears probable that the number of killed will not exceed one hundred, and of wounded, fifty. Fortunately the earthquake has not been followed by rains, which gives an opportunity to disinter the public archives, as also many of the valuables contained in the dwellings of the citizens. The movements of the earth still continue, with strong shocks; and the people, fearing a general swallowing up of the site of the city, or that it may be buried under some sudden eruption of the volcano, are hastening away.” In 1859 the city was again in order, as the seat of government, after an ineffectual attempt to remove it to the plain of Santa Tecla, ten miles distant.
The birth of the volcano of Izalco occurred in 1770. It is, indeed, only a lateral opening of the volcano of Santa Ana, which, like Ætna, is a mother of mountains. San Marcellino, Naranjo, Tamasique, Aguila, San Juan, Launita, and Apaneca all seem to be her offspring. Near the base of the main volcano was, previous to 1770, a large cattle rancho. At the close of 1769 the people on this estate were alarmed by subterranean noises and earthquake shocks, which continued to increase in loudness and severity until February 23, when the earth opened about half a mile from the houses on the hacienda, emitting fire, smoke, and lava. The house-people fled from so terrible a neighbor; but the vaqueros, or cowboys, who came daily to see the new monster, declared it grew worse and worse, throwing out more smoke and flame daily, and that while the flow of lava sometimes stopped for a while, vast quantities of sand and stones were thrown out instead. For more than a century this action has gone on, and the ejecta have formed a cone more than six thousand feet high, or higher than Vesuvius. At intervals of from ten to twenty minutes, loud explosions occur, with dense smoke and a puff of cinders and stones. By night the view from Sonsonate is very attractive, as the cloud of smoke is illuminated by the molten mass within, and the red-hot stones shoot through this darker mass and seem to ignite vapors, which flash like lightning. As these stones roll down the steep sides of the cone, they leave a faint track some distance (optical, probably), and sometimes the caldron boils over, sending rills of molten lava down the cone. Well may the sailors call this “El faro de Salvador,”—the lighthouse of Salvador. Like Stromboli, it is always active; and while most volcanoes are noted for the irregularity of their eruptions, Izalco is exceedingly regular, though sometimes acting with unusual violence (1798, 1869, 1870). The volcano of Tanna, in the western Pacific, exhibits this same pulsating character.
San Miguel is the largest active volcano in San Salvador, rising from the plain to a height of perhaps sixty-five hundred feet. Like most of the Central American volcanoes, its mass is a very regular cone, and its form, size, and beautiful colors render it one of the grandest objects of its class. From the deep green of the forest which surrounds its base, the color fades to the light green of the upland grass, then to the deep red of the scoriæ, and the top is grayish-white. Above all, the ever-changing cloud of smoke floats lazily away. Of all the accounts of ascents of Central American volcanoes, I have selected the account published many years ago by Don Carlos Gutierrez of his ascent of San Miguel, because it seems to convey a fair idea of the simplest form of mountain-climbing and of the appearance of an active cone. He says:—
“We started from the city of San Miguel on the afternoon of the 7th of December, 1848, directing our course towards the western border of the plain where rises the dark bulk of the volcano. At eleven o’clock at night we reached the foot of the mountain, distant four leagues from the town. Although the moon shone with extraordinary brilliancy and the night was one of serenest beauty, yet we considered it safer to take shelter in an Indian hut for the remainder of the night than trust ourselves among the fissures of the mountain in the treacherous moonlight. At four in the morning, with the earliest dawn of day, we commenced our ascent on horseback. We however soon found our course so much impeded by masses of lava, over which it was difficult to force the animals, that we were compelled to dismount and pursue our journey on foot. About half way up the mountain the dikes of lava became less frequent, and the ground more firm and open, and, although quite precipitous, yet not difficult of ascent. This open belt, however, does not extend to the summit, and long before we reached it we were again driven upon the beds of sharp, rough, and unsteady lava.
“Our course now lay through a deep channel formed between two vast currents of lava, composed of enormous crags, which in 1844 had flowed out from fissures in the side of the volcano. We had not proceeded far between these walls of rock when we found the scoriæ beneath our feet so yielding and unsteady that we could scarcely retain our foothold. Frequently we slid back three or four yards, thus losing in a moment the advance which it had cost us great labor to accomplish. Nevertheless, after many efforts and through much exertion, and after having suffered several severe falls, we succeeded in reaching the throat of the mountain. Here the lava was solid and the scoriæ firm; and though the slope was very steep and dangerous, yet we found it easier to proceed here than over the soft and yielding ashes below.
“About mid-day we reached the summit proper of the mountain and stood on the edge of the great crater, which is surrounded by a wall of immense rocks, irregular in height, and having a circuit of a mile and a half. The area within these strange bulwarks is level; but on descending, we found with alarm that it was traversed in every direction by profound fissures, varying from one foot to five yards in width, from which escaped dense clouds of sulphurous smoke. About in the centre of this area was the yawning, active crater, or mouth of the crater, or mouth of the volcano. Our guide peremptorily refused to advance farther, insisting that we were liable at any moment to sink into some one of the numerous fissures which yawned beneath the superficial crust. He added further that in the neighborhood of the crater the gases were so pungent and the sulphurous odor so overwhelming that we could not escape suffocation.
“The alarm with which our guide endeavored to inspire us did not, however, get the better of our curiosity, and we determined to reach the crater. Providing ourselves with long staves with which to test the nature of the ground, we advanced carefully and slowly. At every step the clouds of smoke became more dense, and the odor of the gases escaping from the multitudinous fissures more overpowering. Our efforts, however, were amply repaid by the sight which met our eyes when we finally reached the brink of the crater. Nothing could be grander or more magnificent.
“A few months before, I had seen the volcano of Izalco, with its crown of living fire and its flashing tongues of flame, throwing out floods of incandescent lava; but sublime as was the spectacle, it paled and grew tame in comparison with that before us. The crater, as before observed, is in the centre of the level area which I have described. It is of irregular width, in some places only ten or twelve yards broad; in others, fifty or sixty, dividing the greater crater from side to side. The depth of this orifice, or cleft, is so great that the eye cannot fathom it. One sees only a vast gulf of molten lava, over which plays a pale and sulphurous flame, reflected again and again from burned and blistered rocks, fantastic in shape and capricious in position, which form the walls of the orifice. Thick whorls of smoke drifted up from all sides, so that at times I was unable to distinguish my companion, distant only a few yards. An indescribable magnetic influence or fascination seemed to rivet our eyes on the molten floods surging below us, and which, from their roar and vibrations, seemed to threaten momentarily to rise and overwhelm us, as if the volcano were on the verge of eruption.
“Our contemplations of this fearful orifice were therefore brief, the smoke and odor overpowered us; and in a few moments we were forced to abandon our positions and seek a breath of pure air at a distance. We returned rapidly to the place where we had left our guide; and casting a farewell glance over the strange area before us, commenced our descent, reaching San Miguel at six o’clock in the evening, weary and exhausted.”
Volcan de Coseguina, from the Sea.
Of the eruptions of the Central American volcanoes none in the historical period have surpassed that of Coseguina in 1835. This mountain forms the eastern gate-ward of the Gulf of Fonseca, Conchagua rising on the other side of the rather narrow entrance. Not remarkably high (3,600 feet), it rises directly from the sea, and by its irregular outline, scarred slopes, and desolate appearance conveys the impression of a greater than its real mass. On the 20th of January, 1835, the disturbance began with very loud explosions, heard for a hundred leagues. Above the mountain rose an inky cloud which spread outwards precisely as Pliny describes the terrible cloud that rose above Vesuvius in 79, spreading like an Italian pine. From this column of heated vapor and sand darted lightning-flashes, produced either by the friction of the immense quantity of rough mineral particles, or by the sudden projection of hot gases and minerals into the much cooler atmosphere. As the cloud spread, the light of the sun was obscured, everything looked sickly in the yellow light, and the falling sand irritated both eyes and lungs. For two days the explosions grew more frequent and louder, while the eruption of sand increased; and on the third day the terrible noises were loudest in an almost absolute darkness. The rain of sand continued until a deposit of several feet had formed for many leagues around the crater. At Leon, in Nicaragua, more than a hundred miles away, the sand was several inches deep, and it fell in Vera Cruz, Jamaica, Santa Fé de Bogota, and over an area nearly two thousand miles in diameter. At Belize the noise of the explosions was so loud that the commandant mustered his troops and manned the forts, thinking there was a naval action off the anchorage. For eight hundred miles these noises were heard, and the vibrations near the volcano must have been indeed terrible. We can credit the accounts of the terror of the wild things of Nature as well as of human beings. For thirty leagues around, the astounded people believed that the Last Judgment had come, and in the darkness, thick with the falling ashes, groped hither and thither, bearing crosses and uttering prayers inaudible to themselves in the crash of elements. At the end of forty-three hours the earthquakes and explosions ceased, and with a strong wind the ashes were gradually blown away from the atmosphere. The returning light of day showed a gloomy outlook. Ashes covered the country on every side. On Coseguina a crater had opened a mile in diameter, and vast streams of lava had flowed into the gulf on one side, and into the ocean on the other. While the verdure was gone from the land, pumice covered the sea for a hundred and fifty miles.
Terrible as was this outbreak, the explosive violence was not so great as of the eruption from some unknown vent whose deposits are about Quiché in Guatemala, in the valley of the Chixoy, and elsewhere; and Pacaya has in some prehistoric time thrown out sand and pumice in greater quantity than did Coseguina, as we see by the deposits about the Lago de Amatitlan.
Lago de Ilopango, 1880.
With the mention of the Lago de Amatitlan it occurs to me that the so-called volcanic lakes of Central America deserve a short notice. I would not claim that there are not here genuine pit-craters filled with water and called lagos or lagunas. On the summit of many of the extinct volcanoes are craters filled with water, as Ipala and others, and as Agua was before the destruction of the crater-lip in 1541; while in San Salvador and Nicaragua are many lakes, usually of small extent, but sometimes so large as to mislead the casual observer as to their origin, though of undoubtedly volcanic nature. Of this last class is the Lago de Masaya, from whose deep pool the people of the neighboring village obtain all their water. Coatepeque is another volcanic lake, whose walls are so steep that they can be descended only at certain points by means of ladders and steps cut in the lava rock. Finally there are many pits, sometimes no more than a hundred feet in diameter, but of very great depth, and filled sometimes with fresh water, but more commonly with saline waters so strongly impregnated as to be undrinkable. The great lakes of Amatitlan and Atitlan are not certainly volcanic, although their shores are dotted with hot-springs and guarded by volcanoes,—they are not, that is, actual craters; but the former seems to be the result of a subsidence caused perhaps by the removal of material from lower layers by eruptions of Pacaya, and it is of no considerable depth, while good authority has considered the Lago de Atitlan the result of damming up a valley and streams by the masses of the volcanic group of the same name. A glance at the map of this lake (p. 154) as given by the French geologists whose opinion is quoted, will show that the volcanoes occupy a position not far from the geometrical centre of the Lago, or where they should be if the lake was an ancient crater. Compare with this, if you will, the plan of an undoubted volcanic lake, that of Ilopango in San Salvador. This body of water is not only the seat of volcanic eruptions, as is also the Great Lake of Nicaragua, but probably fills a depression that has been the result of the coalescence of several points of eruption. I have before me the interesting report to the Guatemaltecan Government by my friend Edwin Rockstroh of his observations made on the eruption of one of these craters in 1880. The lake is 9,200 metres wide from east to west, and 7,300 metres from north to south, with an area of 54.3 kilometres. Completely surrounded by precipitous mountains, interrupted only on the southeast by the narrow gorge through which the waters of the lake are discharged, it receives no important affluents from the surface; and as its emissary is of much greater volume at all seasons than these insignificant brooks, it is probably fed by subterranean springs,—indeed one of these, near the south shore, enters with such force as to cause a ripple on the surface of the lake. Soundings indicate a cup-like bottom with an extreme depth of less than seven hundred feet (209.26 metres). The level of the lake has often changed, and in 1880 the surface-level fell more than thirty-four feet, leaving exposed stumps of trees encrusted with calcareous deposits. It was before the last eruption well stocked with fish of the varieties called by the people who lived near by mojarra, burrito (both species of the genus Heros), pepesca, and chimbolo. At times an eruption of sulphurous gases partly asphyxiated the fish, driving them to the shores, where they fell a prey to the fishermen. What the fishermen did on occasion of greater disturbances is told in the following extract from a Guatemaltecan journal;[66] the author, Don Camillo Galvan, formerly Visitador-General, writes as follows:—
“The people of the pueblos around the lake, Cojutepeque, Texacuangos, and Tepezontes, say that when the earthquakes came from the lake, which they knew by the disappearance of fish, it was a sign that the monster lord of those regions who dwelt in the depths of the lake was eating the fish, and probably would consume them all shortly, unless provided with a more delicate and juicy diet worthy of his power and voracity; for they say that the monster only eats fish as men eat fruit, to refresh and allay hunger. The natives, deeply afflicted by the fish famine, the failure of an article of commerce and their ordinary diet, collected at the command of their chiefs. Then the sorcerers (los brujos) commanded the people to throw flowers and fruits into the lake: if the tremblings continued, they were to cast in animals, preferring conies (Lepus Douglassii), taltusas (Geomys heterodus), then armadillos (Dasypus), and mapachines (Procyon cancrivorus). These animals must be caught alive and cast living into the water, under penalty of no less than hanging with the vine zinak. If some days passed, and the tremors continued, and the fish did not come out of their caves, they (the brujos) took a girl of from six to nine years old, decked her with flowers, and at midnight the wizards took her to the middle of the lake and cast her in, bound hand and foot and with a stone fast to her neck. The next day, if the child appeared upon the surface and the tremors continued, another victim was cast into the lake with the same ceremonies.
“Even in the years 1861 and 1862, when I visited these towns, they told me, though with much reserve, that the people of Cojutepeque and Chinameca kept this barbarous custom to prevent the failure of the fish.”
Near the end of November, 1879, a series of earthquakes shook the lake (more than six hundred were counted), and on Jan. 11, 1880, the waters had risen about four feet. On the next day, between half-past four and half-past seven in the afternoon, 13,790,000 cubic metres of water escaped from the outlet of the lake, making a stream of greater volume than the Seine at Paris or the Rhine at Basle. The little river Jiboa, which received this torrent, did great damage to the plantations on its banks.
As is usual, the earthquakes were accompanied by the discharge of sulphuretted hydrogen, now in such quantities as to be very unpleasant at the city of San Salvador. On the 9th of January there appeared floating on the surface numerous flakes of a black foam composed of ferric sulphide, which in contact with flame burned with a slight explosion. On the 20th, at eleven o’clock in the evening, a great disturbance was noticed in the midst of the lake, and the next morning a pile of rocks was seen, from whose midst arose a column of vapor. For more than a month this vapor column was visible, and the pile of rocks near the centre of the lake increased, while the water was heated and the sulphurous vapors extended over all the neighborhood. Beyond this no permanent volcano was formed above the level of the lake (1,600 feet above the sea).
It is dangerous to form conclusions as to the general course of volcanic action anywhere, for science is very much in the dark as to the causes of eruptions and earthquakes, as to the condition of the interior of our globe, whether fluid or solid, and also as to whether the lavas poured out during an eruption have been fluid since the earth was formed, or have been suddenly melted either as cause or effect of what we call an eruption. In the Central American volcanic region, as was stated at the beginning of this chapter, little has been done in the way of scientific exploration, and the facts recorded, beyond popular accounts of some especial disturbance, are so meagre that no large space would be required to present them to the reader. This is not, however, the place to enter into a scientific discussion, and I must content myself with a few bare statements.
In the first place, the volcanoes of the country discharge both ashes and lava, the latter being most frequently trachytic. Basaltic lavas occur, though less frequently than in Mexico and farther northward; and the columnar structure seen so well at Regla in Mexico is very rare in Guatemala. On the other hand, pumice and obsidian, which are classed with the acid or trachytic lavas, are abundant, the latter furnishing material for knives, while the former has many applications in the arts of the present day. I have seen both basalt and basaltic rapilli in eastern Guatemala near the boundary of San Salvador, and basaltic sand is common on the southern coast.
Another feature of the Central American volcanoes is their remarkable regularity of form. This is due to the fact that the emissions consist of ash and lava of slight fluidity. In the Hawaiian Islands, where the basaltic lava is more fluid than in any other volcanic region, the lava-streams often flow for months, and extend fifty or sixty miles from the crater, building by successive eruptions a cone of great diameter in proportion to their height; Mauna Loa having a diameter of ninety miles at the sea-level, with a height of less than fourteen thousand feet and a slope of about seven degrees. The eruptions of the American volcanoes are mainly of masses of rock which are piled regularly about the base, in this way increasing the height, and great quantities of sand which fills the interstices, and finally of lava in a thick, viscid state which clings to the slopes of the growing cone and cements together the sand and larger fragments. No lava-stream, at least of modern times, has been found at any considerable distance from its source.
From the specimens I collected in some of the ravines which traverse the older deposits, I saw that in former ages the outflow was not only different from that of modern times, but of great variety of form in contemporaneous streams, although the chemical composition did not vary essentially.
Earthquakes are mainly due to the injection of intensely heated lava into strata of cold rock in the process of forming dikes. When a volcano pours its lava out of its summit-crater, the eruption may be wholly free from earth tremors, as is often the case on the Hawaiian Islands; and this gives rise to the popular belief that active volcanoes are in some way a safety-valve for the subterranean forces. When, however, the shrinkage of the earth’s crust or the explosive force of pent-up vapors cracks the solid rock, thus giving passage to the molten mass which must be supposed to underlie this volcanic region, the sudden contact of two bodies of very different temperatures (perhaps two thousand degrees) must cause vibrations entirely sufficient to account for the worst earthquake recorded. That the supply of molten rock is ample beneath the crust of this region, we have proof in the constant activity of Izalco, which for more than a century has poured out lava with the other ejections.
This theory of earthquake action is so simple that it must commend itself to any one who has observed the powerful vibrations excited by placing a cold kettle upon a hot stove, or by admitting with force a stream of hot water into a bath-tub partly filled with cold water. It may be stated also that lava is a remarkably poor conductor of heat (I have been able to walk over a crust that bent beneath my weight, and again where I left footprints in the half-hardened lava), and solid lava might retain a temperature of less than two hundred within a few feet of a molten mass ranging among the thousands of degrees. The secular refrigeration of the subterranean molten masses due to the slight conductivity of solid lava is well illustrated in the temperature of hot-springs, that remains unchanged for centuries.
Eruptions are usually of an explosive nature in the Central American region (as described in the outbreak of Coseguina), and the ejected ash is scattered often to a great distance to form by its decomposition layers of soil especially fitted for the cultivation of coffee, sugar, and the vine. Sulphur is not so abundantly deposited as at Ætna, Hekla, or even the Mexican volcanoes.