On the Volcanoes of Jorullo.

[From Humboldt’s Essay on New Spain.]

“THE grand catastrophe in which this volcanic mountain issued from the earth, and by which the face of a considerable extent of ground was totally altered, was perhaps one of the most extensive physical changes, that the history of our globe exhibits.

Geology points out spots in the ocean, where, within the last two thousand years, volcanic islets have arisen above the surface of the sea, as near the Azores, in the Archipelago, and on the south of Iceland: but it records no instance of a mountain of scoriæ and ashes, 517 met. [563 yards] above the old level of the neighbouring plains, suddenly formed in the centre of a thousand small burning cones, thirty-six leagues from the seashore, and forty-two leagues from any other volcano.

This phenomenon remained unknown to the mineralogists and natural philosophers of Europe, though it took place but fifty years ago, and within six days journey of the capital of Mexico.

“Descending from the central flat toward the coasts of the Pacific ocean, a vast plain extends from the hills of Aguasarco to the villages of Toipa, and Patatlan, equally celebrated for their fine cotton plantations.

Between the picachos del Mortero and the cerras de las Cuevas and de Cuiche, this plain is only from 750 to 800 met. [820 to 880 yards] above the level of the sea.

Basaltic hills rise in the midst of a country, in which porphyry with base of green-stone predominates.

Their summits are crowned with oaks always in verdure, and the foliage of laurels and olives intermingled with dwarf fan palms.

This beautiful vegetation forms a singular contrast with the arid plain, which has been laid waste by volcanic fire.

“To the middle of the eighteenth century fields of sugar-canes and indigo extended between two rivulets, called Cuitimba and San Pedro.

They were skirted by basaltic mountains, the structure of which seems to indicate, that all the country, in remote periods, has several times experienced the violent action of volcanoes.

These fields, irrigated by art, belonged to the estate of San Pedro de Jorullo (Xorullo, or Juvriso), one of the largest and most valuable in the country.

In the month of June, 1759, fearful rumbling noises were accompanied with frequent shocks of an earthquake, which succeeded each other at intervals for fifty or sixty days, and threw the inhabitants of the estate into the greatest consternation.

From the beginning of the month of September, every thing seemed perfectly quiet, when in the night of the 28th of that month a terrible subterranean noise was heard anew.

The frightened Indians fled to the mountains of Aguasarco.

A space of three or four square miles, known by the name of Malpays, rose in the shape of a bladder.

The boundaries of this rising are still distinguishable in the ruptured strata.

The Malpays towards the edge is only 12 met. [13 yards] above the former level of the plain, called las playas de Jorullo; but the convexity of the ground increases progressively toward the centre, till it reaches the height of 160 met. [175 yards].

“They who witnessed this grand catastrophe from the top of Aguasarco assert, that they saw flames issue out of the ground for the space of more than half a league square; that fragments of red hot rocks were thrown to a prodigious height; and that through a thick cloud of ashes, illumined by the volcanic fire, and resembling a stormy sea, the softened crust of the earth was seen to swell up.

The rivers of Cuitimba and San Pedro then precipitated themselves into the burning crevices.

The decomposition of the water contributed to reanimate the flames, which were perceptible at the city of Pascuoro, though standing on a very wide plain 1400 met. [1530 yards] above the level of the playas de Jorullo.

Eruptions of mud, particularly of the strata of clay including decomposed nodules of basaltes with concentric layers, seem to prove, that subterranean waters had no small part in this extraordinary revolution.

Thousands of small cones, only two or three yards high, which the Indians call ovens, issued from the raised dome of the Malpays.

Though the heat of these volcanic ovens has diminished greatly within these fifteen years, according to the testimony of the Indians, I found the thermometer rise to 95° [if centig.

203° F.] in the crevices that emitted an aqueous vapour.

Each little cone is a chimney, from which a thick smoke rises to the height of ten or fifteen met. [11 or 16 yards.]

In several a subterranean noise is heard like that of some fluid boiling at no great depth.

“Amid these ovens, in a fissure, the direction of which is from N. N. E. to S. S. E, six large hummocks rise 400 or 500 met. [440 or 550 yards] above the old level of the plain.

This is the phenomenon of Monte Novo at Naples repeated several times in a row of volcanic hills.

The loftiest of these huge hummocks, which reminded me of the country of Auvergne, is the large volcano of Jorullo. It is constantly burning, and has thrown out on the north side an immense quantity of scorified and basaltic lava, including fragments of primitive rocks.

These grand eruptions of the central volcano continued till February 1760.

In the succeeding years they became gradually less frequent.

The Indians, alarmed by the horrible noise of the new volcano, at first deserted the villages for seven or eight leagues round the plain of Jorullo.

In a few months they became familiar with the alarming sight, returned to their huts, and went down to the mountains of Aguasarco and Santa Ines, to admire the sheaves of fire thrown out by an infinite number of large and small volcanic openings.

The ashes then covered the houses of Queretoro, more than 48 leagues [120 miles] in a right line from the place of the explosion.

Though the subterranean fire appears to be in no great activity at present, and the Malpays and the great volcano begin to be covered with vegetables, we found the air so heated by the little ovens, that in the shade, and at a considerable distance from the ground, the thermometer rose to 43° [109·4° F].

This fact evinces, that there is no exaggeration in the report of some of the old Indians, who say, that the plains of Jorullo were uninhabitable for several years, and even to a considerable distance from the ground raised up, on account of the excessive heat.

“Near the cerro of Santa Ines the traveller is still shown the rivers of Cuitimba and San Pedro, the limpid waters of which formerly refreshed the sugar-canes on the estate of Don Andrew Pimantel.

These springs were lost in the night of the 29th of September, 1759: but 2000 met. [near 2200 yards] to the westward, in the soil that has been elevated, two rivulets are seen to break out of the clayey dome of the furnaces, exhibiting themselves as thermal waters, in which the thermometer rises to 52·7° [126·86° F.].

The Indians still give these the names of San Pedro and Cuitimba, because in several parts of the Malpays large bodies of water are supposed to be heard running from east to west, from mountains of Santa Ines to the estate of the Presentation.

Near this estate is a brook, that emits the sulphuretted hidrogen gas: it is more than 7 met. [near 8 yards] wide, and is the most copious hidrosulphurous spring I ever saw.

“In the opinion of the natives these extraordinary changes I have described, the crust of earth raised and cracked by volcanic fire, the mountains of scoriæ and ashes heaped up, are the works of monks; the greatest, no doubt, they ever produced in either hemisphere.

Our Indian host, at the hut we inhabited in the plain of Jorullo, told us, that some missionary capuchins preached at the estate of San Pedro, and, not meeting a favourable reception, uttered the most horrible and complicated imprecations against this plain, then so beautiful and fertile.

They prophesied, that the estate should first be swallowed up by flames issuing out of the bowels of the Earth; and that the air should afterward be cooled to such a degree, that the neighbouring mountains should remain for ever covered with ice and snow.

The first of these maledictions having been so fatally verified, the common people foresee in the gradual cooling of the volcano the presage of a perpetual winter.

I have thought it right to mention this vulgar tradition, worthy a place in the epic poem of the jesuit Landivar, because it exhibits a striking feature of the manners and prejudices of these remote countries.

It shows the active industry of a class of men, who, too frequently abusing the credulity of the people, and pretending to possess the power of suspending the immutable laws of nature, know how to avail themselves of every event for establishing their empire by the fear of physical evil.

“The situation of the new volcano of Jorullo leads to a very curious geological observation.

It has already been observed in the third chapter, that there is in New Spain a line of great heights, or a narrow zone included between the latitudes of 18° 59′ and 19° 12′, in which are all the summits of Anahuac that rise above the region of perpetual snow.

These summits are either volcanoes still actually burning; or mountains, the form of which, as well as the nature of their rocks, renders it extremely probable, that they formerly contained subterranean fire.

Setting out from the coast of the Gulf of Mexico, and procceding westward, we find the peak of Oribaza, the two volcanoes of la Puebla, the Nevado de Toluca, the peak of Tancitaro, and the volcano of Colima.

These great heights, instead of forming the ridge of the cordillera of Anahuac, and following its direction, which is from S. E. to N. W., are on the contrary in a line perpendicular to the axis of the great chain of mountains.

It is certainly worthy remark, that in the year 1759 the new volcano of Jorullo was formed in the continuation of this line, and on the same parallel as the ancient Mexican volcanoes.

“A view of my plan of the environs of Jorullo will show, that the six large hummocks have risen out of the earth on a vein, that crosses the plain from the cerro of las Cuevas to the pichaco del Montero.

The new mouths of Vesuvius too are found ranged along a fissure.

Do not these analogies give us reason to suppose, that there exists in this part of Mexico, at a great depth within the Earth, a fissure stretching from east to west through a space of 137 leagues [343 miles], and through which the volcanic fire has made its way at different times, bursting the outer crust of porphyritic rocks, from the coasts of the Gulf of Mexico to the South Sea?

Is this fissure prolonged to that little groupe of islands, called by Colluet the Archipelago of Regigedo, and round which, in the same parallel with the Mexican volcanoes, pumice stone has been seen floating?

Naturalists who distinguish the facts offered by descriptive mineralogy from theoretical reveries concerning the primitive state of our planet will pardon me for having consigned these observations to the general Map of New Spain, contained in the Mexican Atlas.”