Great Neapolitan Earthquake of 1857/Part II. Ch. XXI

by Robert Mallet

Chapter XXI.

Saponara to Spinosa, and the Entrance of the Valley of the Laderna.

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Leaving Saponara, where there were no authorities but a few gendarmes to be found, one of whom I took on with me to Montemurro, which I proposed to reach late, (as a guide rather than a protection against marauding on the part of the starving people hereabouts,) I rode along the right bank of the Agri eastward, to near the junction with the Moglia, and then forded the former with some difficulty, owing to its swollen state; and after half a mile again forded the Aqua Fredda, or Frigida, which, coming down by the little vallone of the same name, from the heights of Monte dell' Agresto, and the Santo Spirito, falls into the Agri on its left bank. Looking back at Saponara, from 2 miles distant, to the east, and after crossing these rivers again at about 4 miles, I made the sketches (Nos. 255 and 256) of its appearance and relation to the hills around, and to the piano, &c. The afforested low hill in front, is the Bosco di Guardia Maura, and part of the Bosco dell' Aspro. The Agri, with deep and precipitous clay banks, flows between Saponara and the observer.

It is scarcely conceivable that Saponara will ever be rebuilt, the destruction is too absolute, to leave sufficient inducement to remove the mountainous masses of rubble and rubbish, that must form the necessary preliminary. Those associated with the place will find another site, and rekindle their hearths on strange ground, from which their surviving successors, will within another century most probably be driven forth, by a future great earthquake, from houses as unskilfully constructed, as those their sires perished beneath.

As I looked back once more upon the place, I came to understand that thus it has been, that we find in Southern Italy, such numbers of old and new towns of the same name, situated not far apart—such as Corneto, Vecchia e Nova, Tito, Vecchio e Nova, Capaccio, Marsico, and numbers of others—and it recurred to memory that after the great shock of 1783, several of the Calabrian towns, were then rebuilt on new sites—as St. Agatha, Vecchia e Nova, Blanco, Vecchia e Nova, &c.

Sir Charles Lyell's vivid sketch, of the probability of future ages, finding in the formations of to-day, human remains and objects, and records of human art, ('Elements of Geology,' chap. xlvi.), embedded and preserved, too, suggested thoughts of the future state and after history, of the mounds that are alone left where Saponara was.

Beneath these masses lie, some few mangled human remains, that will never probably be found for sepulture—those of domestic animals, and of the mammalian and other vermin that follow man—fragments of every household utensil, personal and domestic ornaments, weapons, tools, and instruments, carved and wrought stone, ivory, hard wood, grain, fruits, food of many sorts, books, records, crumpled pictures, glass and pottery, wrought timber in the splintered joinery, as well as the metallic parts of houses, &c.; under what changed conditions as to geological position may these, if ever, see the light again!

In this vitalizing climate, but a few years will elapse, before the frosts of winter and its torrential rains, will have pulverized and reduced to interstitial soil, much of the dry rubbish: plants and seedlings will root in it; forest-trees will send their searching roots downwards through it, and beneath their fostering shade, a jungle of shrubs, weeds, mosses, and coarse grass, will spring up and conceal with verdure the harsh colouring and form, of the heaps that once were a city; and after but a few generations the fearful fate of its two thousand overwhelmed inhabitants—nay, its very site, will have become a tradition as dim, as that of the neighbouring Grumentum.

About half a mile S.E. of Saponara, upon the level clays of the piano, I passed two square gate-piers of rubble ashlar masonry, leading to an orchard, 3 feet square, and 7 feet in height, both prostrated, and in directions accurately parallel, 140° 30′ E. of north, fractured at the ground level from their foundations. The mortar was bad, and by examination with the hand I judged had not an adhesion

of more than about 2 lbs. per square inch. The wave-path was exactly subnormal to the piers (Fig. 257).

The horizontal velocity for fracture from the equation

$V={\frac {2}{3}}g\times {\frac {bL}{a^{2}}}$ is therefore

$V=5.48$ feet per second.

The horizontal velocity for overthrow after fracture from the equation

$V^{2}={\frac {4}{3}}g\times {\sqrt {a^{2}+b^{2}}}\times ({\frac {1-\cos {\theta }}{\cos ^{2}{\theta }}})$

$\theta$ being 22° 40′, $a$ = 7 feet, $b$ = 3 feet, is $V$ = 5.14 feet per second:

The total horizontal velocity for fracture and overthrow is therefore

$V=5.48+5.14=10.62$ feet per second:

but $e$ = 16° 25′ assumed the same as at Sarconi; therefore

$\mathrm {V} =10.62\times \sec e=11.04$ feet per second,

the actual velocity of the wave in its direct path. This result—deduced from two similar blocks of masonry, of the simplest and best form, natural seismometers in fact, and coinciding so closely with previous and distant determinations—affords a strong confirmation of the correctness of the explanation given, of the nature of the higher velocity that overthrew Saponara, close to which, but down on the level of the plain, we see thus the wave has its ordinary velocity.

I pursued my way towards Montemurro, where I hoped to rest.

At 4 miles S.E. of Saponara, under Spinosa, on the level of the bed of the Agri, at 3^h 15^m Nap. time, the barometer read 29.11 inches, thermo. 42° gives the height above the sea = 649.1 feet.

This may be viewed as about the lowest level of the Piano Mattine, so that its mean level is nearly the same, as that of the great Piano of Diano.

For some miles about the junction of the Moglia and Agri, evidences of prodigious river erosion exist. In many places in the main river-bed—here from 500 to 700 feet, or upwards, in width, though rarely covered wholly with water—great insular masses challenge astonishment, by the rate at which they are being carried bodily off in winter.

One of the more remarkable of these is seen in Sketch No. 258: they all consist of great beds of calcareous breccia, resting conformably upon perfectly level deep beds of extreme thinness of parallel lamination of green, grey, and purple clays, or marls, hard, dense, and unctuous, but rapidly softened and dissolved when wetted. Above the breccia, lies an immense thickness of dense red brown, clay and loam; the laminated marl beds exist, just at the level of the watercourse of the two rivers, and as these get rapidly sapped and cut away, huge masses of the breccia, break off and fall separate into small pieces, and with the clays shed off their summits, are swept away, leaving nothing deposited finally upon the river-beds, but the harder calcareous pebbles and boulders of the breccia, and those still harder travelled boulders, which it contained in abundance. Amongst the latter, are many of sienite and yellow granites, some of a green and white fine sandstone breccia, having lithologically a most suspicious look of indurated chalk, from a green sand formation, and many of variegated jaspers. Large blocks of the latter, banded with green and purple, are found abundantly in the clays and on the slopes to the north side of the valley, and are plainly the product of intense metamorphic action, upon the variegated marl-beds.

Passing beneath Spinosa, I scanned the town narrowly with the telescope; but although many buildings were prostrate and fractured, it did not appear to offer much, to reward the time and labour of ascent; and being only about five miles in a right line from Saponara, ascertainment of direction here was of less importance. I obtained from some houses at the base, however, a satisfactory measurement of the latter from fissures, which gave 134° 30′ E. of north for the wave-path. Owing to circumstances of stone-work and apertures, &c., they could not be relied upon as to emergence, beyond proving that it was from the N.W. The owner of one of those houses informed me, that his business frequently brought him to Castel Saraceno, about ten miles to the south, and that there the shock had been felt from N.W. to S.E., or 135° E. of north.