Travels in Peru, on the Coast, in the Sierra, Across the Cordilleras and the Andes, into the Primeval Forests

by Johann Jakob von Tschudi

San Lorenzo is a small, long-shaped island, about 15 English miles in circumference. It is intersected throughout its whole length by a ridge of sharp crested hills, of which the highest point is about 1387 feet above the level of the sea. On the north-eastern side, the declivity is less steep than on the south-west, where it descends almost perpendicularly into the sea. Seals and sea-otters inhabit the steep rocks of the southern declivity, and swarms of sea-birds nestle on the desolate shore. San Lorenzo is separated on the southern side by a narrow strait, from a small rocky island called El Fronton, which is also the abode of numerous seals.

The coasts of Callao and San Lorenzo have undergone very remarkable changes within a few centuries. Mr. Darwin, the English geologist, is of opinion that this part of Peru has risen eighty-five feet since it has had human inhabitants. On the north-eastern declivity of San Lorenzo, which is divided into three indistinctly marked terraces, there are numbers of shells of those same species of conchyliæ which are at the present time found living on the coast. On an accurate examination of these shells, Mr. Darwin found many of them deeply corroded. "They have," he says, "a much older and more decayed appearance than those at the height of 500 or 600 feet on the coast of Chile. These shells are associated with much common salt, a little sulphate of lime (both probably left by the evaporation of the spray, as the land slowly rose), together with sulphate of soda, and muriate of lime. The rest are fragments of the underlying sand-stone, and are covered by a few inches thick of detritus. The shells higher up on this terrace could be traced scaling off in flakes, and falling into an impalpable powder; and on an upper terrace, at the height of 170 feet, and likewise at some considerably higher points, I found a layer of saline powder, of exactly similar appearance, and lying in the same relative position. I have no doubt that the upper layer originally existed on a bed of shells, like that on the eighty-five feet ledge, but it does not now contain even a trace of organic structure."[2] Mr. Darwin adds, that on the terrace, which is eighty-five feet above the sea, he found embedded amidst the shells and much sea-drifted rubbish, some bits of cotton thread, plaited rush, and the head of a stalk of Indian corn.

San Lorenzo does not appear to have been inhabited in very early ages. The fragments of human industry which have been found mixed in the shells have probably been brought thither by fishermen who visit the island, and often pass the night on it.

Darwin further remarks:—"It has been stated that the land subsided during this memorable shock (in 1746): I could not discover any proof of this; yet it seems far from improbable, for the form of the coast must certainly have undergone some change since the foundation of the old town," &c.—"On the island of San Lorenzo there are very satisfactory proofs of elevation within a recent period; this, of course, is not opposed to the belief of a small sinking of the ground having subsequently taken place."

But satisfactory evidence of the sinking of the coast is not to be obtained in a visit of a few weeks' duration; nor must that evidence rest solely on geological facts, though doubtless they furnish much important data. History must aid the inquiry. Tradition and the recollections of old persons must be attended to. According to these authorities, a change more or less considerable has taken place in the level of the coast, after every great earthquake. If we refer to the account given by Ulloa, and compare the plan of the harbor of Callao, drawn by him in 1742, with the most correct modern charts, we do not find much difference in the representations of the distance between the main-land and San Lorenzo. Four years afterwards the great earthquake occurred, which destroyed the city of Callao, and plunged it into the sea. Subsequently there was a rising of the coast, which could not be inconsiderable, for according to the statements of old inhabitants of Callao, the distance from the coast to San Lorenzo was so inconsiderable that boys used to throw stones over to the island. At present the distance is nearly two English miles. I have no doubt of the general correctness of those statements, for a careful investigation of facts leads to the same conclusion; so that within the last sixty or seventy years the sinking must have been considerable. It must be observed, however, that the ruins on the small tongue of land are not, as Darwin supposes, the remains of the city of Callao, swallowed up by the sea in 1746, but of the Callao which was destroyed by the great earthquake of 1630.

Another proof of the sinking exists in the extensive shallow between the coast of the main-land and San Lorenzo, called the Camotal. In early times this shallow was dry land, producing vegetables, in particular Camotes (sweet potatoes), whence the name of this portion of the strait is derived. The inundation took place in the time of the Spaniards, but before 1746, either in the great earthquake of 1687, or in that of 1630.

Northward of the Bay of Callao, near the plantation of Boca Negra, there is a shallow, where, according to records, there existed a sugar plantation about fifty years ago. Turning to the south of Callao, in the direction of Lurin, we find, at the distance of about two English miles from the coast, two islands or rocks, of which one is called Pachacamac, and the other Santa Domingo. At the time of the Spanish invasion these rocks were connected with the main-land, and formed a promontory. On one of them stood a temple or castle. At what period they were detached from the coast I have not been able to ascertain authentically; but there appears reason to suppose that the separation took place during the violent earthquake of 1586. Attentive investigations to the north of Callao—at Chancay, Huacho, Baranca, &c., would probably bring to light further evidence on this subject.

Between the facts stated by Mr. Darwin and those here adduced, there is considerable discrepancy. On the one hand they denote a rising, and on the other a sinking. But it may be asked, might not both these phenomena have occurred at different times?[3] Mr. Darwin's opinion respecting the still-continued rising of the coast does not appear to me to rest on satisfactory evidence. The relics of human industry which he found embedded among shells, at the height of eighty-five feet above the sea, only prove that the elevation has taken place after the land was inhabited by the human race, but do not mark the period at which that elevation occurred. Pieces of cotton thread and plaited rush are no proofs of a very refined degree of civilisation, such as the Spaniards brought with them to Peru, and cannot therefore be taken as evidence that the elevation took place at any period subsequent to the conquest. Garcilaso de la Vega traces the dynasty of the Incas down to the year 1021, a period when the inhabitants of the coast of Peru were tolerably well advanced in civilisation. Fernando Montesinos furnishes facts connected with the history of Peru, of several thousand years' earlier date; and, judging from the number of dynasties, the nature of the laws, &c., it may be inferred that civilisation existed at a period of even more remote antiquity. It cannot therefore be determined with any accuracy at what time the deposit at San Lorenzo, now eighty-five feet high, was level with the sea, or whether the rise suddenly followed one of those frightful catastrophes which have so often visited the western coast of South America. Then, again, the different degrees of decay presented by the beds of shells seem to indicate that the rising has been gradual; and it may have been going on for thousands of years. Had the coast risen eighty-five feet since the Spanish conquest—that is to say, within the space of three hundred and sixty-two years—the Camotal would long since have again risen above the surface of the sea; for it is very improbable that it sank to a depth exceeding ninety or ninety-five feet. It is evident that risings and sinkings have occurred at various times, and that causes contingent on earthquakes have produced the variations in the rising and falling of the coast.

It is probable that the accurate sounding of the depth of water in the Camotal, at stated intervals, would furnish the best means of ascertaining the rising and sinking of the coast. A variety of circumstances combine to favor the practicability of calculation by this method. For example, no river flows into that part of the bay in which the Camotal is situated. The Rimac, whose mouth lies further to the north, is not sufficiently large to carry any considerable deposit into the bed of the bay: moreover, there is but little tide, and the bay is always calm, being sheltered on the south by the island of San Lorenzo, and north breezes are rare and never violent.

I may here mention a singular phenomenon which has in latter times often occurred at Callao, and which, in 1841, I had myself the opportunity of observing. About two in the morning the sea flowed from the shore with greater force than in the strongest ebb; the ships farthest out were left dry, which is never the case in an ebb tide. The alarm of the inhabitants was great when the sea rushed instantly back with increased force. Nothing could withstand its fury. Meanwhile there was no commotion of the earth, nor any marked change of temperature.