CHAPTER XXIII.

THE EVIDENT VOLCANIC ORIGIN OF THE DEAD SEA, AND THE INFERENCES RELATIVE TO THE FUTURE.

SEVERAL speculations have been made as to the probable causes of the depression of the Dead Sea, its peculiar saltness, the remarkable straightness of the Valley of the Jordan, and of the corresponding valley running from the south end of the Dead Sea to the east arm of the Red Sea, called the Akabah. With one exception, all the appearances of the last-mentioned valley will suggest that it was an ancient channel between the Dead Sea and the Red Sea, carrying off the waters of the Jordan and the Lake of Tiberias south to the latter. This singular cleft in the land reaches farther north than the Lake of Tiberias, running even up to the valley Et Teim, at the base of Hermon, and beyond till it opens into the plain of the Buka'a, which appears to be only an elevated extension of the same remarkable crevasse. It has, therefore, an unbroken course from a very high northern part of the Lebanon, along the broad valley of the Buka'a through the Lebanon bases at Mount Hermon, down to the water of Merom, through the Lake of Tiberias, the Jordan, the Dead Sea, the Ghor, or valley at the south of the sea, and onward along the distinct valley 'Araba to the Red Sea. Nor does it stop here, but, preserving the general contour it had before reaching the Red Sea, it is in part filled with the water of that sea, and thus runs down as an estuary one hundred miles farther before it comes to the normal limits of the Red Sea. general valley-line is regular and apparently unbroken for about three hundred and fifty miles, from the Upper Buka'a

The

to the waters of the Red Sea at the head of the Akabah Gulf. The exception, referred to above, made against the supposition that the waters of the Lebanon ever flowed through to the Red Sea, is as follows :-The facts that the level of the Dead Sea is thirteen hundred and sixteen feet below the Mediterranean, and the level of the waters of the Red Sea vary but little from those of the Mediterranean, plainly show that water from the Dead Sea must run up hill to reach the supposed exit at the Red Sea. But, in answer to this, it appears, as we shall see, that the whole country north and south of the Dead Sea has undergone at some time a subsidence, more or less sudden, reducing it to its present level. This is evident from the dip of the rock east and west of the sea, from the singular contortions of the rock at the sea, and from the sudden variations between the eastern and western character of the crevasse of the Jordan. This depression or subsidence of the land has not only increased the volume of the waters of the Dead Sea by cutting off their ancient exit to the Red Sea, but has also increased their saltness and bitterness, as they have consequently received all the salts of the rain-washed sides of the mountains east and west, and of the waters of the Jordan. The latter brings into the Dead Sea annually not only an immense supply but a variety of salts from a tract of country reaching up to the Lebanon ranges. Moreover, the depression of the sea-basin itself has enabled it to retain the vastly-increased waters, with their salts; and, the surface having thus become increased, the evaporation became proportionally greater until it became equal to the supply. Then the lake-area remained stationary, and in this condition it continues to the present day. During the same time, however, the sea, constantly receiving the above-mentioned supplies of salts of various characters, and giving off in evaporation only the water which held them in solution, would in time concentrate within its own waters such a quantity of various saline material as would result in the character indicated by the analyses we have given. These

EFFECT OF EARTHQUAKES.

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appear to be the geological relations in the history of the sea and the most reasonable method of accounting for the saltness of its waters. Against this supposed volcanic depression, as explanatory of the concavity of the sea-bed, there are only two objections urged that a violent depression of the bed of the Dead Sea would require us to suppose that the mountains adjoining would be subject to the same depression; and that the water-courses south of the Dead Sea, leading to the water-course which we have supposed to be the ancient exit of the Dead Sea, do not have a southerly course,-which is necessary to the supposition that the Jordan had formerly continued southward to the Red Sea. These objections may be answered, first, by referring to similar instances in other regions, and about which there seems to be but little doubt. Depressions frequently occur in volcanic regions, wherein for miles the land suddenly sinks, breaking off abruptly from adjoining sections, especially near craters. With the Peak of Teneriffe as a centre, there is a fault or sudden depression nearly eight miles in diameter, wherein a tract of land from eighteen to twenty miles in circumference, from some volcanic cause, has been let down into the earth abruptly, leaving the sides of the country in the same relative horizontal position to the surrounding land as exists between the Dead Sea and the mountains on the west and east of it. Abrupt elevations, the result of volcanic action, are known to exist; and why may not the same forces, by their withdrawal as a sustaining power, permit the opposite result-namely, a depression? Such a depression would leave the surrounding country perfectly horizontal. During the earthquake in Calabria in 1783, circular hollows in the plain of Rosarno were formed, cross-sections of which presented the form of the similar section of a funnel, the inner portions having sunk abruptly and forming an apparent crater of great size. The extensive slips of land near Cinquefrondi during the same earthquake of Calabria, with the crevasse-openings and the deep circular pits formed and

270

OBJECTION TO A VOLCANIC ORIGIN.

afterward filled with subterranean waters, which have so frequently occurred after earthquakes, and which are described by Mr. Lyell and others, sufficiently answer the objection to a volcanic depression in the case of the Dead Sea, which has been based upon the fact that the mountains in the vicinity are horizontal. The second objection, found in "the absence of all south-tending valleys south of the point-now, at least of the great depression," is answered by presenting the fact that the rock of this region is so easily affected by attrition that the simple force of long-continued torrents would be quite sufficient, during the lapse of many centuries, to change or modify the direction of water-courses-especially when the two following facts are taken into consideration. First, that the courses of the wadys in this region, even where there now exists a southern current into which they run-as, for instance, into the Jordan-are not all south-tending. This is seen in the Wady Hesbon, Wady Zurka, Wady Abu Seyud, and the three parallel Wadys Zedy, Dan, and El Ghar, given by Dr. Porter, which for the greater part of their courses run north-west, and turn suddenly only when near the Jordan. So on the west of the Jordan several run east instead of south, as the Wadys Kelt and Nawaimeh. Yet the descent of the Jordan is rapid and directly south. Again, it must be remembered that a line drawn from a short distance north of the Lake of Tiberias due south to about thirty-five miles south of the Dead Sea would nearly fill up this depression, and, in restoring the country, would show a remarkable level, which is nearly continuous from the south of Mount Hermon to the Red Sea. This level, modified by preexisting local elevations, would not require that many south-tending valleys should now exist to prove that the course of a stream was anciently southward. Taking into consideration these facts, therefore, the impressibility of rock throughout this region, the centuries which have elapsed during which the torrents have exercised their force, and then the fact that the existing wadys, even with a

downward plain, are not always southward, I think it will appear that south-tending wadys between the Dead Sea and the gulf, or Red Sea, are not to be demanded in proof of a pre-existing channel-connexion between the two. In addition to this, there are several very interesting coincidences, which, at least, are suggestive. The similarity between the Dead Sea, the Jordan, and the Lake Tiberias, and the South American Lake Aullagus, the river Desaguadero, and the Lake Titicaca, lying between Bolivia and Peru, is very striking. The latter connect with each other in the same way and have no outlets; and one is becoming salt from the same cause in part, if not altogether. It is worthy of consideration that the region, though there is no active crater in its immediate vicinity, is nevertheless volcanic, and to the west has the active cone Arequipa, at the distance from the lake that the Lejah east of Tiberias is from the Dead Sea. In this place (the Lejah) there are extinct craters, as Dr. Porter has shown.* Some violent upheaval or disturbing force is evident from the "steepness of the general dip and the contortions of the limestones in the neighbourhood of the sea." Another interesting fact is mentioned by Mr. Hogg, in a paper on the geology of Mount Sinai, on no less an authority than that of Humboldt, -that specimens of a shell, porites elongata (of Lamarck), have been obtained from the Dead Sea,- "interesting, because this species is not in the Mediterranean, but only in the Red Sea, which, according to Valenciennes, has but few organisms in it which are found in the Mediterranean.”+

*So also with another lake referred to by Lieutenant Maury,Lake Tadjura. "There are connected with it the remains of a channel by which the water ran into the sea; but the surface of the lake is now five hundred feet below the sea-level, and it is salting up." From some cause immediately local, as in Lake Titicaca, Tadjura, and others, their ancient communication with the sea has been, perhaps, suddenly and violently cut off. Why may not the Dead Sea be added to the list?

† Jamieson's Edin. Journal, vol. xlix. p. 290, cited in an interesting work by Captain Wm. Allen, R.N., entitled, "The Dead Sea a