Physical History of the Dead Sea, the Jordan Valley and Palestine

Abstract

PROF. E. HULL, LL.D., F.R.S., delivered an interesting lecture on the above subject on March 2, in the Theatre of the Royal Dublin Society's premises, Kildare Street. Prof. Hull said:—“There is no country which possesses for us an interest equal to that which I have to treat of this evening. Its religious and historical associations stand alone amongst those of all nations, and will ever maintain in the history of the world an undying import. But while this is true as regards the religious and social aspects of Palestine, I hope to show that in its physical aspect it possesses points of interest which render it unique amongst all countries, and which have attracted to it the attention of naturalists during a lengthened period down to the present day. Probably no country has been so often described. Its physical features have attracted the attention of observers of natural pheinmena from Strabo downwards to the recent admirable work of M. Lartet and the Due de Luynes, to which I am largely indebted. In more recent times we have the observations of Humboldt, of the late Dr. Hitchcock, of Lieut. Lynch of the United States Navy, who carried out a systematic series of soundings over the bed of the Dead Sea, and more recently of the Rev. Dr. Tristram, of Prof. Roth, Burkhardt, and others, including the Survey made by the officers of the Royal Engineer. It is curious however that the remarkable physical phenomenon which renders the Holy Land unique among all countries (regarded in its physical aspect) was not discovered till the year 1836–37, when Heinrich Von Schubert and Prof. Roth determined by barometric observations that the surface of the Dead Sea lies no less than 1300 feet below the level of the Mediterranean, a fact not suspected by previous observers. It is the deep depression of the Jordan Valley, deeper by far than any river valley elsewhere, which is the key to the physical history of the whole country; and in endeavouring to trace out its origin I shall reproduce in as general a manner as I can the successive phases through which the region bordering the Meditsrranean, and extending eastwards towards the Euphrates and southwards to the Dead Sea, has passed. The fundamental basis of the geological formation of Palestine is the gneissic granite, of Archsean age and metamorphic origin, which rises into the mountains of Idumea, and is the rock from which the huge monoliths of Egypt have been hewn, snob as Cleopatra's Needle' the obelisk of Luxor, and the ealumns which adorn the Piazza of Venice. This foondation rock formed part of a continental area down to the Carboniferous period, when it was sob- merged, and a great sandstone formation was spread over it known as “the Nobian sandstone.” After another interval of time the sandstone itself was overspread by limestone deposits of Cretaceons and Tertiary age, deposited over the floor of the ancient sea, and down to the close of the Eocene period the waters of the sea overspread the greater portions of Asia Minor, Paletinc, and the adjoining districts of the Asiatic and African continents. The first appearance of Palestine and the adjoining districts as a land snrface dates from the succeeding Miocene period, when the bed of the sea was npraised into dry land, and at the same period a great fissure corresponding with the line of the Jordan valley svas prodnced. Along this fissure, which has been traced frono the Lebanon sonthwards towards the Gulf of Akaba —the strata on the eastern (or Moabite) side have been relatively elevated those on the western relatively depressed;—so that the strata on the opposite sides of the Jordan valley and the Dead Sea do not correspond with each other. This great fissure is the key to the physical formation of the whole region, because it gave origin to a river which once flowed dosvn from the mountains of Lebanon—southwards through the Gorge of Arabah (discovered by Bnrkhardt)—into the Red Sea in a remarkably straight line rnnning north and sonth for a distance of over 250 miles. This is now the Jordan. The depression of the valley continuing through the succeeding Pliocene epoch, the district of the Ghor and the Jordan valley was conveyed into a lake, which Prof. Hull considered ultimately extended from the southern end of the Dead Sea, north. wards nearly to the Lake Merom, and included the Sea of Galilee. This lake would then have had a length of 160 miles and an average breadth of ten miles. During “the Pluvial period,” which succeeded “the Glacial,” the waters probably reached their maximum elevation, and contisued to flow southwards through the Gorge of Arabah and the Gulf of Akaba into the Red Sea; but from the increasing dryness of the climate they gradually decreased, and the surface of the lake became contracted, and ultimately reduced to its existing limits. During this lowering of the surface, the remarkable terraces noticed by most travellers were formed. Dr. Tristram has taken the barometric level of several of these above the Dead Sea. They range up to 750 feet, and even higher. They appear to be undoubtedly old lake margins, and indicate the successive levels at which the lake stood. The 750-foot terrace very closely corresponds to the summit-level of the Gorge of Arabah. When the waters were reduced so low as not to pass through the Gorge of Arabah, they became brackish, and ultimately salt—the salinity increasing as the area became diminished. All lakes not having an outlet become saline; and the contrast of the waters of the Sea of Galilee and those of the Dead Sea form a striking illustration of the law just stated. The saline ingredients in the surface waters of the Dead Sea are 24.57 lbs. in 100lbs. of the water, while that of the Atlantic only contains 6 lbs. in the same quantity. The Dead Sea water is therefore over four times as strongly impregnated with salts as that of the ocean, and in the deeper waters the salinity amounts to saturation, as saline deposits are forming over the floor of the Dsad Sea. This remarkable inland sea had assumed somewhat of its present contracted dimensions, and was known as “the Salt Sea” as far back as the time of the Patriarch Abraham. Near its borders stood the doomed cities of Sodom and Gomorrah—not beneath its waters, as was often supposed—but near its upper margin. With the call of Abraham the political and religious history of Palestine begins, and the narrative of the physical historian ends.