Synopsis

The two large lakes named Samra and Lisan existed in the Dead Sea graben from 350,000 to 120,000B.p. and 60,000 to 12,000B.p. Their sediments tentatively are correlated with the European Riss and Würm glacial epochs. Thick marls are the chief sediments in the deep water north basin. Rocksalt deposition dominated within the troughs of both north and south basins throughout the intervening Riss-Würm Interglacial stage. Lithology of Lisan Formation (Würm) in that basin indicates rapid and extreme fluctuations of level. Eight major climatic cycles are recorded during Würm glaciation when the level fluctuated between -180 m m.s.l. and probably lower than -400 m m.s.l. Rocksalt was deposited within both basins during warm dry phases of the Lisan stage. At the present state of knowledge no specific tectonic or volcanic activities can be tied to these climatic events. The Holocene Period was similar lithologically to that of the Lisan Formation and transition between them was gradual. Primarily the difference between the two was change in relative time span between alternate wet and dry phases. Dry phases of Holocene gradually became longer while wet ones with Dead Sea transgressions became shorter. Tectonic regimes during the first part—the Natufian age to Early Bronze III, 12,000 to 4400 B.P.—seem to have been milder than later ones, end of Early Bronze III to the present. The severe earthquake that destroyed Sodom and Gomorrah in 4350 B.P. was followed by a 300-year long subphase of gradually warming climate that became extremely dry during the latter part of the Intermediate Bronze age. Climatic Wet Phase III began about 3900 B.P. It was the longest, about 800 years, and most intense wet phase of Holocene and it probably was associated with volcanism. No abrupt cultural or demographic changes are known during transition from Epi-Paleolithic or Geometric Kebaran from the last glacial phase of the Pleistocene Period through Natufian to the early part of Holocene Pre-Pottery Neolithic. The reason for this stability is not clear especially because average temperatures of global oceans during the latest Pleistocene glaciation were appreciably lower than those during Early Holocene (Emiliani, 1978).

Environmental Data for Specific Sites within the Dead Sea Region

Discussion of Early Bronze cultural history at Bab edh-Dhr’a and Numeira sites east of the Lisan Peninsula and on the northeast flank of the Dead Sea south basin is guided mostly by Rast (1987) and Rast and Schaub (1974, 1978, 1980, and 1981). This epoch was divided by Rast and Schaub into two sections according to traditional archaeological chronology. The first section is the urban period of Bab edh-Dhr'a (4890 to 4340 B.P.) including Early Bronze I, II, and III. The second is the posturban period (4340 to 4190 B.P.), Early Bronze IV or the Intermediate Bronze age according to Kochavi (1967), Kenyon (1979), Gophna (1992), and R. Amiran and Kochavi (1985) as well as Middle Bronze I according to Albright (1962). Although no prominent cultural hiatus separates these two sections, the transition between them contains abundant indications of extensive destruction and fire events brought about by natural disasters such as earthquakes. Donahue (1980, 1981) considered that not just one but two severe earthquakes occurred, one about 4400 B.P. and the other 4350 B.P. Numeira was totally and finally abandoned after the second earthquake, whereas Bab edh-Dhr’a was reinhabited apparently as a result of conquest by seminomadic people of the same cultural background. This second earthquake probably was the one by which Sodom and Gomorrah were totally destroyed. Abrupt cultural changes also were recorded in the southeast Negev at Uvda Valley during transition from Early Bronze III to Middle Bronze I about 4300 B.P. These changes were from a gradually increasing population within a walled city having a life-style based on a combination of agriculture and animal husbandry into a more nomadic community with unfortified houses and primarily a grazing economy. According to Avner (1990, p. 133) “Subsequent to a brief climatic crisis at the end of the third millennium BC the climate improved, allowing the new culture to blossom in the desert.” This climatic crisis could have been extreme dryness. By the middle of the Intermediate Bronze age at about 4200 B.P., Bab edh-Dhr’a, the last Early Bronze site to survive was totally abandoned and the Dead Sea south basin remained basically unsettled for more than 1,500 years until Hellenistic time.

Introduction

The thrilling biblical saga of Sodom and Gomorrah leaves a deep impression on the spirit of its readers, especially the young. Basic ethical concepts such as right and wrong were dramatically portrayed by that simple and cruel, yet humane, story. Memories of even more ancient disastrous geological events apparently were interwoven into the saga. A geologist cannot remain indifferent when investigating the Dead Sea region and observing stratigraphical and structural evidence of past and continuing similar events. Forceful dynamics indicated by vertically tilted beds of rocksalt layers that have penetrated upward through the ground and by later processes that have shaped some beds into pillars trigger association with the ancient story. Such features are abundant and clearly recognizable along the foot of the diapiric structure of Mount Sedom (Arabic Jebel Usdum). A gas blowout during the drilling of a water well near the Amazyahu fault in 1957 only by good luck failed to produce a gush of fire and smoke. Such an event could have happened in ancient times as a natural result of faulting. Knowledge of the regional geological background permits translation of the biblical descriptions into scientific terms, which suggests that the sagas of Sodom, Gomorrah, and Jericho described real events that occurred during ancient times before much was known about geology. Thirty-five years of the authors' professional experience in the Dead Sea region encompasses many geological aspects of the basin: deep and shallow stratigraphy, structural history, seismology, sedimentological processes, and the physical and chemical properties of the water. Archaeological studies in the region are reviewed. Although most of these studies are applicable to exploration for oil and gas or extraction of salts from brines, their results illuminate the role of changing paleogeography and paleolimnology on human environments. Climate changes and lake-level fluctuations have occurred since Mid-Pleistocene, especially during the past 50,000 years. Studies of sediments from shallow core holes delimit coastal areas that when exposed by drops in the level of the Dead Sea, quickly developed soils that could be used for agriculture.

Climate Inferred from Geology and Archaeology

Early climatic interpretations for the Lisan and later formations (Late Pleistocene and Holocene—Neev and Emery, 1967, figs. 16, 17) were supported and updated by information from additional coreholes. Although most new and old coreholes bottomed at relatively shallow depths, 20 to 30 m, four of them reached greater depths, 74, 80, 161, and 285 m beneath the 1960 floor of the Dead Sea south basin. The sequences consist of alternating layers of marl and rocksalt. Most marls were deposited from dilute brine during high lake levels and contain alternating laminae of chemical deposits of white aragonite, gray gypsum, and fine-grained detritus consisting of yellowish, brown, green, or dark gray carbonates, quartz, and clay. The detrital fraction is coarser and more dominant toward the deltas, especially near Amazyahu escarpment in the south. Rocksalt layers indicate deposition from more concentrated brine when the levels dropped to about -400 m m.s.l. Lower elevations could have been reached when the sea continued to shrink and when the runoff-to-evaporation ratio diminished, bringing the south basin to complete dessication. As neither the geochemical nature (ionic ratios) of the brines nor the physiography of the terminal water body has changed at least since Late Pleistocene or Lisan Lake time (Katz, Kolodny, and Nissenbaum, 1977), it is probable that through the past 60,000 years rocksalt was precipitated only when the water surface was at or below the critical level of -400 m m.s.l. Gamma-ray logs for some of the new coreholes provide more objective and precise depths of marl and rocksalt layers than do actual samples of sediments. Content of radiogenic minerals in the rocksalt is negligible compared with that in the marl; thus, these layers identify changing physical environments and climates as well as correlating stratigraphy. On gamma-ray logs the peaks or highest intensities of positive anomalies indicate that marl layers or wet climatic subphases and their thicknesses on the logs are proportional to their duration. Presence of negative anomalies or very low levels of gamma radiation show both the existence and thickness of rocksalt layers that denote dry climatic phases.

General Geology

The Dead Sea occupies a linear down-dropped region between two roughly parallel faults along the central segment of the major northsouth- trending crustal rift that extends about 1,100 km from the Red Sea through the Gulf of Elath to Turkey. This rift or geosuture separates the Arabian crustal sub-plate on the east from the Sinai one on the west. An origin as early as Precambrian is possible (Bender, 1974; Zilberfarb, 1978). Crystalline crust along the north-south trough of the Sinai sub-plate is about 40 km thick in contrast with a thickness of half as much above ridges along both flanks (Ginsburg and Gvirtzman, 1979). Toward the north the ridges appear to converge (Neev, Greenfield, and Hall, 1985). Since the Miocene period the Arabian plate has moved north about 105 km relative to the Sinai plate. This sort of crustal movement along either side of a rift is termed strike-slip faulting. One result of it was the opening of the Red Sea relative to the Gulf of Suez. The Dead Sea graben, a down-dropped block between two roughly parallel faults, occupies the central segment of the long crustal rift. The boundary between these is rather sharp along the east shore of the sea (Frieslander and Ben-Avraham, 1989). Actual post-Miocene movement was along not just a single major fault but was distributed among numerous sub-parallel faults that form a 100-km-wide belt in which movements were transferred from one fault to another (Eyal et al., 1981; Gilat and Honigstein, 1981). Recent movements have occurred along the south segment of the north-south-trending Arava fault south of the Amazyahu transverse fault (Zak and Freund, 1966). These strike-slip movements probably did not continue after Miocene along the main East fault of the Dead Sea, which is the north extension of the Arava wrench fault. In contrast, recent movements have been present along the north-northeast- trending Jordan or Dead Sea fault (Ben-Menahem et al., 1977, fig. 1). The movements extend south from east of Jericho in the north along the base of the west submarine slope of the sea and the elongate salt diapir of Mount Sedom as far as the Amazyahu fault in the south.

Coordination of Biblical and Scientific Information

Much knowledge of biblical events is from narratives of ancient oral tradition that justify analysis and respect because they may reflect genuine and unique historical information. The problems involved with such study are demonstrated by descriptions of three different events related in the stories of Sodom and Gomorrah, Jericho, and the narrative of Noah’s Flood. All three are associated with two processes: geologictectonic activity of vast areas with resulting submergence of soils or destruction of settlements. The first two tell about tectonism within the Dead Sea region at south basin and Jericho where many sites are identifiable. The Sodom and Gomorrah event could have happened only at the end of Early Bronze III, as implied from archaeological chronology and outline of the biblical story. The same could be true also for Jericho if not for a significant difference in chronology of the two stories. Expulsion of rebellious Asiatic tribes from Egypt is recorded in Egyptian history to have taken place during the 13th century B.C. At least some of these seminomadic ex-slaves reportedly invaded Canaan from the east near the end of the Late Bronze age (Kenyon, 1979, pp. 205, 210) and conquered Hazor and other cities. No archaeological data were found to indicate the existence of defense walls or of a large densely populated city at Jericho during Late Bronze so the question of conquest remains open. Invasions by nomadic tribes from the east and conquests of Jericho had occurred earlier—for example, 1,000 years prior to the end of Early Bronze III (Kenyon, 1979, p. 91). Evidence for collapse of Jericho’s defense walls during earthquakes and for fires during conquests in late Early Bronze III were found by archaeologists. The importance of the capture of Jericho after the Exodus was so great for Judaic history that the story may have been enhanced by inclusion of information from earlier oral traditions of the Sodom and Gomorrah earthquake.

Sodom and Gomorrah Event

About 7800 B.P. after the first effects of warmings and droughts associated with the Atlantic Interval, many people of the Mideast moved into river floodplains where suitable agricultural soils and freshwater were available. Prominent examples are in Mesopotamia, the Nile Valley, and along the Jordan-Dead Sea rift. The extremely dry climates occasionally improved because of small fluctuations within the Chalcolithic and a larger one during Early Bronze II, when there was a 250-year wet interval. These climatic changes explain the settling, flourishing, and abandonment by the Ghassulians about 6000 B.C. and of the city of Arad, 4900 to 4650 B.P. at the fringe of the desert (R. Amiran and Gophna, 1989, n. 18; D. Amiran, 1991; Gilead, 1993). During the Early Bronze ages overall the climatic conditions in the Dead Sea region were not appreciably different from those at present, as attested by fossil flora found in excavations at Bab edh-Dhr’a and Numeira (McCreery, 1980). High yields of agriculture in fertile irrigated areas were an incentive to settle in the Plain of Sodom. This settling gradually intensified within the fertile plains of the Jordan-Dead Sea region as well as in Canaan through Early Bronze I and II but weakened toward the end of Early Bronze III. This is indicated by the pattern of settlements that developed from individual villages to city-states with satellite villages—mostly because of economic and social motivations— which later were changed into fortified communities (Esse, 1989). A gradual increase in fortification of Early Bronze settlements along the Dead Sea and Jordan Valley basins and the position of some of them along the narrow elevated step-faulted strip of the east foothills (Zori, 1962;Ben-Arieh, 1965; Rast, 1987 and personal communication, 1989) indicate increased need for defense by settlers against raids and invasions. These evidences of stress probably resulted from gradual climatic drying and warming. Investments in defense facilities were worthwhile if increased productivity was tempting enough. Such areas could have been found not only along the east foothills but also at the foot of the Amazyahu fault escarpment and in the delta of Nahal Zohar north of Mount Sedom if fresh or slightly brackish water was available there during the Early Bronze age.