The Dead Sea is an integral part of the geologic structure of the Middle East, and there are many unique and interesting aspects of the Dead Sea that make it significant geologically. These have been outlined below according to the specific geologic characteristics of the Dead Sea region.
Dead Sea Transform Fault Zone:
This fault which runs through the Dead Sea region is a left-lateral strike-slip fault, which is a fault where movement is mostly horizontal and parallel to the strike. When a strike-slip fault is left-lateral, such as in the case of the Dead Sea fault, visible features such as hills and streams are displaced to the left. This is evident in many areas of the Dead Sea region. The slip rate, or rate of movement along the fault ranges from 1-10 mm annually. The fault connects the diverging plate boundary in the Red Sea to the Taurus converging plate boundary in the north, between Turkey and Syria, and runs along the Araba Valley, a 160 km stretch from the Dead Sea to the Gulf of Aqaba. The Dead Sea fault has been the source of several large historical earthquakes, but has not produced many recently, with the last major one being the 1995 earthquake that hit the Gulf of Aqaba and measured 7.3 on the Richter scale. In fact, there is little microseismicity along the fault except at the Dead Sea and Gulf of Aqaba, where the fault forms into complex pull-apart basin fault systems. The Dead Sea itself is surrounded by faults, which border its eastern, western, and southern shorelines. On the western shore there is a fault zone that runs parallel to the main fault, along which there are horsts and grabens. Geologists predict that given the slip rate, the Dead Sea fault running through the Araba Valley should trigger 7.0 earthquakes every 200 years.
Image of the displaced wall showing left-lateral slip at Talith Castle. Source: Geophysical Journal International
Dead Sea Minerals:
The Dead Sea is incredibly rich in minerals. In fact, it is not simply the most salinated water body, but also is the most mineral-rich large water body in the world! As mentioned previously, as a result of having no outlet, existing minerals and those flowing into the sea from the Jordan River are trapped in the Dead Sea, having nowhere else to go. With evaporation, the dissolved minerals are left behind, leading to high concentrations of minerals in the sea, such as sodium, potassium, calcium, bromine, and magnesium salts. Erosion of the surrounding horizontal strata also contributes to the high concentration of minerals. Also, along the shoreline there are thermo-mineral springs containing many minerals, predominantly sulphur. There are 21 minerals in the Dead Sea, twelve of which are not found in any other water body. Rock types that are found in the area include granite, other igneous rocks, acidic silicates, gravel, clay, sandstone, rock salt, and alluvial deposits.
Geological cross-section in the Hever south site. Source: Geological Survey of Israel
Geological Resources at the Dead Sea:
The fact that the Dead Sea is so rich in minerals makes it a desirable and profitable location for mineral extraction. While the northern basin has remained mostly untouched by industry and has been primarily set aside for tourist use, the southern basin, which is shallow and extremely rich in minerals, is being tapped for its mineral resources. The two major companies involved in mineral extraction at the southern basin are the Dead Sea Works and the Arab Potash Company. The Dead Sea Works is the world's fourth largest producer and supplier of potash products, as well as other chemical products such as magnesium chloride, industrial salts, de-icers, bath salts and table salts, and raw materials for the cosmetics industry. They use a very unique method to take potash and other minerals from the Dead Sea. Rather than mining them, Dead Sea Works harnesses the solar energy that evaporates the water in the Dead Sea by constructing evaporation ponds, two metre deep ponds that criss-cross the mining area to aide in extracting pure potash and other minerals. However, despite the great profit being generated from mineral extraction in the Dead Sea, some fear that potash production will upset the environmental stability of the area by emitting dust, carbon dioxide, sulphur dioxide, and carbon monoxide into the air, as well as by producing ozone-depleting methyl-bromide.
Aerial view of the Dead Sea Works production plant and evaporation ponds. Source: Dead Sea Works
Dead Sea Sinkholes:
The shorelines of the Dead Sea are dotted with hundreds of sinkholes clustered at twenty sites surrounding the sea. They are a more recent geological phenomenon in the region, first appearing in the 1980's. Their dimensions reach up to 10 metres in depth with a diameter of 25 metres. The sinkholes are distributed with a trend similar to the tectonic features of the Dead Sea rift. An important condition that contributes to the formation of sinkholes on the surface is the presence of a salt layer. Geologists with the Geological Survey of Israel believe that the Dead Sea sinkholes were formed when, as a result of the continuing drop in the water level of the Dead Sea, subsurface salt layers came into contact with groundwater, flowing through joints in the salt layer and dissolving the salt, leading to caverns which eventually result in the collapse of the overlain strata creating sinkholes on the surface. Another possibility the geologists put forth is that the decrease in the Dead Sea's water level led to a drop in hydrostatic pressure within pre-existing cavities, causing them to collapse. Sinkholes present a serious problem to the Dead Sea region, threatening resorts, hotels, as well as the potash and mineral plants on the southern basin.
Sinkhole on alluvial sediments at the Hever south site. Source: Geological Survey of Israel
Dead Sea Graben and Geological History:
As with many things in history, geological or otherwise, the Dead Sea didn't just happen over night. It took several million years before it formed into its current state. It likely began its formation millions of years ago when activity at the boundary between the Sinai subplate and the Arabian plate caused major upheavals of the Mediterranean seabed, which covered most of modern-day Israel at the time. Between these two plates a block of crust sank, forming a graben. As the Mediterranean evaporated some water was retained in the graben, creating a series of lakes in the graben that disappeared and reappeared as a result of climatic changes in the area. The last of these lakes, Lake Lisan, which stretched from the northern portion of the Araba Valley to the Sea of Galilee, eventually dried up 15 000 years ago leaving behind the current Dead Sea.
Aerial view of the northern end of the Dead Sea. Source: BiblePlaces.com