Dead Sea Sinkholes
February 02, 2013
Photographer: Menashe Davidson
Summary Author: Menashe Davidson
Sinkholes are depressions or holes in the land surface caused by karst processes that generally takes place slowly but can open suddenly, drawing in everything above. These craters, abundant on the western side of the Dead Sea (near Ein Gedi, Israel), stem from a severe water shortage, magnified in recent years by the reduction in the amount of water flowing in the Sea's main tributary, the Jordan River. The Dead Sea's water level has declined over 80 ft (25 m) from 1939 to 1999 -- it's now shrunk by about one third of its mid-1960s volume.
These swallow holes or sinkholes form when a subterranean salt layer, buried about 65-230 ft (20–70 m) beneath the surface that once bordered the sea, is dissolved by underground fresh water. As the sea level drops, groundwater from adjacent aquifers flows in to replace the retreating seawater. This fresh water meets a layer of rocky salts and dissolves it, creating an underground void. The surface usually stays intact until there's no longer sufficient support, when a sudden collapse can happen.
The above picture was taken on Jan 13, 2013, from a hill near the town of Draga (6 mi or 10 km north of Ein Gedi). Sinkholes began appearing here in the 1970s. Note the lines showing retreating water levels during the past several decades. The smaller picture was taken on the same day but in the Ein Gedi date palm plantation, at a higher elevation than the area in the top photo. Note that sinkholes are bigger and deeper here and walls are falling down.
The number of sinkholes in the western bank of the Dead Sea is estimated to be around 2,500 based on an aerial photo survey in 2008. They're observed along a narrow strip approximately 37 mi (60 km) long and about 0.6 mi (1 km) wide. They spread roughly parallel to the fault system associated with the Dead Sea Transform rift valley. Sinkholes have been forming faster here in the last few years. There are now estimated to be about 150 each year. These sinkholes are a dramatic danger to human life and to new development in the region. Work is being done to better identify their signatures and to stop their quickening spread.
Photo details: Top - Camera Model: NIKON D80; Focal Length: 40.0mm (35mm equivalent: 60mm); Aperture: f/16.0; Exposure Time: 0.0063 s (1/160); ISO equiv: 100; Software: Ver.1.00. Inset - Same except: Focal Length: 18.0mm (35mm equivalent: 27mm); Aperture: f/13.0; Exposure Time: 0.0063 s (1/160).