Dead Sea

Topic: Oceans: Hydrological Cycle, Relief of the Ocean Floor, Temperature and Salinity · NCERT: Class 11, Ch 12 "Water (Oceans)"

Meaning

The Dead Sea is a landlocked salt lake (a lake with no outlet to the sea) in the Jordan Rift Valley. It lies between Jordan to the east and Israel and the West Bank to the west. Its shore is the lowest land on Earth, at more than 430 m below sea level. NCERT gives its salinity as 238‰.

It matters for two reasons. It is a classic example of how heavy evaporation makes water extremely salty. It is also a case study of a lake shrinking because people divert its water.

Explanation

How the Dead Sea becomes so salty

• Water comes in, but cannot flow out.
• Almost all its water comes from the Jordan River, which flows in from the north [2].

• The lake has no outlet to the sea, so water leaves only by evaporation.

• Evaporation leaves the salt behind.

• The hot, dry climate evaporates water quickly.
• Only the water escapes into the air, and the salt stays in the lake.

• Over a long time, salt builds up to levels far above the ocean average of about 35‰.

• Its basin lies very low.

• The lake sits in the Jordan Rift Valley. A rift valley is a long, deep valley formed where a block of the Earth's crust has sunk between faults (cracks in the crust).
• That is why its shore is the lowest land point on Earth.

Why people float on it

• More salt makes water denser.
• Salinity and temperature together decide the density of water (how heavy a given volume of it is).
• The Dead Sea's water is so salty that it is much denser than the human body.
• So a person floats easily without swimming.

Why its level is falling

• Less water flows in.

• Since the 1960s, Israel and Jordan have diverted much of the Jordan River's water for farms and towns [2].

• Water is taken out for minerals.

• Lake water is pumped into evaporation ponds (shallow pools where the sun dries the water so minerals can be collected) [2][3].

• Result: the level is falling faster.

• The level fell by about 0.7 m a year in the 1970s–1980s [2].

• In recent decades it has fallen by about 1.2 m a year [2].

• Effects on the lake:

• The lake is getting saltier, especially near the surface.
• Salt is coming out of the water and settling on the lake floor as a crust [2].

The salinity figures do not agree

• NCERT figure: 238‰. This puts the Dead Sea second, after Lake Van (330‰) and ahead of the Great Salt Lake (220‰).
• Modern sources: usually give the Dead Sea about 340‰. On that figure, the Dead Sea, not Lake Van, is the saltiest of the three.
• Exam rule: use NCERT's order in NCERT-based questions. In open or analytical answers, mention the disagreement.

Where it occurs

• World:
• Dead Sea: in the Jordan Rift Valley in West Asia, between Jordan to the east and Israel and the West Bank to the west. The Jordan River feeds it from the north [2].

• Similar very salty water bodies in the NCERT box:

  • Lake Van in Turkey (330‰)
  • Great Salt Lake in Utah, USA (220‰)

• India: India has no salt lake at the Dead Sea's level. The closest Indian links are:

• Rann of Kutch, Gujarat: very salty coastal water and salt flats that are worked for salt. Shallow hypersaline lagoons (lagoons saltier than normal seawater) in hot, dry areas like this can reach about 70‰.
• Chilika (Odisha) and Pulicat (Andhra Pradesh–Tamil Nadu border): brackish-water lagoons. Like the Dead Sea, they depend on the right amount of fresh water flowing in.

Don't confuse with

• Lake Van (Turkey): NCERT ranks it saltiest at 330‰. In fact it is the world's largest soda lake (rich in sodium carbonate, not common salt). Its salinity is only about 23 g per litre, its pH is about 10 (strongly alkaline), and its main salts are sodium carbonate and sodium sulphate [4]. The Dead Sea is a salt lake, not a soda lake.
• Great Salt Lake (Utah, USA): also a landlocked salt lake, but third in NCERT's list at 220‰, below the Dead Sea's 238‰.
• Red Sea: despite the word "Sea" in both names, the Red Sea is a real arm of the ocean that is salty because of high evaporation. The Dead Sea is a landlocked lake with no link to the ocean.
• Brackish water (for example, the Baltic Sea or Chilika): the opposite extreme. Its upper limit is 24.7‰ (NCERT), less salty than seawater. The Dead Sea is many times saltier than seawater.

Prelims Hooks

• Dead Sea: lowest land point on Earth, with its shore more than 430 m below sea level. It lies in the Jordan Rift Valley, between Jordan and Israel/West Bank.
• NCERT order of saltiest water bodies: Lake Van (330‰) > Dead Sea (238‰) > Great Salt Lake (220‰).
• Trap: modern sources give the Dead Sea about 340‰, which would make it saltier than Lake Van. Use NCERT's order for NCERT-based questions.
• Feeder river: almost all its water comes from the Jordan River, which flows in from the north [2].
• Level fall: about 0.7 m a year in the 1970s–1980s and about 1.2 m a year in recent decades [2].
• Why people float: very high salinity → very dense water → the body floats.

Mains Points

• Water diversion and lake decline (GS-III, environment):
• Since the 1960s, Jordan River water has been diverted for farms and towns, so the Dead Sea now falls about 1.2 m a year [2].
• Pumping into evaporation ponds for minerals speeds up the loss [3].

• The lake is getting saltier, and salt is settling on the lake floor as a crust [2].

• Lessons for India (GS-III):

• Lagoons such as Chilika and Pulicat need a balance between fresh water from rivers and the sea mouth.

• When river flow falls, seawater moves further inland. This salinity ingress harms farms and drinking water.

• Physical geography (GS-I):

• The Dead Sea shows how salinity rises when evaporation is high and no outlet exists.
• It also shows how salinity sets density, which explains why people float on it.

Related concepts

• Salinity
• Brackish water
• Factors affecting salinity
• Lake Van

Read more

• Salinity: meaning, factors and the extremes