Lake Assal (Djibouti)
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Lake Assal ( , lit. “Honey Lake”) is a
crater lake Crater Lake ( Klamath: ) is a volcanic crater lake in south-central Oregon in the Western United States. It is the main feature of Crater Lake National Park and is a tourist attraction for its deep blue color and water clarity. T ...
in central-western
Djibouti Djibouti, officially the Republic of Djibouti, is a country in the Horn of Africa, bordered by Somalia to the south, Ethiopia to the southwest, Eritrea in the north, and the Red Sea and the Gulf of Aden to the east. The country has an area ...
. It is located at the western end of Gulf of Tadjoura between Arta Region, and Tadjoura Region, touching Dikhil Region, at the top of the
Great Rift Valley The Great Rift Valley () is a series of contiguous geographic depressions, approximately 6,000 or in total length, the definition varying between sources, that runs from the southern Turkish Hatay Province in Asia, through the Red Sea, to Moz ...
, some west of
Djibouti city Djibouti (also called Djibouti City and Jibuti in early Western texts) is the capital city of the Djibouti, Republic of Djibouti. It is located in the coastal Djibouti Region on the Gulf of Tadjoura. Djibouti has a population of around 780,000 ...
. Lake Assal is a saline lake that lies below
sea level Mean sea level (MSL, often shortened to sea level) is an mean, average surface level of one or more among Earth's coastal Body of water, bodies of water from which heights such as elevation may be measured. The global MSL is a type of vertical ...
in the Afar Triangle, making it the lowest point on land in
Africa Africa is the world's second-largest and second-most populous continent after Asia. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 20% of Earth's land area and 6% of its total surfac ...
and the third-lowest point on Earth after the
Sea of Galilee The Sea of Galilee (, Judeo-Aramaic languages, Judeo-Aramaic: יַמּא דטבריא, גִּנֵּיסַר, ), also called Lake Tiberias, Genezareth Lake or Kinneret, is a freshwater lake in Israel. It is the lowest freshwater lake on Earth ...
and the
Dead Sea The Dead Sea (; or ; ), also known by #Names, other names, is a landlocked salt lake bordered by Jordan to the east, the Israeli-occupied West Bank to the west and Israel to the southwest. It lies in the endorheic basin of the Jordan Rift Valle ...
. No outflow occurs from the lake, and due to high evaporation, the salinity level of its waters is 10 times that of the sea, making it the fifth most saline body of water in the world, behind Garabogazköl, Lake Retba, Gaet'ale Pond and
Lake Elton Lake Elton (; ) is a salt lake in Volgograd Oblast, Russia, near the Kazakhstan-Russia border, border with Kazakhstan. It has an area of and is normally about deep, and about in spring. Its surface is below sea level. The lake's name originat ...
. The salt in the lake is exploited under four concessions awarded in 2002 at the southeast end of the lake; the major share of production (nearly 80%) is held by Société d’Exploitation du Lac and Société d’Exploitation du Salt Investment S.A de Djibouti. The lake is a protected zone under Djibouti's National Environmental Action Plan of 2000. However, the law does not define the boundary limits of the lake. Since the exploitation of the salt from the lake was uncontrolled, the Plan has emphasized the need for managing the exploitation to avoid negative impact on the lake environment. The Government of Djibouti has initiated a proposal with
UNESCO The United Nations Educational, Scientific and Cultural Organization (UNESCO ) is a List of specialized agencies of the United Nations, specialized agency of the United Nations (UN) with the aim of promoting world peace and International secur ...
to declare the Lake Assal zone and the Ardoukoba volcano as a
World Heritage Site World Heritage Sites are landmarks and areas with legal protection under an treaty, international treaty administered by UNESCO for having cultural, historical, or scientific significance. The sites are judged to contain "cultural and natural ...
.


Geography

Lake Assal is located in the middle of
Djibouti Djibouti, officially the Republic of Djibouti, is a country in the Horn of Africa, bordered by Somalia to the south, Ethiopia to the southwest, Eritrea in the north, and the Red Sea and the Gulf of Aden to the east. The country has an area ...
, in a closed depression at the northern end of the
Great Rift Valley The Great Rift Valley () is a series of contiguous geographic depressions, approximately 6,000 or in total length, the definition varying between sources, that runs from the southern Turkish Hatay Province in Asia, through the Red Sea, to Moz ...
. Situated in the
Danakil Desert The Danakil Desert (or Afar Desert) is a desert in northeast Ethiopia, southern Eritrea, and northwestern Djibouti. Situated in the Afar Triangle, it stretches across of Desert climate, arid terrain. It is inhabited by a few Afar people, Afar, w ...
, it is bounded by hills on the western region. The lake lies at an elevation of below sea level, making it the lowest point of Africa. The lake is characterized by two parts. The dry part of the lake, resulting from evaporation of the lake waters, is a white plain dry lake bed on the west/northwest side, which is a large expanse of salt. The second part is the highly saline water body. The watershed area of the lake is . Lake Assal, in an oval shape (length and width ), consists of two distinct parts; one is "crystallised salt surface" zone of and the other is the high saline brine area of . The crystallised salt zone extends to a depth of more than whose estimated resource is about 300 million
tonne The tonne ( or ; symbol: t) is a unit of mass equal to 1,000  kilograms. It is a non-SI unit accepted for use with SI. It is also referred to as a metric ton in the United States to distinguish it from the non-metric units of the s ...
s. The lake measures and has an area of liquid brine . The maximum depth is , whereas the mean depth is , which makes for a water volume of . Salt extraction by the Afar nomad tribes of camel drivers and Issas from Lake Assal's salt bank established the ancient caravan routes. These linked the lake with the mountains of Ethiopia for barter trading such items as
sorghum ''Sorghum bicolor'', commonly called sorghum () and also known as great millet, broomcorn, guinea corn, durra, imphee, jowar, or milo, is a species in the Poaceae, grass genus ''Sorghum (genus), Sorghum'' cultivated for its grain. The grain i ...
,
coal Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other Chemical element, elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. Coal i ...
, and other commodities. Salt was also bartered with South
Abyssinia Abyssinia (; also known as Abyssinie, Abissinia, Habessinien, or Al-Habash) was an ancient region in the Horn of Africa situated in the northern highlands of modern-day Ethiopia and Eritrea.Sven Rubenson, The survival of Ethiopian independence, ...
for items like
coffee Coffee is a beverage brewed from roasted, ground coffee beans. Darkly colored, bitter, and slightly acidic, coffee has a stimulating effect on humans, primarily due to its caffeine content, but decaffeinated coffee is also commercially a ...
,
ivory Ivory is a hard, white material from the tusks (traditionally from elephants) and Tooth, teeth of animals, that consists mainly of dentine, one of the physical structures of teeth and tusks. The chemical structure of the teeth and tusks of mamm ...
,
musk Musk is a class of aromatic substances commonly used as base notes in perfumery. They include glandular secretions from animals such as the musk deer, numerous plants emitting similar fragrances, and artificial substances with similar odors. ' ...
, and also (historically)
slaves Slavery is the ownership of a person as property, especially in regards to their labour. Slavery typically involves compulsory work, with the slave's location of work and residence dictated by the party that holds them in bondage. Enslavemen ...
. It was a source of wealth for the local tribes. Since 1990, industrial mining has been revived with development of roads linking with the Ghoubbet-el-Kharab bay by the Gulf of Tadjoura. The present road to Lake Assal is paved. The lake is from Djibouti city. It is also reported that the lake water level is receding as discerned from a mark on the banks of the lake from the present water level.


Climate

Located in the hot desert, the lake experiences summer temperatures as high as from May to September. Winter temperatures are not low at from October to April, with the coastal area experiencing rains. Strong, dry, hot winds are part of the environment. The monthly temperature variation is reported to be . During the summer season, the dry hot winds blow in two directions; namely, the Sabo winds from the southwest and the Khamsin winds from the northwest. Winds during October and April blow from the east, resulting in sporadic rains. Incidence of rainfall varies widely with January, April, May, and October recording rains. June to August are dry months. The mean annual rainfall in 1993 and 1997 was reported as and , respectively. The lowest rainfall of was recorded in 1996. Water temperature of the lake is reported to reach . However, when the wind velocity and evaporation are low, the temperature recorded was found to be for surface water and above at shallow depths of the lake. The lake water colour also changes over the duration of the day, at times appearing in fluorescent colours. In the middle of the day, the water looks unusual with its emerald color on the background of the snow-white shore.


Geology


History

The lake's geological history was studied by French geologists who compared it with the geology of Danakil lakes. According to this study, the lake originally contained freshwater overlying the mantle of
tufa Tufa is a variety of limestone formed when carbonate minerals precipitation (chemistry), precipitate out of water in ambient temperature, unheated rivers or lakes. hot spring, Geothermally heated hot springs sometimes produce similar (but less ...
s, marls and
calcrete Caliche () is a soil accumulation of soluble calcium carbonate at depth, where it precipitates and binds other materials—such as gravel, sand, clay, and silt. It occurs worldwide, in aridisol and mollisol soil orders—generally in arid or s ...
s. At an elevation of "''Melanoides tubeculatus'' ''(Melania tuberculata)'', ''Corbicula consobrina'' and ''Coelatura teretiuscula''" were reported "resting on the basalts". At the present bed level, the formations of marls with ''Ervilius purpura'' and ''cerithium sp.'', are indicative of gradual transformation over the centuries to saline water lake; the reason could be on account of
lagoon A lagoon is a shallow body of water separated from a larger body of water by a narrow landform, such as reefs, barrier islands, barrier peninsulas, or isthmuses. Lagoons are commonly divided into ''coastal lagoons'' (or ''barrier lagoons'') an ...
or marine intrusion.
Diatomite Diatomaceous earth ( ), also known as diatomite ( ), celite, or kieselguhr, is a naturally occurring, soft, siliceous sedimentary rock that can be crumbled into a fine white to off-white powder. It has a particle size ranging from more than 3 ...
with Navicula sp., kankar and nodules of
gypsum Gypsum is a soft sulfate mineral composed of calcium sulfate Hydrate, dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, drywall and blackboard or sidewalk ...
are discerned above the saline band. These bands are converted into gypsiferous layers succeeded by rock salt layers; these layers are seen up to the lake level.


Evolution

Two interpretations have been considered for the evolution of the present highly saline lake over the rock salt layers. One view, by Degoutin, is that the lake was flooded by the sea from the Ghoubbet el Kharâb, and the second view is by Dreyfuss who attributes it to the rise in sea level resulting in subterranean flows that were established to the lake from the sea. Another theory mooted by the explorer Major Harris is that the volcanic convulsions could have been the cause for severing the original link of the lake with the Gulf of Tadjoura. This has been further substantiated by the level difference of between the gulf and the lake level and if this depth is added to that of the lake, the level becomes which is the level that exists at the head of the Ghoubbet el Kharâb. The geological setup around Lake Assal consists of
volcanic A volcano is commonly defined as a vent or fissure in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often fo ...
basalt Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial ...
(3.4 – 1.0 Mya) formations. The nearest volcano to the lake, to its southeast, is the Ardoukôka, about away from the shores of the lake, which is marked on topographic map with (-) contour line. The southern part of the lake has sand patches whose width varies from about . There is hardly any arable land in the catchment. The important feature, from the point of view of the sources of water to the lake, is the Assal-Ghoubbet Rift, which is formed of recent basaltic formations (less than 1 Mya). Considering its geological evolution, the lake periphery now has crystal bands of salt and remarkable white gypsum above which are the distinct overlay of black basalt formations.


Hydrology

The watershed area of the lake measures . There is a residual
surface runoff Surface runoff (also known as overland flow or terrestrial runoff) is the unconfined flow of water over the ground surface, in contrast to ''channel runoff'' (or ''stream flow''). It occurs when excess rainwater, stormwater, meltwater, or other ...
of fresh water into the lake from the sporadic rainfall from ephemeral streams; there are no defined streams in the catchment. Runoff from rainfall is in the form of flash floods which may last from several hours up to two or three days depending on the intensity of rainfall. This flow pattern affects the lake by inundating the salt pans. Temporary water courses are identified in the southern part of the lake, while the Kalou River valley has a permanent water source. The main source of supply, however, is subsurface geothermal springs with aquifers linked to the sea water from the Ghoubbet El Kharab bay, which is to the southeast of the lake. The bay is part of the Gulf of Tadjoura, a western extension of the
Gulf of Aden The Gulf of Aden (; ) is a deepwater gulf of the Indian Ocean between Yemen to the north, the Arabian Sea to the east, Djibouti to the west, and the Guardafui Channel, the Socotra Archipelago, Puntland in Somalia and Somaliland to the south. ...
. The subterranean flow from the Gulf of Ghoubbet of the
Red Sea The Red Sea is a sea inlet of the Indian Ocean, lying between Africa and Asia. Its connection to the ocean is in the south, through the Bab-el-Mandeb Strait and the Gulf of Aden. To its north lie the Sinai Peninsula, the Gulf of Aqaba, and th ...
is through a fissured channel of length by gravity in basalt formations of mountains existing on the east side of Lake Assal, as spring. The spring that emerges into the lake has a salt content of 39 g/L which is close to that of seawater. The lake water fluctuates by about with subsurface inflow estimated at per second. The seawater-derived geothermal aquifer of the Asal-Fiale area is located in an exposed and actively extending continental rift that will become an arm of the Red Sea. In particular, Lake Assal is eligible as an experimental site to study the evolution of the deep hot brines of the Red Sea. Indeed, by observing the strontium composition of the Red Sea brines, it is easy to deduce how these salt waters found at the bottom of the Red Sea could have evolved in a similar way to Lake Assal, which ideally represents their compositional extreme.


Demographics

The lake precincts are inhabited by
Afar people The Afar (), also known as the Danakil, Adali and Odali, are a Cushitic peoples, Cushitic ethnic group inhabiting the Horn of Africa. They primarily live in the Afar Region of Ethiopia and in northern Djibouti, as well as the entire southern co ...
who extract salt from the lake for trading for their living. The Economic Development of Lake Assal has assessed the population of the Assal region as a whole at 20,000. Now, a settlement of 2,000 people has been established near the lake.


Wildlife

The vegetation in the lake area consists only of scattered, low, thorny bushes or shrubs on the right bank shores, except for one lone palm tree which is bypassed by the road. The lake water is rich in minerals but the only signs of life are a rich abundance of common
bacteria Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of Prokaryote, prokaryotic microorganisms. Typically a few micr ...
. The region has witnessed terrestrial fauna species of
antelope The term antelope refers to numerous extant or recently extinct species of the ruminant artiodactyl family Bovidae that are indigenous to most of Africa, India, the Middle East, Central Asia, and a small area of Eastern Europe. Antelopes do ...
s (small buck near the stream beds),
camel A camel (from and () from Ancient Semitic: ''gāmāl'') is an even-toed ungulate in the genus ''Camelus'' that bears distinctive fatty deposits known as "humps" on its back. Camels have long been domesticated and, as livestock, they provid ...
s, birds,
lizard Lizard is the common name used for all Squamata, squamate reptiles other than snakes (and to a lesser extent amphisbaenians), encompassing over 7,000 species, ranging across all continents except Antarctica, as well as most Island#Oceanic isla ...
s and insects. The lake area does not support any kind of aqua fauna. However, near the hot spring source to Lake Assal, some shoals of minnow fish species are reported, which are said to be similar to '' Cyprinodon variegatus'' which is a common species found in the
Caribbean The Caribbean ( , ; ; ; ) is a region in the middle of the Americas centered around the Caribbean Sea in the Atlantic Ocean, North Atlantic Ocean, mostly overlapping with the West Indies. Bordered by North America to the north, Central America ...
and
South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...
n salt works.


Chemical composition

The chemical composition of the lake water is 300 g/L NaCl which is assessed with varying potential reserves of 4 to 8 million
tonne The tonne ( or ; symbol: t) is a unit of mass equal to 1,000  kilograms. It is a non-SI unit accepted for use with SI. It is also referred to as a metric ton in the United States to distinguish it from the non-metric units of the s ...
s. The hot spring, which is source of supply to Lake Assal from the gulf, has the same salinity level as that of seawater. The salinity concentration in the lake is a result of wind and sun action, which results in an annual average evaporation rate of 460 million m3. The lake water is stated to be maintaining an equilibrium. Lake Assal is the most saline body of water on earth after Don Juan Pond with 34.8% average salt concentration (up to 40% at depth); higher than the 33.7% level in the
Dead Sea The Dead Sea (; or ; ), also known by #Names, other names, is a landlocked salt lake bordered by Jordan to the east, the Israeli-occupied West Bank to the west and Israel to the southwest. It lies in the endorheic basin of the Jordan Rift Valle ...
. The dissolved salts include NaCl, KCl, MgCl2, CaCl2, CaSO4 and MgBr2, with NaCl dominating in Lake Assal and MgCl2 in the Dead Sea. The surface concentration of salts is 268.8 g/L for the Dead Sea and 276.5 g/L for Lake Assal; the concentration increases to 326.6 g/L at depth in the Dead Sea and to 398 g/L at depth in Lake Assal.


Salt extraction

By 1893, the French government had sold to businessman Léon Chefneux the right to refine and export salt from Lake Assal. Chefneux agreed to pay into the colonial office the sum of $10,000 a year, and if, during the fifty years that he was to have the exclusive right to export salt from Lake Assal, the annual product exceeded 50,000 tonnes, he was to pay a tax of 20 cents for every tonne in excess. The government also designated a part of the lake where the local people could procure all the salt they wanted without tax or hindrance. Salt production on a semi-commercial basis started in 1988 by small private enterprises. Thereafter, extraction of salt from the lake peaked in 1998–2000 when there was a conflict between
Eritrea Eritrea, officially the State of Eritrea, is a country in the Horn of Africa region of East Africa, with its capital and largest city being Asmara. It is bordered by Ethiopia in the Eritrea–Ethiopia border, south, Sudan in the west, and Dj ...
and
Ethiopia Ethiopia, officially the Federal Democratic Republic of Ethiopia, is a landlocked country located in the Horn of Africa region of East Africa. It shares borders with Eritrea to the north, Djibouti to the northeast, Somalia to the east, Ken ...
.
Djibouti Djibouti, officially the Republic of Djibouti, is a country in the Horn of Africa, bordered by Somalia to the south, Ethiopia to the southwest, Eritrea in the north, and the Red Sea and the Gulf of Aden to the east. The country has an area ...
replaced Eritrea in supplying salt to Ethiopia at highly attractive prices (250% of the earlier sale price) when it came to be known as the "white gold." Commercial industrial production rose between 2004 and 2008. In 2004, after an initial low of 17,745 tonnes due to import duty of 53% imposed by Ethiopian exports, production increased and recorded a high of 110,000 tonnes in 2008. However, since 2008 the production has increased manifold as a result of the Government of Djibouti Department of Industries initiating action plans, in 2002, to expand the salt extraction process from Lake Assal by adopting modern mechanical processes so that a crude salt production of 6 million tonnes could be achieved annually, eventually. After instituting a feasibility study for the purpose, the Salt Investment S.A., in a joint agreement, in March 2008, between Emerging Capital Partners LLC (ECP), Société d’Exploitation du Lac (SEL) and Hardtechnologies Group S.L. ("Hardtech"), have been made responsible for "developing the salt project further and are established under the laws of Djibouti for the purposes of harvesting, refining, storing, transporting and exporting salt extracted from Lake Assal." The project envisages extraction at the rate of 1,000 tonnes per hour, supported by a 250 tonnes per hour mechanical salt washing and upgrading plant. The target of 4 million tonnes was expected to be achieved by 2012. While most commercial salt extractions are done from the huge deposits on the shores of the lake, there is also another novel way of extraction done by wading through the lake waters. The extracted salt is found in the form of spheres formed out of salt crystals and marketed in the name of
Djibouti Djibouti, officially the Republic of Djibouti, is a country in the Horn of Africa, bordered by Somalia to the south, Ethiopia to the southwest, Eritrea in the north, and the Red Sea and the Gulf of Aden to the east. The country has an area ...
salts. The extraction process involves whole family of indigenous people wading through the lake. Men wade deep into the lake and gather the pearls in baskets. Women help in sorting the collected spheres according to size by hand. They are then dried, stored in bags and transported to the harbour for sale.


Development projects

The geothermal resources of this rift valley surrounding Lake Assal, which shows a high temperature variation, was studied for development in the Fiale area near Lava Lake, about north of Lake Assal. It is proposed to establish a
geothermal power Geothermal power is electricity generation, electrical power generated from geothermal energy. Technologies in use include dry steam power stations, flash steam power stations and binary cycle power stations. Geothermal electricity generation i ...
station of 30 MW capacity. Wind power potential available in the Lake Assal area is also proposed to be exploited with a Wind Power station about from Lake Assal, near the geothermal plant. Considering the seismic and volcanic activity in the lake region, exploration for mineral deposits of
gold Gold is a chemical element; it has chemical symbol Au (from Latin ) and atomic number 79. In its pure form, it is a brightness, bright, slightly orange-yellow, dense, soft, malleable, and ductile metal. Chemically, gold is a transition metal ...
was initiated in 2001 jointly by Djibouti and an American company. The Lake Assal area, the Ghoubbet El Kharab bay and the Ardoukoba Volcano were proposed to be developed as tourist attractions.


See also

*
Lake Afrera Lake Afrera (in Italian Lake Giuletti) is a hypersaline lake in northern Ethiopia. Located in Kilbet Rasu, Afar Region, it is one of the lakes of the Danakil Depression. It has a surface of and holds 2.4 km3 of brine. The maximal depth of Lake A ...


References


Sources


Microbiological Study of a Hypersaline Lake in French Somaliland
{{Authority control Assal Assal Tadjourah Region Asal Extreme points of Earth Lowest points of countries Saline lakes of the Great Rift Valley