The Messinian salinity crisis (MSC), also referred to as the Messinian event, and in its latest stage as the Lago Mare event, was a geological event during which the

Mediterranean Sea The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the ...

went into a cycle of partial or nearly complete desiccation (drying-up) throughout the latter part of the Messinian age of the

Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...

epoch, from 5.96 to 5.33 Ma (million years ago). It ended with the Zanclean flood, when the Atlantic reclaimed the basin. Sediment samples from below the deep seafloor of the Mediterranean Sea, which include

evaporite An evaporite () is a water- soluble sedimentary mineral deposit that results from concentration and crystallization by evaporation from an aqueous solution. There are two types of evaporite deposits: marine, which can also be described as ocean ...

minerals,

soil Soil, also commonly referred to as earth or dirt Dirt is an unclean matter, especially when in contact with a person's clothes, skin, or possessions. In such cases, they are said to become dirty. Common types of dirt include: * Debri ...

s, and

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

plants, show that the precursor of the Strait of Gibraltar closed tight about 5.96 million years ago, sealing the Mediterranean off from the Atlantic. This resulted in a period of partial desiccation of the Mediterranean Sea, the first of several such periods during the late Miocene. After the strait closed for the last time around 5.6 Ma, the region's generally dry climate at the time dried the Mediterranean basin out nearly completely within a thousand years. This massive desiccation left a deep dry basin, reaching deep below normal sea level, with a few

hypersaline A hypersaline lake is a landlocked body of water that contains significant concentrations of sodium chloride, brines, and other salts, with saline levels surpassing that of ocean water (3.5%, i.e. ). Specific microbial species can thrive in hi ...

pockets similar to today's Dead Sea. Then, around 5.5 Ma, less dry climatic conditions resulted in the basin receiving more freshwater from

river A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases, a river flows into the ground and becomes dry at the end of its course without reaching another body of w ...

s, progressively filling and diluting the hypersaline lakes into larger pockets of

brackish water Brackish water, sometimes termed brack water, is water occurring in a natural environment that has more salinity than freshwater, but not as much as seawater. It may result from mixing seawater (salt water) and fresh water together, as in estuari ...

(much like today's

Caspian Sea The Caspian Sea is the world's largest inland body of water, often described as the world's largest lake or a full-fledged sea. An endorheic basin, it lies between Europe and Asia; east of the Caucasus, west of the broad steppe of Central Asia ...

). The Messinian salinity crisis ended with the Strait of Gibraltar finally reopening 5.33 Ma, when the Atlantic rapidly filled up the Mediterranean basin in what is known as the Zanclean flood. Even today, the Mediterranean is considerably saltier than the North Atlantic, owing to its near isolation by the Strait of Gibraltar and its high rate of evaporation. If the Strait of Gibraltar closes again (which is likely to happen in the near future in

geological time The geologic time scale, or geological time scale, (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geochron ...

), the Mediterranean would mostly evaporate in about a thousand years, after which continued northward movement of Africa may obliterate the Mediterranean altogether.

Naming and first evidence

In the 19th century, the Swiss geologist and paleontologist

Karl Mayer-Eymar Karl David Wilhelm Mayer-Eymar (29 July 1826 – 25 February 1907) was a Franco-Swiss paleontologist and geologist known for his work on classifying the stratigraphy of the Tertiary into 12 stages. He was born Karl Mayer but added the anagram Eymar ...

(1826–1907) studied fossils embedded between

gypsum Gypsum is a soft sulfate mineral composed of calcium sulfate 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, blackboard or sidewalk chalk, and drywal ...

-bearing,

brackish Brackish water, sometimes termed brack water, is water occurring in a natural environment that has more salinity than freshwater, but not as much as seawater. It may result from mixing seawater (salt water) and fresh water together, as in estu ...

, and freshwater sediment layers, and identified them as having been deposited just before the end of the

Epoch. In 1867, he named the period the Messinian after the city of Messina in

Sicily (man) it, Siciliana (woman) , population_note = , population_blank1_title = , population_blank1 = , demographics_type1 = Ethnicity , demographics1_footnotes = , demographi ...

, Italy. Since then, several other salt-rich and gypsum-rich

layers throughout the Mediterranean region have been dated to the same period.

Further evidence and confirmation

Seismic surveying of the Mediterranean basin in 1961 revealed a geological feature some below the seafloor. This feature, dubbed the ''M reflector'', closely followed the contours of the present seafloor, suggesting that it was laid down evenly and consistently at some point in the past. The origin of this layer was largely interpreted as related to salt deposition. However, different interpretations were proposed for the age of salt and its deposition. Earlier suggestions from Denizot in 1952 and Ruggieri in 1967 proposed that this layer was of Late

age, and the same Ruggieri coined the term ''Messinian Salinity Crisis''. New and high-quality seismic data on the M-reflector were acquired in the Mediterranean Basin in 1970. At the same time, the salt was cored during Leg 13 of the

Deep Sea Drilling Program The Deep Sea Drilling Project (DSDP) was an ocean drilling project operated from 1968 to 1983. The program was a success, as evidenced by the data and publications that have resulted from it. The data are now hosted by Texas A&M University, alth ...

conducted from the '' Glomar Challenger'' under the supervision of co-chief scientists William B.F. Ryan and Kenneth J. Hsu. These deposits were dated and interpreted for the first time as deep-basin products of the Messinian salinity crisis. Gypsum cones

The first drilling of the Messinian salt at the deeper parts of the Mediterranean Sea came in the summer of 1970, when geologists aboard the '' Glomar Challenger'' brought up drill cores containing arroyo gravels and red and green

floodplain A floodplain or flood plain or bottomlands is an area of land adjacent to a river which stretches from the banks of its channel to the base of the enclosing valley walls, and which experiences flooding during periods of high discharge.Goudi ...

silts; and

anhydrite Anhydrite, or anhydrous calcium sulfate, is a mineral with the chemical formula CaSO4. It is in the orthorhombic crystal system, with three directions of perfect cleavage parallel to the three planes of symmetry. It is not isomorphous with the ...

rock salt Halite (), commonly known as rock salt, is a type of salt, the mineral (natural) form of sodium chloride ( Na Cl). Halite forms isometric crystals. The mineral is typically colorless or white, but may also be light blue, dark blue, purple, pi ...

, and various other

minerals that often form from drying of brine or seawater, including in a few places

potash Potash () includes various mined and manufactured salts that contain potassium in water-soluble form.

, left where the last bitter, mineral-rich waters dried up. One drill core contained a wind-blown cross-bedded deposit of deep-sea

foraminifera Foraminifera (; Latin for "hole bearers"; informally called "forams") are single-celled organisms, members of a phylum or class of amoeboid protists characterized by streaming granular ectoplasm for catching food and other uses; and commonly ...

l ooze that had dried into dust and been blown about on the hot dry

abyssal plain An abyssal plain is an underwater plain on the deep ocean floor, usually found at depths between and . Lying generally between the foot of a continental rise and a mid-ocean ridge, abyssal plains cover more than 50% of the Earth's surface. ...

sandstorm A dust storm, also called a sandstorm, is a meteorological phenomenon common in arid and semi-arid regions. Dust storms arise when a gust front or other strong wind blows loose sand and dirt from a dry surface. Fine particles are transpo ...

s, mixed with quartz sand blown in from nearby continents, and ended up in a brine lake interbedded between two layers of

halite Halite (), commonly known as rock salt, is a type of salt, the mineral (natural) form of sodium chloride ( Na Cl). Halite forms isometric crystals. The mineral is typically colorless or white, but may also be light blue, dark blue, purple, p ...

. These layers alternated with layers containing marine fossils, indicating a succession of drying and flooding periods. The massive presence of salt does not require a desiccation of the sea. The main evidence for the evaporative drawdown of the Mediterranean comes from the remains of many (now submerged) canyons that were cut into the sides of the dry Mediterranean basin by rivers flowing down to the

. For example, the

Nile The Nile, , Bohairic , lg, Kiira , Nobiin: Áman Dawū is a major north-flowing river in northeastern Africa. It flows into the Mediterranean Sea. The Nile is the longest river in Africa and has historically been considered the longest ...

cut its bed down to several hundred feet below sea level at

Aswan Aswan (, also ; ar, أسوان, ʾAswān ; cop, Ⲥⲟⲩⲁⲛ ) is a city in Southern Egypt, and is the capital of the Aswan Governorate. Aswan is a busy market and tourist centre located just north of the Aswan Dam on the east bank of the ...

(where Ivan S. Chumakov found marine

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Foraminifera Foraminifera (; Latin for "hole bearers"; informally called "forams") are single-celled organisms, members of a phylum or class of amoeboid protists characterized by streaming granular ectoplasm for catching food and other uses; and commonly ...

in 1967), and below sea level just north of

Cairo Cairo ( ; ar, القاهرة, al-Qāhirah, ) is the Capital city, capital of Egypt and its largest city, home to 10 million people. It is also part of the List of urban agglomerations in Africa, largest urban agglomeration in Africa, List of ...

. In many places in the Mediterranean, fossilized cracks have been found where muddy sediment had dried and cracked in the sunlight and drought. In the Western Mediterranean series, the presence of pelagic oozes interbedded within the

s suggests that the area was repeatedly flooded and desiccated over 700,000 years.

Chronology

Based on palaeomagnetic datings of Messinian deposits that have since been brought above sea level by tectonic activity, the salinity crisis started at the same time over all the Mediterranean basin, at 5.96 ± 0.02 million years ago. This episode comprises the second part of what is called the "Messinian" age of the

epoch. This age was characterised by several stages of

tectonic Tectonics (; ) are the processes that control the structure and properties of the Earth's crust and its evolution through time. These include the processes of mountain building, the growth and behavior of the strong, old cores of continents ...

activity and sea level fluctuations, as well as

erosion Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is dis ...

al and depositional events, all more or less interrelated (van Dijk et al., 1998). The Mediterranean-Atlantic strait closed tight time and time again, and the Mediterranean Sea, for the first time and then repeatedly, partially desiccated. The basin was finally isolated from the

Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe ...

for a longer period, between 5.59 and 5.33 million years ago, resulting in a large or smaller (depending on the

scientific model Scientific modelling is a scientific activity, the aim of which is to make a particular part or feature of the world easier to understand, define, quantify, visualize, or simulate by referencing it to existing and usually commonly accepted ...

applied) lowering of the Mediterranean sea level. During the initial, very dry stages (5.6–5.5 Ma), there was extensive erosion, creating several huge canyon systems (some similar in scale to the Grand Canyon) around the Mediterranean. Later stages (5.50–5.33 Ma) are marked by cyclic evaporite deposition into a large "lake-sea" basin ("Lago Mare" event). About 5.33 million years ago, at the start of the

Zanclean The Zanclean is the lowest stage or earliest age on the geologic time scale of the Pliocene. It spans the time between 5.332 ± 0.005 Ma (million years ago) and 3.6 ± 0.005 Ma. It is preceded by the Messinian Age of the Miocene Epoch, and ...

age (at the start of the

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Zanclean flood; Garcia-Castellanos et al., 2009), favouring slope destabilization. The basin has not desiccated since.

Several cycles

The amount of Messinian salts has been estimated as around (but this estimate may be reduced by 50 to 75% when more information becomes available) and more than 1 million cubic kilometres, 50 times the amount of salt normally in the Mediterranean waters. This suggests either a succession of desiccations or a long period of hypersalinity during which incoming water from the Atlantic Ocean was evaporated with the level of the Mediterranean brine being similar to that of the Atlantic. The nature of the strata points strongly to several cycles of the Mediterranean Sea completely drying and being refilled (Gargani and Rigollet, 2007), with drying periods correlating to periods of cooler global temperatures; which were therefore drier in the Mediterranean region. Each refilling was presumably caused by a seawater inlet opening, either

ally, or by a river flowing eastwards below sea level into the "Mediterranean Sink" cutting its valley head back west until it let the sea in, similarly to a

river capture Stream capture, river capture, river piracy or stream piracy is a geomorphological phenomenon occurring when a stream or river drainage system or watershed is diverted from its own bed, and flows instead down the bed of a neighbouring stream. T ...

. The last refilling was at the

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58Strait of Gibraltar broke wide open permanently. Upon closely examining the Hole 124 core, Kenneth J. Hsu found that: Research since then has suggested that the desiccation-flooding cycle may have repeated several times during the last 630,000 years of the Miocene epoch. This could explain the large amount of salt deposited. Recent studies, however, show that the repeated desiccation and flooding is unlikely from a

geodynamic Geodynamics is a subfield of geophysics dealing with dynamics of the Earth. It applies physics, chemistry and mathematics to the understanding of how mantle convection leads to plate tectonics and geologic phenomena such as seafloor spreading, mo ...

point of view.Garcia-Castellanos, D., A. Villaseñor, 2011. Messinian salinity crisis regulated by competing tectonics and erosion at the Gibraltar Arc. ''Nature'', 2011-12-1
pdf hereLink
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Synchronism versus diachronism—deep water versus shallow water evaporites

Some major questions remain concerning the beginning of the crisis in the central Mediterranean Basin. The geometric physical link between the evaporitic series identified in marginal basins accessible for field studies, such as the

Tabernas Desert The Tabernas Desert ( es, Desierto de Tabernas) is one of Spain's semi-arid deserts, located within Spain's south-eastern province of Almería. It is in the interior, about north of the provincial capital Almería, in the Tabernas municipalit ...

and Sorbas Basin, and the evaporitic series of the central basins has never been made. Using the concept of deposition in both shallow and deep basins during the Messinian (i.e. assuming that both Basin types existed during this period), two major groupings are evident: one that favours a synchronous deposition (image c) of the first evaporites in all the basins before the major phase of erosion; and the other that favours a diachronous deposition (image a) of the evaporites through more than one phases of desiccation which would first have affected the marginal basins and later the central basins. Another school suggests that desiccation was synchronous, but occurred mainly in shallower basins. This model would suggest that the sea level of the whole Mediterranean basin fell at once, but only shallower basins dried out enough to deposit salt beds. See image b. As highlighted in the work of van Dijk (1992)van Dijk, J.P. (1992, d); Late Neogene fore-arc basin evolution in the Calabrian Arc (Central Mediterranean). Tectonic sequence stratigraphy and dynamic geohistory. With special reference to the geology of Central Calabria. Geologica Ultrajectina, 92, 288 pp. and van Dijk et al. (1998) the history of desiccation and erosion was complexly interacting with tectonic uplift and subsidence events, and erosional episodes. They also questioned again like some previous authors had done, whether the basins now observed as "deep" were actually also deep during the Messinian Episode and gave different names to the end-member scenarios described above. Distinguishing between these hypotheses requires the calibration of gypsum deposits. Gypsum is the first salt (calcium sulphate) to be deposited from a desiccating basin.

Magnetostratigraphy Magnetostratigraphy is a geophysical correlation technique used to date sedimentary and volcanic sequences. The method works by collecting oriented samples at measured intervals throughout the section. The samples are analyzed to determine their '' ...

offers a broad constraint on timing, but no fine detail. Therefore,

cyclostratigraphy Cyclostratigraphy is a subdiscipline of stratigraphy that studies astronomically forced climate cycles within sedimentary successions. Orbital changes Astronomical cycles (also known as Milankovitch cycles) are variations of the Earth's or ...

is relied upon to compare the dates of sediments. The typical case study compares the gypsum evaporites in the main Mediterranean basin with those of the Sorbas basin, a smaller basin on the flanks of the Mediterranean Sea that is now exposed in southern

Spain , image_flag = Bandera de España.svg , image_coat = Escudo de España (mazonado).svg , national_motto = ''Plus ultra'' (Latin)(English: "Further Beyond") , national_anthem = (English: "Royal March") , i ...

. The relationship between these two basins is assumed to represent the relationships of the wider region. Recent work has relied on

to correlate the underlying marl beds, which appear to have given way to gypsum at exactly the same time in both basins. The proponents of this hypothesis claim that cyclic variations in bed compositions are astronomically tuned, and the beds' magnitude can be calibrated to show they were contemporaneous—a strong argument. In order to refute it, it is necessary to propose an alternative mechanism for generating these cyclic bands, or for erosion to have coincidentally removed just the right amount of sediment everywhere before the gypsum was deposited. The proponents claim that the gypsum was deposited directly above the correlated marl layers, and slumped into them, giving the appearance of an unconformable contact. However, their opponents seize upon this apparent inconformity, and claim that the Sorbas Basin was exposed—therefore eroding—while the Mediterranean sea was depositing evaporites. This would result in the Sorbas Basin being filled with evaporites at 5.5 million years ago (Ma), compared to the main basin at 5.96 Ma.). Recent works have highlighted a pre-evaporite phase corresponding to a prominent erosional crisis (also named " Messinian erosional crisis"; the termination of the "Mes-1" unconformity bound depositional sequence of van Dijk, 1992) responding to a major drawdown of the Mediterranean seawater. Assuming that this major drawdown corresponds to the major Messinian drawdown, they concluded that the Mediterranean bathymetry significantly decreased before the precipitation of central basins evaporites. Regarding these works, a deep water formation seems unlikely. The assumption that central basin evaporites partly deposited under a high

bathymetry Bathymetry (; ) is the study of underwater depth of ocean floors (''seabed topography''), lake floors, or river floors. In other words, bathymetry is the underwater equivalent to hypsometry or topography. The first recorded evidence of water ...

and before the major phase of erosion should imply the observation of a major detritic event above evaporites in the basin. Such a depositional

geometry Geometry (; ) is, with arithmetic, one of the oldest branches of mathematics. It is concerned with properties of space such as the distance, shape, size, and relative position of figures. A mathematician who works in the field of geometry is ...

has not been observed on data. This theory corresponds to one of the end-member scenarios discussed by van Dijk et al.

Causes

Several possible causes of the series of Messinian crises have been considered. While there is disagreement on all fronts, the most general consensus seems to agree that climate had a role in forcing the periodic filling and emptying of the basins, and that tectonic factors must have played a part in controlling the height of the sills restricting flow between the Atlantic and Mediterranean. The magnitude and extent of these effects, however, is widely open to interpretation (see, e.g., van Dijk et al. (1998).van Dijk, J.P., Barberis, A., Cantarella, G., and Massa, E. (1998); Central Mediterranean Messinian basin evolution. Tectono-eustasy or eustato-tectonics? Annales Tectonicae, 12, n. 1-2, 7-27. In any case, the causes of the closing and isolation of the Mediterranean Sea from the Atlantic Ocean must be found in the area where the Strait of Gibraltar is now. One of the tectonic boundaries between the

African Plate The African Plate is a major tectonic plate that includes much of the continent of Africa (except for its easternmost part) and the adjacent oceanic crust to the west and south. It is bounded by the North American Plate and South American Plate ...

and the European Plate and its southern fragments such as the Iberian Plate is there. This boundary Zone is characterised by an arc-shaped tectonic feature, the

Gibraltar Arc The Gibraltar Arc is a geological region corresponding to an arcuate orogen surrounding the Alboran Sea, between the Iberian Peninsula and Africa. It consists of the Betic Cordillera (south Spain), and the Rif (North Morocco). The Gibraltar Arc i ...

, which includes southern Spain and

northern Africa North Africa, or Northern Africa is a region encompassing the northern portion of the African continent. There is no singularly accepted scope for the region, and it is sometimes defined as stretching from the Atlantic shores of Mauritania in t ...

. In the present day area of the Mediterranean Sea, are three of these arc-shaped belts: the

, the Calabrian Arc, and the Aegean Arc. The kinematics and dynamics of this plate boundary and of the Gibraltar Arc during the late Miocene are strictly related to the causes of the Messinian salinity crisis: tectonic reconfiguration may have closed and re-opened passages, as the region where the connection with the Atlantic Ocean was situated is permeated by strike-slip faults and rotating blocks of continental crust. As faulting accommodated the regional compression caused by Africa's convergence with

Eurasia Eurasia (, ) is the largest continental area on Earth, comprising all of Europe and Asia. Primarily in the Northern and Eastern Hemispheres, it spans from the British Isles and the Iberian Peninsula in the west to the Japanese archipelago ...

, the geography of the region may have altered enough to open and close seaways. However, the precise tectonic activity behind the motion can be interpreted in a number of ways. Any model must explain a variety of features of the area: * Shortening and extension occur at the same time in close proximity; sedimentary sequences and their relations to fault activity constrain the rates of uplift and subsidence quite precisely * Fault-bounded continental blocks can often be observed to rotate * The depth and structure of the lithosphere is constrained by records of

seismic Seismology (; from Ancient Greek σεισμός (''seismós'') meaning "earthquake" and -λογία (''-logía'') meaning "study of") is the scientific study of earthquakes and the propagation of elastic waves through the Earth or through other ...

activity, as well as

tomography Tomography is imaging by sections or sectioning that uses any kind of penetrating wave. The method is used in radiology, archaeology, biology, atmospheric science, geophysics, oceanography, plasma physics, materials science, astrophysics, ...

* The composition of

igneous rock Igneous rock (derived from the Latin word ''ignis'' meaning fire), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rock is formed through the cooling and solidification of magma o ...

s varies—this constrains the location and extent of any subduction. There are three contending geodynamic models that may fit the data, models which have been discussed in an equal way for the other arc shaped features in the Mediterranean: *A moving subduction zone may have caused periodic regional uplift. Changes in

volcanic rock Volcanic rock (often shortened to volcanics in scientific contexts) is a rock formed from lava erupted from a volcano. In other words, it differs from other igneous rock by being of volcanic origin. Like all rock types, the concept of volcanic ...

s suggest that subduction zones at the rim of the

Tethys Sea The Tethys Ocean ( el, Τηθύς ''Tēthús''), also called the Tethys Sea or the Neo-Tethys, was a prehistoric ocean that covered most of the Earth during much of the Mesozoic Era and early Cenozoic Era, located between the ancient continents ...

may have rolled back westwards, changing the chemistry and

density Density (volumetric mass density or specific mass) is the substance's mass per unit of volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' can also be used. Mathematical ...

magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma is found beneath the surface of the Earth, and evidence of magmatism has also been discovered on other terrestrial planets and some natural sa ...

underlying the western Mediterranean. However, this does not account for the periodic emptying and refilling of the basin. *The same features can be explained by regional

delamination Delamination is a mode of failure where a material fractures into layers. A variety of materials including laminate composites and concrete can fail by delamination. Processing can create layers in materials such as steel formed by rolling a ...

or the loss of a layer of the entire lithosphere. *Deblobbing, the loss of a "blob" of

lithospheric mantle The lithospheric mantle is the uppermost solid part of Earth's mantle. The lithospheric mantle is subdivided into the subcontinental lithospheric mantle associated with the continental lithosphere and oceanic lithospheric mantle, associated with ...

, and the subsequent upward motion of the overlying crust (which has lost its dense mantle "anchor") may also have caused the observed phenomena although the validity of the "deblobbing" hypothesis has been called into question. Of these, only the first model, invoking rollback, seems to explain the rotations observed. However, it is difficult to fit it with the pressure and temperature histories of some

metamorphic rock Metamorphic rocks arise from the transformation of existing rock to new types of rock in a process called metamorphism. The original rock ( protolith) is subjected to temperatures greater than and, often, elevated pressure of or more, caus ...

s . This has led to some interesting combinations of the models which at first hand looked bizarre, in attempts to approach the true state of affairs. Changes in climate must almost certainly be invoked to explain the periodic nature of the events. They occur during cool periods of

Milankovic cycles Milankovitch cycles describe the collective effects of changes in the Earth's movements on its climate over thousands of years. The term was coined and named after Serbian geophysicist and astronomer Milutin Milanković. In the 1920s, he hypot ...

, when less solar energy reached the northern hemisphere. This led to less evaporation of the North Atlantic, hence less rainfall over the Mediterranean. This would have starved the basin of water supply from rivers and allowed its desiccation. Contrary to many people's instincts, there is now a scientific consensus that global sea level fluctuations cannot have been the major cause, although it may have played a role. The lack of ice caps at the time means there was no realistic mechanism to cause significant changes in sea level—there was nowhere for the water to go, and the morphology of ocean basins cannot change on such a short timescale.

Relationship to climate

The climate of the abyssal plain during the drought is unknown. There is no situation on Earth directly comparable to the dry Mediterranean, and thus it is not possible to know its climate by direct observation of comparable geographic settings. Simulation using a

general circulation model A general circulation model (GCM) is a type of climate model. It employs a mathematical model of the general circulation of a planetary atmosphere or ocean. It uses the Navier–Stokes equations on a rotating sphere with thermodynamic ter ...

can indicate physically consistent responses to the desiccation. There is no consensus as to whether the Mediterranean Sea dried out completely; it seems likeliest that at least three or four large brine lakes on the

s remained at all times. The extent of desiccation is very hard to judge, owing to the reflective seismic nature of the salt beds, and the difficulty in drilling cores, making it difficult to map their thickness. Atmospheric forces can be studied to arrive at a speculation on the climate. As winds blew across the "Mediterranean

Sink A sink is a bowl-shaped plumbing fixture for washing hands, dishwashing, and other purposes. Sinks have a tap (faucet) that supply hot and cold water and may include a spray feature to be used for faster rinsing. They also include a drain t ...

", they would heat or cool adiabatically with altitude. In the empty Mediterranean Basin, the summertime temperatures would probably have been extremely high. As a first approximation, using the dry adiabatic lapse rate of around per kilometer, the maximum possible temperature of an area below sea level would be about warmer than it would be at sea level. Under this extreme assumption, maxima would be near at the lowest points of the dry

, permitting no permanent life but

extremophile An extremophile (from Latin ' meaning "extreme" and Greek ' () meaning "love") is an organism that is able to live (or in some cases thrive) in extreme environments, i.e. environments that make survival challenging such as due to extreme temper ...

s. Further, the altitude below sea level would result in 1.45 to 1.71 atm (1102 to 1300 mmHg)

air pressure Atmospheric pressure, also known as barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The standard atmosphere (symbol: atm) is a unit of pressure defined as , which is equivalent to 1013.25 millibars ...

, further increasing heat stress. However, these simple estimates are likely far too extreme. Murphy et al.'s 2009

experiments showed that for completely desiccated conditions, the Mediterranean basin would warm by up to in summer and in winter, while for a depressed water surface, temperatures would warm by only about in summer and in winter. In addition, the model results indicated global stationary wave response to the introduction of the topographic depression causes patters of warming and cooling by up to around the Northern Hemisphere. Today the evaporation from the Mediterranean Sea supplies moisture that falls in frontal storms, but without such moisture, the

Mediterranean climate A Mediterranean climate (also called a dry summer temperate climate ''Cs'') is a temperate climate sub-type, generally characterized by warm, dry summers and mild, fairly wet winters; these weather conditions are typically experienced in the ...

that we associate with Italy,

Greece Greece,, or , romanized: ', officially the Hellenic Republic, is a country in Southeast Europe. It is situated on the southern tip of the Balkans, and is located at the crossroads of Europe, Asia, and Africa. Greece shares land borders ...

, and the

Levant The Levant () is an approximate historical geographical term referring to a large area in the Eastern Mediterranean region of Western Asia. In its narrowest sense, which is in use today in archaeology and other cultural contexts, it is ...

would be limited to the

Iberian Peninsula The Iberian Peninsula (), ** * Aragonese and Occitan: ''Peninsula Iberica'' ** ** * french: Péninsule Ibérique * mwl, Península Eibérica * eu, Iberiar penintsula also known as Iberia, is a peninsula in southwestern Europe, def ...

and the western

Maghreb The Maghreb (; ar, الْمَغْرِب, al-Maghrib, lit=the west), also known as the Arab Maghreb ( ar, المغرب العربي) and Northwest Africa, is the western part of North Africa and the Arab world. The region includes Algeria, ...

. Climates throughout the central and eastern basin of the Mediterranean and surrounding regions to the north and east would have been drier even above modern sea level. The

eastern Alps Eastern Alps is the name given to the eastern half of the Alps, usually defined as the area east of a line from Lake Constance and the Alpine Rhine valley up to the Splügen Pass at the Alpine divide and down the Liro River to Lake Como in t ...

, the

Balkans The Balkans ( ), also known as the Balkan Peninsula, is a geographical area in southeastern Europe with various geographical and historical definitions. The region takes its name from the Balkan Mountains that stretch throughout the who ...

, and the Hungarian plain would also be much drier than they are today, even if the westerlies prevailed as they do now. However, the Paratethys ocean provided water to the area north of the Mediterranean basin. The Wallachian-Pontic and Hungarian basins were underwater during the Miocene, modifying the climate of what is now the Balkans and other areas north of the Mediterranean basin. The

Pannonian Sea The Pannonian Sea was a shallow ancient lake, where the Pannonian Basin in Central Europe is now. The Pannonian Sea existed from about 10 Ma (million years ago) until 1 Ma, during the Miocene and Pliocene epochs, when marine sediments were dep ...

was a source of water north of the Mediterranean basin until the middle Pleistocene before becoming the Hungarian plain. Debate exists whether the waters of the Wallachian-Pontic basin (and the possibly connected Pannonian Sea) would have had access (thus bringing water) to at least the eastern Mediterranean basin at times during the Miocene.

Effects

Effects on biology

The Messinian event also provided an opportunity for many African species, including antelopes,

elephant Elephants are the largest existing land animals. Three living species are currently recognised: the African bush elephant, the African forest elephant, and the Asian elephant. They are the only surviving members of the family Elephantidae ...

s and

hippopotamus The hippopotamus ( ; : hippopotamuses or hippopotami; ''Hippopotamus amphibius''), also called the hippo, common hippopotamus, or river hippopotamus, is a large semiaquatic mammal native to sub-Saharan Africa. It is one of only two extan ...

es, to migrate into the empty basin, close to the descending great rivers, to reach interior wetter cooler highlands such as

Malta Malta ( , , ), officially the Republic of Malta ( mt, Repubblika ta' Malta ), is an island country in the Mediterranean Sea. It consists of an archipelago, between Italy and Libya, and is often considered a part of Southern Europe. It lies ...

as the sea level was dropping, as such species would not have been able to cross the wide, hot, empty sink at maximum dryness. After the return of the sea water, they remained on the islands, where they underwent

insular dwarf Insular dwarfism, a form of phyletic dwarfism, is the process and condition of large animals evolving or having a reduced body size when their population's range is limited to a small environment, primarily islands. This natural process is disti ...

ing during the Pleistocene, giving rise to species known from

Crete Crete ( el, Κρήτη, translit=, Modern: , Ancient: ) is the largest and most populous of the Greek islands, the 88th largest island in the world and the fifth largest island in the Mediterranean Sea, after Sicily, Sardinia, Cyprus, ...

('' Hippopotamus creutzburgi''),

Cyprus Cyprus ; tr, Kıbrıs (), officially the Republic of Cyprus,, , lit: Republic of Cyprus is an island country located south of the Anatolian Peninsula in the eastern Mediterranean Sea. Its continental position is disputed; while it is ge ...

('' H. minor''),

('' H. melitensis'') and

Sicily (man) it, Siciliana (woman) , population_note = , population_blank1_title = , population_blank1 = , demographics_type1 = Ethnicity , demographics1_footnotes = , demographi ...

('' H. pentlandi''). Of these, the Cyprus dwarf hippopotamus survived until the end of the

Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was finally confirmed in ...

or early

Holocene The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togeth ...

. But some of these species may have crossed the sea when it was flooded, washed out to sea on rafts of floating

vegetation Vegetation is an assemblage of plant species and the ground cover they provide. It is a general term, without specific reference to particular taxa, life forms, structure, spatial extent, or any other specific botanical or geographic characte ...

, or with some species (e.g. elephants) by swimming.

Global effects

The water from the Mediterranean would have been redistributed in the world ocean, raising global sea level by as much as . The Mediterranean basin also sequestered below its

seabed The seabed (also known as the seafloor, sea floor, ocean floor, and ocean bottom) is the bottom of the ocean. All floors of the ocean are known as 'seabeds'. The structure of the seabed of the global ocean is governed by plate tectonics. Most of ...

a significant percentage of the salt from Earth's oceans; this decreased the average salinity of the world ocean and raised its

freezing point The melting point (or, rarely, liquefaction point) of a substance is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depend ...

.Lecture 17: Mediterranean

Dehydrated geography

The notion of a completely waterless Mediterranean Sea has some corollaries. *At the time, the Strait of Gibraltar was not open, but other seaways (the

Betic corridor The Betic Corridor, or North-Betic Strait, was a strait of water connecting the Mediterranean Sea with the Atlantic Ocean that once separated the Iberian plate from the Eurasian plate through the Betic Cordillera. Its closure approximately 5.96 ...

to the north where the Sierra Nevada or

Baetic Cordillera The Baetic System or Betic System ( es, Sistema Bético) is one of the main systems of mountain ranges in Spain. Located in the southern and eastern Iberian Peninsula, it is also known as the Cordilleras Béticas (Baetic Mountain Ranges) or B ...

is now, or to the south where the Rifean corridor or corridors where the

Rif Mountains The Rif or Riff (, ), also called Rif Mountains, is a geographic region in northern Morocco. This mountainous and fertile area is bordered by Cape Spartel and Tangier to the west, by Berkane and the Moulouya River to the east, by the Mediterrane ...

are now) linked the Mediterranean to the Atlantic. These must have closed, isolating the basin from the open ocean. *The high level of salinity cannot be tolerated by many known organisms, a factor in reducing the

biodiversity Biodiversity or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic (''genetic variability''), species (''species diversity''), and ecosystem (''ecosystem diversity'') l ...

of much of the basin. *The basin's low altitude would have made it extremely hot during the summer through

adiabatic heating In thermodynamics, an adiabatic process (Greek: ''adiábatos'', "impassable") is a type of thermodynamic process that occurs without transferring heat or mass between the thermodynamic system and its environment. Unlike an isothermal process, an ...

, a conclusion supported by the presence of

, which is only deposited in water warmer than . *Rivers emptying into the basin would have cut their beds much deeper (at least a further in the case of the

, as the buried canyon under

shows) and in the Rhone valley. There is an opinion that during the Messinian, the Red Sea was connected at

Suez Suez ( ar, السويس '; ) is a seaport city (population of about 750,000 ) in north-eastern Egypt, located on the north coast of the Gulf of Suez (a branch of the Red Sea), near the southern terminus of the Suez Canal, having the same bou ...

to the Mediterranean, but was not connected with the

Indian Ocean The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or ~19.8% of the water on Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia to the east. To the south it is bounded by t ...

, and dried out along with the Mediterranean.

Replenishment

When the Strait of Gibraltar was ultimately breached, the

would have poured a vast volume of water through what would have presumably been a relatively narrow channel. This refill has been envisaged as resulting in a large

waterfall A waterfall is a point in a river or stream where water flows over a vertical drop or a series of steep drops. Waterfalls also occur where meltwater drops over the edge of a tabular iceberg or ice shelf. Waterfalls can be formed in severa ...

higher than today's

Angel Falls Angel Falls ( es, Salto Ángel; Pemon language: ''Kerepakupai Merú'' meaning "waterfall of the deepest place", or ''Parakupá Vená'', meaning "the fall from the highest point") is a waterfall in Venezuela. It is the world's tallest unint ...

at , and far more powerful than either the

Iguazu Falls Iguazú Falls or Iguaçu Falls ( gn, Chororõ Yguasu , es, Cataratas del Iguazú, links=no ; pt, Cataratas do Iguaçu ) are waterfalls of the Iguazu River on the border of the Argentine province of Misiones and the Brazilian state of Paraná ...

or the

Niagara Falls Niagara Falls () is a group of three waterfalls at the southern end of Niagara Gorge, spanning the border between the province of Ontario in Canada and the state of New York in the United States. The largest of the three is Horseshoe Fall ...

, but recent studies of the underground structures at the Gibraltar Strait show that the flooding channel descended in a rather gradual way to the dry Mediterranean. An enormous deposit of unsorted debris washed in by a massive catastrophic flood-wash has been found in the seabed southeast of the south corner of

Sicily (man) it, Siciliana (woman) , population_note = , population_blank1_title = , population_blank1 = , demographics_type1 = Ethnicity , demographics1_footnotes = , demographi ...

. This is suspected to have been deposited by the Zanclean flood.
(an
see this image)
Phys Org, February 2018, ''Scientists find new evidences of the megaflood that ended the Messinian Salinity Crisis in the eastern Mediterranean'', February 27, 2018. by Ictja-Csic, Institute of Earth Sciences, Jaume Almera

References

External links

* * Arizona University: Geology 212, Lecture 17:
When the Mediterranean Dried Up
. (Accessed 7/16/06)

by Ian West (Internet Archive copy)
A brief history of the Messinian on Sicily
by Rob Butler
Archived

Messinian online
{{DEFAULTSORT:Messinian Salinity Crisis Events in the geological history of Earth History of the Mediterranean Messinian Paleogeography Regional geology Articles containing video clips

Naming and first evidence

Further evidence and confirmation

Chronology

Several cycles

Synchronism versus diachronism—deep water versus shallow water evaporites

Causes

Relationship to climate

Effects

Effects on biology

Global effects

Dehydrated geography

Replenishment

References

Further reading

External links