
In the Messinian salinity crisis (also referred to as the Messinian event, and in its latest stage as the Lago Mare event) 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 east by the Levant in West Asia, on the north by Anatolia in West Asia and Southern Eur ...
went into a cycle of partial or nearly complete
desiccation
Desiccation is the state of extreme dryness, or the process of extreme drying. A desiccant is a hygroscopic (attracts and holds water) substance that induces or sustains such a state in its local vicinity in a moderately sealed container. The ...
(drying-up) throughout the latter part of the
Messinian
The Messinian is in the geologic timescale the last age or uppermost stage of the Miocene. It spans the time between 7.246 ± 0.005 Ma and 5.333 ± 0.005 Ma (million years ago). It follows the Tortonian and is followed by the Zanclean, the fir ...
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
The Zanclean flood or Zanclean deluge is theorized to have refilled the Mediterranean Sea 5.33 million years ago.
This flooding ended the Messinian salinity crisis and reconnected the Mediterranean Sea to the Atlantic Ocean, although it i ...
, 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 oce ...
minerals,
soil
Soil, also commonly referred to as earth, is a mixture of organic matter, minerals, gases, water, and organisms that together support the life of plants and soil organisms. Some scientific definitions distinguish dirt from ''soil'' by re ...
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 preserve ...
plants, show that the precursor of the
Strait of Gibraltar
The Strait of Gibraltar is a narrow strait that connects the Atlantic Ocean to the Mediterranean Sea and separates Europe from Africa.
The two continents are separated by 7.7 nautical miles (14.2 kilometers, 8.9 miles) at its narrowest point. Fe ...
closed 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 pockets similar to today's
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 ...
. Then, around 5.5 Ma, wetter climatic conditions resulted in the basin receiving more fresh water from
river
A river is a natural stream of fresh water that flows on land or inside Subterranean river, caves towards another body of water at a lower elevation, such as an ocean, lake, or another river. A river may run dry before reaching the end of ...
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 estuary ...
(much like today's
Caspian Sea
The Caspian Sea is the world's largest inland body of water, described as the List of lakes by area, world's largest lake and usually referred to as a full-fledged sea. An endorheic basin, it lies between Europe and Asia: east of the Caucasus, ...
). 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
The Zanclean flood or Zanclean deluge is theorized to have refilled the Mediterranean Sea 5.33 million years ago.
This flooding ended the Messinian salinity crisis and reconnected the Mediterranean Sea to the Atlantic Ocean, although it i ...
.
Even today, the Mediterranean is considerably
saltier than the
North Atlantic
The Atlantic Ocean is the second largest of the world's five oceanic divisions, with an area of about . It covers approximately 17% of Earth's surface and about 24% of its water surface area. During the Age of Discovery, it was known for ...
, owing to its near isolation by the Strait of Gibraltar and its high rate of
evaporation
Evaporation is a type of vaporization that occurs on the Interface (chemistry), surface of a liquid as it changes into the gas phase. A high concentration of the evaporating substance in the surrounding gas significantly slows down evapora ...
. 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 geochronolo ...
), 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 (1826–1907) studied fossils embedded between
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 ...
-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 estuari ...
, and freshwater sediment layers, and identified them as having been deposited just before the end 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. In 1867, he named the period the Messinian after the city of
Messina
Messina ( , ; ; ; ) is a harbour city and the capital city, capital of the Italian Metropolitan City of Messina. It is the third largest city on the island of Sicily, and the 13th largest city in Italy, with a population of 216,918 inhabitants ...
in
Sicily
Sicily (Italian language, Italian and ), officially the Sicilian Region (), is an island in the central Mediterranean Sea, south of the Italian Peninsula in continental Europe and is one of the 20 regions of Italy, regions of Italy. With 4. ...
, Italy. Since then, several other salt-rich and gypsum-rich
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 oce ...
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
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 ...
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 Project conducted from the ''
Glomar Challenger'' under the supervision of co-chief scientists
William B. F. Ryan and
Kenneth Hsu. These deposits were dated and interpreted for the first time as deep-basin products of the Messinian salinity crisis.

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. Floodplains stretch from the banks of a river channel to the base of the enclosing valley, and experience flooding during periods of high Discharge (hydrolog ...
silts; and
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 ...
,
anhydrite,
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
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 oce ...
minerals that often form from drying of
brine
Brine (or briny water) is a high-concentration solution of salt (typically sodium chloride or calcium chloride) in water. In diverse contexts, ''brine'' may refer to the salt solutions ranging from about 3.5% (a typical concentration of seawat ...
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 unicellular organism, single-celled organisms, members of a phylum or class (biology), class of Rhizarian protists characterized by streaming granular Ectoplasm (cell bio ...
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 . 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. They ...
by
sandstorms, mixed with quartz sand blown in from nearby continents, and ended up in a
brine
Brine (or briny water) is a high-concentration solution of salt (typically sodium chloride or calcium chloride) in water. In diverse contexts, ''brine'' may refer to the salt solutions ranging from about 3.5% (a typical concentration of seawat ...
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, pi ...
. 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)
canyon
A canyon (; archaic British English spelling: ''cañon''), gorge or chasm, is a deep cleft between escarpments or cliffs resulting from weathering and the erosive activity of a river over geologic time scales. Rivers have a natural tendency t ...
s that were cut into the sides of the dry Mediterranean basin by rivers flowing down to the
abyssal plain
An abyssal plain is an underwater plain on the deep ocean floor, usually found at depths between . 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. They ...
.
For example, the
Nile
The Nile (also known as the Nile River or River Nile) is a major north-flowing river in northeastern Africa. It flows into the Mediterranean Sea. The Nile is the longest river in Africa. It has historically been considered the List of river sy ...
cut its bed down to 200 metres (660 feet) below sea level at
Aswan
Aswan (, also ; ) 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 Nile at the first cataract. The modern city ha ...
(where Ivan S. Chumakov found marine
Pliocene
The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58[Foraminifera
Foraminifera ( ; Latin for "hole bearers"; informally called "forams") are unicellular organism, single-celled organisms, members of a phylum or class (biology), class of Rhizarian protists characterized by streaming granular Ectoplasm (cell bio ...](_blank)
in 1967), and below sea level just north of
Cairo
Cairo ( ; , ) is the Capital city, capital and largest city of Egypt and the Cairo Governorate, being home to more than 10 million people. It is also part of the List of urban agglomerations in Africa, largest urban agglomeration in Africa, L ...
.
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
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 oce ...
s suggests that the area was repeatedly flooded and desiccated over 700,000 years.
Chronology

Based on
palaeomagnetic datings of
Messinian
The Messinian is in the geologic timescale the last age or uppermost stage of the Miocene. It spans the time between 7.246 ± 0.005 Ma and 5.333 ± 0.005 Ma (million years ago). It follows the Tortonian and is followed by the Zanclean, the fir ...
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
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. This age was characterised by several stages of
tectonic
Tectonics ( via Latin ) are the processes that result in the structure and properties of the Earth's crust and its evolution through time. The field of ''planetary tectonics'' extends the concept to other planets and moons.
These processes ...
activity and sea level fluctuations, as well as
erosion
Erosion is the action of surface processes (such as Surface runoff, water flow or wind) that removes soil, Rock (geology), rock, or dissolved material from one location on the Earth's crust#Crust, Earth's crust and then sediment transport, tran ...
al and
depositional events, all more or less interrelated.
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 borders of the oceans, oceanic divisions, with an area of about . It covers approximately 17% of Earth#Surface, Earth's surface and about 24% of its water surface area. During the ...
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 an activity that produces models representing empirical objects, phenomena, and physical processes, to make a particular part or feature of the world easier to understand, define, quantify, visualize, or simulate. It ...
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
The Grand Canyon is a steep-sided canyon carved by the Colorado River in Arizona, United States. The Grand Canyon is long, up to wide and attains a depth of over a mile ().
The canyon and adjacent rim are contained within Grand Canyon Nati ...
) 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 f ...
age (at the start of the
Pliocene
The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58[Zanclean flood
The Zanclean flood or Zanclean deluge is theorized to have refilled the Mediterranean Sea 5.33 million years ago.
This flooding ended the Messinian salinity crisis and reconnected the Mediterranean Sea to the Atlantic Ocean, although it i ...](_blank)
,
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
In geology and related fields, a stratum (: strata) is a layer of Rock (geology), rock or sediment characterized by certain Lithology, lithologic properties or attributes that distinguish it from adjacent layers from which it is separated by v ...
points strongly to several cycles of the Mediterranean Sea completely drying and being refilled,
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
tectonic
Tectonics ( via Latin ) are the processes that result in the structure and properties of the Earth's crust and its evolution through time. The field of ''planetary tectonics'' extends the concept to other planets and moons.
These processes ...
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. The last refilling was at 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 ...
/
Pliocene
The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58[Strait of Gibraltar
The Strait of Gibraltar is a narrow strait that connects the Atlantic Ocean to the Mediterranean Sea and separates Europe from Africa.
The two continents are separated by 7.7 nautical miles (14.2 kilometers, 8.9 miles) at its narrowest point. Fe ...](_blank)
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 point of view.
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 () is a desert located within Spain's south-eastern province of Almería. It is in the interior, about north of the provincial capital Almería, in the Tabernas municipality in Andalusia. It is the only desert in Europe, ...
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)
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
Spain, or the Kingdom of Spain, is a country in Southern Europe, Southern and Western Europe with territories in North Africa. Featuring the Punta de Tarifa, southernmost point of continental Europe, it is the largest country in Southern Eur ...
. The relationship between these two basins is assumed to represent the relationships of the wider region.
Recent work has relied on
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 ...
to correlate the underlying
marl
Marl is an earthy material rich in carbonate minerals, Clay minerals, clays, and silt. When Lithification, hardened into rock, this becomes marlstone. It is formed in marine or freshwater environments, often through the activities of algae.
M ...
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''), river floors, or lake floors. In other words, bathymetry is the underwater equivalent to hypsometry or topography. The first recorded evidence of wate ...
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 a branch of mathematics concerned with properties of space such as the distance, shape, size, and relative position of figures. Geometry is, along with arithmetic, one of the oldest branches of mathematics. A mathematician w ...
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.
[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
The Strait of Gibraltar is a narrow strait that connects the Atlantic Ocean to the Mediterranean Sea and separates Europe from Africa.
The two continents are separated by 7.7 nautical miles (14.2 kilometers, 8.9 miles) at its narrowest point. Fe ...
is now, the location of one of the tectonic boundaries between the
African plate and the
European plate and its southern fragments such as the
Iberian plate. This boundary zone is characterised by an arc-shaped tectonic feature, the
Gibraltar Arc, which includes southern Spain and
northern Africa
North Africa (sometimes Northern Africa) is a region encompassing the northern portion of the African continent. There is no singularly accepted scope for the region. However, it is sometimes defined as stretching from the Atlantic shores of t ...
. In the present day area of the Mediterranean Sea, are three of these arc-shaped belts: the
Gibraltar Arc, 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 closely related to the causes of the Messinian salinity crisis. Tectonic movements may have closed and re-opened passages, as the region where the connection with the Atlantic Ocean was situated is permeated by
strike-slip fault
In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic ...
s and rotating blocks of continental crust. As faulting accommodated the regional compression caused by Africa's convergence with
Eurasia
Eurasia ( , ) is a continental area on Earth, comprising all of Europe and Asia. According to some geographers, Physical geography, physiographically, Eurasia is a single supercontinent. The concept of Europe and Asia as distinct continents d ...
, 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
A lithosphere () is the rigid, outermost rocky shell of a terrestrial planet or natural satellite. On Earth, it is composed of the crust and the lithospheric mantle, the topmost portion of the upper mantle that behaves elastically on time ...
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 (or generally, quakes) and the generation and propagation of elastic ...
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, cosmochemistry, ast ...
* The composition of
igneous rock
Igneous rock ( ), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rocks are formed through the cooling and solidification of magma or lava.
The magma can be derived from partial ...
s varies; this constrains the location and extent of any
subduction
Subduction is a geological process in which the oceanic lithosphere and some continental lithosphere is recycled into the Earth's mantle at the convergent boundaries between tectonic plates. Where one tectonic plate converges with a second p ...
.
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
Subduction is a geological process in which the oceanic lithosphere and some continental lithosphere is recycled into the Earth's mantle at the convergent boundaries between tectonic plates. Where one tectonic plate converges with a second p ...
may have caused periodic regional uplift. Changes in
volcanic rock
Volcanic rocks (often shortened to volcanics in scientific contexts) are rocks formed from lava erupted from a volcano. Like all rock types, the concept of volcanic rock is artificial, and in nature volcanic rocks grade into hypabyssal and me ...
s suggest that subduction zones at the rim of the
Tethys Sea may have
rolled back westwards, changing the
chemistry
Chemistry is the scientific study of the properties and behavior of matter. It is a physical science within the natural sciences that studies the chemical elements that make up matter and chemical compound, compounds made of atoms, molecules a ...
and
density
Density (volumetric mass density or specific mass) is the ratio of a substance's mass to its volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' (or ''d'') can also be u ...
in
magma
Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma (sometimes colloquially but incorrectly referred to as ''lava'') is found beneath the surface of the Earth, and evidence of magmatism has also ...
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 or the loss of a layer of the entire
lithosphere
A lithosphere () is the rigid, outermost rocky shell of a terrestrial planet or natural satellite. On Earth, it is composed of the crust and the lithospheric mantle, the topmost portion of the upper mantle that behaves elastically on time ...
.
*Deblobbing, the loss of a "blob" of
lithospheric mantle, 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 the Serbian geophysics, geophysicist and astronomer Milutin Milanković. In the ...
, 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.
Glacioeustatic sea level falls with an amplitude of around that began approximately 6.14 Ma were likely responsible for modulating the connection between the Mediterranean and the Atlantic. One particularly major glacioeustatic fluctuation, a sea level drop of about , occurred around 5.26 Ma, around the Miocene-Pliocene boundary.
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 terms for ...
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
abyssal plain
An abyssal plain is an underwater plain on the deep ocean floor, usually found at depths between . 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. They ...
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 (also known as ''basin'' in the UK) is a bowl-shaped plumbing fixture for washing hands, dishwashing, and other purposes. Sinks have a tap (faucet) that supplies hot and cold water and may include a spray feature to be used for fas ...
", 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
The lapse rate is the rate at which an atmospheric variable, normally temperature in Earth's atmosphere, falls with altitude. ''Lapse rate'' arises from the word ''lapse'' (in its "becoming less" sense, not its "interruption" sense). In dry air, ...
of around per kilometre, 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
abyssal plain
An abyssal plain is an underwater plain on the deep ocean floor, usually found at depths between . 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. They ...
, permitting no permanent life but
extremophile
An extremophile () is an organism that is able to live (or in some cases thrive) in extreme environments, i.e., environments with conditions approaching or stretching the limits of what known life can adapt to, such as extreme temperature, press ...
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 air pressure or barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The Standard atmosphere (unit), standard atmosphere (symbol: atm) is a unit of pressure defined as , whi ...
, further increasing heat stress. However, these simple estimates are likely far too extreme. Murphy et al.'s 2009
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 terms for ...
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 patterns 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 climate, described by Köppen and Trewartha as ''Cs'', is a temperate climate type that occurs in the lower mid-latitudes (normally 30 to 44 north and south latitude). Such climates typic ...
that we associate with Italy,
Greece
Greece, officially the Hellenic Republic, is a country in Southeast Europe. Located on the southern tip of the Balkan peninsula, it shares land borders with Albania to the northwest, North Macedonia and Bulgaria to the north, and Turkey to th ...
, and the
Levant
The Levant ( ) is the subregion that borders the Eastern Mediterranean, Eastern Mediterranean sea to the west, and forms the core of West Asia and the political term, Middle East, ''Middle East''. In its narrowest sense, which is in use toda ...
would be limited to the
Iberian Peninsula
The Iberian Peninsula ( ), also known as Iberia, is a peninsula in south-western Europe. Mostly separated from the rest of the European landmass by the Pyrenees, it includes the territories of peninsular Spain and Continental Portugal, comprisin ...
and the western
Maghreb
The Maghreb (; ), also known as the Arab Maghreb () and Northwest Africa, is the western part of the Arab world. The region comprises western and central North Africa, including Algeria, Libya, Mauritania, Morocco, and Tunisia. The Maghreb al ...
. 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
The Eastern Alps are usually defined as the area east of a line from Lake Constance and the Alpine Rhine valley, up to the Splügen Pass at the Main chain of the Alps, Alpine divide, and down the Liro (Como), Liro River to Lake Como in the south. ...
, the
Balkans
The Balkans ( , ), corresponding partially with 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 throug ...
, 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
The Paratethys sea, Paratethys ocean, Paratethys realm or just Paratethys (meaning "beside Tethys"), was a large shallow inland sea that covered much of mainland Europe and parts of western Asia during the middle to late Cenozoic, from the lat ...
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 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 salinity crisis resulted in major extinctions of marine fish and other marine fauna native to the basin.
The present day biodiversity gradient of the Mediterranean, where diversity decreases eastward, developed after the crisis. The land mammal faunas of the Mediterranean also suffered diversity losses. Due to the fusion of the Iberian Peninsula and North Africa, a
faunal interchange between the two regions occurred. The crisis also allowed the dispersal of terrestrial animals to remote landmasses such as the
Balearic Islands
The Balearic Islands are an archipelago in the western Mediterranean Sea, near the eastern coast of the Iberian Peninsula. The archipelago forms a Provinces of Spain, province and Autonomous communities of Spain, autonomous community of Spain, ...
, where several animal species, such as the goat-antelope ''
Myotragus,'' would continue to be isolated until the
Holocene
The Holocene () is the current geologic time scale, geological epoch, beginning approximately 11,700 years ago. It follows the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene to ...
, over 5 million years later.
Dehydrated geography
The notion of a completely waterless Mediterranean Sea has some corollaries.
*At the time, the
Strait of Gibraltar
The Strait of Gibraltar is a narrow strait that connects the Atlantic Ocean to the Mediterranean Sea and separates Europe from Africa.
The two continents are separated by 7.7 nautical miles (14.2 kilometers, 8.9 miles) at its narrowest point. Fe ...
was not open, but other seaways (the
Betic corridor to the north where the
Sierra Nevada
The Sierra Nevada ( ) is a mountain range in the Western United States, between the Central Valley of California and the Great Basin. The vast majority of the range lies in the state of California, although the Carson Range spur lies primari ...
or
Baetic Cordillera
The Baetic System or Betic System () 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 Baetic Mountains. The n ...
is now, or to the south where the
Rifean corridor or corridors where the
Rif Mountains
The Rif (, ), also called Rif Mountains, is a geographic region in northern Morocco. It is bordered on the north by the Mediterranean Sea and Spain and on the west by the Atlantic Ocean, and is the homeland of the Rifians and the Jebala people. ...
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 is the variability of life, life on Earth. It can be measured on various levels. There is for example genetic variability, species diversity, ecosystem diversity and Phylogenetics, phylogenetic diversity. Diversity is not distribut ...
of much of the basin.
*The basin's low altitude would have made it extremely hot during the summer through
adiabatic heating, a conclusion supported by the presence of
anhydrite, 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
Nile
The Nile (also known as the Nile River or River Nile) is a major north-flowing river in northeastern Africa. It flows into the Mediterranean Sea. The Nile is the longest river in Africa. It has historically been considered the List of river sy ...
, as the buried canyon under
Cairo
Cairo ( ; , ) is the Capital city, capital and largest city of Egypt and the Cairo Governorate, being home to more than 10 million people. It is also part of the List of urban agglomerations in Africa, largest urban agglomeration in Africa, L ...
shows) and in the Rhone valley.
There is an opinion that during the Messinian, the Red Sea was connected at
Suez
Suez (, , , ) is a Port#Seaport, seaport city with a population of about 800,000 in north-eastern Egypt, located on the north coast of the Gulf of Suez on the Red Sea, near the southern terminus of the Suez Canal. It is the capital and largest c ...
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 approximately 20% of the water area of Earth#Surface, Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia (continent), ...
, and dried out along with the Mediterranean.
Replenishment
When the
Strait of Gibraltar
The Strait of Gibraltar is a narrow strait that connects the Atlantic Ocean to the Mediterranean Sea and separates Europe from Africa.
The two continents are separated by 7.7 nautical miles (14.2 kilometers, 8.9 miles) at its narrowest point. Fe ...
was ultimately breached, the
Atlantic Ocean
The Atlantic Ocean is the second largest of the world's five borders of the oceans, oceanic divisions, with an area of about . It covers approximately 17% of Earth#Surface, Earth's surface and about 24% of its water surface area. During 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 any 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 seve ...
higher than today's
Angel Falls at , and far more powerful than either the
Iguazu Falls or the
Niagara Falls
Niagara Falls is a group of three waterfalls at the southern end of Niagara Gorge, spanning the Canada–United States border, border between the Provinces and territories of Canada, province of Ontario in Canada and the state of New York (s ...
, 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
Sicily (Italian language, Italian and ), officially the Sicilian Region (), is an island in the central Mediterranean Sea, south of the Italian Peninsula in continental Europe and is one of the 20 regions of Italy, regions of Italy. With 4. ...
. 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''. 27 February 2018. by Ictja-Csic, Institute of Earth Sciences, Jaume Almera
See also
* Messinian evaporite
*Atlantropa
Atlantropa, also referred to as Panropa, was a Macro-engineering, gigantic engineering and colonisation idea that Germany, German architect Herman Sörgel devised in the 1920s, and promoted until his death in 1952. The proposal included several H ...
References
Further reading
*
*
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
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