MESSINIAN SALINITY
CRISIS
Around
6 million years ago, tectonic movements caused the merger of the strait of
Gibraltar and the Mediterranean Ocean became the Mediterranean Desert, it was temporarily
cut off from the Atlantic Ocean, and as time passed excess evaporation of seawater
led to the formation of huge deposits of salt kilometers-thick throughout the entire
basin, as much as 6% of the ocean’s salt was transformed into giant
deposits left on the Mediterranean seafloor due to sedimentation.
The event is called the Messinian Salinity Crisis, as it happened during the Messinian epoch on the Geological Time Scale (GTS).
The
consequences of this event were drastic shifts in both aquatic and land ecosystems
due to changes in regional climate and harsh geochemical conditions.
Eventually,
the same tectonic forces that caused the crisis pulled apart the African and
European Plates and opened up the Strait of Gibraltar, and reconnected the Mediterranean
to the Atlantic around 5.3 million years ago, at the Miocene–Pliocene boundary
in the GTS.
Geologic evidence suggests that the Mediterranean filled up rapidly (most of the Mediterranean basin seems to have been refilled in no more than two years ) after the opening of the Strait of Gibraltar, and the Messinian salinity crisis ended with a Megaflood that carved the ocean floor and a huge (At peak discharge water poured in at a rate of 100 million cubic meters per second.) waterfall formed at the Strait of Gibraltar as imagined in this illustration published in The Atlantic Monthly.
Some recent evidence suggests that during the end of the Messinian
salinity crisis the quick disappearance of a land bridge between Europe and
Africa affected the migration of mammals, had the connection not disappeared,
“hominins might have arrived in Europe much earlier than 1.2 million years ago.”, however, there is more
to the story.
The
Desertification of the Mediterranean caused an increase in volcanic activity
in the surrounding region, it worked a bit like this:
Large-scale evaporation and rapid sea-level fall in the
Mediterranean basin would have unloaded the crust and reduced the burden on the
underlying mantle
This caused a Mantle decompression and led to partial melting of rocks underneath,
The same process allowed more magma to migrate towards the surface via dykes (vertical magma tubes), generating increased volcanism at the surface
Bibliography :
https://www.bbc.co.uk/programmes/p00fzsth
Hsü, K. J. The Mediterranean was a Desert (Princeton Univ. Press, 1983).
