The Zanclean flood is a flood

Flood

A flood is an overflow of an expanse of water that submerges land. The EU Floods directive defines a flood as a temporary covering by water of land not normally covered by water...

 theorized to have refilled the Mediterranean Sea

Mediterranean Sea

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

 5.33 million years ago, at the beginning of the Zanclean

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 and 3.6 Ma ± 0.005 Ma . It is preceded by the Messinian age of the Miocene epoch, and followed by the Piacenzian age....

 age, between the Miocene

Miocene

The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...

 and Pliocene

Pliocene

The Pliocene Epoch is the period in the geologic timescale that extends from 5.332 million to 2.588 million years before present. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch...

, which ended the Messinian salinity crisis

Messinian salinity crisis

The Messinian Salinity Crisis, 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 went into a cycle of partly or nearly complete desiccation throughout the latter part of the Messinian age of the Miocene...

. The term was coined by Maria Bianca Cita in 1972 during the Deep Sea Drilling Project study which investigated specifically the transition between the Messinian

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 5.332 ± 0.005 Ma...

 and Zanclean ages in the Mediterranean. The Mediterranean had undergone several cycles of drying out and replenishment of which this was the last occasion before human history.

According to this model, when water from the Atlantic Ocean

Atlantic Ocean

The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...

 refilled the cut-off inland seas in the Mediterranean basin

Mediterranean Basin

In biogeography, the Mediterranean Basin refers to the lands around the Mediterranean Sea that have a Mediterranean climate, with mild, rainy winters and hot, dry summers, which supports characteristic Mediterranean forests, woodlands, and scrub vegetation...

 that had become desiccated

Desiccation

Desiccation is the state of extreme dryness, or the process of extreme drying. A desiccant is a hygroscopic substance that induces or sustains such a state in its local vicinity in a moderately sealed container.-Science:...

 due to increased evaporation

Evaporation

Evaporation is a type of vaporization of a liquid that occurs only on the surface of a liquid. The other type of vaporization is boiling, which, instead, occurs on the entire mass of the liquid....

 and thus higher salinity

Salinity

Salinity is the saltiness or dissolved salt content of a body of water. It is a general term used to describe the levels of different salts such as sodium chloride, magnesium and calcium sulfates, and bicarbonates...

, flooding occurred through the basin. A channel opened from the Atlantic Ocean, through the modern-day Gibraltar Strait, and carried ocean water over a distance of over 200 km

Kilometre

The kilometre is a unit of length in the metric system, equal to one thousand metres and is therefore exactly equal to the distance travelled by light in free space in of a second...

. The Mediterranean Sea was filled over a period estimated between several months and two years. Sea level rise in the basin may have reached rates at times greater than ten metres per day.

Water rushed down a drop of a few kilometres, and with a volume far greater than present day Iguazu

Iguazu Falls

Iguazu Falls, Iguassu Falls, or Iguaçu Falls are waterfalls of the Iguazu River located on the border of the Brazilian State of Paraná and the Argentine Province of Misiones. The falls divide the river into the upper and lower Iguazu. The Iguazu River originates near the city of Curitiba. It flows...

 or the Niagara

Niagara Falls

The Niagara Falls, located on the Niagara River draining Lake Erie into Lake Ontario, is the collective name for the Horseshoe Falls and the adjacent American Falls along with the comparatively small Bridal Veil Falls, which combined form the highest flow rate of any waterfalls in the world and has...

falls, but studies of the underground structures at the Gibraltar Strait show that the flooding channel descended in a rather gradual way toward the bottom of the basin, rather than forming a steep waterfall.