10 September 2024: Day 4, Tarifa and birding on the Strait of Gibraltar, WINGS Spain in Autumn. Click on right here for a map appearing the place I’m lately.
We are actually on the Strait of Gibraltar, the nearest level between Europe and Africa. At its narrowest the Strait is handiest 13 km (8.1 miles) throughout, flanked on each and every facet via mountains.
The passage is longer east-to-west than it’s huge –> 58 km (36 miles) from starting to finish. Its present, water float and variable intensity give scientists clues as to the way it used to be shaped.
Water flows throughout the Strait kind of incessantly, each east and west, however the steadiness of water strikes eastward from the Atlantic into the Mediterranean. That’s since the Mediterranean evaporates sooner than tributaries and precipitation can fill it. The Atlantic pours in however the Mediterranean remains saltier than the Atlantic Ocean.
In truth, Mediterranean waters are such a lot saltier that they sink under the continuously incoming Atlantic and shape a heat extremely saline layer of backside water known as a thermohaline. You’ll be able to see this within the schematic of the Camarinal Sill which is west of the Narrows.
Whilst the Camarinal Sill is the shallowest level (280 m = 920 feet deep), the inner most level is on the Narrows (900 m = 3,000 feet deep). Deep water is black in this underwater topo map.
With handiest 25km (15.5 miles) between the 2 issues the float incessantly generates inner (subsurface) waves that may be noticed from satellites, although they don’t appear to be waves in floor navigation.
About 6 million years in the past plate tectonics(*) closed the relationship between the Mediterranean and the Atlantic. With out an inflow of water all the Mediterranean Sea evaporated, leaving at the back of salt and gypsum deposits. This Messinian Salinity Disaster lasted more or less 700,000 years. Then, fairly all at once, a leak evolved between Africa and Europe. It briefly eroded a deep channel to the Mediterranean and eroded backwards (upstream) to create the Gulf of Cadiz. This video of an experimental dam failure displays how that appears.
The Zanclean Flood came about slightly hastily! The Mediterranean crammed up inside of two years!
90% of the Mediterranean Basin flooding happened impulsively throughout a duration estimated to were between a number of months and two years, following low water discharges that may have lasted for a number of thousand years. Sea degree upward thrust within the basin will have reached charges every now and then more than ten meters in line with day (30 ft in line with day).
The result’s an underwater topography carved via the flood. This diagram displays the marine flooring however isn’t to scale (described under). It comes from ScienceDirect: The Zanclean megaflood of the Mediterranean – In search of unbiased proof — Daniel Garcia-Castellanos et al.
Everybody needed to run clear of the flood whilst the Strait used to be being shaped.
(*) p.s. Plate tectonics closed the Strait 6 million years in the past. At the present the African Plate is subducting below the Eurasian Plate within the Mediterranean area. Africa is slamming into Europe, albeit very slowly.