Dear anyone whose interested,
Some 5.5 million years ago the force of Africa colliding with Europe, closed the straits of Gibraltar, sealing off the Med, which then evaporated over 2000 years. The straits were then breached by the Atlantic and the basin filled up again over 100 years. This happened many times and resulted in massive salt accumulations. The Nile and Rhone created deep canyons as they cut down to the deep desert basin than had once been the Med ( I guess the Ebro did something similar but on a smaller scale). Many species migrated from one continent to another and to ‘island’ habitats, within the basin, some which are now islands others submerged areas of elevated sea floor. When the straits were breached the biggest water fall that we have evidence for, is believed to have existed - 70 km3 of water per day cascaded into a basin up to 3000m deep and 2 500 000 km2 in area! The width perhaps 5-10km …..wide and 300 times bigger than Niagara. I guess this record must also belong to Morocco….the Pillars of Hercules are really deserving of their name!
There are other ‘smaller’ mega water falls that would have been great to witness:
The collapse of the Dover Straits (in the past a ridge of high land linked what is now the sea floor between Dover and Calais) as part of 2 flood events 425,000 and 225,000 bp . It is believed the ‘Dover to Calais’ ridge held back an ice dammed lake on the southern North Sea Plain, it collapsed catastrophically, due to its weak structure ie chalk and perhaps moraine. These waterfalls/cascades resulted in the Thames, Rhine, Meuse and Seine flowing into a larger river within the Channel during times of glacial low sea level. Either waterfall/cascade probably did not exceed 10, 000km3 of water being released.
The collapse of the ice dammed lake Agassiz 8000bp, 700,000km2 in area and 75-150,000km3 in volume. This was held within the Laurentide Ice sheet that covered much of North America. It collapsed releasing most of this lake’s water into the Atlantic and raised global sea levels by 20-40cm almost immediately!
The overflowing of the Med into the deep basin (up to 2200m deep), which is now the Black sea around 7600 bp, due to sea level rise after the last ice age. This is an area of 450,000km2 and it is believed 43 km3 of water cascaded through the Bosporus per day for nearly a year (200 times as big as Niagara)! Though some scientists contest this event.
In the Tertiary the Red Sea closed ( ie no access to the Indian Ocean) and evaporated, leaving a deep basin that was later flooded by the Indian Ocean . The Red Sea is 450 000km2……up to 2500m deep very approx 500 000km3 in volume……another huge cascade.