What is a Dry Sea

Question

I wanted to create my own unique worlds. I wanted to take my readers to places they wouldn’t go to in any other story and show them things they wouldn’t see anywhere else. For instance, the Dry Sea in The View from the Mirror quartet^* – a stifling, salt-coated wilderness four kilometers below sea level, is an environment that hasn’t existed on Earth for five million years.

I've asked this question in worldbuilding, didn't get a response. They told me to come here. Can someone here explain to me what a Dry Sea is? I've tried to do my own research, but I couldn't find anything on the Dry Sea Ian Irvine stated in the Interview, I copied and pasted from.

^{* That is a book}

Answer 1

Your reference to 5 million years makes me think you are referring to the desiccation of the Mediterranean Sea. The entire basin almost totally dried out in what is known as the Messinian salinity crisis, about 6.0 to 5.3 million years ago. JOIDES deep sea drilling has proved the desiccation by drilling into salt deposits and subaerial sediments, immediately overlain by deep sea sediments in what are now some of the deepest basins of the Mediterranean. It all came to an end when erosion broke through the Rif-Betic Arc, which was a land bridge between Africa and Europe. When the Atlantic broke through it produced what was probably the most spectacular waterfall in world history - and we missed it by only 5.3 million years, dammit!

Your reference mentions '4 kilometres below sea level'. The average depth of the Mediterranean is only 1.5 km, whereas the deepest part is 5.27 km. It is probable that the Nile kept the very deepest part wet even when the rest of the Mediterranean was dry, but desiccation during the late Neogene, to 4 kilometres below current sea level could very well be close to the reality. I can't think of anywhere else in the world where such deep desiccation could have occured. The Dead Sea doesn't even come close. So the reference is probably to the dry sea, rather than a dry sea.

Later additional point, I have just recalled that Bischofite, hydrated magnesium chloride, was recovered from the Eastern Mediterranean deep basin at a depth of -3580 metres. This is further proof of near total desiccation, with Mg being concentrated, by solar evaporation, to a brine at nearly 200 x the normal sea-water concentration.

Answer 2

A dry sea is a location where there was once a sea, but no longer exists or one where the sea only occasionally fills with water before it rapidly dries out. As the water evaporates, salt that was once dissolved in the water precipitates and deposits on what was the sea bed, now the land surface. Dry seas are larger versions of dry lakes.

Sometimes dry seas form naturally and on other occasions, as with the Aral Sea, their formation is due to human interference with nature.