The holes concerned were formerly an Ice Age limestone cave system – much like the Yorkshire holes that cavers like to explore on rope and rafts (see www.physorg.com/print205158392.html ). They are now known as the blue holes of the Bahamas as after the Ice Age sea levels rose and flooded the caves. It seems more than likely that the Bahamas were an extensive tract of land – possibly even connected to the mainland of North America. Rather, the continental shelf around North America. Or at least separated by a fairly narrow channel. Stalagmites laid down during the Ice Age are now being studied in order to ascertain what the climate was like at that time – which will prove to be interesting. What if the Bahamas had been part of a land mass that included an elongated Florida as well as Cuba and Hispanola. That would effectively have affected ocean currents. The caves, or blue holes, have already produced evidence of swings in sea level and spikes in iron containing dust. The latter is assumed to have an origin in the Sahara and is taken to be evidence of drought where the wind blows top soil/ dust from the surface. Even nowadays red dust sometimes turns up in northwest Europe falling with the rain, and has been traced back to the Sahara. It doesn’t necessarily follow that red dust in the Ice Age had such an origin, but want of a better explanation would seem to mean they are right. Or does it?
Elsewhere in the abstract we learn that over the last 20 million years sea levels have varied by as much as 300 to 400 feet which must also indicate something as yet not understood was going on. That is a big jump. Some researchers have dived as deep as 275 feet – but there are huge cave systems down there, with galleries and passages that have never been explored by scientists, and one hole is estimated to be 663 feet deep. This story is ongoing and will surface again in the coming months and years. For example, in modern Britain limestone caves are formed by underground streams – but do they go as deep, or deeper than sea level?