Ever heard about “blue holes?” Uh, wait a second, we don’t mean black holes. That’s an astronomical wonder. You read it right, blue holes, something here on Earth. They are elusive underwater cave systems that appear blue due to the ocean, and hence the name. These underwater cadavers are a diver’s Holy Grail; and are quite a gapping portal that holds the mystery to the ancient past. Dear friends, welcome to Andros, the largest island in the Bahamas that’s home to several blue holes.
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Talking Blues: They Say Your Hole Is Too Big For A Dive
Andros is the largest island in the Bahamas, located is 50 kilometers (30 miles) west across the tongue of the ocean from the national capital of Nassau on New Providence Island. Despite its famous beaches and azure waters, its also home to at least 200 underwater blue holes — its actually what’s beneath the ocean that makes these natural cadavers so alluring.
These blue holes could reach depths of almost 300 meters (1,000 feet) underwater, and are home to ancient limestone caves carved underneath the ocean bed. Divers daring enough to explore beneath the ocean often encounter precarious stalagmites and dripstones — a form of sedimentary limestone that could only form above water. A testament to how old these caves are. Here’s the catch: how on Earth in the depths of the ocean did these biological time capsules came to be? That’s a long story.
During the ice ages, a glacial runoff might be the best possible theory to explain this mystery. The glaciers might have eroded the limestone, and as they melted away, the sea levels rose and the caves were flooded, forming the mysterious blue hole cave systems. These blue holes are named for their indigo centers and light blue perimeters; and hosts all sorts of aquamarine species — coral reefs, fishes, sea turtles — and also prone to tides as usual.
A Time Capsule. Sounds Familiar?
Blue holes aren’t the only thing Andros has to offer. The island also hosts several inland blue holes as well (they’re not blue on land though, but you know what we mean). There are more 175 inland blue holes which are hidden in the woodlands of the island, are quite different from the offshore blue holes, and not like anything else here on Earth. A mystery, huh?
They appear dark and devoid of light due to the accumulation of dead bacteria from the debris of trees and leaves. On earth, they look like swamps, but what lies underneath is amazing. These blue holes are somehow stratified with a thin layer of freshwater on the surface due to weak tides. This prevents oxygen from reaching the dense saltwater beneath, and results in an ecological anomaly — an underwater world of prehistoric species still capable of surviving in an oxygen-free environment.
The absence of oxygen gives rise to hydrogen sulfide, a gas that’s potentially fatal to humans. Its just recently that people now dare to dive these dangerous inland blue holes, however, scientists have now begun investigating just how otherworldly these blue holes actually are. And in 2011, biologists conducted Deoxyribonucleic acid (DNA) analysis on several microbes across five different Bahamian blue holes and discovered no trace of similar species.
The Holy Grail For Divers
So are these underwater caves safe to dive in? Short answer: try! Each year, thousands of experienced divers flock to Andros to get a taste of these underwater cadavers, and lo and behold, its a dream come true for most. Snorkeling the surface is now a popular sports for vacationers, but if for whatever reason you want to stay dry, you can try hiking as well. But come on, dive in a blue hole and you’d encounter one of nature’s hidden mysteries of the past.
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Written by: Nana Kwadwo, Tue, May 21, 2019.