A marine biologist says that he found a huge underwater sinkhole in Australia's Great Barrier Reef while using Google Maps.

Blue Holes

Also known as blue holes, these large marine sinkholes most often formed during the past ice ages when the sea levels were much lower. They were subjected to erosion from chemical weather and rain but the erosion ceased after they were submerged, leaving deep blue caverns.

Marine geologist Pete van Hengstum, from Texas A&M University at Galveston, explained that blue-holes are water-filled sinkholes that formed in carbonate rock, which eventually dissolves in the subsurface to form caves or cavities.

Blue holes with darker blue color tend to extend deeper below sea levels. Other examples of these marine sinkholes include the Great Blue Hole in Belize and the Dragon Hole in the South China Sea.

Spotted On Google Maps

Johnny Gaskell said that he found the anomaly of the deep, dark blue while looking satellite imagery of a stretch of the reef on the internet. He decided to conduct further investigations after spotting the deep blue hole on Google Maps.

"We decided to head far offshore, out further than our normal Reef trips to see what dwelled within," he shared on Instagram.

Gaskell and colleagues found a thriving ecosystem at the site. There were super elongated Staghorn Corals (Acropora) and huge Birds Nest Corals (Seriatopora) at depths between 15m and 20m. Gaskell claims these are the biggest and most delicate colonies he has seen.

The scientist also noted that the blue hole appeared to be totally unaffected despite that a Category 4 cyclone hit this region of the Great Barrier Reef just five months earlier.

"The position of this deep hole within the lagoon walls has obviously protected these corals for decades."

Australia's Great Barrier Reef In Danger

It is no surprise that such a large feature on the Great Barrier Reef can go undiscovered for a long time. The Great Barrier Reef stretches more than 1,400 miles and covers an area of about 133,000 square miles, making it the largest structure on Earth created by living organisms.

The Great Barrier Reef, however, is in danger. Scientists reported that huge sections of the reef stretching across hundreds of miles of its northern sector is already dead. The phenomenon is attributed to hot seawater likely caused by global warming.

Illegal fishing and rapid coastal development are also being blamed for the destruction of the Great Barrier Reef.