An ocean sinkhole, known popularly as a blue hole, is a large marine sinkhole that occurs close to the island made of coral reef and limestone.The opening of an ocean sinkhole is mostly formed on the surface and is visible to the eye, and can actually extend quite deep down into the ocean, far enough to even expose some submerged passages. Ocean sinkholes were first discovered towards the end of the 20th century by recreational divers and fishermen.Today, travelers and adventurers from across the world want to know more about underwater sinkholes. Sinkholes, whether blue holes or those that form on land, are usually the result of carbonate or limestone-based surfaces being in touch with water. Over time, the water dissolves the limestone, leading to the formation of the sinkhole. There are several blue sinkholes found all over the world, but a few that stand out are The Great Blue Hole of Belize, Dean’s Blue Hole in The Bahamas, and the Dragon Hole of the South China Sea. Often confused with Cenotes, blue holes are formed of fresh, marine, or mixed seawater, while cenotes comprise fresh groundwater.Read on to know more about underwater sinkholes.Exploring And Naming SinkholesFirst found during the late 20th century by fishermen and divers, these blue holes extend quite deep down into the ocean and require a good skill level to be explored.Recreational divers who want to explore ocean sinkholes, like that in Belize, are required to have predetermined levels of skill and training before they are allowed to go diving in these blue holes.Recently, there’s been a lot of interest in ocean sinkholes as scientists and explorers find more sinkholes. For example, in Florida, a new ocean sinkhole, named Green Banana was discovered in 2020, which gained the attention of scientists of the National Oceanic and Atmospheric Administration of America. Prior to this in 2019, another Floridian Blue Hole, named Amberjack Hole was investigated which led to the discovery of important facts, particularly the composition of blue hole waters, marine life within and around them, and the composition of the bottom of these sinkholes, by the geological society.The Great Blue Hole, discovered by a team of divers and scientists, revealed useful information like the presence of stalactites, which are mineral formations that you may have seen in caves. The discovery also uncovered the presence of a thick layer of hydrogen sulfide on the ocean floor. Because they did this exploration using modern technology, they could create a 3D map of the interior as well.The first recorded blue hole exploration, however, was in 2009, when a huge team was recruited to explore the many sinkholes in The Bahamas.The Formation Of A SinkholeInitial records of the earliest forms of blue sinkholes point toward the Ice Ages, when the sea level was much lower, making them easy targets for chemical erosion because of rain.This was a common factor in all landscapes rich in limestone formations near the water’s surface.Today, evidence suggests that there can be different factors causing the formation of these sinkholes. Weathering away of water’s surface because of chemical erosion during heavy rains or thunderstorms is still one of them. Other factors include the glacial erosion process of limestone, such as that of the Great Blue Hole. The building up of coral reefs together is also another common reason for their formation.Sinkholes Throughout The WorldThe most popularly known sinkholes in the world include-The Great Blue Hole of Belize- also declared a world heritage site, it’s the largest ocean sinkhole in the world overall.The Amberjack Hole in Florida - a popular site with scientists.The Green Banana Blue Hole- situated near the deep coast of Florida.The Red Sea Blue Hole of Egypt- also named Divers Cemetery because this deep mysterious blue hole has caused the death of almost 40 divers who went to explore it.The Dragon Hole of the South China Sea- the deepest mysterious blue hole in the world at a depth of over 984.3 ft (300 m).Dean’s Blue Hole- located in The Bahamas, this is the second deepest blue hole in the world with a depth of 666.7 ft (202 m).Marine Life And SinkholesBlue sinkholes are said to be hotspots of marine life, however, the depth of the blue hole can impact how much marine life is active.There can be a variety of sea species found in and around blue sinkholes, including but not limited to coral reefs, sea turtles, mollusks, sharks, and more. The Great Blue Hole of Belize, for example, is located in the middle of a coral reef. This reef is called the Lighthouse Reef, and is one of the three atolls (which is a ring-shaped reef) present in Belize.Flora And Fauna In SinkholesBlue holes are known for being anoxic, which means they don’t have oxygen.This means that deep blue holes actually do not support a lot of marine life. However, sinkholes do support a wide range of different bacteria. Coral reefs are also another feature of blue holes and can be found in abundance nearby to sinkholes.
An ocean sinkhole, known popularly as a blue hole, is a large marine sinkhole that occurs close to the island made of coral reef and limestone.
