Mysterious “blue holes” in seas

While many scientists are continuously exploring to unveil the mysterious blue hole, their opinions still have much controversy over how such large holes were formed in seas. A blue hole is a large sinkhole in the middle of the sea. It is also called a vertical cave because of its deep pit.

Two most convincing theories of how the vertical cave is made are by a collapse of an underwater cave and by underwater rock’s erosion. The adventure drama movie, “Sanctum,” is based on a real story of a vertical cave. The 3-D thriller follows a team of divers on an expedition to the unexplored underwater Esa’ala Cave system in New Guinea.

The most well known vertical cave is the Great Blue Hole. It is the largest sinkhole off the coast of Belize. The sinkhole is circular in shape, over 300 meters across and 124 meters deep. The Great Blue Hole was formed as surface of the sea rose and limestone melted about 65,000 years ago, but this is not scientifically confirmed yet. The sinkhole is chosen as a World Heritage Site by the United Nations Educational, Scientific and Cultural Organization (UNESCO). The World Heritage Site only includes few places in the world with special cultural or physical significance. This specific sinkhole is listed because of its significant and unusual sightings of fish such as Caribbean reef sharks, Blacktip sharks, bull sharks, and hammerheads.

The Dean’s Blue Hole in the Bahamas is the deepest sinkhole on Earth. The Dean’s Blue Hole has roughly circular shape with 202 meters in depth, but rather has a small diameter ranging from 25 to 35 meters. The Dean’s Blue Hole began to get an additional spotlight from media on April. 19 when William Trubridge swam to a depth of 95 meters on a single breath without any equipments for three minute and 56 seconds in the Dean’s Blue Hole last year.

Every single one of the blue holes in the world has spectacular sightings and public is taking attention as more world-class diving contests have begun to take place in the sinkhole. Like the name implies, even divers find their way back into the hole fallen by its mysterious attractiveness.

http://www.koreatimes.co.kr/www/news/tech/2011/10/325_96022.html