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Blue Hole (Prairie County, Arkansas)
A blue hole is a large marine cavern or sinkhole, which is open to the surface and has developed in a bank or island composed of a carbonate bedrock (limestone or coral reef). Their existence was discovered in the late 20th century by fishermen and recreational divers. Blue holes typically contain tidally influenced water of fresh, marine, or mixed chemistry. They extend below sea level for most of their depth and may provide access to submerged cave passages. Well-known examples are the Dragon Hole (in the South China Sea) and, in the Caribbean, the Great Blue Hole and Dean's Blue Hole. ''Blue holes'' are distinguished from ''cenotes'' in that the latter are inland voids usually containing fresh groundwater rather than seawater. Description Blue holes are roughly circular, steep-walled depressions, and so named for the dramatic contrast between the dark blue, deep waters of their depths and the lighter blue of the shallows around them. Their water circulation is poor, and the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Great Blue Hole
The Great Blue Hole is a giant marine sinkhole off the coast of Belize. It lies near the center of Lighthouse Reef, a small atoll from the mainland and Belize City. The hole is circular in shape, across and deep. It has a surface area of . It was formed during several episodes of quaternary glaciation when sea levels were much lower. Analysis of stalactites found in the Great Blue Hole shows that formation took place 153,000, 66,000, 60,000, and 15,000 years ago. As the ocean began to rise again, the cave was flooded. The Great Blue Hole is a part of the larger Belize Barrier Reef Reserve System, a UNESCO World Heritage Site. Exploration The site was made famous by Jacques Cousteau, who declared it one of the top five scuba diving sites in the world. In 1971 he brought his ship, the '' Calypso'', to the hole to chart its depths. Investigations by this expedition confirmed the hole's origin as typical karst limestone formations, formed before rises in sea level in at least fo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
