Bermuda Caves, one of the Earth’s last unexplored frontiers

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For the past 400 years, Bermuda has recognised the system of caves that honeycomb the limestone island. There are four large caves that are accessible to the public. The Fantasy and Crystal Caves have guided tours almost hourly year-round. Grotto Beach, just east of the island’s international airport, has two caves that are approachable. One of them, Prospero’s, has been turned into a bar, the other, Cathedral Cave, holds a large underground lake, in which visitors can dive. These majestic caves are deep with clear underground pools of azure blue water.

Clear, deep lake in Church Cave- Image courtesy of Bermuda Deep Water Caves 2011 Exploration, NOAA-OER

About 30 million years ago volcanic eruptions on the floor of the Atlantic formed a mountain approximately 13,000 feet high, reaching the surface of the ocean. Marine life and coral reefs began to inhabit this submarine mountain and during Ice Ages, when the sea level dropped, sediments calcified. In time, the chemical reaction between the limestone and water created channels and caves, the largest of which are in the Walsingham Formation located between Harrington Sound and Castle Harbour. Bermuda probably has more caves per square mile than anywhere else in the world. They can be divided into “primary caves” and “secondary collapse caves,” based on how they were formed. Primary caves are the product of tunnelling out of limestone by flowing water. Flooded primary caves, navigable only by scuba divers, are found in the Green Bay and Red Bay cave systems on the southwestern side of Harrington Sound. Formed by the progressive enlargement of flooded conduits, such caves can ultimately evolve into chambers of sufficient lateral span that they become vulnerable to collapse. Collapse caves are, thus, formed when the roofs of laterally expansive primary caves fall in.

Caves in Bermuda were first discovered during the early colonization in 1600s. Shakespeare’s The Tempest was inspired by Sir George Somers’s 1609 shipwreck in Bermuda that takes place in and around the island cave. Sir George Somers was the first to discover the Prospero’s Cave, located on Grotto Bay Beach Resorts Property, this is now a Natura Spa. However, Captain John Smith was the first to make a published reference of a Bermudian cave in 1623. Located in Hamilton Parish, Admiral’s Cave is one of the largest dry caves in Bermuda. Named for the British Admiral Sir David Milne that discovered it, this cave used to be a show cave but suffered from vandalism and is difficult to access. The cave is full of mineral formations and has one large sink hole entrance and two other smaller entrances. There are several lakes inside which are connected to the sea through underground passages. In early 1907, two twelve-year-olds, Carl Gibbons and Edgar Hollis, made the discovery of a lifetime when they were searching for a lost cricket ball –the subterranean wonder now known as the Crystal Cave. They discovered a small hole, which had at one point been covered with stones. Unable to move the bigger rocks, the boys fetched their parents who managed to widen the hole to about two feet by four feet to allow one of the men to squeeze through. Lowering himself on a rope he found that for fifty feet or so the hole did not expand, but then opened into the spectacular world of stalagmites and stalactites inside of what now known as Crystal Cave. This site today is a haven for tourists. With a depth of 17 meters, Crystal Cave has been installed with lighting systems, and an accessible walkway. Though these amenities provide easy access to a beautiful subterranean landscape, there is only one route through the cave. Church and Bitumen Caves are located beneath Ship’s Hill on the grounds of the Marriott Castle Harbour. Church Cave contains the largest underground lake in Bermuda with an area of 1500 m2 and a maximum depth of 22.5 meters. Bitumen Cave, just north of Church Cave, is the deepest underwater cave in Bermuda containing within its main chamber an 8 meters pit that reaches a tidal salt-water pool, which extends down to a depth of 25.5 meters. There are at least eleven cave species that are endemic to the lakes of these caves which nine of them are listed as critically endangered by the International Union for the Conservation of Nature (IUCN) Red List and many are primitive forms that represent ancient lineages. Walsingham Nature Reserve also contains a great many caves. Causeway Cave is right on the coast, looking out towards the ocean. This little cave is flooded with sea water and is the perfect mini shaded grotto. The ceilings are exceptionally low, though. Subway Cave in the nature reserve is dry and contains dramatic limestone formations. The stalactites jut down from the top, so a helmet is recommended when exploring this cave. Walsingham Cave is the crowned jewel of caves and is one that many swim in, although swimming is not advisable as it is harmful to the delicate ecosystem that lives within the cave’s water. Unfortunately, many caves that were once grand attractions are now no longer accessible to the public. Church Cave, which has the largest underwater lake of any cave, and Leamington Cave, are both now part of private property.

Caves tell much about the geologic history of Bermuda, including Ice Age and recent sea level change, making them as an important biodiversity hotspot of global scientific value. Fossils of existing and extinct species such as birds, tortoises and invertebrates have been found in these caves, some date back thousands of years. They did not necessarily live in the cave, but may have been washed into it, covered, and preserved. The submerged caves contain more endemic species than any other habitat and it is highly likely that there are organisms here that have not yet been discovered. They have adapted to live in the caves over millions of years and cannot survive outside of them. These animals are obligate cave-adapted species – meaning they evolved in these caves over millions of years and cannot survive elsewhere. Destruction of a single cave or cave system could result in extinction of one or more species.

The formations in Bermuda’s caves, like stalactites and stalagmites, are formed by dripping water over thousands of years. These beautiful features are extremely fragile and are easily broken by human activities. Intentional vandalism has sadly been seen in several caves, as well as accidental damage during development. Development of hotels, over-exploitation for tourism, even lights which cause algae to grow in the darkness, are all threats to local caves. Litter is also a severe problem as many caves are connected in underground systems that stretch for kilometres. Floating garbage from the sea makes its way into the cave system with the tide. Groundwater pollution is also a serious threat to as its contaminating the habitat. In the future Bermuda’s caves will likely be affected in unforeseen ways by climate change, ocean acidification and rising sea level. Some protection of cave habitats is offered by the Cave Protection Area zoning under the Bermuda Plan 2008. A number of nature reserves featuring caves include Walsingham Nature Reserve, the Idwal Hughes Nature Reserve, Blue Hole Park, and Sears Cave Nature Reserve.

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