One has only to say "Bermuda", and the image of the Bermuda triangle inevitably pops up in the memory - a mysterious trap in which ships and planes disappear one after another. In recent years, geographers have become increasingly interested in a unique natural phenomenon discovered right under the feet of tourists vacationing on the beaches of these islands.
We are talking about a huge system of underground caves filled with sea water (for underground caves on the Yucatan Peninsula, read "3-s", 3/11. This labyrinth was formed about a million years ago, but even now it has not been explored by scientists. more than one and a half hundred flooded caves, and how many have not yet been mapped!
In the summer of 2011, a scientific expedition took place to this wonderful world. Scientists of different specialties have explored previously unknown underwater corridors and halls, discovered dozens of species of plants and animals that settled here.
The first of the caves located at the bottom of the Bermuda Triangle were discovered at the beginning of the 19th century. And then, and subsequently, they were opened most often by accident. So, in 1905, two twelve-year-old boys discovered Crystal Cave, the "Crystal Grotto", when the ball they were playing cricket with fell into a crevice, and they climbed to look for it. Today it is one of the most famous Bermuda caves. Among the crystal clear water that fills it, countless stalactites and stalagmites flaunt.
But why are so many caves formed in the depths of Bermuda? The answer must be sought in the geological history of this atoll - the only coral atoll in the North Atlantic.
Ascended at the top of the volcano
Bermuda was born on fire. About 35 million years ago, an underwater volcano was located in this part of the ocean. His next eruption was so powerful that a layer of lava, thrown out by him, formed an island. Unlike many other islands that were once part of the land, and then cut off from it by the sea, Bermuda, although they lie close to the coast of North America, have never connected with it.
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Over time, the wind and waves washed away the top of the volcanic cone, and corals settled on its underwater slopes, which began their leisurely construction work. Thanks to the warm waters of the Gulf Stream that washed this island, favorable conditions for their life have developed here. This is how the northernmost coral reef on our planet was created. Its limestone strata now forms the skeleton of the archipelago.
The climate changed about a million years ago. The ice age began, a significant part of the water turned into ice, and the sea level was about 100 meters below today's level. Thus, a chain of coral reefs emerged from under the water, now defenseless against wind and rain. Through the cracks in the porous limestone, rainwater easily seeped, eroding them more and more noticeably. Crevasses and grooves turned into underground corridors and halls. Of course, this is not unusual. Karst phenomena, that is, phenomena associated with the dissolution of rocks by natural waters, are widespread on our planet.
However, the history of Bermuda was still far from completion. Over time, most of the ice sheet that bound the northern hemisphere melted, and the water level in the Atlantic Ocean rose markedly. The ocean conquered most of Bermuda. Salt sea water also penetrated into underground caves formed in the limestone, flooding almost all of them. So in the depths of Bermuda, a unique, unlike anything biotope arose - the world of "Little Seas", lost underground.
Some of the caves can be accessed from the surface of the islands. As a rule, these caves have already been studied by researchers. Although you can look into other grottoes, because of the water that flooded them, it will not be possible to survey them without special equipment. But often underground caves can only be penetrated by plunging into the sea. Little is known about them. Many of them, as geologists believe, have not yet been found. Their search was the main goal of the participants of the expedition "Bermuda Deep Water Caves 2011: Dives of Discovery".
Heirs of the tetis
They discovered a world inhabited by a wide variety of organisms. To start the story about these "Sea" inhabitants, who have taken root in the depths of the islands, right under the feet of tourists, it is necessary, perhaps, with the "guests" - with those who look here only from time to time. These are animals that inhabit the Atlantic Ocean and only occasionally visit caves, penetrating into them through crevices in the underwater part of the reefs. They swim, climb, spend some time in caves, as a rule, rarely moving away from the entrance. They will stay, rest and return to the open sea again. These "Temporary Lodgers" include a variety of fish, as well as more primitive animals that use the watercourse to obtain nutrients. Among them are sponges and polyps, literally clinging to stone walls and arches.
However, if you look deep into the cave, the picture changes dramatically. As the current subsides and the amount of nutrients contained in the water decreases, the density of the organisms that have settled here also becomes lower. These typical cave dwellers, the so-called stygobits, are perfectly adapted to life in underground corridors and halls. Often they do not even have eyes, and the body is devoid of any pigmentation.
“Basically, stigobites have long been known to inhabit freshwater caves,” notes the American biologist Tom Ilife. However, such animals have been found for the first time in caves flooded with sea water”. Only in the caves of Bermuda, 75 species of such animals have been found. Most of them are crayfish, but there are also snails, ticks and worms.
It is curious that one of the amphipods found here is a relative of the crustaceans that live in the Mediterranean region. In the new light, he is not seen anywhere except Bermuda. It is not yet clear why related animal species were separated thousands of kilometers from each other.
According to one hypothesis, many cave dwellers inhabited our planet 200 million years ago, when all continents were united into a single whole and made up one huge supercontinent. When it split into pieces, these animals were scattered across the globe. So amphipods from underground caves in Bermuda can be considered living fossils that have been preserved since ancient times.
According to another hypothesis, these animals originally settled in the deep-sea part of the Atlantic Ocean. From there they entered the underwater caves and took root there.
Another hypothesis says that representatives of the local fauna inhabited the ancient ocean of the Tetis, and when it retreated, they remained trapped in caves, unable to get out into the open sea.
Ebb and flow
The underworld of Bermuda offers its inhabitants a wide variety of living conditions. Some caves are cold, others warm; in some - pitch darkness reigns, in others - the sun's rays penetrate; some caves are flooded with sea water; in others, fresh water. In many grottoes, the water recedes with the tide. When the tide begins, fresh sea water rushes there again, bringing plankton, the main food of the local living creatures.
Here is an example of one of these caves - Tuckers Town Cave in the north of the main island of the archipelago. In general, the whole of it is one large corridor located 20 meters below sea level. It leads to a salt lake. Light hardly penetrates here. The waters of the lake are shrouded in darkness. Cavers have not been able to establish how it connects with the sea, but, nevertheless, the water level in this lake, as if cut off from the sea, fluctuates in the same rhythm of ebb and flow, attention, only with an hour's delay. As the iliffe believes, perhaps at the bottom of the lake, among the sand, a funnel is hidden, which leads to another cave located in the depths, and this one is connected to the sea. But the mysterious hole was never found.
Life on the brink of extinction
This world of "Underground Bermuda" is as unique as it is vulnerable. More and more caves, as well as their inhabitants, are becoming victims of our economic activities. Some are covered with rubble and earth in order to build another hotel over them; others are used for landfills.
Bermuda is one of the ten countries with the highest population density, and also, as noted by that ilife, "There is more than anything in the world of landfills and garbage pits on the Soul of the Population." Untreated wastewater contaminates the soil (and hence underground caves) with nitrates, heavy metals, drug residues and other chemicals. Even caves, which are constantly visited by tourists, are under the threat of infection.
As a result, 25 species of animals living in caves were on the verge of extinction. The probability of their survival is estimated at only 50 percent. The situation is especially alarming with the animals inhabiting caves flooded with sea water, because some of them are found only in one - the only cave and can hardly take root in other bodies of water.
Some of the caves have already been destroyed, such as the Government Quarry Cave. It was discovered in 1969 when they drilled into the bottom of a quarry where limestone was mined. This cave was located at a depth of 18 meters below sea level. Subsequently, it turned out that it consisted of two salt lakes connected to each other. Numerous faults and tunnels led far down, as it was assumed, to a depth of 30 meters.
However, scientists were never able to explore this cave before the world formed here was destroyed. In the 1980s, a huge amount of garbage was dumped here with the help of bulldozers. Due to the high concentration of harmful substances that got into the lakes, life in them became unbearable for most of the animals that lived here. As a result, this Bermuda cave became post - rush than the Bermuda triangle. What happens to the rest? Will the same fate await them?