The aspiring Jersey Island Geopark is working with Jersey Heritage to gain formal UNESCO recognition for the Island’s internationally significant landscape, seascape, culture and natural environment. As part of this, the Geopark promotes the importance of Jersey’s geoheritage and its connection to the Island’s cultural and natural environment.
Continuing a series of articles, head of Geopark Paul Chambers shines a light of some of Jersey’s hidden geological features – so hidden, in fact, that they might not exist at all.
THE Caribbean island of Bermeja, situated just off the Yucatan peninsula, had for centuries been subject to territorial claims by the USA and Mexico. Neither country had actually colonised the island but in 1997 the Mexican government sent a ship to map it as part of a planned claimed to the surrounding seabed.
The survey party could find no trace of Bermeja and nor did several other surveys. In 2012, the Mexican government admitted that Bermeja, which had featured on nautical charts for centuries, did not actually exist. It was a phantom island.
Phantom islands are geographical enigmas that feature in atlases, charts and maps but which cannot then be found by sailors, surveyors or satellites. Around fifty are known, mostly from rarely visited sea areas although there are, of course, always exceptions.
One such is a hazardous reef called Les Bancs Grelets which was said to lie about halfway between St Helier and Les Minquiers. At five miles long and two miles wide, the reef was a jumbled expanse of rocks and sandbanks which for centuries had appeared on charts although, as anyone who has taken a ferry to St Malo will know, Les Bancs Grelets doe not exist. It is Jersey’s very own phantom island.
The origin of Les Banc Grelets is obscure. The oldest known depiction is on a 1670 chart and the youngest is in 1840. The reef is shown found on most 18th century charts and as late as 1824, sailing guides were warning navigators to avoid ‘this dangerous rocky bank.’
It was Captain Martin White, an Admiralty surveyor, who called time on the reef. In 1805, White began mapping Channel Island waters and in 1815 wrote to the Admiralty to tell them that the reef was mythical. Nonetheless, it kept featuring on charts which led White to state publicly that: ‘The Banc Grelets, hitherto laid down between Les Minquiers rocks and Jersey, has positively no existence.’
Presumably local mariners must have known this already, not least because Les Bancs Grelets should have been clearly visible from Noirmont. Even so, it was not until publication of White’s Admiralty charts (minus Les Bancs Grelets) in the 1830s that the myth ended.
Some believed that the reef existed but had ‘sunk’ below the surface although White pointed out that he had found nothing but deep water in the area. He suggested that it had been mistaken for Les Caux, an area of rock and sand north-east of Les Minquiers. For a time, some charts even labelled Les Caux as Les Grelets.
Les Bancs Grelets is classic phantom island in that, like Bermeja, it never actually existed. There are, however, other types of phantom island such as the Île de Maurepos (‘bad anchorage island’) which, on some eighteenth century charts, is shown off Jersey’s north-east coast.
Maurepos is clearly a real feature as it aligns with La Tour de Rozel or, as it is better known today, White Rock. (NB The name has nothing to do with Captain White but because its summit is painted white.) A narrow crevice separates White Rock from the adjacent headland but some historical charts have widened this into a fully-fledged sea passage. By 1800 Île de Maurepos had been joined to Jersey and was consistently being called La Tour de Rozel.
The legend of Les Bancs Grelets and (to a lesser extent) Maurepos are rare examples of phantom islands within European waters. What is unusual is that they should have survived on charts until the nineteenth century which perhaps reflects the Channel Islands’ reputation for strong tides and dozens of rocks. It would have been a brave sea captain who would risk testing a legend by sailing into it.
