Heligoland located on terrain feature Heligoland archipelago
Heligoland (; German: Helgoland, pronounced [ˈhɛlɡoˌlant] (listen); Heligolandic Frisian: deät Lun, lit. 'the Land', Mooring Frisian: Hålilönj, Danish: Helgoland) is a small archipelago in the North Sea. A part of the German state of Schleswig-Holstein since 1890, the islands were historically possessions of Denmark, then became the possessions of the United Kingdom from 1807 to 1890, and briefly managed as a war prize from 1945 to 1952.
The islands are located in the Heligoland Bight (part of the German Bight) in the southeastern corner of the North Sea and had a population of 1,127 at the end of 2016. They are the only German islands not in the vicinity of the mainland. They lie approximately 69 kilometres (43 miles) by sea from Cuxhaven at the mouth of the River Elbe. During a visit to the islands, August Heinrich Hoffmann von Fallersleben wrote the lyrics to "Deutschlandlied", which became the national anthem of Germany.
In addition to German, the local population, who are ethnic Frisians, speak the Heligolandic dialect of the North Frisian language called Halunder.Geology
The island of Heligoland is a geological oddity; the presence of the main island's characteristic red sedimentary rock in the middle of the German Bight is unusual. It is the only such formation of cliffs along the continental coast of the North Sea. The formation itself, called the Bunter sandstone or Buntsandstein, is from the early Triassic geologic age. It is older than the white chalk that underlies the island Düne, the same rock that forms the White Cliffs of Dover in England and cliffs of Danish and German islands in the Baltic Sea. A small chalk rock close to Heligoland, called witt Kliff (white cliff), is known to have existed within sight of the island to the west until the early 18th century, when storm floods finally eroded it to below sea level.
Heligoland's rock is significantly harder than the postglacial sediments and sands forming the islands and coastlines to the east of the island. This is why the core of the island, which a thousand years ago was still surrounded by a large, low-lying marshland and sand dunes separated from coast in the east only by narrow channels, has remained to this day, although the onset of the North Sea has long eroded away all of its surroundings. A small piece of Heligoland's sand dunes remains—the sand isle just across the harbour called Düne (Dune). A referendum in June 2011 dismissed a proposal to reconnect the main island to the Düne islet with a landfill.