The shingle and sand island appears to have originated from a former spit extending from the coast, and longshore drift means that it is slowly moving to the west and inshore.
This isolated island has been largely undisturbed by human activity apart from service as an artillery range in World War II, and it is of international importance because of the extensive research into its geomorphology over nearly a century.
[1] The 737 ha (1820 acres)[2] island is composed almost entirely flint pebbles, mostly rounded by wave action, and sand; other minerals make up less than one per cent of the material.
[6] The island is served by a ferry from Burnham Overy Staithe which runs from April to September, and there is a 1 km (1,100 yd) nature trail with information boards.
Both modern and Neanderthal people were present in the area between 100,000 and 10,000 years ago, before the last glaciation, and humans returned as the ice retreated northwards.
[8] Deposits of peat between layers of marine or salt marsh sediments date from 1980–1780 BC, indicating that the sea had retreated, leaving this area as dry land during that era.
Support for this theory comes from boreholes and from radiocarbon dating of a shell to 837AD, that appeared to indicate the existence of saltmarshes behind the shingle barrier at that time.
A 1585 map also appears to show a spit at this location,[11] and a 1630 inventory of the lands of Robert of Brancaster, the local Lord of the Manor, did not list the island as a separate entity.
[12] On the death of Simms Reeve, Lord of Brancaster, in 1922, earlier disputes over the ownership of the island were resolved with his executors retaining the southern part, and the Earl of Orford the northern section.
[16] The SS Vina, an 1894 cargo steamer, was anchored near the west end of the island in 1944 for use as an RAF target where the wreck can still be seen at low tide.
[8] A steel wreck or hulk measuring around 72m long and 15m wide was also brought to the island during World War II for military target practice.
[29] Insects include the intertidal ground beetle Dicheirotrichus gustavii which emerges from cracks or holes to feed on the salt marshes after dusk.
Despite living in a coastal environment, it has no cycle of behaviour linked to the tides, simply scurrying for dry land when caught by the approaching sea.
[30] Another intertidal beetle, Bledius spectabilis, shows very unusual behaviour for an insect in that it actively protects its larvae from the parasitic wasp Barycnemis blediator and from the predatory Dicheirotrichus gustavi.
[4] Outdoor recreation is important to the economy of north Norfolk, and a 2005 survey at six coastal sites found that 39 per cent of visitors gave birdwatching as the main purpose of their visit.