The island is a civil parish and is linked to the town of Marazion by a causeway of granite setts, passable (as is the beach) between mid-tide and low water.

The key discovery was of a leaf-shaped flint arrowhead in a shallow pit on the lower eastern slope, now part of the gardens.

[6] None of the flints so far recovered can be positively dated to the Bronze Age (c. 2500 to 800 BC), although any summit cairns would have most likely been destroyed when building the castle.

Defensive stony banks on the north-eastern slopes are likely to date to the early 1st millennium BC, and are considered to be a cliff castle.

[6] The mount is one of several candidates for the island of Ictis, described as a tin trading centre in the Bibliotheca historica of the Sicilian-Greek historian Diodorus Siculus, writing in the first century BC.

[21][22] John de Vere, 13th Earl of Oxford, seized and held it during a siege of 23 weeks against 6,000 of Edward IV's troops in 1473–1474.

The sea rose six feet (2 m) in 10 minutes at St Michael's Mount, ebbed at the same rate, and continued to rise and fall for five hours.

The 19th-century French writer Arnold Boscowitz claimed that "great loss of life and property occurred upon the coasts of Cornwall.

[32] After the war, the decommissioned battleship HMS Warspite was beached near the mount, and was scrapped in place after attempts to refloat the wreck failed.

Sixty-five years after the Second World War, it was suggested based on interviews with contemporaries that the former Nazi Foreign Minister and one-time ambassador to London, Joachim von Ribbentrop, had intended to live at the mount after the planned German conquest.

Archived documents revealed that during his time in Britain in the 1930s, when he had proposed an alliance with Nazi Germany, von Ribbentrop frequently visited Cornwall.

[23] The chapel of St Michael, a 15th-century building, has an embattled tower, one angle of which is a small turret, which served for the guidance of ships.

Chapel Rock, on the beach, marks the site of a shrine dedicated to the Virgin Mary, where pilgrims paused to worship before ascending the mount.

Queen Victoria disembarked from the royal yacht at St Michael's Mount in 1846, and a brass inlay of her footstep can be seen at the top of the landing stage.

[39] Some studies indicate that any rise in ocean waters as well as existing natural erosion would put some of the Cornwall coast at risk, including St Michael's Mount.

The rock exposures around St Michael's Mount provide an opportunity to see many features of the geology of Cornwall in a single locality.

These steep W-E trending veins are thought to have formed by hydraulic fracturing,[41] when the fluid pressure at the top of the granite reached a critical level.

As the area cooled, the veins became open to fluids from the surrounding country rock and these deposited sulphides, e.g. chalcopyrite and stannite.

The chronicler John of Worcester[46] relates under the year 1099, that St Michael's Mount was located five or six miles (10 km) from the sea, enclosed in a thick wood, but that on the third day of November the sea overflowed the land, destroying many towns and drowned many people as well as innumerable oxen and sheep; the Anglo-Saxon Chronicle records under the date 11 November 1099, "The sea-flood sprung up to such a height, and did so much harm, as no man remembered that it ever did before".

[47] The Cornish legend of Lyonesse, an ancient kingdom said to have extended from Penwith toward the Isles of Scilly, also talks of land being inundated by the sea.

One of the earliest references to the mount (originally named "Dynsol" or "Dinsul"), was in the mid 11th century when it was "Sanctus Michael beside the sea".

The poem drew together various traditions from the Bible, classical mythology and local folklore to offer an elegy for the pagan world that had faded away.

[citation needed] According to legend, the island was once home to a giant named Cormoran, who lived on the Mount and stole livestock from local farmers.