During the last Ice Age, sea levels were lower and the Solent was part of a river flowing southeast from current day Poole Harbour towards mid-Channel of Doggerland. The Bouldner Cliff archaeological site is 1 km long, 8000 year old wooden platform at the neolithic river bank, and now submerged 12 m below sea level.[9] As sea levels rose, the river valley became flooded, and the chalk ridgeline west of the Needles breached to form the island.[10] The Isle of Wight is first mentioned in writing in Geography by Ptolemy.

Source: Isle of Wight – Wikipedia