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. As sea levels rose, the river valley became flooded, and the chalk ridgeline west of the Needles breached to form the island. The Isle of Wight is first mentioned in writing in Geography by Ptolemy.
Source: Isle of Wight – Wikipedia