Poole Bay is a bay in the English Channel, off the coast of Dorset in southern England, which runs from the mouth of Poole Harbour in the west to Hengistbury Head in the east. It consists of steep sandstone cliffs and several 'chines' that allow easy access to the sandy beaches below. Poole Bay is a relatively shallow embayment delimited by the Poole Harbour tidal inlet to the southwest and Hengistbury Head/Christchurch Ledge. The coast along the bay is continuously built up, and is part of the South East Dorset conurbation, including parts of the towns of Poole, Bournemouth and Christchurch. The bay is often erroneously referred to as Bournemouth Bay, because much of it is occupied by Bournemouth. Many of the beaches along Poole Bay were replenished during the winters of 2005 and 2006 with 1.1 million m³ of sand dredged from Poole Harbour and 700,000 m³ of sand dredged from a Licensed Area off the Isle of Wight. A dedicated website has more information and charted progress with photos and a daily diary . The project was completed on January 23, 2007.
The area of Poole Bay was predominantly created during the Pleistocene period, when the Solent river ran across the whole of South East Dorset and West Hampshire, out past the Isle of Wight The solid geology of the cliffs, and the seabed beneath Poole Bay, is composed of rocks of the Tertiary Bracklesham Group, consisting of a sequence of fine, medium and coarse sands. At Hengistbury Head there are younger rocks of the Bartonian group, forming an outlier . The Barton Clay here is made up of a series of sands and interbedded clays, with four distinct bands of ironstone nodules. These formations dip eastwards and are cut out by a north-west to south-east trending fault. This defines the eastwards boundary of Christchurch Ledge, which is a seawards continuation of the resistant ironstone strata exposed in Hengistbury Head.