How Chesil Beach was formed is very much open to debate. Formerly classified as a tombolo - 'an island (Portland) attached to the mainland by a narrow piece of land such as a spit or bar', recent research into the geomorphology of the structure has now cleassified Chesil as a 'barrier beach' - '... a barrier beach which has "rolled" landwards, joining the mainland with the Isle of Portland, giving the appearance of a tombolo.'

Initially the products of erosion in East Devon, the deposits worked their way eastwards by the process of longshore drift. These mainly sandy deposits were flooded by the rise in sea level (isostatic readjustment) during the Flandrian Interglacial Period (Holocene) around 12,000 years ago. These rocks were then driven onshore forming a barrier beach that now lies parallel to the coast. PLEASE NOTE: Due to strong coastal currents, swimming is not advised along Chesil Beach.

Chesil Beach consists of billions of pebbles stretching in an arc from West Bay, in the west to Portland in the east. It is 18 miles (29km.) long, 200 metres (660 ft) across at its widest point and up to 18 metres (59 ft) high. The pebbles are naturally graded from west to east: around Burton Bradstock, the size of the pebbles is akin to pea gravel whilst at Portland, the pebbles are the size of a man's fist. It is even said that someone landing on the coast in dense fog could give a rough estimate of their location by inspecting the size of the pebbles beneath their feet. As one would expect, the pebbles consist mainly of the more resistant rock types such as quartzite, chert, flint, granite and porphyry, although pebbles of portland stone, kimmeridge oil shale and even pumice have also been found.

A natural sea defence, but also the site of many shipwrecks, Chesil Beach figures strongly in the history of this part of Dorset. Few people realise that the area has been farmed for oysters since the 11th Century. Stories of smugglers were at one time commonplace and an excellent book to read to get a feel for this period is John Meade Falkner's 'Moonfleet' - a tale of smuggling in the mid 18th century around the fictional coastal village of Moonfleet, first published in 1898. In January 1943, the area was used for trials of Barnes Wallis' bouncing bomb, later used so effectively against the Eder, Möhne and Sorpe dams by the crews of 617 (Dambuster) Squadron as part of Operation Chastise.

The Fleet Lagoon takes its name from the Saxon word 'Fleot' - meaning shallow water. It is the largest tidal lagoon in Britain with an area of 480 hectares (1186 acres). It is over 8 miles (13km.) long and stretches from near Abbotsbury Swannery to Portland Harbour. This shallow area of saline water ranges from 65 metres to 900 metres in width with its depth varying from less than 2 metres in parts to over 4 metres. The Fleet is a SSSI - a Site of Special Scientific Interest and also a Special Protection Area (SPA) within the European Union. The area of rough low lying grassland and shingle beach situated to the east of Fleet lagoon, bordering Portland Harbour is known as the Hamm. It is common land and is itself a SSSI consisting of shallow sand dunes overlying the shingle.

The Fleet can be explored by taking a trip on the Fleet Observer, a glass bottomed boat that travels the lagoon in the summer months.

The area is rich in plant life, with the main species being thrift (ameria maritima), red valerian (centranthus ruber), tree mallow (lavatera arborea) and marsh mallow. The area is rich in birdlife especially wading and migratory birds such as Brent Geese, Turnstone, Ringed Plovers, Sanderling, Wigeon, Bar Tailed Godwit, Dunlin and even Osprey and Kentish Plover. The rare Little Tern are also found here - there are estimated to only be about 200 pairs in the whole of Britain. The area has a diverse range of marine invertebrates and there are a large number of species of algae as well as over 150 types of seaweed and grass.

The area has a wealth of activities ranging from painting, photography and birdwatching through fishing and walking the area to more energetic pursuits such as boating, canoeing, sailboarding and even diving. Paths and boardwalks allow visitors to explore the area whilst also minimising erosion and disturbance to the flora and fauna.

The area receives between 100,000 and 150,000 visitors per year who are catered for largely by the Chesil Beach Centre. Recently redeveloped, the Centre opened its doors on 21st July 2012. It is situated halfway along the causeway from the Weymouth to Portland road, the A354.

The Centre is open every day from 10am to 4pm. Please call 01305 206191 for more details. There is also a Youth Hostel nearby at Fortuneswell on Portland.

The wildlife of Dorset is monitored by the Dorset Wildlife Trust who have an excellent website detailing their work and areas of expertise. There are five Visitor Education Centres throughout the county. They are:

• The Kingcombe Centre, Toller Porcorum, Dorchester
• Lorton Meadows Nature Reserve, Weymouth
• Purbeck Marine Wildlife Reserve Kimmeridge
• Brownsea Island Nature Reserve, Poole
• The Urban Wildlife Centre, Corfe Mullen, Wimborne