5464 x 3070 px | 46,3 x 26 cm | 18,2 x 10,2 inches | 300dpi
Data acquisizione:
30 settembre 2023
Ubicazione:
St Margaret's Bay, Kent, UK
Altre informazioni:
The White Cliffs of Dover are the region of English coastline facing the Strait of Dover and France. The cliff face, which reaches a height of 350 feet (110 m), owes its striking appearance to its composition of chalk accented by streaks of black flint, deposited during the Late Cretaceous. The cliffs, on both sides of the town of Dover in Kent, stretch for eight miles (13 km). The White Cliffs of Dover form part of the North Downs. A section of coastline encompassing the cliffs was purchased by the National Trust in 2016. The cliffs are part of the Dover to Kingsdown Cliffs Site of Special Scientific Interest and Special Area of Conservation. The point where Great Britain is closest to continental Europe, on a clear day the cliffs are visible from France (approximately 20 miles (32 km) away). A celebrated UK landmark, the cliffs have featured on commemorative postage stamps issued by the Royal Mail, including in their British coastline series in 2002 and UK A-Z series in 2012. The cliffs' chalk face shows horizontal bands of dark-coloured flint which is composed of the remains of sea sponges and siliceous planktonic micro-organisms that hardened into the microscopic quartz crystals. Quartz silica filled cavities left by dead marine creatures which are found as flint fossils, especially the internal moulds of Micraster echinoids. Several different ocean floor species such as brachiopods, bivalves, crinoids, and sponges can be found in the chalk deposits, as can sharks' teeth. In some areas, layers of soft, grey chalk known as a hardground complex can be seen. Hardgrounds are thought to reflect disruptions in the steady accumulation of sediment when sedimentation ceased and/or the loose surface sediments were stripped away by currents or slumping, exposing the older hardened chalk sediment. A single hardground may have been exhumed 16 or more times before the sediments were compacted and hardened (lithified) to form chalk.
