The chalk cliffs of Dover, which in some places exceed 100 meters, represent the closest point in England to continental Europe. However, bad weather and strong winds are eroding the very long white expanse which risks retreating if not collapsing.
Sediments formed during the Cretaceous, about 70 million years ago, when Great Britain and much of Europe were submerged under a great sea. It is assumed that they deposited very slowly, probably half a millimeter per year, equivalent to about 180 coccoliths (coccolithophores shells) lined up one on top of the other.
In some areas, up to 500 meters of sediment was deposited. The weight of further sediments accumulated in subsequent eras caused the consolidation, by compression, of the underlying fossil coccolithophores and foraminifera, forming the fine white and very friable limestone we observe today.
The signs of erosion are clearly visible both on the White Cliffs of Dover and on those of Cap Gris-Nez in France. The predominant composition of the British and French coasts, as well as of the seabed, is of very fine-textured limestone, mostly composed of fossils of single-celled marine organisms whose major representatives are coccolithophores and foraminifera.
The former are unicellular algae, while the latter are marine amoebas. Both secrete a calcareous shell, which favors the fossilization process. The death and deposition on the seabed of these organisms has allowed the formation of these reefs over the course of millennia.
A huge traffic of merchant ships crosses the English Channel connecting the Atlantic Ocean to the North Sea and the Baltic Sea, avoiding the most dangerous route north of Great Britain. The Canal is one of the busiest stretches of sea in the world as it is crossed by over 400 merchant ships per day.
This involves close surveillance, 24 hours a day, by the Coast Guard. Added to this traffic are the ferries that shuttle between Dover and Calais. Until the opening of the Channel Tunnel, which took place in 1990, this traffic was much more intense than the current one as it had to completely carry out both the transport of people and goods. The Tunnel runs under the Canal at an average level of 45 meters below the sea floor.