The recoil of cliffs
Cliffs (and more particularly those of chalk) are relatively recent forms in the geologic history. They date approximately times Pleistocene (2,6 million from years to 11430 years) and Holocene (11430 years in today), but it is following the reheating following the last glaciation that the sea went back up until a level almost identical to the current, at about 6000 years, and that the current cliffs really formed.
The morphology of type cliff lives littoral is typically bound to the high periods of the marine level, that is to the warm periods of the ground history. Indeed, when the marine level falls, masses of fallen rocks are more evacuated by the sea and train a basal support which blocks the distribution of the collapses.
The recoil of cliffs is a fast phenomenon today, because we are situated in an interglacial episode
The final scientific report of Interreg IIIa showed that, on the scale of the cell or of the hydrosedimentary sub-cell, the speeds of recoil of cliffs are understood between 0,08 - 0,28 m.an-¹. The annual contribution by cliffs is of the order of 1 million of m ³.
4 geographical areas having different speeds of recoil are distinguished:
- Of Antiiron to Fécamp, the recoil is low 0,08 0,13 m.an-1;
- From Fécamp to Saint Valéry, the recoil is moderated 0,19m.an-1;
- Of Saint Valéry in Dieppe, the recoil is hardly 0,21 - 0,28 m.an-1;
- Of Dieppe in Tréport, the recoil is moderated 0,18 m.an-1.
There is a relation between the type of chalk and the recoil of cliffs.
Articles and links in connection with the recoil of cliffs
Article Hénaff and al.