The transgression in geology is a displacement of the line of shore towards the interior of the grounds, due to a continental depression or a rise in the sea level.

One calls transgression flandrienne the episode where, with the recent Holocène, the end of the last Glaciation of the Wurm, the water of the Inlandsis melted and thus the sea level went up (of approximately 100m): at this time the Flanders was invaded by the sea; from where the name of this episode.

One cuts out Holocene recent in préboréal (towards -10.000), boreal, the Atlantic old one, Atlantic recent, subboréal, subatlantic (- 1000).

One knows that in the Atlantic, water is assembled of 1,2 mm/an on average, with a strong acceleration during the recent time known as of " civilization industrielle" (approximately, after 1850): the cause is not known still scientifically, because this discovery is too recent (Topex-Poséidon, Jason, Envisat…) to be examined on a geological time scale (rather a few thousands of years that a few tens of years!); obviously the effect anthropic is discussed.

Since the the Middle Ages, the man did not cease fighting to regain ground on the sea and thus to create a Polder: this for agricultural reasons.

In 2005, it is definitely defined that, the food shortage not reaching more the populations, it was more important to have a concerted policy of installation of the shore and littoral. An important program of satellite follow-up is engaged to allow the geologists and geographers to take the measurement of the phenomenon. In addition, the measures to the ponds, marshes or peat bogs bordering the shore easily make it possible to go back, on ten thousands of former years, to the calculation of the level of the full sea: thus work of the geologists of ground supplements the work of the geophysicists.

In France, the Netherlands is primarily in both bay S classified of the Atlantic: the bay of the Mount Saint-Michel (the salt meadow lambs are known for their sheep) and the bay of the Somme (low-fields of Cayeux), the Gulf of the morbihan (Quiberon & Vannes), and the Camargue close to the the Mediterranean where the transgression is due to the fall of the alluvia of the Rhone; the sea " corrode the delta" : the same phenomenon is even more visible in the delta of the Nile.

See too

• Geology
• Mount Saint-Michel
• moving Sand