- Valleuse
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FRdot|Le HavreIn the
Pays de Caux ,Normandy ,France a valleuse is a depression in the land surface of theplateau which permits access to thesea . On the rest of thiscoast , that access is prevented by the height of thechalk cliff s.There are three sorts:
* living valleuses: natural depressions as atFécamp ,Yport andÉtretat .
* dead valleuses: to obtain the final access to thebeach it is necessary to set up astairway .
*perched valleuses: simple depressions in the plateau surface which do not descend far enough to permit access to the beach. Elsewhere, it might be called ahanging valley though it is formed, not by a glacier but by maritimeerosion .Origins
The word is peculiar to the Pays de Caux but the feature is not, though it shows itself particularly well here. The
valley s developed while thewater table was much higher in the chalk than it now is so that astream flowed in each of these truncated valleys. It is likely that most of the formation of the valleys in the plateau occurred during cold periods. This region was never covered by anice cap but it has been only about 230 kilometres from one. In those circumstances, the conditions will have beentundra , sometimes verging onperiglacial . When the frozen ground thawed in the spring, the surface soil was very wet because the melted snow andground water could not sink into thepermafrost . Any appreciable slope on the surface will have induced slumping and erosion but we have a plateau so the slopes were not originally great.During the glacial periods, the sea level was low enough to have emptied the
English Channel to the north of the Pays de Caux. The truncated valleys in the chalk, represent the headwaters of streams flowing down to what is now the bottom of the sea. During theinterglacial s the sea eroded the coast and steepened the slope down which they flowed but they will have required ever wetter conditions to keep the water table in the chalk sufficiently high to make the streams flow. In the end, the sea cut the cliff back quicker than the streams cut the valleys downward.
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