Mont Saint Michel [antikvár]

A natural marvel The rock of Mont Saint Michel, like that of Tombelaine, three kilométrés to the north and Mont Dôl, 23 kilométrés to the west, is a vestige of the mountains formed by the upheavals of the Hercynian era, 600 million years ago. The bay which surrounds it, an expanse of 45,000 hectares, is the arena for one of the strongest tides in the world. When the influence of the sun and the moon coincide, a spring tide is caused which at the equinoxes can reach a height of 15 métrés. At such times the tide goes out some 18 kilométrés, then rushes back to cover the sand-flats, advancing at a speed of 62 métrés per minute, or one metre per second! This vast expanse of "tangue" - a mixture of sand and mud - which appears empty and dead, is in reality an extraordinary habitat teeming with shellfish, crustaceans and fish: the bay is a nursery for many and varied species (particularly flat fish) and there the shoals of salmon may be observed swimming up towards the rivers. It is also an exceptional over-wintering site for migratory birds, a real ornithological sanc-tuary. A small colony of seals even lives permanently in its waters. But this unique site is in danger. Since the 1 lth century man has been attempting, through the creation of dykes, to transform the foreshore into fertile agricultural land. This venture has been continuing, but with far more effect ive methods, since 1856: thanks to new dykes, to the canalization of the Couesnon and also to the expertise of Dutch engineers, more than 4,000 hectares of the foreshore have been reclaimed into polders. This drying-out of the bay is furthered even more by the natural phenomenon of silting-up. As each tide goes out, the sea leaves behind a deposit of "tangue" of which the level is rising constantly. Little by little, specific vegetation (spartina and saltwort) is colonizing the shoreline, soon taken over by the plants which make up the "herbu" (the salt marshes). The land is thus fixed and stabilizes for good. Up to the last century, this phenomenon was counteracted by the effect of the flow of water from the rivers which ran into the bay, which pushed back the sediment as it was deposited. But these water courses (Couesnon, Sélune, Sée and Guintre), are now canalized, re-routed and weakened and so do not fulfil their cleansing function and the salt marshes are progressing more and more quickly, encircling the Mont like a giant pair of pincers. Since the 1970s, research has been taking place which should bring about, after some extensive work in the next few years, a stabilization of the silting-up and so the preservation of the island quality which gives the rock all its historical and spiritual meaning. -