The Silting-up Phenomenon

The silting-up of the Bay of Mont-Saint-Michel is a natural phenomenon that can be seen in all bays.

It can be explained by the dissymmetry of the tidal wave. The incoming current corresponding to the rising tide is quicker than the ebb tide, corresponding to the outgoing tide.

So when it approaches the Mont, the tide is filled with sediment which remains in suspension from the moment it enters the bay. When approaching the sea, as the current speed is decreasing, the larger particles are deposited. When the tide goes out, the desposit is completed by the slow withdrawal of a fine film of water leaving behind the finer particles which adhere to the bottom. Progressively, millimetre by millimetre, the bottom of the Bay silts-up.

 The estran with low tide