France Relief and Coasts

France Relief and Coasts

Relief. – The general characteristics of the relief show a systematic distribution of the plains and mountains similar to that which governs the general course of the European relief. It has often been observed that a line, drawn in the direction SO.-NE. from the mouth of the Bidassoa (point where the Spanish border touches the ocean) to the confluence of the Lauter and the Rhine (north of Alsace), it leaves SE. almost all the higher reliefs and a NO. almost all the plains and hills. Indeed, while on the one hand the altitudes above 500 m. they represent more than half of the surface, on the other hand they are almost non-existent. France has the two types of mountain massifs known in Europe and all types of lowlands, except that of the plains of glacial origin,

According to, the recent mountains, of tertiary origin, exceeding 3000 m. in height, which strongly suffered the effects of the Quaternary glaciation and which still contain more or less extensive glaciers, are represented by the Pyrenees, which form the border with Spain, the Alps, which form the border with Italy and the Jura, branch of the latter, which is the border with Switzerland. The highest European peaks rise between France and Italy, between Chamonix and Courmayeur (Mont Blanc 4810 m.). The French Alps contain many peaks near 4000m.; height which the Pyrenees do not reach, whose culminating point, a little beyond the Spanish border, is the Maladetta (3404 m.). The Jura, although it is linked to the alpine folds, does not reach 2000 m. (Crêt de la Neige 1723 m.).

The Hercinian uprisings, whose folding dates back to the primary era, lower and of generally gentle forms, are represented by the Vosges and the Massif Central. Neither point of the two massifs reaches the height of 2000 meters (the highest point of the Vosges is the Ballon de Guebwiller, 1426m; the highest point of the Central Massif is the Puy de Sancy, 1886 meters). Other less elevated Hercinian massifs are found to the NW. of the diagonal mentioned above: the Ardennes massif, extremity of the Rhenish schist massif (culminating point in France 497 meters); the Armorican Massif, even less high (maximum height 417 meters), which forms the peninsula of Cotentin and Brittany and extends as far south as the Loire, with the Vendée.

The lowland and hill regions belong to two types. The one are true alluvial plains, which occupy a sinking area in the midst of Hercinian massifs, such as the plain of Alsace, or a depressed corridor on the edge of a folding arch, such as the Rhone furrow, which extends by beyond the elbow that the river makes in Lyon, with the plain of the Saone (Bresse). The others are rather regions of hills, formed by sedimentary layers of secondary or tertiary age, which are deposited in inland seas or in lake basins in the most depressed parts of the Hercynian area. Such are: the Parisian Basin, enclosed between the Central Massif, the Vosges, the Ardennes and the Armorican Massif; and the Aquitaine Basin, enclosed between the Massif Central and the Pyrenees. The layers of these ancient basins,côtes which is characteristic of the Parisian Basin, that is to say in lines of asymmetrical hills, all of which have a steep front on the side of the nearest Hercian massif.

Coasts. – The outline of the French coasts, which constitute half of the borders of the state, was naturally fixed during the Quaternary. The formation of the Pas de Calais does not seem to be prior to the first glacial periods; and the same can be said of the separation of the Norman Islands from the Cotentin. The meanders of the Seine, which continue sharply under the waters of the estuary, those of the Trieux in Brittany and those of the Aulne, which show the same phenomenon, indicate a positive movement of the sea, the importance of which is confirmed by the soundings, which have revealed Quaternary floods up to 30 m. at least in depth. Subsequently, the sea continued its work of reporting, interrupted by a last transgression of historical date, in the plain of Flanders and in the estuary of the Somma, which continues before our eyes.falaises), retreating rapidly, gave rise to the straight coasts characteristic of Normandy and Picardy, with their valleuses or suspended valleys. Behind the coastlines, the estuaries filled up rapidly, except that of the Seine, where Rouen is preserved as a seaport, while Abbeville sulla Somma can no longer receive but small boats, which go up a canal.

In the Armorican Massif the lower trunks of the valleys were invaded as a result of the transgression, and changed into narrow and branched estuaries, similar to the Spanish rias ; a swarm of small islands formed in correspondence with the banks of hard rocks. No coastline is more indented than that of Cotentin, Brittany and the Vendée; however, the work of regularization of the sea has begun to make its effects felt here and there. On the west coast of Cotentin, at the bottom of the Mont Saint-Michel Bay, and on the southern coast of Brittany, several coastlines block a number of bays and estuaries. South of the Vendée, an ancient gulf corresponding to a depression of the continental relief, in contact with the secondary covering of the ancient massif, formed theMarais poitevin, where some embankments, started in the Middle Ages and continued up to the century. XIX, they hastened the reconquest on the sea, creating a small Holland. Further on, the islands of Ré and Oléron protect some protrusions in connection with limestone reliefs, which rise just above the waves and are partly covered with dunes. South of the mouth of the Gironde, the coast of the Landes begins, bordered for 200 km. from high dunes, which bar the valleys and turn them into freshwater ponds, with a surface of water that is 10 m. above the nearby sea. Only the Bay of Arcachon remains open due to the tidal currents. However, the regularly rectilinear contour of the coast is not due only to accumulation: the sea gnaws almost everywhere on the continent, making the coastline retreat and discovering peat under the dunes.

The Mediterranean coast has two quite different types to the East. and W. of the Rhone delta: on the one hand it is steep, rocky, bumpy by peninsulas and bays and surrounded by islands; on the other it is flat, uniform, with large lagoons, behind coastlines covered with dunes. However, on both sides, the effects of recent positive movement are less visible than on the ocean coast. In Provence, the Alps themselves and their last buttresses plunge into the waters of the Mediterranean with so steep slopes that the sea cannot advance very far; moreover, recent ground movements have led to the emergence of some deltas in certain points, such as that of the Varo near Nice. The floods did not take long to fill some gulfs, such as that of Argens and the plain of Hyères; and one of the islands was re-attached to the mainland, forming the Giens peninsula. But the littoral current carries most of the floods to the Languedoc side. The detritus of the Alps and those of the Pyrenees give such an abundance of floods that the regularization of the littoral cord is perfect; behind these coastlines that lean on ancient limestone islands, like in Cette and Narbonne, or volcanic ones, like in Agde and Leucate, an almost continuous row of lagoons stretches, interrupted only by the great plain of the Aude.

France Coasts

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