Plateaux and massifs
In Lozere more than anywhere else, the earth and the men have been influenced by the nature of the subsoil. Basalt, granite, limestone, schist: this tetralogy alone explains the imposing and sometimes mysterious characteristics of the Lozere landscapes
In the north-west, Aubrac is a thick pile of basaltic layers covering the crystalline base, a continuation of the great volcanic complexes of Auvergne. Particular forms mark the landscape, peaks or walls of basalt as in the Peyre rock or in the Fare de Chirac, prismatic stretches as in the Pont des Nègres... Chiseled by the glaciations of the quaternary period which left glittering lakes and grayish peat bogs, animated by the murmur of the streams, it extends peacefully, covered with moors and meadows. It culminates at the Signal de Malhebiau at 1 471 m, its highest point in Lozère. To the north-east, the crystalline base touches on the whole of the Margeride, one of the largest granite massifs in Europe. High plateaus covered with pastures, but where there are still fragments of forests of Scots pines and beeches, they exceed 1 000 m on average, but are notched on their periphery of deep valleys, with rounded slopes. In the center, it is nothing but harmonious hillocks. The Signal de Randon dominates the whole of its 1 565 m. The decomposition of the granite has left large blocks that dot the moors or sometimes pile up in rocky chaos. The south of the Margeride is constituted by the mountain of Goulet, a schistose massif which rests on the crystalline base. It isolates a small region very unusual in these places: the plain of Montbel, a small highland causse of which one wonders how it could be found there. Often, in Margeride, the land is poor, the climate harsh and rye is the only cereal that men have been able to cultivate in these austere regions. The broom heath dominates, covering itself in spring with an infinity of dazzling yellow spots. In the past, more than 300,000 sheep used to spend their summer vacations here.
Gorges and forests
The Cévennes in the southeast are the domain of schist. The upper course of the Tarn separates them into two large massifs at the top of which the granitic base outcrops: Mount Lozère (1,699 m at Finiels) and Mount Aigoual (1,565 m) in the extreme south of the department. In the center, the Bougès mountain is a transition zone between the northern Cévennes, where moors dominate, and the southern Cévennes covered with forests. On both sides, the "serres" mark the landscape with their schistose crests as if cut with a knife, separated by deep valleys, with steep and tormented slopes which carry thick forests of coniferous trees, beech trees or chestnut trees. The three most important ones are the Vallée Longue, the Vallée Française and the Vallée Borgne, each of which has its own river. For centuries, this region was the richest in the Lozère. As the space was limited, men built terraces, raised the land, and created a network of irrigation canals (béals). They planted vines, fruit trees, vegetables and especially the "tree of life", the chestnut tree. The Cevennes landscape retains deep traces of this intense humanization despite the depopulation that has affected it for a century
In the southwest, everything changes. During the secondary era, the sea advanced on the ancient massif and, for 60 million years, limestone and marl were deposited in alternating layers thousands of meters high. This was the time of the dinosaurs and you can see the traces of some of these animals near Florac, in Saint Laurent-de-Trêves. The rivers, which flowed at a greater rate than today, dug imposing gorges, sometimes more than 500 meters deep, which separate the now barren and arid plateaus: the causses. Human activity is concentrated in a few hamlets or isolated farms, always located near small depressions with clay bottoms, the only places where some crops can be grown. If aridity seems to reign on the causses, whereas it rains on average twice as much as in Paris, water is there, under the surface
So much water!
The water runs down, penetrates the ground through the cracks of the rock, dissolves the limestone and transports it to the depths where it deposits it in the form of calcite jewels in underground cavities. Two of them, explored at the end of the last century, have been developed and constitute one of the strong points of Lozere tourism: the Armand cave, on the Méjean causse, and the Dargilan cave on the Causse Noir. Sometimes on the surface, in the massifs of dolomite (a rock close to limestone), strange forms are born, animals, pillars, monumental arches, as in Montpellier-le-Vieux, Nîmes-le-Vieux or in Arcs-de-Saint-Pierre
With its thousands of springs and streams winding through the meadows, Lozère is a bit like the water tower of France; and it proves it by feeding three basins: the Loire by the Allier, the Rhône by the Luech and the Gardons, the Garonne by the Truyère, the Lot and the Tarn. Let's bet that there is some brooklet, on the Aigoual, which runs directly to the Hérault and the Mediterranean. But one cannot speak about the rivers of Lozere without extending on the Tarn and its famous gorges, entirely Lozerean, in spite of those who, a few years ago, in the neighboring region, wanted to appropriate them... From Ispagnac to Rozier, on 50 km, they are one of the natural wonders of France. The average depth varies from 400 to 500 m, and at the cirque des Baumes the distance between the causses is reduced to 1,000 m. Thanks to their sinuous layout, to the variety of their walls, sometimes rocky, sometimes covered with vegetation, their aspect changes constantly, alternating dark corridors and amphitheatres which shine with a thousand lights.
