In general the Massif Central is an asymmetric basement plate elevated at its southern margin by the Pyrenees orogeny and along its eastern margin by the Alpine orogeny. Along these margins it descends very abruptly to the surrounding grabens. These margins also show the highest elevations, the plate being gently inclined to the Northwest where the basement rocks disappear under the Mesozoic cover of the Aquitaine basin and the Paris Basin. This somewhat simplistic model is locally disturbed by fault lines and graben structures - for instance the massif's highest elevation is positioned in the central section (Puy de Sancy culminating at 1886 meters) as already mentioned.