Patagonia are composed of the Andes mountains to the south and west, and plateaux and vast steppe-like plains to the east.

These plains have succession of rising terraces and covered with an enormous bed of shingles which are almost bare of vegetation. Ponds or lakes of brackish and fresh waters are found in the hollows of the plains.

Towards the Andes, these shingles provide spaces for porphyry, granite, and basalt lavas. Animal life and the presence of luxurious vegetation acquiring the flora of the Western coast are abundant.