We crossed two cols (elev. 1,550 ft.) with a beautiful plain between. Then we descended into a third lovely valley on the north side of the outer wall of the crater. The grazing was perfect for the animals. Clusters of vigorous, healthy burity palms stood in great numbers in the centre and at the sides of the valley. This great valley was bounded by two ridges extending in a northerly direction—two spurs, as it were. The rounded, channelled outer sides of the crater to the north would tend to strengthen the theory that those slopes were formerly a gradual continuation of the present inclined valley. On those slopes of the mountain hardly any vegetation could be noticed, perhaps owing to the fact that hard volcanic rock existed under the thin surface padding of yellowish earth.
The valley was buried in red and grey lapilli and ashes, finely broken up marble cubes, and fragments of other forms of crystallized rock.
As we proceeded from camp Fogasso, the northern slopes of the crater became divided into huge furrows, the vertical upper part of the crater displaying vividly rich red tones. The crater was castellated at the summit, like the walls of a fortress.
The geological formation of that portion of the Matto Grosso plateau interested me greatly. Each individual spur, taken separately, showed slopes sometimes abrupt, sometimes well rounded, separated from the next spur of hills by a V-shaped or angular, or else a concave hollow. At the bottom of those hollows one did not find the slopes continuing the line of the crater, but the valley was there absolutely flat and cut the line of the slope sharply. It would almost appear as if a subsidence of the soil had taken place in that particular locality, or else one might speculate whether those abrupt hills had not been the walls of what was once a subterranean volcanic cauldron—the flat valley, in which we were, having been the bottom of that cauldron. What little rock one found in the river bed in this valley showed signs of having been exposed to intense and prolonged heat, and so did the brilliant red summit of the hill range, which was also of the deep red typical of hard-baked rock.
The Paredãozinho.
Typical Scenery of Matto Grosso.