The Paredão Grande (Matto-Grosso).
At the foot of the vertical giant block on the west many domes of lava, channelled in a quadrangular network pattern, and ridges and cones, were found, all with a slope to the west. I had a great struggle in my research work that day, owing to the thick scrub with vicious thorns that tore one's clothes and skin mercilessly.
We came upon an immense deep crack in the earth surface—a regular cañon—which extended all along the centre of the great valley. On the opposite side of it were again big domes of lava in corrugated designs, also a gigantic circular crater. Many natural crucibles of iron rock, some cylindrical in shape, others oval, others formed not unlike Pompeian lamps—while others still were square or rectangular or lozenge-shaped—were to be seen in many spots on the moraine-like tails that extended southward, like the tentacles of an octopus, and in the heaps of much carbonized rock and solidified froth produced by what was once boiling rock. The mounds of froth were usually collected in depressions.
The west side of the Paredão was decidedly the most interesting of all. Its great arches showed that it must have once formed the sides of a great cauldron—the top of which had subsequently collapsed or been blown off. This seemed quite apparent from the discoloration in the rocky cliff some 50 ft. above the arches, which followed the exact line of what must have been the thickness of the vault. The rock in that discoloured section was perfectly smooth, whereas above that it became much cracked vertically in layers, and gave the appearance of a masonry wall.
Toward the south-western corner there was a prismatic tower. Where the peculiar isolated rocks near the tower formed a spur, a dip was noticeable in the flow of the once molten rock, following what must have been at that time the surface soil over the cauldron's roof.
A huge triangular crater could be seen, from which started an enormous crack of great length in the lava-flow of the valley to the west.
The southern face of that stupendous rocky quadrangle was not quite so vertical as the west and north sides, and was more in tiers or steps of lava—but very steep indeed. It had in its lower part a great spur extending southward.
As I have said, Alcides and I arrived within 30 ft. of the summit of the great Paredão, at an elevation of 2,550 ft., the summit being 2,580 ft.; but owing to the last 30 ft. being absolutely vertical and the top rock of a crumbling nature, and as my object in wishing to obtain a full view of the country to the south had been attained, I did not think it worth while to court an accident for nothing. It was well after sunset when we were up there, and it would take a long time to return to camp. So we hastened on our return journey.