Geometrical Pattern on the Surface of a flow of Lava.
(Caused by sudden contraction in cooling.)
We travelled for long distances on a ridge at an elevation of 1,650 ft. over a thick layer of sand and ashes mixed. Then campos spread before us, and upon them here and there grew stunted vegetation, the trees seldom reaching a greater height than 15 ft.
From our last high point of vantage the crater with fantastic rocks and its continuation we had observed appeared to form a great basin. A subsidiary vent was also noticeable. Farther on our march we found other immense deposits of grey ashes and sand alternately—one great stretch particularly, at an elevation of 1,600 ft. Water at that spot filtered through from underneath and rendered the slope a grassy meadow of the most refreshing green. We were rising all the time, first going north-west, then due north. At noon we had reached the highest point.
From the high point on which we were (1,920 ft.) we obtained a strange view to the west. Above the straight line of the plateau before us rose in the distance a pyramidal, steep-sided, sharply-pointed peak, standing in solitary grandeur upon that elevated plain. Why did it stand there alone? was the question one asked oneself—a question one had to ask oneself frequently as we proceeded farther and farther on our journey. We often came upon mountains standing alone, either on the top of table-lands or in the middle of extensive plains. Their presence seemed at first unaccountable.
Again as we journeyed onward the mules' hoofs were injured by treading over large expanses of lava pellets and sharp-edged, cutting, baked fragments of black rock, myriads of which also lay embedded in reddish half-formed rock or buried in layers of yellowish-red earth.
To the north was a majestic panorama of the most delicate tones of blue and green, with almost over-powering sweeping lines hardly interrupted by a slight indentation or a prominence rising above the sky-line. Only to the north-west in the middle distance was there the gentle undulating line of magnificent campos—most regular in its curves, which spread in a crescent toward the west. The line was interrupted somewhat abruptly by a higher and irregular three-terraced mass, but soon resumed its sweeping and regularly curved undulations beyond. This great crescent almost described a semicircle around the smaller undulations over which we were travelling.
We descended to 1,750 ft. On facing west we had curious scenery on our left (south). A huge basin had sunk in—evidently by a sudden subsidence which had left on its northern side high vertical cliffs supporting the hill-range that remained standing. The undulating centre and sides of the immense depression formed beautiful campos with an occasional bosquet of forest on the top of hills, and also on the lowest points of the undulations. Those bosquets were few and far apart, only to be found where moisture was plentiful. The remains of a high, flat plateau, which had escaped while the rest of the country had subsided, loomed alone in the distance.
One of the central hills was crowned by great black volcanic boulders of the same rock which was visible at the southern edge of this great basin, bounded by vertical cliffs—all of the same composition.