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Before the volcanoes broke out it consisted of trap rocks slowly upraised to the level of the sea by the action of central forces. The internal fires had not yet forced their way through. But at a later period a wide chasm formed diagonally from south-west to north-east, through which was gradually forced out the trachyte which was to form a mountain chain.
The word, here meaning level ground, not, as usual, a canefield, applies especially to the narrow outer rim of the hollow plain; a bristling fortification of bluffs, pointing inwards, and often tilted to quoins 300 feet high, with an extreme of 1,000. Trachyte and basalt, with dykes like Cyclopean walls, are cut to jagged needles by the furious north-easter.
The porphyry vein matter or ore-bearing quartz, having decomposed more readily than the trachyte of the mountains which they intersect, in some instances, as in the peak just above our cabin, they have cut deep notches in the summit of the ridges, making the outline very jagged and rugged looking.
The orifice of eruption was situated at the Plomb du Cantal, formed of solid masses of trachyte, which, owing, as Mr.
The excavations conducted by Pinart in 1887 have proved these figures to be sepulchral monuments. He managed to make a considerable collection of crania and human bones. Round about the crater of the Rana-Raraku volcano, forty of these figures have been counted, all of a similar type, all cut in one piece of solid trachyte rock.
Occasionally eruptions of ash took place from small vents, forming the ash-beds with plants found at Ballypallidy, Glenarm, and along the coast as at Carrick-a-raide. The streams also brought down sand and gravel from the uprising domes of trachyte, and deposited them over the lake-bed along with the erupted ashes.
On either side of the road are well-cultivated farms. Within two miles of Ouray the park narrows into a magnificent gorge, bounded on each side by precipitous cliffs of red sandstone, covered with pines and quaking aspen, the whole crowned by arid peaks. From this gorge you suddenly come upon the town, situated in an amphitheatre of grand gray, trachyte rocks. Our house is in Main Street.
They often assume the most singular forms; I saw a pedestal of the earthy trachyte, covered by a hemispherical portion of a vein, like a great umbrella, sufficiently large to shelter two persons.
Smooth, dark gray tophus predominates; it forms the bed of the Rio Pasig, and rising forms hillocks in the vicinity of the city of Binangonan. Farther on, trachyte and banks of conchiferous sand predominate. The vast plain of Panpanga extends to the north of Manila Bay, to the south of which is situated Mount Arayat, of doleritic nature.
Nowhere throughout this region do beds of trachyte and basalt alternate with one another; in all cases the basalt is the newer of the two varieties of rock, and this is generally the case throughout the region here described. This mountain lies to the north of that of Cantal, and somewhat resembles it in general structure and configuration.
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