10,000 ft. Cotopaxi.
10,000 ft. Caraguairazo.
10,000 ft. Pichincha.
We will now speak more particularly of the Andes of the equator. The mountain chain is built up of granite, gneissoid, and schistose rocks, often in vertical position, and capped with trachyte and porphyry.[60] Large masses of solid rock are rarely seen; every thing is cracked, calcined, or triturated. While in Bolivia the Eastern Cordillera shows a succession of sharp, ragged peaks, in contrast with the conical summits of the Cordillera of the coast, there is no such distinction in the Andes of the equator.[61] The Eastern Cordillera has a greater mean height, and it displays more volcanic activity. Twenty volcanic mountains surround the valley, of which twelve are in the oriental chain. Three of the twenty are now active (Cotopaxi, Sangai, and Pichincha), and five others are known to have erupted since the Conquest (Chiles, Imbabura, Guamani, Tunguragua, and Quirotoa). The truncated cone of Cotopaxi, the jagged, Alpine crest of ruined Altar, and the dome of Chimborazo, are the representative forms of the volcanic summits. The extinct volcanoes usually have double domes or peaks, while the active peaks are slender cones. Antisana and Cayambi are fashioned after Chimborazo, though the latter is table-topped rather than convex; Caraguairazo, Quirotoa, Iliniza, Sincholagua, Rumiñagui, and Corazon, resemble Altar; Tunguragua, Sangai, Llanganati, Cotocachí, Chiles, and Imbabura, imitate Cotopaxi; Pichincha, Atacatzo, and Guamani are irregular. The Ecuadorian volcanoes have rarely ejected liquid lava, but chiefly water, mud, ashes, and fragments of trachyte and porphyry. Cotopaxi alone produces pure, foam-like pumice, and glossy, translucent obsidian.[62] The paucity of quartz, and the absence of basalt, are remarkable. Some of the porphyroids are conglomerate, but the majority are true porphyries, having a homogeneous base. Dr. T. Sterry Hunt calls them porphyroid trachytes. They have a black, rarely reddish, vitreous, or impalpable base, approaching obsidian, with a specific gravity of 2.59 in pure specimens, and holding crystals or crystalline grains of glassy feldspar, and sometimes of pyroxene and hematite. They differ from the Old World porphyries in containing no quartz, and seldom mica.[63] D'Orbigny considers the porphyries of the Andes to have been ejected at the close of the cretaceous period, and formed the first relief of the Cordillera. The prevalence of trachyte shows that the products have cooled under feeble pressure.
From the deluges of water lately thrown out have resulted deep furrows in the sides; and from the prevalence of the east wind, which is always met by the traveler on the crest of either Cordillera, there is a greater accumulation of ashes, and less snow on the west slope. Cotopaxi is a fine example of this. In Pichincha, Altar, and Rumiñagua, however, the western wall is lowest, apparently broken down.[64] There is no synchronism in the eruptions of Cotopaxi and Pichincha. These volcanoes must have independent reservoirs, for the former is 3000 feet higher than the latter, and only thirty miles distant. The reputed eruptions of Pichincha are dated 1534, 1539, 1566, 1575, 1588, and 1660; that of 1534 resting on the assertions of Checa, Garcilazo, and Herrera, indorsed by Humboldt. Excepting the traditional eruption in 1534, which probably is confounded with that of Pichincha, Cotopaxi did not open till 1742; then followed the eruptions of 1743, 1744, 1746, 1766, 1768, 1803, 1851, and 1855. We must mention, however, that, since the recent awakening of Pichincha, Cotopaxi has been unusually silent. There is also a remarkable coincidence (which may not be wholly accidental) in the renewed activity of Pichincha, and the great eruption of Mauna Loa, both occurring in March, 1868. It is generally believed by the natives that Cotopaxi and Tunguragua are sympathetic.
There are fifty-one volcanoes in the Andean chain. Of these, twenty girdle the Valley of Quito, three active, five dormant, and twelve extinct.[65] Besides these are numerous mountain peaks not properly volcanic. Nowhere on the face of the earth is there such a grand assemblage of mountains. Twenty-two summits are covered with perpetual snow, and fifty are over ten thousand feet high.[66]
All of these would be visible from a single stand-point—the summit of Cotopaxi. The lofty peaks shoot up with so much method as almost to provoke the theory that the Incas, in the zenith of their power, planted them as signal monuments along the royal road to Cuzco. The eastern series is called the Cordillera real, because along its flank are the remnants of the splendid highway which once connected Quito and the Peruvian capital.[67] It can also boast of such tremendous volcanoes as Cotopaxi and Sangai. The Western Cordillera contains but one active volcano; but then it can point to peerless Chimborazo and the deep crater of Pichincha. These twenty volcanic mountains rise within a space only two hundred miles long and thirty miles wide. It makes one tremble to think of the awful crevice over which they are placed.[68]