COLOMBIAN SEABOAED AND ISLANDS. 149 



Westwards the system is continued due south with several lofty crests, such as the 

 Paramo de Frontino Citara (11,160 feet), and the San José (9,860). 



Eastwards the ranges approach the Cauca valley so closely that the river seems 

 to flow in a trench of prodigious size. On the west side rises the Cerro Torra, an 

 isolated mass of schistose rocks, containing auriferous quartz veins, found to be 

 12,600 feet high by Robert Blake White, who scaled it in 1878. 



South of the Rio Caramanta the Cordillera, running parallel with the coast, 

 trends slightly westwards, culminating in the Tatama peak (9,850 feet). The 

 scarcely less elevated Munchique, dominating the west side of the upper Cauca 

 valley, projects a spur to the Sotara volcano, south of the Central Cordillera. 

 Beyond this junction the Western Cordillera is abruptly interrupted by the 

 Minama gorge (1,676 feet), which is traversed by the tranquil current of the 

 Patia. Farther on the system merges in the chaos of mountains often called 

 the Tuquerres "plateau," from one of its crests, 13,360 feet high. Yet the 

 Tuquerres is itself overtopped by other summits, such as the Gualcala (13,780), 

 and the above-mentioned Chiles and Cumbal volcanoes. 



Oscillations of the Seaboard — Islands. 



Various phenomena have been observed along the Colombian seaboard 

 indicating frequent changes of level. In several places, and especially east of 

 the Sierra Nevada de Santa Marta, the old beach, covered with shells similar 

 to those now inhabiting the neighbouring seas, stands high above the present 

 shore. Elsewhere sudden changes have been observed, apparently due to volcanic 

 action, but which may be explained by the spontaneous combustion of hydrogen 

 gas escaping from certain " mud volcanoes." The Galera Zamba, one of these 

 safety-valves, 80 feet high, stands on the coast near Cartagena, at the neck of a 

 long tongue of land which projects far seawards, and which is alternately an 

 island and a peninsula. About 1840 an eruption of the cone was followed by the 

 creation of a channel, 25 to 30 feet deep, between the island and the mainland. 

 But in 1848, after another explosion, accompanied by flames visible over 90 

 miles off, the channel was again obliterated for a few weeks, when a great part 

 of the island itself disappeared. The combustion of vapour, attended by the 

 discharge of mud and earth, has been attributed to the electric tension of 

 the carburetted hydrogen gases, which usually escape from the ground with 

 the saline waters percolating from the neighbouring lagoons. 



Most of the islets fringing the Colombian seaboard, such as Zamba and the 

 Cartagena cluster, the Panama archipelago, Tumaco, and the groups at the 

 mouths of the Rios Patia and Mira, are mere geographical dependencies of the 

 mainland. The San Andres and Yieja Providencia groups in the north belong 

 to Central America, and are only politically included in Colombia, like the two 

 oceanic islands of Malpelo and Cocos, at some distance from the Pacific coast. 

 Malpelo, 310 miles west of Buenaventura Bay, is a mere rock, with nearly 

 vertical walls rising 850 feet above a submarine bed, separated from the con- 

 tinent by depths of 1,400 fathoms. Cocos, so named from its coconut- groves. 



