Geologic History
As in the rest of South America, a combination of external and internal tectonic, volcanic, and glacial forces over the eons formed Colombia's present-day geology. Island-like outcroppings in the eastern llanos are visible remnants of Precambrian times when Colombia consisted of metamorphic rocks. During the 332-million-year-long Paleozoic Era, which began 570 million years ago, the ocean again invaded Colombia's Andean zone, as subterranean volcanic eruptions in the western part of the country spouted lava. In the Triassic Period of the 143-million-year-long Mesozoic Era, which began 240 million years ago, the sea that occupied the Andean zone separated into two parts after the Cordillera Central rose. Large layers of sedimentary rock were deposited during the Jurassic Period, which ended with great igneous activity. During the Cretaceous Period, the sea to the east of the Cordillera Central extended to Putumayo region in the south, while subterranean volcanic activity continued to the west of the Cordillera Central. During the 63-million-year-long Tertiary Period of the Cenozoic Era, which began about 65 million years ago, the seas withdrew from most of Colombia's territory, and enormous granite masses formed along the Cordillera Occidental. The three cordilleras began to take shape 12 million years ago. The Cordillera Occidental and the Cordillera Central form the western and eastern sides of a massive crystalline arch, which extends from the Caribbean lowlands to the southern border of Ecuador. The Cordillera Oriental, however, is composed of folded stratified rocks overlying a crystalline core.
Read more about this topic: Geology Of Colombia
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