Sierra Atravesada

The Sierra Atravesada or the Sierra de Niltepec is a mountain range in the state of Oaxaca, Mexico, in the region of the Isthmus of Tehuantepec. It is a mountain range located in the Mexican geographic region of the Pacific South which forms, together with the Sierra de Tres Picos, the northwestern foothills of the Sierra Madre de Chiapas, which straddles the states of Oaxaca and Chiapas. The range extends from east to west and consists mostly of metamorphic and granite rocks, and it forms the most important division of the Isthmus of Tehuantepec. On its eastern slope waters flow into the Rio Uxpanapa system, which flows into the Gulf of Mexico, while the main collector of its western slope is the Rio Chimalapa, which drains into the Pacific Ocean. Its main peaks are the Cerro Azul (2,250 m) and the Cerro Baul (2,050 m). On the eastern slope of this mountain range, the Rio Negro, a tributary of the Grijalva, has its source. Other rivers of importance that have their origins in the Sierra Atravesada are the rivers Salado, Chivela, Chichigua and the Sarabia, all of which are tributaries of the Coatzacoalcos, one of the largest rivers in Mexico. Precipitation in this area is very abundant, being in the path of humid winds blowing south from the Gulf of Mexico. Rainfall varies between 2,800 and 4,000 mm/year, depending on the slope. The relatively high temperatures (with an annual average of 25 ºC) and the high amount of sunshine make the entire region a good example of a tropical rainforest, one of the several types of rainforests.

References

Santiago Niltepec. Instituto nacional para el Federalismo y el Desarrollo Municipal