The range forms, with the Sierra de Tres Picos range, the northwestern foothills of the Sierra Madre de Chiapas that straddle the states of Oaxaca and Chiapas.
The Sierra Atravesada consist mostly of metamorphic and granite rocks, and forms the most important division of the Isthmus of Tehuantepec.
The main peaks of the Sierra Atravesada are: 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 flows into the Pacific Ocean.
The Rio Negro, a tributary of the Grijalva, rises on the eastern slope of this mountain range.
Rain in this area is very abundant, being in the path of humid winds blowing south from the Gulf of Mexico.