How does the Sierra Madre Oriental connect the Gulf of Mexico lowlands with the Mexican Plateau?

The Sierra Madre Oriental serves as a rugged mountain barrier situated on the eastern side of the Mexican Plateau. Rather than acting as a simple wall, the range is characterized by steep-walled, narrow valleys and contains several natural gateways that provide passage between the Gulf of Mexico lowlands and the plateau.12

These mountains, composed largely of folded sedimentary strata such as shales and limestones, rise to average elevations of about 7,000 feet (2,100 metres), with some peaks exceeding 10,000 feet. The range effectively separates the low-lying coastal plains from the high-altitude interior, and its physical structure—marked by north-to-south aligned valleys—facilitates the movement and connectivity between these two distinct physiographic regions.21