What is the name of the mountain range running south from the US border through the states of Chihuahua and Durango, which is part of the same geological system as the Rocky Mountains and the Andes?

• A Sierra Madre Occidental ✓
• B Sierra Madre Oriental
• C Sierra Madre del Sur
• D Sierra Nevada

The Sierra Madre Occidental stretches over 1,200 km and is home to the famous Barrancas del Cobre, a canyon system larger and deeper than the Grand Canyon.