The Rocky Mountains begin in northern New Mexico, where the axial crystalline rocks rise to 12,000 ft (3,700 m) between the horizontal structures of the plains on the east and the plateaus on the west. The upturned stratified formations wrap around the mountain flanks of the range, with ridges and valleys formed on their eroded edges and drained southward by the Pecos river to the Rio Grande and the Gulf of Mexico. The mountains rapidly grow wider and higher northward, taking on new complications of structure and including large basins between the axes of uplift. In northern Colorado and Utah, the mountains become a complex of ranges with a breadth of 300 miles (480 km). In Colorado alone, there are 54 summits over 14,000 ft (4,300 m) in altitude, though none rise any higher than Mount Elb