e caused numerous buildings to shift on their foundations and over many years to slowly sink into the ground. The volcanic axis--with such spectacular snowcapped peaks as Popocatepetl at 17,887 feet (5,452 meters), Ixtaccihuatl at 17,342 feet (5,286 meters), and Toluca at 15,000 feet (4,572 meters)--forms the southern boundary of the Mexican Plateau.On the east and west sides of the plateau lie that country's coastal lowlands. The Gulf Coastal Plain extends from the Texas border to the Yucatan peninsula, a distance of some 900 miles (1,450 kilometers). Characterized by lagoons and low-lying swampy areas, the triangular northern portion is more than 100 miles (160 kilometers) wide near the border and tapers rapidly toward the south. Inland toward the abrupt escarpment of the Sierra Madre Oriental is a series of gently undulating plains dotted by occasional hills and low mountains. Near Tampico an extension of the Sierra Madre Occidental reaches the sea and interrupts the plain's continuity. To the south of Tampico it is narrow and irregular. In several places low hills and isolated volcanic peaks meet the sea and subdivide the plain. It widens at the northern end of the Isthmus of Tehuantepec and then encompasses the limestone formations that underlie the Yucatan peninsula.The Pacific Lowlands are much narrower and less well defined than their east-coast counterpart. Extending from the Mexicali Valley in the north, they terminate near Tuxpan nearly 900 miles (1,450 kilometers) to the south. Bounded on the east by the steep-sided Sierra Madre Occidental, the lowlands are in fact a series of coastal terraces, mesas, and small basins interspersed with river deltas and restricted coastal strips. From the 1940s parts of this arid region have been irrigated for agricultural production.West of the Pacific Lowlands is the Baja California peninsula. This relatively isolated strip of land is nearly 800 miles (1,300 kilometers) long but seldom more...
