Figure 2. Part of Northeast Mexico. Just south of the city of Monterrey, the ridges of the Eastern Sierra Madre turn 
abruptly to the west. Also visible are parts of the Gulf Coast Lowlands, Central Mesa and Basin and Ranges provinces. 
The left half is part of the Chihuahuan Desert. Approximate scale, 1:3,000,000. 
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Figure 3. Central Mexico. In the top, the Neovolcanic Plateau province slopes reach the coast of the Gulf of Mexico (to 
the right). The three highest mountains are visible: Citlalt&petl, Popocatepetl and Iztaccihuatl (just above 
Popocatépetl). The lower half shows part of the Southern Sierra Madre, the most complex region. Here, the Balsas 
River Basin, an inmense deppresion. To the east, the Gulf Coast Lowlands have a marked contrast with the other two 
provinces visible in the image. A curved linear feature south from a line between the Citlalte&pet! and Popocatépetl 
resembles the shape of the west turn of the Eastern Sierra Madre seen in figure 2.. Approximate scale, 1:3,000,000 
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International Archives of Photogrammetry and Remote Sensing. Vol. XXXI, Part B4. Vienna 1996