DESCRIPTION AND
DATA SHEET

Sierra Madre Oriental
Monterrey, Mexico, Earth

The city of Monterrey, Mexico (bright yellow area), is located on the eastern flank of the Sierra Madre Oriental Mountains. In this region, a series of layered sedimentary rocks moved over a slippery basal surface known as a decollement. Compressional deformation roughly 40 to 50 million years ago caused the sedimentary layers to slide along and buckle into a series of folds known as anticlines. (Something similar to this happens when a rug slides on the floor and crumples up at one end.) This process is referred to as decollement folding.

Erosion of these folds has created this series of closely spaced troughs and ridges, some of which reach elevations of 3500 meters. Differential erosion has removed weaker rock layers and exposed more-resistant layers, which are generally composed of sandstones and limestones, forming the ridges. A similar process is responsible for the formation of the Valley and Ridge Province of central Pennsylvania.

The Sierra Madre Oriental is an extension of the North American Cordillera, which divides into an eastern and western branch near Monterrey. Although this mountain chain generally trends northwest-southeast, the tight folds south of Monterrey are oriented east-west. The mechanism controlling this deflection is uncertain, but may be related to (1) a strike-slip fault system in this region, (2) the gravity-sliding of rocks off uplifted basement blocks, or (3) uneven distribution of the weak evaporite layers that formed the base (the decollement) of the folded sequence.

Location:
     25.7 N, 100.4 W
Mission:
     STS 60
Image Numbers:
     60-83-40, 60-83-42
Image Resolution
(Full-Sized View):
     80 meters/pixel
Image Width:
     83 kilometers
Vertical Exaggeration:
     1.3 × Normal
Vertical Resolution:
     69 meters
Spacecraft Altitude:
     307 kilometers
Stereo Baseline:
     81 kilometers
Convergence Angle:
     13°