This high-resolution satellite image shows part of the Sierra Madre Oriental mountain range, on the border between the Coahuila and Nuevo Leon provinces of eastern Mexico. This range is part of the Sierra Madre Mountains that divide Mexico, and which also include the Sierra Madre Occidental on the West coast and the Sierra Madre del Sur in southern Mexico. In the area shown, ancient sedimentary rocks were folded as a result of a tectonic collision that some geologists consider related to the Appalachian folding of eastern North America. This mountain range is drier than the rainforest areas to the south. Image courtesy of USGS.