Sierra Madre Occidental

Sierra Madre Occidental 

a mountain range in Mexico, along the western edge of the Meseta Central. The range is about 1,300 km long and 80–200 km wide. Average elevations vary between 1,500 and 2,000 m; the highest peak is Mount Chorreras (3,150 m).

The Sierra Madre Occidental is composed mainly of Precambrian metamorphic rocks with a mantle of younger sedimentary rocks and granite intrusions, overlain by thick layers of Neogene lavas. Gold and silver are mined in the mountains. The range is deeply dissected by river valleys; in the west there are canyons up to 200 m deep. In the northern part of the range, the slopes are covered mainly by xerophytic shrubs; at elevations of about 2,000 m they give way to thin, dry pine forest. In the southern part of the range there are sclerophyll and summer green forests.