Red Mountain is something of a misfit within its ecoregion. Ecoregions are geographic areas sharing a similar ecology, geology, and climate. They are sorted into four nested levels, from very inclusive to very precise. Red Mountain, all of Alabama, and most of the eastern U.S. are within the Eastern Temperate Forest level I ecoregion. Red Mountain falls within the Ozark, Ouachita-Appalachian Forests ecoregion, one of several level II ecoregions within the Eastern Temperate Forest ecoregion. This ecoregion encompasses the most mountainous regions of Alabama and other eastern states south of New England. At the next level, Red Mountain lies within the Ridge and Valley level III ecoregion, an area of elongated ridges and intervening valleys that stretches from Alabama to New York. This is one of the important ecoregions that make up the Southern Appalachian Mountains.
Finally, Red Mountain is part of the Southern Limestone/Dolomite Valleys and Low Rolling Hills level IV ecoregion, an area of linear valleys between adjacent mountains. The limestone and dolomite (dolostone) are more readily weathered than the durable rocks of their adjacent mountains. As they dissolve over the millennia, springs, sinkholes, and cavern systems are formed (see What Lies Beneath: Karst). Some locations within the valleys are hills of chert. This rock is more resistant to weathering than limestone and dolomite, which is why areas with chert rise above the surrounding landscape.
So why might Red Mountain seem out of place? Well, its level IV ecoregion has few other linear ridges like it. Most long ridges in our area are in the adjacent level IV ecoregion – the Southern Sandstone Ridges. However, Red Mountain wouldn’t fit in well with these other mountains, either. They all have a distinct sandstone cap of younger rock, and none have an iron-rich rock formation like Red Mountain. Red Mountain really is one of a kind.