Western North America
The Rocky Mountains stretch more than 4,800 km forming the north-south continental divide in North America. The northern boundary is the Liard River in northern British Columbia near latitude 60 degrees north. The southern boundary is in New Mexico near latitude 34 degrees north. The highest peak is Mount Elbert, in Colorado, at 4,401 m.
The northern Rockies from Montana northwards, are almost exclusively sedimentary rock and were primarily formed by folding and thrusting between two converging plates. The southern Rockies were primarily formed by uplifting and are cored with granite. The northern Rockies have been very heavily glaciated, resulting in sharply ridged mountains separated by wide, U-shaped valleys gouged by glaciers. In contrast, the southern Rockies are more rounded with river-carved V-shaped valleys.
The Rockies cross so many degrees of latitude that there is a wide variation in the altitude of the alpine zone. At the southern end of the Rockies the alpine zone starts above 3500 m and this reduces to about 2000 m at the northern end of the chain.
While many alpine plants such as Saxifraga bronchialis can be found throughout the Rockies, the flora of the northern Rockies is significantly different to the south because of the differences in geology and the huge latitudinal range affecting climate, particularly average temperatures. The northern limit of the delectable Aqueligia jonesii is Waterton National Park in Southern Alberta where it is rarely seen. Aquilegia jonesii is more common in Glacier National Park just to the south of Waterton and is featured in the Siyeh Pass Hike. Polemonium viscosum which is featured on the Akamina Ridge hike, is another beautiful blue flower which ranges from the Colorado Rockies to Waterton National Park. It is not found further north.
Alpine plants found only in the northern Rockies include the brilliant yellow Saxifraga aretioides and the elegant Androsace chamaejasme which is featured on the Parker Ridge hike.