In topography, prominence (also referred to as autonomous height, relative height, and shoulder drop in US English, and drop or relative height in British English) measures the height of a mountain or hill's summit relative to the lowest contour line encircling it but containing no higher summit within it. It is a measure of the independence of a summit. A peak's key col (the highest col surrounding the peak) is a unique point on this contour line and the parent peak is some higher mountain, selected according to various criteria. Definitions The prominence of a peak may be defined as the least drop in height necessary in order to get from the summit to any higher terrain. This can be calculated for a given peak in the following way: for every path connecting the peak to higher terrain, find the lowest point on the path; the key col (or key saddle, or linking col, or link) is defined as the highest of these points, along all connecting paths; the prominence is the difference between the elevation of the peak and the elevation of its key col. Mount Everest's prominence is defined by convention as its height, making it consistent with prominence of the highest peaks on other landmasses. An alternative equivalent definition is that the prominence is the height of the peak's summit above the lowest contour line encircling it, but containing no higher summit within it; see Figure 1. Illustration The parent peak may be either close or far from the subject peak. The summit of Mount Everest is the parent peak of Aconcagua in Argentina at a distance of 17,755 km (11,032 miles), as well as the parent of the South Summit of Mount Everest at a distance of 360 m (1200 feet). The key col may also be close to the subject peak or far from it. The key col for Aconcagua, if sea level is disregarded, is the Bering Strait at a distance of 13,655 km (8,485 miles). The key col for the South Summit of Mount Everest is about 100 m (330 feet) distant. In mountaineering Prominence is interesting to many mountaineers because it is an objective measurement that is strongly correlated with the subjective significance of a summit. Peaks with low prominence are either subsidiary tops of some higher summit or relatively insignificant independent summits. Peaks with high prominence tend to be the highest