Clean prominence

In topography, prominence characterizes the height of a mountain or hill's summit by the vertical distance between it and 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 is a unique point on this contour line and the parent peak is some higher mountain, selected according to various objective criteria.

There are several equivalent definitions:

The highest peak on any given landmass is, by convention, said to have a prominence equal the elevation of its summit above sea level.

The following mental exercise may illustrate the meaning of topographic prominence. Imagine a peak and imagine that an imaginary sea level (based on an elevation above the Geoid) rises to the peak. Now slowly lower the imaginary sea level and an imaginary island appears beneath your feet. The island will grow and will merge with other islands that emerge. Eventually, the island will touch an island with a higher peak than the initial island (i.e., an imaginary island that existed before lowering the imaginary sea level.) The summit of that island is the parent peak of the summit, the point at which the two islands touch is the key col of the summit, and the elevation rise from the key col to the summit is the topographic prominence of the summit.

The parent peak may be either close or far from the subject peak. The summit of Mount Everest is the parent peak of Aconcagua 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 or far from the subject peak. 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.

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 points around and are likely to have extraordinary views.

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