What is a mountain? How many mountains are there? It turns out that answering these simple questions about global and national topography is not that easy.

If you classify every tiny rise in elevation as a mountain, then there are an infinite number of mountains. A meaningful, objective definition is therefore necessary in order to establish a mountain ranking. Three topographicaly based criteria are used for this calculation: elevation, isolation and prominence.

Isolation

Isolation is the horizontal distance from the peak of a mountain to the nearest point of equal or higher elevation. Thus, the isolation of "Mountain A" is measured in terms of distance to the nearest higher mountain. Isolated mountains are therefore those that are the highest within a wider area.
If the criterion for isolation is a radius of 1 km, then there are more than 1'500 major mountains in Switzerland, 62 mountains within a radius of 10 km and 3 mountains within a 50-km radius. In Switzerland, the Piz Bernina is the most isolated mountain at 137.9 km; the Finsteraarhorn is the nearest higher mountain. The second-most isolated mountain is the Dufourspitze at 78.2 km. Next come the Finsteraarhorn at 51.65 km, the Chasseral at 49.5 km, the Piz Russein (Tödi massif) at 42.05 km and Mont Tendre at 38.7 km.

Prominence

Prominence of a mountain is the difference in elevation between the summit and the highest ridge that leads to a higher summit. In other words: Prominence is the smallest descent that must be made in order to climb a higher mountain. This distance indicates how free-standing a mountain is. The Finsteraarhorn has the largest prominence at 2280 m, followed by Piz Bernina at 2234 m, Dufourspitze at 2165 m and Säntis at 2021 m.

Significance

Finally, a mountain peak can be defined by its significance. This is calculated based on a peak’s isolation, relative prominence and elevation. Indices are calculated for each of these variables, then added together and divided by three. For the category “supreme mountains”, such as Mont Blanc and the Grossglockner, this results in values of less than 1.0; for the “major mountains of a continent”, e.g. Säntis, values are less than 2.0.