The Bernese Alps are a group of mountain ranges in the western part of the Alps, in Switzerland. Although the name suggests that they are located in the Bernese Oberland region of the canton of Bern, portions of the Bernese Alps are in the adjacent cantons of Valais, Lucerne, Obwalden, Fribourg and Vaud. The latter being informally named Fribourg Alps and Vaud Alps respectively.The Rhône valley separates them from the Chablais Alps in the west and from the Pennine Alps in the south; the upper Rhône valley separate them from the Lepontine Alps in the south-east; the Grimsel Pass and the Aar valley separates them from the Urner Alps in the east; their northern edge is not so well defined, describing a line roughly from Lake Geneva to Lake Lucerne.The Bernese Alps are drained by the river Aar and its tributary Saane in the north, the Rhône in the south and the Reuss in the east.One of the most considerable Alpine ranges, the Bernese Alps extend from the gorge of Saint-Maurice, through which the Rhone finds its way to Lake Geneva, to the Grimsel Pass or, depending on the definition, to the river Reuss. The principal ridge, a chain that runs 100 kilometres from west to east, whose highest peak is the Finsteraarhorn, forms the watershed between the cantons of Berne and Valais. Except for the westernmost part, it is also the watershed between the Rhine and the Rhone. This chain is not centered inside the range but lies close to the Rhone river on the south. This makes a large difference between the south, where the lateral short valleys descend abruptly into the deep trench forming the valley of the Rhone and the north, where the Bernese Alps extends through a great part of the canton of Berne, throwing out branches to the west into the adjoining cantons of Vaud and Fribourg. There the mountains progressively become lower and disappear into the hilly Swiss Plateau or into the Lake Thun and Brienz on the eastern part.The main chain west of Gemmi Pass consists mainly of a few large prominent summits slightly above 3,000 metres, generally covered by glaciers. On the eastern part, the main chain became suddenly wider and the peaks reach over 4,000 metres, in the most glaciated part of the Alps.A characteristic in the orography of the Bernese Alps is, that whereas the western of that chain consists of a single series of summits with comparatively short projecting buttresses, the higher group presents a series of longitudinal ridges parallel to the axis of the main chain, and separated from each other by deep valleys that form the channels of great glaciers. Thus the Tschingel Glacier and the Kander Glacier, separate the portion of the main range lying between the Gemmi Pass and the Mittaghorn from the equally high parallel range of the Doldenhorn and Blümlisalp on its northern side. To the south the same portion of the main range is divided from the still higher parallel range whose summits are the Aletschhorn and the Bietschhorn by the Lötschental and the Lötschenlücke. To this again succeeds the deep trench through which the lower part of the Aletsch Glacier flows down to the Rhone, enclosed by the minor ridge that culminates at the Eggishorn.It is in the central and eastern portions of the range only that crystalline rocks make their appearance; the western part is composed almost exclusively of sedimentary deposits, and the secondary ridges extending through Berne and the adjoining cantons are formed of jurassic, cretaceous, or eocene strata.