the north of the main chain of the Alps and include the region between the Alps and the Jura. If matters are examined more carefully, it can be noted that the Rhône and Rhine valleys are shut off from that of the Aare (and of the Thur) by the great northern outlier of the Alps, which consists of the Bernese and Glarus Alps. Two wide and undulating valleys (Aare and Thur) and two deeply cut trenches (Rhône and Rhine) thus lie on the northern slope of the Alps, to the north and south respectively of the great northern outlier of the Alps. The main chain of the Alps rises in Swiss territory to the height of in the loftiest summit or Dufourspitze (wholly Swiss) of Monte Rosa, though the Dom (), in the Mischabel range, is the highest mountain mass which is entirely within Switzerland. The great northern outlier attains a height of in the Finsteraarhorn, while the lowest level () within the Confederation, is on Lake Maggiore (on the course of the Ticino). The highest permanently inhabited village in Switzerland is Juf () at the head of the Avers valley (a tributary of the Rhine), while the lowest is Ascona (), on Lake Maggiore. Geology Different geological phenomena shaped the actual landscapes of Switzerland. The Alpine orogeny had the most visible effects on the landscape: this term covers entire geological movements contributing to the Alps’ formation. A crystalline basement formed at the beginning of the Paleozoic era, between 540 and 360 million years ago. Later, between 205 and 96 million years ago, the alpine ocean or Tethys Ocean formed between Eurasia and Africa. The ocean reached its maximum width at the end of Jurassic period, 135 million years ago. The collision between the Eurasian and African plates made it progressively disappear. This plate collision (still in progress) began 100 million years ago. The Alps resulted from this geological movement, the two plates creating folding zones. The Central Plateau is mainly composed of molasse, a sedimentary rock that formed at the bottom of the Tethys ocean. Switzerland is situated in a relatively tectonically inactive area, although the city of Basel was completely destroyed in 1356 by an earthquake, the largest historical seismic event in central Europe. The most seismically active regions are the Rhine Rift Valley (region of Basel) and the Valais. Physiographic divisions Switzerland is divided in three main