About 100 million years ago the process of spreading was halted in the Tethys Ocean and the African continent broke away from the South American plate, beginning a northward movement. Caught in the middle of the merging continents, the area of the Tethys Sea between Africa and Eurasia began to shrink. The southern (African) landmass then continued its northward movement over some one thousand kilometers. The slow folding and pleating of the sediments as they rose up from the depths is believed to have initially formed a series of long east-west island chains. In the final stage of the Tethys Sea's disappearance (its remainder would become the Atlantic Ocean), the large mass of material that was originally far to the south was pressed onto and over the deep ocean layers.

As Africa moved north, the European continent was subducted underneath it. The Alps are made up of piles of sliced off sheets (termed nappes by Alpine geologists) from the European margin, with sheets of the southern continental margin on top. The European Alps consist mainly of material that was transported over a thousand kilometers northward by the movement of the African plate. Formation of the Mediterranean Sea is a more recent development and does not mark the northern shore of the African landmass. The same mechanism shaped the Himalayan range, where the Indian continent is moving northward and pressing into and under the Asian landmass. This was happening the elements were at work weathering these soft materials at a high rate and filling the newly-made valley (what was formerly thethys Sea basin) with sediment layers of mixed composition.

In a later period, after the mountains had been formed, a series of low limestone mountains (Jura) were created and stretch from Paris to southern Germany and along the northern border of Switzerland, forming the Neuchatel region. Measurements in the road and railway tunnels show that the Alps continue to rise somewhere between a millimeter and a centimeter each yeare and there are many active seismic areas under the mountains that show that stresses continue to be released along deep fault lines. The last glacier advance ended only "yesterday" in geologic terms (some 10,000 years ago in this area) and left the large lake now known as Lake Neuchatel. The ice in this region reached some 1000 meters in depth and flowed out of the region behind Lake Geneva some 100 km to the south. Today large granite boulders are found scattered in the forests in the region. These were carried and pushed by the glaciers that filled this part of the western plain for some 80,000 years during the last ice age.

As the last ice age ended, it is believed that the climate changed so rapidly that the glaciers retreated back into the mountains in only some 200 to 300 years time. Besides leaving an arctic-like wasteland of barren rock and gravel, the huge moraine of material that was dropped at the front of the glaciers blocked huge masses of melt water that poured onto the central plain during this period. A huge lake resulted, flooding the region to a depth of several hundred meters for many years. The old shoreline can be seen in some places along the low hills at the foot of the mountains -- the hills actually being glacial side-moraines. As the Aare River, which now drains western Switzerland into the Rhine River, eventually opened the natural dam, the water levels in the plain fell to near the present levels.

 

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