The map below shows the cross-section of the Alps, as determined from tunneling and seismic data. The white material comes from folded ocean sediments, while the darker striped material are older rocks that cracked and piled up as the crust relaxed. due to buckling.

This shows that the theoretical model presented on the previous page is in accord with the actual situation.

During the slow compression of the rock in the crust, the heat is slowly released to the atmosphere without significant effect on the climate, except that the ground water is warmer than now. However, during the rapid expansion of the crust in the process of mountain formation, the same amount of heat is absorbed by the rocks in the crust that was released during the compression. Since the rocks are relatively poor heat conductors, the absorbed heat cannot be quickly obtained from the hotter inner layer, and therefore the temperature has to drop.

The changes in climate, brought about by the cycling process of compression and relaxation of the solid crust, with the associated temperature fluctuations and glaciations, play likely the dominant role in biological evolution.

During the last ice age, many species that could not adapt to the cold climate perished, and new species emerged. Among the plants evolved grasses that were cultivated into the grain-producing varieties, and among the animals, mammoth, bison, and related species evolved into cattle, while wolves were bred into dogs. Among birds, dark colored species, such as crows emerged
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Reproduced from Handbuch der Geophysik with permission by Gebrueder Borntraeger.

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