All the mountains we can admire on our planet, from low hills to the highest ranges of Himalaya, are the product of the continuous geological activity of our planet that have been transforming the earth crust since its formation, about 4.5 billions years ago.
These changes are very little and slow, if referred to the human lifespan and even to the duration of human civilization but, after millions of years, they can radically change the Earth landscape.

During all this long history, surely, dramatic and fascinating like a great romance, mountains are created and destroyed so that the first mountain chains formed in the Pre-Cambrian Age, ended 600 millions years ago, or in the first half of the Paleozoic Age (400 millions years ago) don't exist anymore.
Instead, the Himalaya started to form only 38-40 millions years ago and the Alps, the Pirenees, the Caucasus, and the Anatolian mountains are even more recent (dating back to 25 millions years ago) and are among the youngest of our planet, with sharp forms, deep valleys and high peaks.

Other mountain chains are in an intermediate situation; they still exist but they show their ancient origin with their smooth and round shape and a relatively modest height.
Some examples are the Jura, in the east of France (from which one of the three ages of the Mesozoic, the Jurassic, derives its name), born about 200 millions years ago, the Highlands in Scotland, the Appalachian mountains in the U.S. and the Urals in Russia.

The force that created all these mountains from flat sedimentary sea bottoms or continental alluvional planes is the immense pressure unchained by the many large plates in which the earth crust is fracturated.
These plates are in slow relative shift and are pushed by the circular convective motions of the underlying fluid rocks of the MANTLE, acting like gigantic and slow conveyor belts.
Some plates go away the one from the other, like the American Plate from the European and African ones that are still slowly enlarging the Atlantic Ocean, after the separation of these continents about 200 millions years ago.

Other plates, instead, collide the one against the other, bending, cracking and pushing upwards the rocky layers on one or both sides of the edge between the plates.

In various cases, the crust of one plate subsides under the other one, until reaching the upper and molten layer of the mantle, where the subsiding rocks melt.
So doing, these molten rocks, less dense of the mantle,

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