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The fundamental cause of the construction of nature's most common buildings - mountains is the movement of plates and their tectonic movements.
 While new ocean crust is constantly being created at mid-ocean ridges, old crust must either be destroyed or reduced simultaneously. Otherwise the planet would be continually expanding and increasing in volume. The plates, therefore, emerging along mid-ocean ridges, sliding over the athenosphere, and grinding past other plates along transform faults, are almost all headed on a collision course. When two continents carried on opposing plates ram into each other, they crumple and fold under the enormous pressure, creating great mountain ranges.
The highest mountain range in the world, the snow-capped Himalayas, is a classic example of a continent-to-continent collision. This string of towering peaks is still being thrust up as India, a part of the Indo-Australian Plate, continues to crunch relentlessly into Tibet, which is located on the southern edge of the Eurasian Plate.
When archaeologists found the fossilized remains of ancient sea-creatures near the peaks of the Himalayas they were puzzled. Intriguing questions were raised. Was there once an ocean or other large body of water at the top of this enormous mountain range? Not very likely.
Had the entire planet, Himalayas and all, at some point in Earth's long history, been submerged underwater? Possibly - but highly improbable, since if the water did reach that level, where did it go?. No theory could fully explain this mystery. Until the theory of plate tectonics was put to test.
As the Indo-Australian Plate, with India firmly embedded, approached the Eurasian continent 20 million years ago, its leading edge, comprised of oceanic crust, was first to be crumpled and uplifted. Slowly, the Himalayas rose and the leading oceanic crust of the Indian subcontinent, carrying the fossilized remains of its ancient ocean inhabitants, was thrust up by the crumpling crust in its wake. Thus, plate tectonics explains how the majestic peaks of one of the world's great mountain ranges were once the deep sea-floors of an ancient drifting plate.
The European Alps have been formed in similar fashion, starting some 80 million years ago when the outlying continental fragments of the African Plate collided with the Eurasian Plate. Unyielding pressure between the two plates continues even today, resulting in the gradual closing up of the Mediterranean Sea.
Pictures- Top Right- A common mountain peak; Bottom Center- Construction of a mountain
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