Mount Everest

The Birth of a Mountain
Mountains aren't just big piles of dirt, they're made of solid rock. Believe it or not, the rocks that make up the Himalayan mountains used to be an ancient sea floor. Over millions of years, rivers washed rocks and soil from existing mountains on the Indian subcontinent and nearby Asia into a shallow sea where the sediment was deposited on the floor. Layer upon layer of sediment built up over millions of years until the pressure and weight of the overlying sediment caused the stuff way down deep to turn into rock. Then about 40 million years ago, in a process called "uplifting", the sea floor began to be forced upward forming mountains.

Plate Tectonics in Action
What caused the sea floor to be pushed up toward the sky was the result of the action of plate tectonics. The theory of plate tectonics was developed about thirty years ago by scientists who discovered that the earth's crust is made up of many "plates" which are constantly moving around. They are still moving around, even today, but the speeds at which they move are REALLY SLOW. In human terms the movement can't even be seen, but it can be felt occasionally when we have earthquakes. Earthquakes happen when plate margins (edges) move past, or bump into each other. In the case of the Himalayan mountains, the continent of India is part of a plate that "crashed" into southwest Asia, but it didn't stop when it hit. It continued to push northward, crushing and rumpling the earth's crust, resulting in the mountains we see today. If you go back to the map of the Himalayas, you can see that the mountains look kind of like a rumpled blanket. India is still pushing northward today, raising the Himalayas even higher!
How Do They Know?
Scientists know this because they've been measuring the increasing height of the mountains. There have also been a lot of earthquakes recorded down deep in the mountains, which indicates continuing movement. The Himalayas are growing, but only about an inch a year. That's not very much in human terms, but imagine how much that would be over millions of years! You may be thinking, "That would have been kinda cool to be here on earth 40 million years ago to be able to watch the Himalayas forming". You would have been really bored, though. The movement that took many millions of years to form the mountain range is still taking place today, and I doubt you would stake out a camp at the foot of the mountains just to watch them grow. You'd be waiting