Fun fact for you: scientists don't really know how the Himalayas formed. I mean yeah, they realize that the India tectonic plate is slamming into the Eurasia plate and has been for about 50 million years, but the mystery is why the mountain range is still growing. Usually when two continents collide it's like a car wreck — there may be a bunch of mangled crust in the middle (mountains), but both vehicles stop moving.

Turns out, India appears to be sinking into the mantle. A new study based on computer models of the two plates shows that the formation and continued growth of the world's highest mountain range makes the most sense if a dense piece of India is down in the mantle, dragging the rest of the continent down with it.

That may not sound so weird but continents are buoyant; they're supposed to float, not sink. All the subduction you hear about all over the world is dense ocean crust sinking underneath continents. Except in the Himalayas. It's as though two cars collided, and one started to sink into the pavement.

This video gives you a rough outline of the old idea of how the Himalayas form. India's bending here, but it doesn't start heading it into the mantle on its own:

Notice how India seems to float magically into Eurasia, and then just keeping going. But why? Why would a continent willingly flatten itself against another continent? Doesn't make sense. That's the big problem with the old idea.

Now, it's by no means certain that the researchers in the new study — led by Fabio Capitanio of Monash University in Australia — have nailed this thing. It's one of the most persistent mysteries about plate tectonics on the planet. But if Capitanio and his team are wrong, it would mean we still don't understand how Earth's greatest mountain range got there, or why it's getting taller to this day.

Source: Nature Geoscience (sub required for full article)