Here's why:
* Erosion is a constant process: Weathering and erosion constantly break down mountains, transporting the material away. This process is relentless, but slow.
* Tectonic plates collide: Mountain ranges are formed when tectonic plates collide. The immense pressure pushes rock upwards, creating mountains.
* Uplift counteracts erosion: Even as erosion wears down the mountains, the tectonic forces continue to push the land upwards. This uplift essentially "renews" the mountains, balancing out the erosion.
Think of it like this: Imagine you have a pile of sand. You continuously remove sand from the pile, but at the same time, you also keep adding more sand to the pile. The pile might change shape, but it won't disappear completely. Similarly, mountains are constantly being worn down, but also constantly being pushed up by tectonic forces.
This dynamic process of uplift and erosion is why we still have ancient mountains like the Himalayas and the Appalachians, even though they've been around for millions of years.
