How were mountains formed?

Mountains are formed in two ways. When the tectonic plates move, they collide against each other. When the heavy oceanic part of the plate collides with the continental part, it submerges below it. The Andes, for instance, were formed in this way. The other way is when two continents collide with each other, the plates bend at the point of contact and fold up steeply. The Himalayas or the Alps were formed in this way around 35 million years ago and are counted among the 'young' mountains of the world. Old mountains, such as Black Forest or the Harz Mountains, are lower ranges because peaks have been worn down by rain, ice, and wind over time.