Which mountains are among world's oldest?

The Urals are among the world's oldest extant mountain ranges. For its age of 250 to 300 million years of age, the elevation of the mountains is unusually high. They were formed during the Uralian orogeny due to the collision of the eastern edge of the supercontinent Laurussia with the young and rheologically weak continent of Kazakhstania, which now underlies much of Kazakhstan and West Siberia west of the Irtysh, and intervening island arcs. The collision lasted nearly 90 million years in the late Carboniferous – early Triassic.