This may be due to far distant continental collisions in the build up of Pangea.
There were several episodes of continental collision, compression and subduction which resulted in mountain building during this time.
The idea of continental collisions building mountains "up" is therefore rather a simplification.
The high mountain ranges produced by continental collisions are immediately subjected to the forces of erosion.
Figure 3 shows the sequence of events illustrating the obduction model following continental collision.
When two plates move towards one another, they form either a subduction zone or a continental collision.
A protracted episode of continental collision started at about 610 Ma ago and continued for about 50 million years.
Next time Ruby went home the troll mountains were going to receive their biggest shake-up since the last continental collision.
The Alps have a complex geology, but the general structure is the same as for other mountain ranges formed by continental collision.
Leucogranites have been reported from a variety of orogenies involving continental collisions.