>>12409406The collapse of the North Tower dumped a few thousand tons of burning skyscraper on it, causing serious structural damage and fires on the south side of the building. Firefighters on the scene who got close enough to see the damaged side all described a massive gash in excess of 20 stories long running down the south face, deep enough that it was exposing structural supports.
Just like with Towers 1 and 2 - thermal weakening and expansion exacerbated impact damage and led to a collapse, the cause of the impact damage is the only difference. Same physics, different initial conditions.
