I noticed three distinct “explosions” of what appears to be the same molten material seen poring out of the South Tower moments before it’s collapse.
At first, I thought they were just pieces of this molten debris hitting the side of the building. Upon zooming in, however, it looks as if they are “exploding” outward from in between the columns.
#1 in the video appears to come straight out a very high speed, and continues its horizontal trajectory for over 60 frames of the video. Other molten debris continues to rain down around it while it continues on a horizontal trajectory.
#2 is not in frame for very long, I haven’t put much time into it.
#3 is very interesting, as it appears between two other pieces of molten debris falling. There is a very bright flash, and explosion of molten material. This explosion seems to come from an object seen slowly falling or sliding down and out of a window. The top of this falling object also appears to be glowing as it falls.
This just may be a large chunk of molten mass falling from above, hitting a window sill, and continuing down(did the towers have “window sills”?). Or, maybe a column being cut ? There is definitely an object there that appears after the burst.
The second part of the video focuses on flashes that appear on the Northeast corner column of the upper “block” of the South Tower as it is falling. These flashes or explosions cause actual physical damage to the columns they occur on, and you can see not only the column damage, but also a pressure wave go through the dust ejections as the explosions occur.