North Tower Exploding...

[gyroscope]

39. From what I read

before 9/11 there were actually no steel-framed skyscrapers that have ever been demolished by a controlled demolition, surprisingly enough.

may or may not be true, but recalling all the videos I ever saw of known and acknowledged controlled demolitions of tall buildings I realized they were all made of concrete or steel-reinforced concrete. they were not steel-frame skyscrapers. so if what I read is true then the WTC towers could be the first modern steel-frame skyscrapers to be brought down that way.

sort of makes sense. explosives would be ideal for blasting through concrete pillars and supports.
but thermite, an incendiary commonly used by welders to cut through thick steel, may be more suited for cutting through the structural steel columns and beams found in steel-framed skyscrapers.

Civilian Uses
Thermite reactions have many uses. Thermite is not an explosive; instead it operates by exposing a very small area of metal to extremely high temperatures. Intense heat focused on a small spot can be used to cut through metal or weld metal components together both by melting metal from the components, and by injecting molten metal from the thermite reaction itself.

http://en.wikipedia.org/wiki/Thermite#Civilian_uses

the bolded would explain the large pools of molten metal witnesses saw in the aftermath of the collapses.