Comment: It was a portion of the North tower's core, not the entire core.

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In reply to comment: Simple question. No answers. (see in situ)

It was a portion of the North tower's core, not the entire core.

What sharkhearted wrote in reply, about it being perimeter walls, is completely false. It was part of the core, and while it was significant, it appears it was ultimately only a minimal fraction of the core's total circumference (let's be fair and say that, at its widest, it was 1/6 that remained standing.)

I don't have the definite answer for how it remained standing, if there were planted explosives/demolition weapons, but it sure helps destroy the official story "pancake" collapse nonsense. Especially since it then suddenly, completely collapsed to the ground, when it was enough of the core to have strength-wise remained standing.

When the South tower collapsed, there were several perimeter wall sections that landed in the pavement and were jutting up, standing almost vertically straight. When the North tower collapsed, there could have been similar pieces of debris that had hit the ground (during the first part of the collapse,) that then fell over into the base area of the part that remained standing, causing it to fail.

We can't know for certain because the base is obscurred by the clouds of dust, at the moment of complete failure and collapse of the spire. Personally, I think that it was either North tower debris or demolition weapons that caused the failure and collapse (I say weapons because any explosives used on 9/11 would have been just that - weapons.)