Why did the collapsed towers look so flat?
Before the terrorist attack, the Twin Towers were 110 stories tall. Constructed of lightweight steel around a central core, they were about 95% air. After they collapsed, the hollow core was gone. The remaining rubble was only a few stories high.
I would guess that the weight of the collapsed buildings created craters.... piles of cement and steel.
But...but...what about the guy who "skiied" down the crumbling building as it fell? Or the back-pack guy? Or the back of the 20-dollar bill when folded?