Building 7's Collapse
Features of a Textbook Implosion
|These three images (cropped from larger photographs) show WTC 7 at three different moments in its collapse.|
The total collapse of WTC 7 at 5:20 PM on 9/11/01 shows all of the features of an implosion engineered through controlled demolition.
Controlled demolition is the use of pre-positioned explosive charges to destroy structures. Depending on the nature of the structure and constraints imposed by its surroundings, a controlled demolition may require a great deal of precision in its planning and execution. That is especially true of tall steel buildings in urban settings, given the natural tendency of such structures to topple. Controlled demolitions of buildings in cities are designed to implode the structures, making them sink into their footprints and fold in on themselves into a small consolidated rubble piles
Observing the collapse of 47-story WTC 7 shows it to have all of the features of an implosion engineered by controlled demolition.
- The collapse of the main structure commences suddenly (several seconds after the penthouse falls).
- The building sinks in a precisely vertical manner into its footprint.
- Puffs of dust emerge from the building's facade early in the event.
- The collapse is total, producing a rubble pile only about three stories high.
- The main structure collapses totally in under 7 seconds, only about a second slower than it would take a brick dropped from the building's roof to reach the ground in a vacuum.