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9-11 Photos: Attack on the World Trade Center

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10:28 a.m.: The WTC North Tower Collapses
People flee the New York World Trade Center after the towers collapsed

People flee the New York World Trade Center after the towers collapsed

Photo — Ezra Shaw / Getty Images
Because the jets struck the World Trade Center Towers on the upper floors, the weight of the buildings caused their own collapse. As each concrete slab floor gave way, it smashed into the floor below. The massive downward crush of floors crashing, or pancaking, on floors, sent out enormous clouds of debris and smoke.

At 10:28 a.m. Eastern Time, the north tower of the World Trade Center collapsed from the top down, pancaking into dust. Researchers estimate that the rush of air displaced—faster than the speed of sound—caused sonic booms.

Learn More About September 11, 2001:

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