The biggest explosion before atom bombs hit a town with a 52-foot-tall tidal wave

On the morning of December 6, 1917, an explosive shockwave tore through Halifax, Nova Scotia, ripping the coastal city apart.

The event leveled the entire neighborhood of Richmond, killing thousands. It tossed a ship onto the harbor shores like a toy. A giant tidal wave even rushed into low-laying areas.

The source of the detonation - a French ammunition ship - almost completely vanished. Only the vessel's anchor and one of its guns were found miles away.

The magnitude of the blast was equivalent to about 6 million pounds of TNT, making it the largest human-made explosion at the time. The record would hold for nearly three decades, until the United States surpassed it by detonating the first atomic weapon near the end of WWII.

Here's the incredible story of how the Halifax Explosion went down.