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

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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.

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By December 1917, WWI had been raging for three years. Halifax, located on Canada's east coast, served as an important port for shipping troops and supplies to Europe.

By December 1917, WWI had been raging for three years. Halifax, located on Canada's east coast, served as an important port for shipping troops and supplies to Europe.

On December 6, a Norwegian cargo ship, the SS Imo, was departing Halifax on its way to New York. The ship was en route from the Netherlands to ferry supplies back to a war-ravaged Belgium.

On December 6, a Norwegian cargo ship, the SS Imo, was departing Halifax on its way to New York. The ship was en route from the Netherlands to ferry supplies back to a war-ravaged Belgium.

Source: NASA Safety Center

At the same time, the SS Mont Blanc was bound to return to France carrying a host of highly explosive materials: 2,367 tons of picric acid, 62 tons of guncotton, 250 tons of TNT, and 246 tons of benzol in barrels below deck.

At the same time, the SS Mont Blanc was bound to return to France carrying a host of highly explosive materials: 2,367 tons of picric acid, 62 tons of guncotton, 250 tons of TNT, and 246 tons of benzol in barrels below deck.

Source: NASA Safety Center

To exit the Bedford Basin, where the ships were docked, they had to pass through a slim channel. The Imo — behind schedule and on the wrong side of the channel — refused to give way and crashed into the Mont Blanc.

To exit the Bedford Basin, where the ships were docked, they had to pass through a slim channel. The Imo — behind schedule and on the wrong side of the channel — refused to give way and crashed into the Mont Blanc.

Though the collision occurred at low speed, the barrels of benzol spilled, and sparks from the crash ignited the fuel. Minutes later, the Mont Blanc exploded with the force of 2,989 tons of TNT.

Though the collision occurred at low speed, the barrels of benzol spilled, and sparks from the crash ignited the fuel. Minutes later, the Mont Blanc exploded with the force of 2,989 tons of TNT.

Source: NASA Safety Center

The shockwave from the blast covered 325 acres of ground, and leveled the Richmond neighborhood. The temperature in blast exceeded 9,000°F. The water around the Mont Blanc vaporized and pushing a 52-foot-tall tidal wave three blocks into town.

The shockwave from the blast covered 325 acres of ground, and leveled the Richmond neighborhood. The temperature in blast exceeded 9,000°F. The water around the Mont Blanc vaporized and pushing a 52-foot-tall tidal wave three blocks into town.

Source: NASA Safety Center

The force of the explosion lifted the Imo and threw it onto the shore. The Mont Blanc was ripped apart and completely destroyed. Almost no part of the ship survived the explosion.

The force of the explosion lifted the Imo and threw it onto the shore. The Mont Blanc was ripped apart and completely destroyed. Almost no part of the ship survived the explosion.

A 1,140 pound piece of its anchor was found buried more than two miles away from the explosion. A barrel from one of the ship's guns traveled three and a half miles.

A 1,140 pound piece of its anchor was found buried more than two miles away from the explosion. A barrel from one of the ship's guns traveled three and a half miles.

Source: NASA Safety Center

Much of the city was leveled, with 12,000 buildings destroyed or made uninhabitable, leaving a huge portion of the city's population without shelter from the frigid December weather.

Much of the city was leveled, with 12,000 buildings destroyed or made uninhabitable, leaving a huge portion of the city's population without shelter from the frigid December weather.

Source: NASA Safety Center

Almost every window in the city shattered — some reportedly 50 miles away. Even the buildings left standing were severely damaged.

Almost every window in the city shattered — some reportedly 50 miles away. Even the buildings left standing were severely damaged.

Source: NASA Safety Center

About 1,600 people died instantly in the blast, and 350 later succumbed to injuries. An estimated 9,000 people were injured in the accident and 22% of the city's population were casualties.

About 1,600 people died instantly in the blast, and 350 later succumbed to injuries. An estimated 9,000 people were injured in the accident and 22% of the city's population were casualties.

Source: NASA Safety Center

The casualties would have been even worse had a railway dispatcher, Vincent Coleman, not halted a train carrying 300 people towards the train station directly in front of the burning ship.

The casualties would have been even worse had a railway dispatcher, Vincent Coleman, not halted a train carrying 300 people towards the train station directly in front of the burning ship.

Source: Maritime Museum of the Atlantic

Coleman's final action was sending a telegraph warning up the tracks: "Hold up the train. Ammunition ship afire in harbor making for Pier 6 and will explode. Guess this will be my last message. Good-bye boys."

Coleman's final action was sending a telegraph warning up the tracks: "Hold up the train. Ammunition ship afire in harbor making for Pier 6 and will explode. Guess this will be my last message. Good-bye boys."

Source: Maritime Museum of the Atlantic

The force of the Halifax explosion was so large that it remained the largest manmade explosion ever until the United States developed atomic weaponry in 1945.

The force of the Halifax explosion was so large that it remained the largest manmade explosion ever until the United States developed atomic weaponry in 1945.
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