Accidents happen, especially in times of war. Be it due to friendly fire, miscalculations, or maybe because of wrong decisions or unfollowed orders. However, some accidents could not be shrugged off, as the effects were too huge and devastating. The Halifax Explosion in Canada was one of them; when a naval accident caused an explosion so powerful that it flattened an entire city. While life goes on after some accidents, this one was different as the blast was heard throughout the globe, making headlines about the devastating effects of the accident.

Expert Mariners

Before the explosion made headlines all over the world on December 6, 1917, it all started with a collision at sea of two ships sailing with their own separate missions. The first was a Norwegian war-relief ship called the SS Imo. The second was the SS Mont-Blanc, a rusty French tramp steamer that was basically a floating bomb stuffed to the gunwales with almost 3,000 tons of picric acid, gun cotton, and TNT. Not only that but there were also hundreds of barrels of highly flammable benzol fuel piled high on her deck. As one veteran Royal Navy officer said later on, “I’m surprised that people on the ship didn’t leave in a body when they saw the nature of the cargo she had been ordered to carry.”

Both ships were about to begin their voyages in clear and mild weather, with calm seas, veteran harbor pilots guiding the ships, and two experienced mariners for captains. What could possibly go wrong?

The Collision

Going into or out of Bedford Basin past the city of Halifax required vessels to pass through a strait called the Narrows, which was, well, narrow. To prevent ships from colliding in the area, they were expected to keep close to the side of the channel and pass oncoming vessels “port to port.” They were also restricted to a speed of 5 knots (5.8 mph) within the harbor. Before 9 am, the SS Imo was headed to out to Halifax Harbour when she found that she was on a collision course with Mont-Blanc. They exchanged warning signals, and both of them cut their engines. Their momentum still carried them right on top of each other at a slow speed.

Mackey, an experienced harbor pilot, ordered Mont-Blanc to steer hard to port and crossed Imo’s bow in the last-second bid to avoid a collision. They almost made it, with the two ships parallel to each other, when Imo suddenly indicated that the ship was reversing its engines.
The cargoless ship’s height in the water and the transverse thrust of the right-hand propeller caused the ship’s head to swing into the Mont-Blanc, and Imo’s prow pushed into the starboard side of her number one hold.

House destroyed in Halifax explosion. (Toronto History from Toronto, CanadaCC BY 2.0, via Wikimedia Commons)

The Explosion

The barrels of deck cargo toppled and flooded the deck with tons of benzol. The Imo then decided to reverse engines and withdraw her bow from the hole she had made in the side of the Mont-Blanc. As you might expect this caused sparks to fly as the two metal hulls dislodged from each other. This ignited the Benzol vapors and a fire broke out in the cargo hold with thick black smoke billowing out of it. Worried that the ship might explode immediately, the captain of the Mont Blanc immediately ordered the crew to abandon the ship, all while frantically shouting warnings to Halifax citizens who were starting to form a crowd on the street along the Narrows to watch.  Homes and businesses were emptying out as news spread of the collision and more and more people gathered.  Unfortunately, the noise and confusion drowned out these warnings. The now abandoned and burning Monte-Blanc drifted off and grounded at pier 6 in the harbor.

The Halifax Herald press was two miles from the Halifax Explosion. All the windows exploded, and equipment was knocked over, causing damage. A small staff stayed to board up windows and produce the paper by hand. (From Dennis, W.A., “Genealogies and Sagas: Dennis, Miller, Archibald,” published privately and shared with family, 1960., CC0 1.0, via Wikimedia Commons)

Just after 9:04 am, the vessel exploded. Mont-Blanc was completely blown apart, and the blast wave traveled at more than 3,300 feet per second, sending 9,000 °F of heat and pressures of thousands of atmospheres from the center of the explosion.  Shards of smoldering iron rained down Halifax and Dartmouth starting fires all over both cities.  Every single building within a 1.6 mile radius was destroyed while further out, the shock wave blew in doors and windows and caused fires from turned over oil lamps.

The blast was felt as far as Cape Breton, about 129 miles away, and Prince Edward Island, 110 miles away.