A view of the “cauliflower-like plume” from the explosion.
December 6 1917, Halifax–The manufacture and transport of high explosives was dangerous work in normal times, and the greatly increased demand during the war only increased the risk. Explosions and fires had already cost hundreds of lives at manufacturing plants (in Virginia, New Jersey, and London, among others), at a depot near Istanbul (crippling Turkish efforts in Palestine), and most infamously in Jersey City (though this was caused by German agents). These incidents would all pale in comparison with today’s events, however.
The French ship Mont-Blanc, laden with TNT, guncotton, and picric acid, was being piloted through the approach to Halifax harbor on the morning on December 6. Bringing its cargo from New York, it was planning to wait in Halifax for a convoy to Europe. It encountered the Norwegian ship Imo, en route to New York to acquire supplies for the Belgian relief effort. The Imo was on the far left side of the channel (contrary to usual practice), and both ships indicated that they would not change their course despite an imminent collision. At the last moment, the Mont-Blanc turned towards the far shore (a turn in the opposite direction would have grounded her), while the Imo attempted a U-turn, also turning towards the far shore. They collided at low speed at around 8:46AM, but this spilled multiple barrels of highly-flammable benzol (a mixture of benzene and toluene) that were improperly stored on the deck of the Mont-Blanc. When the Imo reversed to separate herself from the Mont-Blanc, this created sparks that ignited the benzol, creating an intense fire. The crew of the Mont-Blanc, expecting an imminent explosion, evacuated ship and ran inland.
The empty ship, meanwhile, drifted across the channel to Richmond, on the north end of Halifax. Due to wartime precautions against submarines and sabotage, the Mont-Blanc was not marked as having explosives on board. A firefighting effort was conducted on the Richmond side, but this was mainly to prevent the fire on the Mont-Blanc from spreading into town. One of the few people who knew it contained explosives, notified the local railway office, whose staff quickly evacuated. However, one of the dispatchers, Vince Coleman, returned to his desk in an attempt to prevent additional train traffic from coming into the area–most especially an inbound train with 300 passengers that was scheduled to stop near the Mont-Blanc in a matter of minutes. At 8:49, he sent this telegram:
Hold up the train. Ammunition ship afire in harbour making for Pier 6 and will explode. Guess this will be my last message. Good-bye, boys.
At 9:04:35 AM, the Mont-Blanc exploded. The explosion killed around 1600 people instantly and another 300-400 would die of their injuries. Over two square miles of Richmond were destroyed, and additional damage was caused by fires and (on both sides of the channel) by a resulting tsunami. The explosion was the largest caused by mankind until Hiroshima, and had about a tenth of its strength. A mushroom cloud rose into the air; a British admiral described it as “a most wonderful cauliflower-like plume of white smoke, twisting and twirling and changing color in the brilliant sunlight of a perfect Canadian early winter morning.”
As with most similar incidents, German sabotage was immediately suspected. The Norwegian ship Imo that collided with the Mont-Blanc was the subject of most of the suspicion–much of the crew, including her captain, were killed in the explosion, and they were thus unable to defend themselves. Recriminations were soon put aside, however, for the sake of the recovery and relief effort, though this was crippled the next day by a blizzard that shut down the railway system. As a result, aid from the United States, especially Boston, was critical in the immediate aftermath. To this day, Boston’s official Christmas tree is a gift from the government of Nova Scotia in appreciation of their relief efforts in 1917.
Today in 1916: The Fall of Bucharest
Today in 1915: Marshal Putnik No Longer Chief of Serbian General Staff
Today in 1914: Pope Benedict XV Calls for Christmas Truce
Sources include: John U. Bacon, The Great Halifax Explosion