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Halifax Explosion Memorial

The Mont Blanc, a 3121 ton, 320 foot French wartime munitions ship, and the Imo, a 5043 ton, 430 foot metal-hulled Belgian relief ship, collided in Halifax Harbour on Thursday, December 6, 1917, sparking a fire and explosion that killed 2000, wounded 9000, and levelled much of Halifax and surrounding communities. It still ranks today as the largest accidental, non-nuclear explosion.

The port of Halifax in Nova Scotia was busy preparing relief and supplies convoys for the trip across the Atlantic to the battlefields of the First World War. Ships constantly passed each other in The Narrows, a constriction in the waterway located right next to downtown Halifax. Common naval practice dictated that vessels pass to the right of each other; the Imo, which was leaving port, decided to stay to the left of an incoming ship, so that ship could more easily access the docks.

Behind that ship was the Mont Blanc, travelling in the usual right-side channel. The Imo was dead ahead. Both captains, with horns, signalled their intention to remain on course. At the last minute the captain of the Mont Blanc attempted to veer left. The Imo attempted to reverse course, which pulled it to the right, back onto a collision course with the Mont Blanc. Both ships collided at 8:45 am. The collision, and the subsequent pulling back, sent up a shower of sparks that ignited fires on the deck of the Mont Blanc.

The First World War was the beginning of large-scale production and use of high explosivesHalifax Explosion Mushroom Cloud. The Mont Blanc was carrying 2,300 tons of wet and dry picric acid, 200 tons of TNT, 10 tons of gun cotton and 35 tons of benzol. The crew made initial attempts at fire control but, knowing their cargo, quickly headed for lifeboats, made the Dartmouth shore, and ran for the hills. The fire drew assistance from several nearby Navy ships, and a crowd of several hundred onlookers gathered on the docks to watch. Many more Haligonians watched from behind their house windows.

At 9:04 am the Mont Blanc exploded with an estimated force of 3 kilotons of TNT. The blast sent a mushroom cloud 1.9 kilometers into the sky. The Narrows was momentarily emMont Blanc Anchor Shaftptied of water as an 18 meter tsunami swept the waterfront. The blast wave obliterated or seriously damaged much of Halifax, Dartmouth, and surrounding communities. It could be heard and felt up to 360 kilometers away. Approximately a 1.6 kilometer blast radius was totally destroyed. The Mont Blanc became thousands of shards of hot metal, which fell on the remains of Halifax and started fires. A portion of its anchor shaft, weighing 517 kilograms, fell to earth 3.7 kilometers away. Home fires and cooking stoves contributed to the disaster.

An estimated 2000 people in the city of 50,000 died in the blast, fires, and severe cold of the next day’s blizzard. Over 9000 were injured, including many eye injuries from flying glass. Area hospitals and aid crews were overwhelmed, and outside relief had difficulty getting through the following day’s storm. The city of Boston sent trainloads of doctors, nurses, and other supplies; Nova Scotia thanks them every year by sending the city a huge Christmas tree.

The Halifax Relief Commission was struck six weeks later to begin rebuilding. The rebuilding of communities took several years, and many historic buildings were permanently lost.


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