The world's largest man made non nuclear wartime explosion

The Halifax Explosion occurred on Thursday, December 6, 1917, when the City of Halifax, Nova Scotia, Canada, was devastated by the huge detonation of a French cargo ship, fully loaded with wartime explosives, that had accidentally collided with a Norwegian ship in "The Narrows" section of the Halifax Harbour. Approximately 2,000 people (mostly Canadians) were killed by debris, fires, or collapsed buildings, and it is estimated that over 9,000 people were injured. This was the largest man-made explosion until the first atomic bomb test explosion in 1945 and is still one of the world's largest man-made, conventional explosions to date.

At 8:40 in the morning, Mont-Blanc, a French cargo ship which was chartered by the French government to carry munitions, collided with the unloaded Norwegian ship Imo, chartered by the Commission for Relief in Belgium to carry relief supplies. Mont-Blanc caught fire ten minutes after the collision and exploded about twenty-five minutes later (at 9:04:35 AM). All buildings and structures covering nearly two square kilometres along the adjacent shore of the exploded ship were obliterated, including those in the neighbouring communities of Richmond and Dartmouth. The explosion caused a tsunami in the harbour, and a pressure wave of air that snapped trees, bent iron rails, demolished buildings, grounded vessels, and carried fragments of the Mont-Blanc for kilometres.