Halifax Explosion 100th anniversary

[terrynorthend]

Originally Posted by OldDartmouthMark

I'm surprised that they are still saying there are only 150 casualties as I expected it to be in the thousands based on the videos.

Horrible situation, and totally unnecessary. Very poor management of the stored 2,750 tonnes of ammonium nitrate!

There is an interesting article on Wired Science about this. It's possible the "charge strength" of Beirut is larger than Halifax, however the nature of the explosives is key.

Ammonium Nitrate can be very volatile especially if it's formulated for mining and not agricultural fertilizer. Videos of the warehouse prior showing the label Nitrophil suggest a mining application. That said, it's nowhere near as efficient as a military grade high-explosive, even in 1917.

In comparison the materials in Halifax were high-grade explosives. The difference as explained in the article was the over pressure created by the detonation. There are two types of blast wave, a pressure wave or a shock wave. A pressure wave doesn't move as fast and builds more slowly. A shock wave goes from 0 to Max almost instantly and moves hyper-sonically. The difference to people who are hit is akin to falling down a steep hill and rolling to a stop vs. falling from the high in the air and hitting flat ground at terminal velocity.

By measuring videos of the condensation cloud in Beirut, they determine that the explosion created a pressure wave, not a shock wave. This greatly reduced catastrophic injury at distance.

Halifax's explosion almost certainly created a shockwave which would have caused instantly fatal injuries to those unlucky enough to be in the way.

[ns_kid]

The Washington Post picked up on the parallels with the Halifax Explosion in this piece by John Bacon that appeared on the weekend:

How the explosive destruction of Halifax holds lessons — and hope — for Beirut

Bacon authored the 2017 book The Great Halifax Explosion: A World War I Story of Treachery, Tragedy, and Extraordinary Heroism. It's a very readable book, if a bit US-centric. In my opinion the best book about the Explosion remains Curse of The Narrows: The Halifax Disaster of 1917 by Laura MacDonald (2005). MacDonald saw the parallels between Halifax and another traumatic event of our time, the 9/11 destruction of the World Trade Centre (which she watched from the window of her Harlem apartment). Both books are worth reading.

A final note, for those who haven't seen it. CBC reported a few weeks ago the discovery of what appears to be a previously unknown photo of the Explosion.
A municipal archives in Belleville ON discovered the photo in a collection they acquired in 2012. The validity of the photo is still uncertain, but the research done so far seems to support the theory the image was shot by Reginald Stevens, a mate aboard HMCS Niobe at the time of the Explosion.

The photo and the article:

Is this 'surreal nightmare' an unpublished photo of the Halifax Explosion?

[OldDartmouthMark]

Originally Posted by terrynorthend

There is an interesting article on Wired Science about this. It's possible the "charge strength" of Beirut is larger than Halifax, however the nature of the explosives is key.

Ammonium Nitrate can be very volatile especially if it's formulated for mining and not agricultural fertilizer. Videos of the warehouse prior showing the label Nitrophil suggest a mining application. That said, it's nowhere near as efficient as a military grade high-explosive, even in 1917.

In comparison the materials in Halifax were high-grade explosives. The difference as explained in the article was the over pressure created by the detonation. There are two types of blast wave, a pressure wave or a shock wave. A pressure wave doesn't move as fast and builds more slowly. A shock wave goes from 0 to Max almost instantly and moves hyper-sonically. The difference to people who are hit is akin to falling down a steep hill and rolling to a stop vs. falling from the high in the air and hitting flat ground at terminal velocity.

By measuring videos of the condensation cloud in Beirut, they determine that the explosion created a pressure wave, not a shock wave. This greatly reduced catastrophic injury at distance.

Halifax's explosion almost certainly created a shockwave which would have caused instantly fatal injuries to those unlucky enough to be in the way.

Interesting info. Thanks for posting it.

Probably a couple other factors that contribute to the higher death rate in the Halifax Explosion were as follows (IMHO):

1) The Beirut explosion occurred in an industrial area that offered a bit of a buffer zone for the residential areas. In 1917 Halifax, although there was industrial activity in the city, residential was pretty much built right down to the water.

2) Structural integrity of Halifax's wooden buildings of the time would not have stood up to the blast as well as more modern structures, plus would not have been as susceptible to fire - many of the deaths in Halifax happened from building collapse and the resultant fire as in December everybody had a wood or coal stove heating their home/business.

Additionally there was a lot of blindness in Halifax caused by broken glass when people were looking out their windows towards the fire.

Interesting discussion.

ns_kid, thanks for posting the link but unfortunately it's behind a paywall. I don't want to sign up for it at the moment, but it sounds interesting.

I also have been following the discussion on that photo that turned up on CBC - IMHO it's the real deal.