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Q: Cause, the chemistry, and the consequences of the Halifax explosion. ( Answered,   0 Comments )
Subject: Cause, the chemistry, and the consequences of the Halifax explosion.
Category: Science > Chemistry
Asked by: ardo-ga
List Price: $8.00
Posted: 08 Mar 2003 11:53 PST
Expires: 07 Apr 2003 12:53 PDT
Question ID: 173543
1- What reactants were involved in this disaster? How did they come to
be chemically combined?

2- Why did the explosion occur? Could it have been prevented? How?

3- What were the economic and social costs?

4- What was done to cope with the immediate and long-termeffects of
the disaster?

Request for Question Clarification by aceresearcher-ga on 08 Mar 2003 13:46 PST
Greetings, ardo!

You have asked 4 good Questions, and to get equally good Answers, you
may want to consider raising your fee.

For guidelines on pricing your Questions, I encourage you to take a
look at the Google Answers Pricing Guidelines at


Subject: Re: Cause, the chemistry, and the consequences of the Halifax explosion.
Answered By: chromedome-ga on 08 Mar 2003 21:30 PST
Hello, Ardo-ga:

Your question literally strikes "close to home" for me; my living room
window overlooks the site of the explosion.  My maternal
great-grandparents and most of their extended families lived in the
North End at the time of the explosion.  Like most Haligonians, they
lost several family members; the entire North End was essentially
obliterated.  My grandmother remembers it vividly, if confusedly (she
was only three at the time).

Evidence and artifacts of the explosion are everywhere in Halifax to
this day.  At my daughter's school (the same one her great-grandfather
attended in the 1920's), pride of place in the principal's office is
given to a photo of the shattered hulk of the building as it looked in
1917.  In the clock tower of City Hall, downtown at the corner of
Barrington and Duke streets, the clock face remains permanently set to
9:05...the time it was stopped by the explosion.


I will preface the answers to your four specific questions by briefly
setting the scene, and summarizing the events of the explosion.

Halifax played a major role as a centre for convoying in both world
wars.  This is due to two factors: its location in the most easterly
region of North America; and its status as one of the world's finest
all-weather ports.  The harbour's entrance is wide and well-protected;
the innermost section (Bedford Basin) is not only sheltered but large
enough to accomodate hundreds of vessels at a time.  Connecting the
two wider sections of the harbour is a stretch known as The Narrows,
for the obvious reason.  Bounded today by the city's two bridges, it
is no wider than a long city block.

The two vessels involved in the explosion were the Imo; a Norwegian
vessel on its way to New York to pick up a cargo of relief materials
for Belgium: and the Mont Blanc; a French vessel carrying munitions. 
On the morning of December 6 1917 the Mont Blanc, which had arrived
too late to enter the harbour the previous night, was making for her
planned anchorage in Bedford Basin.  The Imo, behind schedule, was
making greater-than-usual speed as it entered the Narrows on its way
to the harbour mouth and ultimately New York.

The Imo was well out of its lane as it entered the narrows: well to
the Dartmouth side of the harbour; and directly in the path of the
Mont Blanc's dumfounded captain, Aime Le Medec.  Le Medec signalled
that he was in the correct lane, the Imo responded that she would pass
even FURTHER to the wrong (Dartmouth) side.  After another fruitless
exchange of signals, Le Medec ordered his vessel to pull to the
Halifax side in an effort at avoiding the larger vessel. 
Unfortunately, Captain From of the Imo also ordered his vessel to
reverse engines, and the two ships collided.  Sparks from the
metal-on-metal collision ignited the highly explosive and flammable
benzol which formed part of the Mont Blanc's cargo.

Le Medec, keenly aware that his vessel was a floating bomb,
immediately ordered his crew to abandon ship.  Expecting a blast at
any moment, he and the crew (one imagines that they were as unhappy as
they were motivated) pulled energetically to the sparsely settled
Dartmouth side of the harbour.

Twenty minutes after the collision, at 9:05 on the morning of December
6, 1917, the Mont Blanc exploded.


So, having come this far, let's take a moment to address your specific

1) What reactants were involved in this disaster? How did they come to
be chemically combined? 

The Imo was a non-factor as far as the blast was concerned; her only
(unfortunate) part in the tragedy was to ignite the initial fire.

The Mont Blanc, on the other hand, was a floating arsenal.  Included
in her cargo were 35 tons of Benzol, similar to a high-octane
gasoline; three hundred artillery rounds; ten tons of gun cotton (a
more-stable variant of gunpowder); 2300 tons of picric acid in both
wet and dry form; and 200 tons of TNT.

It is not thought that a chemical reaction caused the blast, except in
the narrowly technical sense that burning is a chemical reaction. 
Sparks from the collision ignited the benzol, which burned merrily
(other cargo on the Mont Blanc included flammable items such as
lumber) for some time.  Eventually, the flames triggered one of the
high explosives on the ill-fated vessel; probably the picric acid.  In
its dry form (which was part of the ship's cargo) picric acid is
notoriously unstable and accident-prone.  Once the initial explosion
occurred, of course, the remainder of the ship's cargo detonated
within a fraction of a second.

A technical description of picric acid may be found here:

A similar description of benzol may be found here:

2) Why did the explosion occur? Could it have been prevented? How? 

Understandably, this was a burning question in the months (and years)
after the tragedy.  Initially, it was thought that the Germans might
have had something to do with it; witnesses claimed to have seen
Zeppelins above the city.  This was later discredited, though some
old-timers persisted in the notion that it was somehow "the Germans'

The captain and bridge crew of the Imo were killed in the blast, but
the crew of the Mont Blanc all survived, except for one crewman who
died from loss of blood.  The Mont Blanc crew were initially charged
with manslaughter and jailed; though they were later set free.  In
April 1918 a Nova Scotia court declared the Mont Blanc solely at
fault, but the following year the Supreme Court of Canada ruled on
appeal that the ships were equally at fault.  This was confirmed by a
ruling of the Privy Council in London, at that time the highest court
ruling on Canadian affairs.  It is hard to escape the impression that
the Mont Blanc crew were seen as a handy scapegoat in the spring of

So how did it happen?  Well, Captain Haakon From of the Imo was never
able to tell his side of the tale, but much was made later of the fact
that the Mont Blanc was not flying the red pennant which was the
internationally recognized symbol of explosives on board.  Captain Le
Medec of the Mont Blanc, for his part, contended that the red pennant
was customary, not mandatory, and that in any case it would be suicide
for a vessel in wartime...especially one as slow as the Mont Blanc,
with her top speed of 7 1/2 knots.  Official inquiries later pointed
to an inadequate supply of harbour pilots, language problems, and many
areas in which wartime urgency had overridden the harbour's safety
guidelines.  All of these things may have contributed to the disaster,
but there is no way to know for certain.

What is certain is that Captain From was travelling faster than was
customary in the Narrows, and was out of his correct lane.  The rest
seems to have been a tragically large-scale version of the dance that
strangers do when meeting in a doorway.

Could it have been prevented?  As long as there have been humans,
there has been human error; ultimately that is the underlying story of
the explosion.

3) What were the economic and social costs? 

These were, of course, immense; and in some respects incalculable.  In
a city of 50-60,000 people roughly 2000 lost their lives; 9000 more
were injured (some severely); 6000 were left homeless, and
approximately 20,000 were underhoused due to structural damage across
most of the city's residential neighbourhoods.

The names of the 1,951 "known dead" from the blast are preserved in
the Halifax Explosion Memorial Book, available online by courtesy of
the Provincial Archive.  The link I've provided takes you to the first
page of the book.  If you look down the left-hand column of the page,
you will find the names of Amy and Elsie Allen on Allen St in the
relatively intact west side of the city; and Mrs. E. Allen and John R
Allen of Kaye St in the devastated North end.  They were my relatives.
 You will also note that the address "Protestant Orphanage" is given
for several victims; nearly half of those killed in the explosion were
children.  The orphanage was rebuilt and is a community centre today,
located two blocks from my apartment (it was briefly visible in the
film "K-19", which was filmed here).  Here is the link:

Canada's National Archives have preserved a letter from W. E.
McLelland, Halifax postal inspector, to his superior R. M. Coulter,
the Deputy Postmaster-General, in Ottawa.  I will offer it as an
example of the city's condition in the days immediately following the

Writing five days after the explosion, McLelland is happy to report
that none of his staff were killed, though all were injured to some
extent.  McLelland was one of the twenty thousand who were
underhoused, he writes that "My house was badly wrecked though at the
extreme South End, two miles from the explosion...One room, and only
one, was left to us for shelter."

You may read the full text of the letter, with McLelland's comments on
the shaken state of his city and staff, at this link:

The physical destruction wrought by the blast is difficult to imagine,
comparable to that of an atomic bomb.  Dr. Robert Oppenheimer, in
fact, is known to have reviewed data from the Halifax disaster in
order to judge the probable impact of the Hiroshima and Nagasaki
bombs.  To put this into perspective, consider how nuclear devices are
measured: in kilotons (a kiloton is equivalent to 1000 tons of TNT)
and megatons (equivalent to a million tons of TNT).  The Halifax blast
would have weighed in at roughly 2.5-3 kilotons; the Hiroshima bomb
was approximately 13.

Throughout the twin cities of Halifax and Dartmouth, there was almost
no glass left intact.  Windows were broken in Truro, 60 miles away;
and the blast was audible as far as Charlottetown, Prince Edward
Island, hundreds of miles from Halifax. The blast was followed by a
tsunami (tidal wave) which flattened anything left standing from the
explosion itself; some vessels were even cast up on shore.  Worse,
fires immediately took root in the bustling but cheaply-built North
End; gutting much of the wreckage and incinerating many who were
trapped in their homes by the blast.  To add to the misery, one of the
worst blizzards in living memory swept the city that night; followed
over the ensuing few days by a terrible rainstorm and another
blizzard.  Undoubtedly many of the disaster's casualties were claimed
by exposure in the ruined city.

To give you some idea of the devastation, consider the photograph at
this link (taken from a vantage point corresponding to where I sit as
I type this):

You are looking toward the downtown Halifax, over the smoldering
wreckage of the civilian shipyard, the naval base, and what had been
the city's idustrial area.  The North End, then a suburb known as
Richmond, had essentially ceased to exist.  Approximately 20% of the
city was destroyed or damaged; only that portion shielded by Citadel
Hill (a fortification overlooking the downtown) escaped relatively

The damage was estimated at $35 million (in 1917 dollars); in today's
terms that would be roughly a hundred times more.  The impact is
difficult to assess.  In those days, Nova Scotia's industrial sector
was fighting a losing battle against the newfound economic power of
Ontario and Quebec.  The North End was the industrial section of
Halifax; its manufacturing and sugar-refining industries were never

The greatest cost was undoubtedly not material, though, but human.
Hundreds were blinded. Thousands were maimed or crippled, and needed
extensive retraining and rehabilitation.  In fact a dwindling handful
of survivors receive explosion-related pensions to this day! Many
individuals are known to have committed suicide in the wake of the
disaster; either because they'd lost all their loved ones, or in some
cases because of strangers whom they'd tried and failed to save. 
Thousands were emotionally scarred by what we would now term
"Post-Traumatic Stress Disorder."  In fact, the Halifax Explosion
provided one of the first steps toward defining that term.

Dr. Samuel Henry Prince, a pastor and a professor at Dalhousie
University, saw much of this first hand.  Narrowly avoiding injury
himself in the blast, he was one of the first volunteers to arrive on
the scene.  Beginning by personally aiding the injured, he went on to
organize relief efforts, and ultimately held responsible positions
within the Relief Commission (more on this shortly) until 1950.

Dr. Prince's experience with the aftermath of the Explosion (he also
counselled survivors of the Titanic) led him to investigate the
effects of major traumas on their victims.  The thesis he wrote for
his doctorate at Columbia; "Catastrophe and Social Change", was
published in 1920 and re-issued in 1926 and 1928.  It was the first
in-depth study of a disaster and its consequences, and remains a minor
classic in academia. He is remembered today in the Samuel Henry Prince
Award, awarded by the Canadian Traumatic Stress Network to individuals
or organizations noteworthy for humanitarian efforts in disaster
relief.  See the CTSN's website:

4) What was done to cope with the immediate and long-term effects of 
the disaster?

Response to the tragedy was all but immediate.  Massachusetts, and
Boston in particular, took a lead role in the international relief
effort.  The first train filled with relief supplies and medical
personnel left Boston on the evening of December 6th, the very day of
the disaster.  Ultimately, over $30 million (1917 dollars) in relief
was received from as far away as Australia and New Zealand, with the
federal government accounting for roughly half of the total.

Of all the assistance received, however, it was the warm, immediate,
and practical response from Boston that would be remembered most
vividly.  To this day, the civic Christmas tree which is raised every
year in Boston's Prudential Plaza is provided as a memorial by the
grateful people of Nova Scotia.

In the days immediately following the disaster, impromptu committees
were raised to oversee relief efforts.  These were quickly centralized
into the official Halifax Relief Commission; created by the federal
government in January 1918.  The commission oversaw the administration
of all benefit claims and their resultant pensions, and looked to the
rehabilitation and rehousing of victims.  The Commission was disbanded
only in 1976, when its remaining pensioners were transferred to the
care of the federal Department of Veterans Affairs.

Much good grew out of the disaster.  When the city was rebuilt, the
formerly lackadaisical attitude of its administration to matters of
public health and medical care was no longer in evidence.  Healthcare
facilities and budgets were greatly improved, and Halifax remains
today a centre of medical excellence.  Regulations governing the use
of the harbour were also revamped and much improved.  The city's
ramshackle trolley system was replaced with new, state-of-the-art
trams, and for the first time (from sheer necessity) many women found
jobs within the transit system.

Perhaps the longest-lasting benefit to the city was the rebuilding
process itself.  Halifax's glory days had begun to pass with the end
of the age of sail; the years-long rebuilding process brought a degree
of bustle and activity to the city which minimized the postwar
economic slump.  Further, Halifax served as something of a laboratory
for one the world's leading figures in urban planning.

Scottish-born Thomas Adams was given the opportunity to rebuild the
North End in accordance with the latest theories.  Together with
protege Horace Llewellyn Seymour, Adams (arguably the most influential
urban planner of his day) laid out a new North End of broad streets,
grassy boulevards, and (a hard-won lesson) fireproof housing. 
Constructed on non-uniform patterns from cinder blocks (known as
"hydrostones" at the time) the Hydrostone District remains the
centrepiece of today's North End.

For a brief outline of Thomas Adams' life and work, read this page in
the online version of the Canadian Encyclopedia:

Horace Seymour, in the online Canadian Encyclopedia:

Further information about the rebuilding process will be found at the
resources listed below.


Search strategy/Useful resources

The Halifax Explosion was one of the more noteworthy disasters of the
twentieth century (which certainly had no lack of disasters).  While
the passage of time has left this tragedy little known outside of the
immediate area, there are a wealth of resources available both on- and
off-line for further study.

A simple Google search on the phrase "Halifax Explosion" will yield
over 3000 hits; far too many to slog through at any one sitting. 
There are a few, however, which are more immediately useful than the

First and foremost is the City of Halifax's own official "Explosion"
page.  It may ve found at this link:

The Maritime Museum of the Atlantic has an informative display, which
includes a copy of the Memorial Book mentioned earlier.  Their website
is also very informative:

A local high school has created one of the best websites concerning
the explosion; marshalling maps, photos, and contemporary newspaper
and eyewitness accounts.  If you click on the "Maps" tab, and then
zoom the map, my apartment is roughly equidistant between the site of
the explosion and the "R" in "Richmond".

The online version of the Canadian Encyclopedia has a terse but
informative article at this URL:

There is a clickable link to the article on the Relief Commission. 
You may also wish to follow the link at the bottom of the page to a
one-minute film dramatizing the actions of Vince Coleman, one of the
"everyman" heroes of the day.  The link to the film (requires
Quicktime) is here:

Many of those killed or injured were firefighters or naval personnel
attempting to bring the blaze under control before the blast. 
Immediately beside my son's junior high is Fire Station 6, which lost
most of its crew in the blast.  A memorial stands outside the station
today.  The Canadian Armed Forces website has a brief description of
the actions of the naval vessels which attempted to avert the

On a related note, you may find useful information in this table of
vessels involved in the explosion.  It is from the Nova Scotia
Museum's website:

There are many firsthand accounts in print of the explosion and its
aftermath.  The Halifax Herald company, which publishes the leading
local dailies, wrote these articles in 1992 to commemorate the 75th
anniversary of the disaster:

Web portal, in their end-of-the-century review, published
this article from the Canadian Press:

One of the many volunteers who came to Halifax to assist in the relief
work was New Glasgow, NS shopkeeper Everett Charlton.  In 1976 (a year
before his death) Charlton told the story to his granddaughter, who
was doing a school project.  The tape was eventually aired on CBC
radio; the audio file may be heard here:

If you are located in Canada, the National Film Board has produced a
fine 18-minute documentary of the explosion, titled "Just One Big
Mess: The Halifax Explosion 1917."  You will find it at NFB branches,
as well as many public and university libraries.  The listing on the
NFB's site is here:

Canada's National Archive has numerous documents pertaining to the
explosion; they are catalogued here:

If you have the opportunity to visit Halifax, you will find a great
deal of further information by visiting the Nova Scotia Archives, the
Nova Scotia Museum, and the Maritime Museum of the Atlantic.  The
museums will also be able to furnish you with information about other
explosion-related sites and memorials throughout the city.


Thank you, Ardo-ga, for an opportunity to tell a story that has a
great deal of personal meaning for me.  Several of my fellow
researchers have heard a shorter version of this answer in the past;
thanks to Larre-ga and Aceresearcher-ga for calling my attention to
your question.

I will end here with a link to a photo of the city's official
memorial.  It stands on top of Needham Hill (you'll see it referred to
as "Fort Needham" in many of the pages listed above); two blocks
uphill from my apartment.  On still days, I can hear the carillon
ringing the hours.  Every year on December 6th at 9:05 a memorial
service is held here to honour those who died, and those who lived to

In the photo on the right, you can clearly see the gap in the
bell-tower structure.  If you stand there, you may look straight down
Richmond Street, past my apartment, past the modern-day shipyard, to
the place where - for one brief moment - the harbour's bottom was
visible to a few stunned survivors of the blast.

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