CBC News is live streaming the commemoration ceremony marking the 100th anniversary of the Halifax Explosion

A century ago, Halifax's great harbour sloshed itself against the shores as the city awoke for another day.

By 7:30 a.m. on Dec. 6, 1917, the late fall sun was high enough to erase the night. A brisk day dawned under blue skies.

Officials with the Royal Navy, the Royal Canadian Navy and civilian authorities checked their schedules to ensure harbour traffic flowed smoothly to feed the Great War taking place across the ocean. Healthy soldiers arrived from across Canada to join the European theatre. Broken men returned through the same port.

In the harbour, warships hulked over the three small ferries shuttling people between Dartmouth and Halifax. Fishing boats and pleasure crafts sailed amid the giants. The rules of the harbour were familiar: keep right (starboard), signal your intentions and pay attention to other ships.

That system had worked for three long war years. And while the city of 50,000 dove into another busy morning, some 2,000 would not live to see sunset that night.

The ruins of the Army & Navy Brewery in Dartmouth. The brewery's manager and 11 other employees were killed in the Halifax Explosion. (Nova Scotia Archives & Record Management)

Maude Houghton was a girl of six that day. "I remember going to school. I had just got to the corner and boom! The explosion. I was scared," she told CBC News.

Houghton, now 106, is one of only 17 known living survivors of the Halifax Explosion; each of them has been invited to the main commemoration ceremony taking place this morning at the city's Fort Needam Memorial Park.

The Halifax Explosion Memorial Bell Tower at Fort Needham in Halifax. (The Canadian Press)

She remembers going with her family to the city's Common, where they met up with her father. "I just remember that I wanted to go home so bad," she said. "My mother was strong, like me."

Much of the day was "too horrible" to recall. "I wanted to get away from it all," Houghton said. "Lots of people crying. Mothers were grabbing their kids and hugging them."

A horrible day that had started as any other in the port city.

Men heading to work, children to school

Prior to the blast, trains chugged into the North Street terminals near the harbourfront, bringing supplies for the ships and soldiers. Horses clopped over the cobblestones, sharing the road with the odd automobile. Old trams delivered workers to their offices and factories.

Men on their way to work removed their winter coats as the sun warmed the day beyond usual December temperatures. Tardy children rushed to school, jackets opened.

In Halifax's north end, Viola Desmond sat alone in a kitchen highchair as her father popped into the washroom. He was caring for his three-year-old daughter while her mother and sibling rode a train en route to a family funeral.

Four women walk from Africville following the Halifax Explosion. (City of Toronto Archives, Fonds 1244, Item 2451)

Thomas Raddall, 14, had just sung the morning hymn at Chebucto School. "We were just sitting down and of course that always produced a clatter, but this particular morning, the results were terrific," the writer told the CBC 50 years later.

Vince Coleman's daughter started her day at school as he worked the telegraph dispatch. His actions later that morning — staying at his post after realizing the looming disaster — would make him a hero and end his life.

The watch owned by Vince Coleman is among the artifacts from the Halifax Explosion currently displayed at the Maritime Museum of Atlantic in Halifax. (Robert Short/CBC)

Outside the harbour, the munitions ship Mont-Blanc fired up and prepared to enter. In the Bedford Basin, the relief ship Imo started its engines to exit.

The ships should have passed each other a day earlier, if at all. The Mont-Blanc had arrived just after the gates closed, and the crew slept another night on the sea.

The Imo crew had prepared to leave that same day, but its coal arrived too late, so it dozed safely in the basin for one last night.

Failure to yield

As it entered the harbour narrows, the Mont-Blanc blew its whistle once, saying it would maintain its course. The Imo whistled twice, indicating it was staying in the same lane. Whistles clashed in the air, and then the ships collided.

The clock on Halifax City Hall ticked over to 8:45 a.m. A tendril of smoke escaped the gash in the French ship.

People watched the crew of the Mont-Blanc abandon the burning ship. Unguided, it drifted toward Halifax as the flames closed in on the raw ingredients of a bomb concealed in its belly.

The Norwegian steamship Imo is beached on Dartmouth shore after the Halifax Explosion. (Nova Scotia Archives & Record Management/Canadian Press)

Across the harbour in Maskwiekati Malpek, or Tufts Cove, Rachel Cope and her brother spotted the burning ship as they left their Mi'kmaq community to go to school. She would survive. He would not.

A tower of black smoke, lit by flame bursts, smeared the sky. Hundreds of people stopped to watch the spectacle. Many mothers and young children looked through plate glass windows.

The blast to come would spew glass and other debris through the air, levelling two square kilometres of Halifax. An estimated one in 50 survivors had significant eye damage — the largest mass blinding in Canadian history.

The charred shell of the Patricia after the Halifax Explosion. (Halifax Firefighters Monument Committee)

Meanwhile, firefighters rushed to Pier 6 as the Mont-Blanc bumped into the wooden pier. Billy Wells drove the shiny red Patricia, the city's first motorized fire truck, to the burning ship. He would be the only survivor of his six-man crew.

A dozen horse-pulled wagons clattered to the rescue. The firefighters rolled out their hoses.

The clock at City Hall ticked through the fourth minute of the ninth hour of the sixth day of the twelfth month of 1917. Just before it would have turned to 9:05 a.m., the Mont-Blanc exploded in a brilliant flash, stopping the clock forever.

A funeral for some of the victims of the Halifax Explosion. (City of Toronto Archives, Fonds 1244, Item 2455)

It was the biggest blast the world would see until the advent of the atomic bomb.

Pieces of the Mont-Blanc — the shaft of its 500-kilogram anchor and a twisted, massive cannon from the ship's stern — hurtled through the air in different directions, each landing more than three kilometres away.

In addition to the 2,000-person death toll, more than 9,000 were injured, about 20 per cent of the city's population.