​Almanac: The explosion that leveled Halifax

And now a page from our "Sunday Morning" Almanac: December 6th, 1917, 98 years ago today ... the day an immense explosion wiped out much of the port city of Halifax, Nova Scotia.

A cloud rises from an explosion aboard the Mont Blanc, in Halifax, Nova Scotia, Dec. 6, 1917. Library and Archives Canada

The Mont Blanc, a French ship carrying tons of munitions bound for the Allies during World War I, had collided with a relief ship.

The crash triggered a fire and then a mammoth explosion ... the biggest human-caused explosion of the pre-nuclear era.

The explosion and its shock wave killed more than 1,800 people, and injured another 9,000.

More than 1,600 homes were destroyed, leaving thousands of people homeless just before Christmas.

As for the Mont-Blanc, it was blown to bits. A half-ton portion of its anchor was later found two miles away.

Emergency aid for the victims quickly poured into the wounded city, particularly from Massachusetts, which sent doctors and an entire warehouse full of relief supplies.

Halifax has long since been rebuilt, but memories of the disaster are still fresh. That recovered anchor part is the centerpiece of a monument to the Mont Blanc.

And to this day, Nova Scotia sends a Christmas tree to the city of Boston as a thank-you gift for the help that was offered in Halifax's hour of need.

This year's tree was lit on Boston Common just this past Thursday night.

The lighting of the Christmas tree - a gift from the people of Halifax - on Boston Common. CBS News

Rumors ran wild in the wake of the explosion of the Mont Blanc -- among them, that it had been the work of German saboteurs. But Allied and German military records both show there were no German spies operating in Halifax.

For more info: