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    What we know about the Great Molasses Flood of 1919

    A view of the Great Molasses Flood aftermath, looking north across North End Park.
    Boston Globe Archive/Jan. 16, 1919
    A view of the Great Molasses Flood aftermath, looking north across North End Park.

    Sunday marks the 98th anniversary of the Great Molasses Flood of 1919 in Boston, one of history’s most bizarre disasters and one that has remained a topic of grim fascination ever since.

    The catastrophe happened after a giant storage tank at the Purity Distilling Co. on Commercial Street in Boston’s North End ruptured, releasing a massive wave of molasses that killed 21 people, injured 150, crushed buildings, and tore a firehouse from its foundation.

    The disaster, which occurred shortly after noon on Jan. 15, 1919, submerged two city blocks within seconds, overcoming people in the streets.

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    The gooey molasses — more than 2.3 million gallons — formed a tidal wave that initially was 25 feet tall — nearly as high as a football goalpost — and 100 yards wide.

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    A winter chill rapidly cooled the molasses as it streamed through the streets, complicating rescuers’ frantic efforts to free victims, according to Harvard researchers.

    Outrunning the torrent was out of the question: A Harvard researcher said the sticky tsunami raced through the cobblestone streets at 35 miles per hour, propelled by its sheer weight.

    The devastation was far-reaching. A large section of elevated train tracks nearby collapsed. Horses were carried off to their demise or were shot to end their suffering. At least one man was swept away and dropped in Boston Harbor.

    “Men and women, their feet trapped by the sticky mass, slipped and fell and were suffocated,” the Globe reported in a 1968 retrospective. “The stronger tried to save others, and many of them died for their heroism.”

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    In 2015, a study shed light on the cause of the collapse, finding that the tank was stressed well beyond capacity and made from a steel susceptible to fracture — the same type used on the Titanic.

    In 2013, science writer Ferris Jabr took a look at the scientific qualities of molasses in Scientific American, endeavoring to answer why the flood of brown, goopy sweetener proved far more destructive than a flood of water would have.

    Unlike water, molasses is a non-Newtonian fluid, meaning that its viscosity, or thickness, changes based on the outside forces that are applied. For example, if a non-Newtonian fluid like yogurt is shaken or stirred rapidly, it becomes thinner and can be poured from a container.

    “Consider non-Newtonian fluids such as toothpaste, ketchup, and whipped cream,” Jabr then wrote. “In a stationary bottle, these fluids are thick and goopy and do not shift much if you tilt the container this way and that. When you squeeze or smack the bottle, however, applying stress . . . the fluids suddenly flow. Because of this physical property, a wave of molasses is even more devastating than a typical tsunami.”

    “In the beginning, the molasses was moving so quickly and there was so much of it that it had enough force to rip buildings apart,” Jabr told the Globe in 2013. “As it went on, it slowed down and became more and more viscous.”

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    Trying to swim through the molasses would have been futile; anyone trapped in the gelatinous molasses “would stay in place, like a gnat trapped in tree sap,” Jabr wrote.

    Peter Schworm and Colin A. Young contributed to this report. Material from the Associated Press was also used in this report.