A 25-Foot Wave of Molasses Once Devastated Boston
On January 15, 1919, a massive storage tank burst in Boston's North End, releasing over two million gallons of fermented molasses. The resulting wave reached heights of 25 feet and traveled at roughly 35 miles per hour through the streets. It knocked down buildings, trapped horses, killed 21 people, and left the neighborhood smelling sweet for years.
The Rupture on Commercial Street
On January 15, 1919, the temperature in Boston rose unusually fast, climbing from the freezing depths of around two degrees Fahrenheit up to above forty degrees in a matter of days. Around midday in the densely populated North End neighborhood, workers and residents were going about their routines along Commercial Street. Standing tall over the waterfront was a massive steel storage tank owned by the Purity Distilling Company, measuring fifty feet high and ninety feet across. Inside, it held more than two million gallons of industrial molasses, recently delivered from the Caribbean and waiting to be processed into industrial alcohol.
Shortly after noon, the giant structure groaned and gave way with a violent crash. Witnesses described hearing a sound like rapid machine-gun fire as the rivets holding the steel plates popped out under tremendous pressure. The tank split completely open, unleashing an enormous dark wave estimated at twenty-five feet tall at its crest. Moving at a speed of roughly thirty-five miles per hour, the dense wave surged into the streets, crushing everything in its path before witnesses had time to comprehend what had burst.
The sheer momentum of the heavy liquid flattened nearby buildings, ripped an engine house from its foundations, and damaged the girders supporting the Boston Elevated Railway on Atlantic Avenue. Streetcars were knocked off their tracks, and wagons, trucks, and horses were swept away in the torrent. Within moments, several city blocks were submerged under two to three feet of thick, viscous sludge, creating a disaster unlike anything the city had ever prepared for.
The Lethal Physics of Molasses
A wave of molasses behaves very differently from a wave of water due to its extreme density and non-Newtonian fluid properties. Molasses is roughly one and a half times as dense as water, giving a moving wall of syrup immense kinetic energy and crushing physical force. When the tank wall failed catastrophically, the stored potential energy of millions of gallons translated instantly into a fast-moving front that acted more like a solid wall than an ordinary liquid splash.