"In 1919, a tank of molasses in Boston collapsed. Molasses is thick, so you might think it would flow out slowly, but it didn't. The wave of molasses swept down

"In 1919, a tank of molasses in Boston collapsed. Molasses is thick, so you might think it would flow out slowly, but it didn't. The wave of molasses swept down the streets too fast to outrun, demolishing buildings and killing 21 people." From (https://what-if.xkcd.com/111/ https://what-if.xkcd.com/111/), where I originally learned about this event :P