An underground steam pipe that exploded last year in the Flatiron district of Manhattan sent hot steam and debris into the air. Thankfully nobody was injured. However, that explosion resembles one that occurred nearly 12 years ago in which one person was killed and several more were severely injured. The exact cause of this particular underground utility pipe explosion in Manhattan is still determined but some experts have suggested the cause of the two separate explosions could be the same. The phenomenon is called a "water hammer" and occurs when cool water comes into contact with hot pipes carrying live steam. The temperature differential causes the steam pipes to fail and an explosion results.
An underground explosion in New York City earlier this month left over a hundred residents without power and one man without a car. Thankfully, there were no injuries as a result of this terrifying explosion but only luck kept innocent victims out of harm's way.