This is the best video I’ve found of the explosion in Beirut, Lebanon yesterday. It shows the explosion from 4 different vantage points. The second version points out why you shouldn’t stand in front of a glass window if you witness an explosion. You will see the flash before the shock-wave hits. All that glass just might be turned into shrapnel. The 3rd and 4th seem to show the fireworks going off. And the 4th is a good explanation for why you should not stick around to take that interesting video.
Popular Mechanics tries to stem the rumor of an atomic explosion. The people taking the video, and the cameras, would not have survived. Massive Beirut Explosion Shows Mushroom Clouds Aren’t Just for Nukes
This phenomenon is called the Rayleigh-Taylor instability, which describes the interaction between two materials (fluids or gasses) of different densities when they’re forced together.