During this violent time, much of the debris would have resembled comets - dirty snowballs thought to be mostly slushy water surrounding a rocky core - slamming into Earth at velocities greater than 25 km per second (16 miles per second).
Not long after, in just a matter of minutes, the tide came roaring back and hit the barriers along the Galle Face Green with such a force that there were walls of water over 15 feet high shooting over the barriers and slamming on the areas where the people were standing not two minutes ago.