Krakatoa's shockwave spread over the earth 4 times over.

By 1883, weather stations in scores of cities across the world were using barometers to track changes in atmospheric pressure. Six hours and 47 minutes after the Krakatoa explosion, a spike of air pressure was detected in Calcutta. By 8 hours, the pulse reached Mauritius in the west and Melbourne and Sydney in the east. By 12 hours, St. Petersburg noticed the pulse, followed by Vienna, Rome, Paris, Berlin, and Munich. By 18 hours the pulse had reached New York, Washington, D.C., and Toronto. Amazingly, for as many as five days after the explosion, weather stations in 50 cities around the globe observed this unprecedented spike in pressure recurring like clockwork, approximately every 34 hours. That is roughly how long it takes sound to travel around the entire planet.