At 9:12 a.m., the ammonium nitrate reached an explosive threshold from the combination of heat and pressure. The vessel then detonated, causing great destruction and damage throughout the port. The tremendous blast sent a 15-foot (4.5 m) wave that was detectable nearly 100 miles (160 km) off the Texas shoreline. The blast leveled nearly 1,000 buildings on land. The Grandcamp explosion destroyed the Monsanto Chemical Company plant and resulted in ignition of refineries and chemical tanks on the waterfront. Falling bales of burning twine from the ship's cargo added to the damage while the Grandcamp's anchor was hurled across the city. Two sightseeing airplanes flying nearby had their wings shorn off,[5] forcing them out of the sky. 10 miles (16 km) away, half of the windows in Galveston were shattered.[6] The explosion blew almost 6,350 short tons (5,760 metric tons) of the ship's steel into the air, some at supersonic speed. Official casualty estimates came to a total of 567, including all the crewmen who remained aboard the Grandcamp. All but one member of the 28-man Texas City volunteer fire department were killed in the initial explosion on the docks while fighting the shipboard fire. With fires raging throughout Texas City, first responders from other areas were initially unable to reach the site of the disaster.
