The catastrophe is know as "The Delft Thunderclap" from the town where it happened, and took place at 11 in the forenoon of 12th October, 1654.
At that hour the powder magazine, which then stood within the town, and at that moment contained between 80,000lb and 90,020lb of powder (not much under 40 tons English), blew up; and so terrific was the force of the explosion that it was felt throughout the whole of Holland, Utrecht, and even on the island of Texel. Immediately afterwards was seen on the spot where had stood the magazine a large pool of water some 15ft or 16ft deep, but not a trace of its foundation remained.
The misery and disaster which resulted from it are impossible to describe properly and in proportion to the facts; because so great was the noise, to the surprise of all who heard it far from or near this town, from which, after the clap, they saw such a frightful mixture of smoke and vapor rise, just as if the pools of hell had opened their throats to spew out their poisonous breath over the whole world to cover it and darken it.”— Dirck van Bleyswijck
On Monday, October 12, 1654, shortly after half past eleven in the morning, one of Delft's powder magazines exploded and devastated a large part of the city. The "Delfische Donderslag" (Delft Thunderclap) was said to have been heard as far away as the island of Texel, seventy miles north of Delft. The magazine, known as the Secreet van Hollandt, had been established in the former Clarissenklooster (Convent of Saint Clare) in the northeastern corner of Delft in 1572. When the magazine, large parts of which were underground, exploded, it contained about ninety thousand pounds of gunpowder. The force of the blast was so great that most houses in the immediate vicinity were destroyed and buildings throughout the city were damaged. The two major churches, the Oude and the Nieuwe Kerk, were also damaged. Although the number of people killed is not known, it has been estimated that deaths were in the hundreds. Among the casualties was one of Delft's most famous painters, Carel Fabritius. News of the event spread rapidly throughout the country. The States General sent a note of condolence; Elizabeth, queen of Bohemia, paid a visit; and many other people came to survey the devastation.