What was the size of the Krakatau explosion probably the result of?

The 1883 eruption of Krakatoa (Indonesian: Krakatau ) in the Sunda Strait began on the afternoon of Sunday, 26 August 1883-with origins as early as May of that year-and peaked on the late morning of Monday, 27 August 1883, when over 70% of the island of Krakatoa and its surrounding archipelago were destroyed as it collapsed into a caldera.