On August 27th, 1883, the volcanic island of Krakatoa in Indonesia blew up.
The events leading up to the eruption began in May of that year (if not earlier) with steam being seen venting from the volcano. Eruptions continued on and off until August 26th, when they entered their final phase, culminating on August 27th in four enormous explosions, the largest of which was heard over 3,000 miles away.
The fourth explosion was so powerful that it ruptured the eardrums of sailors and is estimated to be four times as powerful as the most powerful thermonuclear weapon ever detonated, the Tsar Bomba. Deaths were in the tens of thousands, tsunamis hit coastal areas, and effects of the eruption were even seen in the English Channel on the other side of the world.
Much of Krakatoa had vanished, and the effects on the global climate were noticeable for at least five years afterwards.
Image Source: Public Domain via Wikicommons (commons.wikimedia.org/wiki/File:Krakatoa_eruption_lithograph.jpg)