In France, on 6 April 1815, Napoleon surrendered his throne in favor of his sons. The coalition that opposed him were still in the midst of sorting out a way to deal with the French conquerer when on the other side of the world—on the Indonesian island of Sumbawa—the largest volcanic explosion in human history took place.
The exact date that Mount Tambora erupted is lost to obscurity since the populace of the area was mostly killed. Those who were far enough for safety yet near enough to note the event didn’t make a priority of recording the date. Best estimates of modern science make the date for 10 April 1815.
The eruption event blew 100 cubic kilometers of pyroclastic trachyandesite into the air, and ripped about 4,000 feet off the top of the caldera—leaving the once 13,000 foot hight peak at about 9,000 feet. The explosion threw enough debris into the air that a mild volcanic winter resulted; it caused crop-killing frosts in North America in June, and dubbed 1816 to be The Year Without a Summer.
It’s common for major volcanic activity to affect the weather, and usually for the cooler, but never to the scale observed in 1816. The eruption of Mount Tambora is the largest in recorded history, though dwarfed by some prehistoric events. It is a hint of just how much havoc a volcano can wreak. On several nearby islands everything died, including vegetation. The immediate effects of the blast— the pyroclastic flows, toxic gases, and hot ash— killed 10,000 people. Some 82,000 more died in the vicinity and the ruins that remained. But the global aftermath is much harder to measure.
In North America, June generally brought average temperatures of about 68-77° Fahrenheit; in June of 1816 there were major snowstorms in Pennsylvania, crops were killed by frost, and rivers remained iced over. Food was scarce, and most items that were harvested were triple the price they had been the year previous. It’s impossible to know how many died from the resulting famine.