This Day In History: April 10

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On April 10, the most powerful volcanic eruption in human history begins in earnest when Indonesia's Tambora volcano sends ash 20 miles into the atmosphere and boiling liquified rock starts streaming down its slopes. Its "cacophony of explosions" could be heard hundreds of miles away and, within hours, nearby villages ceased to exist, forests were incinerated and massive lava flows plowed into the sea, redrawing maps of the island.

The volcano, which had begun rumbling on April 5, killed almost 100,000 people directly and far more indirectly. The eruption was the largest ever recorded and its effects were noted throughout the world.

Tambora is located on Sumbawa Island, on the eastern end of the Indonesian archipelago. There had been no signs of volcanic activity there for thousands of years prior to the 1815 eruption.

So much ash was expelled that the sun was not seen for several days. Flaming hot debris thrown into the surrounding ocean caused explosions of steam. The debris also caused a moderate-sized tsunami. In all, so much rock and ash was thrown out of Tambora that the volcano sank into itself and its height reduced from 14,000 to 9,000 feet.

The worst explosions were heard hundreds of miles away, causing rulers to send out their armies in search of what they were sure was a coming military invasion. The eruptions of Tambora also affected the climate worldwide. Enough ash had been thrown into the atmosphere that global temperatures were reduced over the next year; it also caused spectacularly colored sunsets throughout the world. The eruption was blamed for snow and frost in New England during June and July that summer.

Ten thousand people died from the eruptions, most on Sumbawa Island. In subsequent months, more than 80,000 people died in the surrounding area from starvation due to the resulting crop failures and disease. A widespread cholera epidemic attributed to the eruption caused untold more death.