Mount Tambora had been dormant for perhaps 1,000 years before 1815. It was the tallest peak in the region, rising over 14,000 feet. The people of Sumbawa knew it as a mountain, not as a volcano. Then, in 1812, the mountain began to rumble.

Small eruptions and earthquakes increased over the following years. On April 5, 1815, a major explosion sent an ash column into the sky. The sound was mistaken for cannon fire by the British garrison at Yogyakarta, 800 miles away, who sent troops to investigate. But this was just the beginning.

The main eruption occurred on April 10. The explosion was one of the most powerful in human history - measuring 7 on the Volcanic Explosivity Index, the same as the Bronze Age eruption that may have destroyed Minoan civilization. The eruption column reached 27 miles into the atmosphere. Pyroclastic flows raced down the mountain at over 100 miles per hour. The entire top of the mountain was blown off - Tambora dropped from 14,000 feet to 9,000 feet.

The noise was heard 1,600 miles away in Sumatra. Ash fell on Borneo, 800 miles distant. The darkness was total for hundreds of miles around. Ships at sea reported pumice floating in the water for months afterward.

An estimated 10,000-12,000 people died immediately from the eruption itself - from the blast, the pyroclastic flows, and the tsunamis that struck coastal areas. But far more died in the following months. The ash buried crops. Contaminated water killed livestock. Famine spread across Sumbawa and neighboring islands.

The total death toll on the Indonesian islands is estimated at 71,000 or more. It was the deadliest volcanic eruption in recorded history. But the deaths in Indonesia were just a fraction of Tambora's ultimate toll. The ash that circled the globe would kill many more.

The ash and sulfur dioxide ejected by Tambora spread through the upper atmosphere, reflecting sunlight and cooling the Earth. In 1816 - the 'Year Without a Summer' - global temperatures dropped by about 0.5°C. It doesn't sound like much. It was enough to cause catastrophe.

In New England, frost killed crops in June, July, and August. Snow fell in Vermont in June. In Europe, cold rain fell through the summer, destroying wheat harvests and causing widespread famine. Food riots broke out in France and Germany. An estimated 200,000 people died in Europe from famine and disease. The poor, already exhausted from the Napoleonic Wars, suffered most.

In June 1816, a group of friends gathered at a villa on Lake Geneva to wait out the gloomy, rainy summer - the product of Tambora's ash. Among them were the poet Percy Bysshe Shelley, his future wife Mary Godwin, and Lord Byron. To pass the time, Byron suggested they each write a ghost story.

Mary Shelley, then 18 years old, conceived the story of Victor Frankenstein and his monster - born from a nightmare during that sunless summer. The novel, published in 1818, became one of the foundational works of science fiction and horror. Frankenstein was a child of Tambora, created in the gloom of a volcanic winter. The mountain that killed 71,000 people also birthed a literary monster that lives forever.