How did a volcanic eruption create Frankenstein?

A volcano helped create Frankenstein by ruining a holiday. In April 1815, Mount Tambora in present-day Indonesia exploded in the most powerful eruption in recorded history. It blasted sulfur dioxide into the stratosphere, where it formed a veil that dimmed the sunlight around the world. The result, in 1816, was the Year Without a Summer.

That summer, 18-year-old Mary Shelley, the poet Percy Shelley and Mary's stepsister Claire Clairmont travelled to Geneva to visit Lord Byron at the Villa Diodati by the lake. They got weather more like winter. Stuck indoors with Byron's physician, John Polidori, the group sat around a log fire reading German ghost stories.

Then Byron threw down a challenge: each of them would write a ghost story. Mary was stuck. Every morning someone asked whether she had thought of a story yet, and every morning she had to admit she hadn't. Then one night, unable to sleep, she had a waking dream: a pale student of unhallowed arts kneeling beside the thing he had put together, and watching it stir to life.

That vision became Frankenstein, published on 1 January 1818, when Mary was 20. The same rainy contest also produced Polidori's The Vampyre. Two classics of horror were born from one volcano's bad weather.