This article was first published in the March/April 2025 issue of IQ, the exclusive magazine for Mensa members. Find out more about becoming a Mensa member here.
Words: Katie Cutforth
In early April 1815, the inhabitants of the Maluku Islands (or Moluccas) in present-day Indonesia heard what sounded like a thunderous detonation. By the next morning, volcanic ash was raining down on the island of Java and sounds like gunfire were reported in Sumatra and as far away as Laos and Thailand.
These strange rumblings were originating thousands of kilometres away on what is now the Indonesian island of Sumbawa. Mount Tambora, a stratovolcano on the island, which had lain dormant for centuries, had begun to erupt on 5 April, causing small tremors and pyroclastic flows.
By the evening of 10 April, the volcano’s rumblings reached their terrible climax. Three plumes of fire erupted from the mountain and merged, blowing it apart. Around 150 cubic kilometres of ash, pumice and aerosols were expelled into the atmosphere and across the island of Sumbawa and beyond. Rivers of incandescent ash poured down the volcano on all sides and the ground shook, causing tsunamis to rise up across the Java Sea. Ash and debris rained down for weeks, destroying homes and contaminating water.
It was the largest and most destructive volcanic eruption in recorded history. An estimated 10,000 people perished in the blast, and tens of thousands on Sumbawa and the neighbouring island Lombok died from starvation and disease in the immediate aftermath. Mount Tambora itself was transformed, its height reduced from 4,300 metres to 2,851m, with a caldera – a cauldron-like hollow – some six kilometres in diameter left behind.
But the devastating consequences of the eruption stretched far beyond the shores of Sumbawa. Millions of tonnes of sulfurous gas ejected into the stratosphere created a haze of ash and dust that encircled the Earth, blocking sunlight and triggering a global cooling known as a volcanic winter.
In 1816, which became known as ‘the year without a summer’, global average temperatures are thought to have plummeted by up to a whole degree Celsius. Freezing weather and floods killed trees, crops and livestock across the world, with snowfall in August in the US and weeks of unrelenting rain in Europe. Food riots became commonplace in the UK and France. Famine and disease followed, including an outbreak of typhus in Europe and a mutation of Bengal cholera in the Indian subcontinent. Conditions even had an impact on literature: young Mary Shelley, holidaying in a storm-battered Switzerland, was inspired by German ghost stories and the weather to write Frankenstein.
Along with more than 1,500 other volcanoes across the globe, Mount Tambora remains active today. Its 1815 eruption remains the most devastating in recent history but, over 200 years later, scientists warn we may be overdue for another.
Markus Stoffel, a climate professor at the University of Geneva, has estimated that there is a one-in-six chance of a massive eruption in this century, the consequences of which are likely to be even more catastrophic in a highly populated world dealing with the impact of climate change.
Image credit: Shutterstock
