15 Fascinating Facts About 'The Year Without a Summer'

The annals of natural disasters are filled with storms, floods, and even asteroids, yet some of the most captivating calamities originated deep within the Earth itself, fueled by volcanic activity. While eruptions such as the one that buried Pompeii, Italy, are a mainstay of history textbooks, few volcanoes had such a devastating and dramatic impact as Mount Tambora. Its violent eruption in 1815 caused a global cooling effect, blocking sunlight and leading to 1816 being dubbed “the year without a summer.”

1. The eruption of Mount Tambora lasted for nearly two weeks.

Prior to its catastrophic eruption in April 1815, Tambora was a towering 14,000-foot peak located on the Indonesian island of Sumbawa. The eruption released billions of tons of gas and debris into the atmosphere. While much of the heavier ash and debris settled on nearby islands and seas, a significant portion entered the atmosphere, spreading globally and diminishing the sunlight for months. The eruption resulted in the death of tens of thousands—or even hundreds of thousands—due to pyroclastic flows, choking ashfall, and tsunamis.

2. The explosion of Tambora was far more severe than some of the more widely known eruptions.

Indonesia is home to some of the world’s most intense geological activity. The eruption of Krakatoa in Indonesia on August 27, 1883, is one of the most notorious volcanic disasters in history, claiming tens of thousands of lives and influencing global weather for months. However, just a few decades earlier, Mount Tambora unleashed a much more destructive eruption than Krakatoa, Washington’s Mount St. Helens, or even Pompeii’s Vesuvius.

Tambora’s eruption reached a VEI-7 on the Volcanic Explosivity Index, a scale measuring the magnitude of eruptions from VEI-0 (non-explosive) to VEI-8 (megacolossal). In comparison, Krakatoa had a VEI-6 rating, while both Mount St. Helens and Vesuvius were rated VEI-5.

3. It triggered a volcanic winter.

While we’re familiar with the greenhouse effect, where certain gases and particles in the atmosphere trap heat and drive up global temperatures, volcanic eruptions can have the opposite effect. The two primary mechanisms behind this cooling effect are the reflection of sunlight by particulates ejected by volcanoes, which prevents solar radiation from reaching the Earth's surface, and the sulfur dioxide released during eruptions. The sulfur dioxide turns into sulfuric acid, which forms aerosols that remain in the atmosphere for years, blocking solar radiation and cooling the planet.

4. Tambora’s eruption brought a snowstorm in June.

The volcanic winter that followed the catastrophic eruption of Mount Tambora wreaked havoc on communities worldwide. Ironically, the effects of the volcanic winter were most noticeable during the summer months, particularly in eastern North America. In the northeastern United States, residents reported heavy snowfalls as late as mid-June, with one report mentioning half a foot of snow on June 6, 1816.

5. The freezing temperatures destroyed crops throughout Europe and Asia.

The sudden and severe temperature drop caused massive damage to agriculture across the globe. In addition to frost and freezes that devastated crops in the United States, cold and wet weather conditions also ruined harvests in Europe and Asia. These widespread crop failures led to famine in many parts of the world, claiming the lives of countless individuals.

6. A global spread of diseases occurred.

Beyond the weather disasters and famine, the eruption’s aftermath also contributed to the spread of disease. The disruption of the typical monsoon season in India triggered a drought, which likely allowed the cholera bacterium to mutate into a more deadly strain. This new form of the pathogen spread globally, causing frequent epidemics throughout the 19th century. Millions perished, but this tragedy also pushed advancements in modern medicine.

7. Mount Tambora’s eruption inspired Frankenstein ...

The dreary weather in Europe during the Year Without a Summer spoiled the vacation plans of tourists. A group of literary icons—including Percy Bysshe Shelley and Mary Wollstonecraft Godwin (later Mary Shelley), Lord Byron, and John Polidori—spent their summer of 1816 at Lake Geneva, only to be confined indoors by the cold and rainy weather. It was within this extended 'staycation' that Mary Shelley conceived her famous novel Frankenstein; or: The Modern Prometheus, while John Polidori was inspired to write The Vampyre, which later influenced Bram Stoker's Dracula.

8. ... and stunning sunsets.

Brilliant sunsets are often caused by sunlight refracting through moisture in the atmosphere, producing stunning displays of warm hues that contrast with the darkening sky. Volcanic ash and dust particles in the atmosphere can further intensify these colorful phenomena, causing them to persist for months following an eruption. Art historians suggest that the spectacular sunsets of 1816 may have inspired the soft, glowing color technique of British painter J.M.W. Turner.

9. The eruption might have contributed to the rise of Mormonism.

One of the more unexpected consequences of the climate changes caused by Mount Tambora’s eruption is its potential influence on the emergence of Mormonism. Joseph Smith’s family, along with thousands of others, fled Vermont during the unusually cold summer of 1816. They eventually settled in New York, where a young Joseph Smith experienced the events that led to the publication of the Book of Mormon.

10. The Year Without a Summer played a role in the invention of the bicycle.

When crop failures due to the extreme weather of 1816 led to a shortage of food, it wasn’t just humans who were affected. The rising cost of oats made it increasingly difficult for people to afford horses for transport. In search of a new mode of travel, German inventor Karl Drais created a device known as the laufmaschine, or “running machine.” This precursor to the modern bicycle was operated by pushing with the feet instead of using pedals.

11. Crop failures drove a Founding Father deeper into debt.

We don’t typically think of U.S. leaders as individuals who struggle with money—but in the early days of the nation, this was sometimes the reality. Thomas Jefferson spent much of his life buried in debt, and the summer of 1816 only worsened his financial situation. The extreme weather that year caused Jefferson's crops to fail for several years, exacerbating the Founding Father’s growing debt. He never managed to recover financially and spent his final years owing creditors a sum that would amount to millions of dollars today.

12. The cooling period sparked a new era in Arctic exploration.

Weather is nature’s way of trying to stabilize the atmosphere. When one part of the world experiences extreme conditions, another region often experiences the opposite in an effort to restore balance. Following the eruption of Mount Tambora, while much of the globe experienced a cooling trend, the Arctic saw such significant warming that much of Greenland’s usual sea ice melted. Whaling ship captain William Scoresby, Jr. informed the British Admiralty that the waters were clear, enabling British explorers to chart the area and pursue the Northwest Passage.

13. The collapse of agriculture fueled the opium trade.

One of the primary drivers behind the global drug trade is poverty—when there are limited alternatives for earning a living, drug dealing becomes an appealing option. After the crop failures of 1816, many farmers in regions like China turned to growing opium as a way to survive. This shift in agricultural practices contributed to the growth of the global opium trade, which continues to thrive today.

14. The Earth’s atmosphere bounced back quickly.

Fortunately, the drastic climatic shift triggered by the eruption was not long-lasting. The global cooling effect lasted only a couple of years after the eruption. As the particles in the atmosphere gradually dispersed and settled back to Earth, the amount of solar radiation reaching the surface returned to normal, allowing global weather patterns to stabilize.

15. A disaster like Tambora could occur again—but it’s unlikely in our lifetimes.

With the growing popularity of TV shows depicting apocalyptic scenarios involving 'supervolcanoes,' there’s increasing concern about the possibility of another eruption on the scale of Tambora (or even larger). However, according to the U.S. Geological Survey, the chances of an eruption at places like the Yellowstone Caldera are extremely low—less than 1 percent annually. If such an eruption were to occur in today’s world, the consequences would be catastrophic. The global population has risen dramatically in the past two centuries, and the impact of an eruption of this magnitude would be devastating. Besides the eruption itself, everyday activities like air travel would be brought to a halt; volcanic ash could disable jet engines and cause crashes. The resulting climate change would likely trigger widespread famine and disease, unparalleled in modern times.