1808 mystery eruption

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The 1808 mystery eruption refers to one or more volcanic events that released a lot of sulfur into the upper atmosphere, dimming sunlight and cooling the planet for a time—an effect similar to the Year Without a Summer in 1816. For many years, scientists thought the cooler weather in the early 1810s was just part of the Little Ice Age. But in 1991, ice cores from Antarctica and Greenland showed a spike of sulfate around early 1809, about half as strong as the famous Tambora eruption of 1815. That raised a question: what eruption or eruptions could have caused this, since there were no clear historical records of something so big?

Later work using bristlecone pine tree rings pointed to 1808 as the year of the eruption(s). At first, researchers thought a single very large eruption caused the sulfate rise and cooling. Now, most evidence suggests it was probably several eruptions in quick succession, including some smaller ones. Geochemical studies of ash layers in ice cores indicate multiple eruptions from different places—Antarctica, Alaska, and Indonesia—around that time. The combination of tropical and extra-tropical eruptions could explain the 1809 sulfate layer and the global cooling, rather than a single event.

Finding written records for such an event was hard. In 2014, researchers found accounts by Francisco José de Caldas, a Colombian scientist who led Bogotá’s Observatory, describing a “transparent cloud” that dimmed the sun and brought unusually cold weather late in 1808. Similar notes came from Peru’s Hipólito Unanue. These reports point to a window around December 4–11, 1808, with a sun-blocking cloud that spread across at least 2,600 kilometers into both northern and southern hemispheres. The most likely source would be a tropical volcano in the southern hemisphere, not far from the equator.

The exact location is still uncertain because the area of the southwestern Pacific between Indonesia and Tonga had few settlers and limited written records at the time. Some nearby eruptions occurred around that period, such as in the Azores (Urzelina) in May 1808 and Taal in the Philippines in March 1808, with another Chilean eruption (Putana) around 1810. None fits perfectly, which is why scientists think the 1809 atmospheric spike came from a cluster of eruptions rather than one single event.

In short, the 1808 mystery eruption seems to be a series of volcanic eruptions in quick succession that released sulfur into the atmosphere and cooled the globe for a while. New historical reports and scientific clues from ice, tree rings, and ash layers support this idea, though the exact mix and timing of the eruptions are still debated.