Thousands of human skeletons were discovered in mass graves in London. For years, archaeologists could not explain what had killed them on such a scale. Radiocarbon dating published in Proceedings of the National Academy of Sciences (PNAS) indicates that they died around 1258, just one year after a massive volcanic eruption on Lombok, Indonesia, whose force may have been unmatched in the past 7,000 years.
The 1257 eruption of Mount Samalas released the largest amount of sulfur into the stratosphere in seven millennia. Its traces have been found in both Arctic and Antarctic ice layers, a level of global dispersion only possible from a colossal eruption.
An estimated 40 cubic kilometers of rock and ash were ejected from the crater, with the finest particles reaching altitudes of up to 40 kilometers in the atmosphere. For comparison, the eruptions of Krakatoa in 1883 and Tambora in 1815, both known for causing the “year without a summer,” are considered comparable to or even smaller than Samalas.
How a Single Eruption Shook the World
The effects of Samalas were felt across the globe with little delay. European texts from the medieval period describe the summer of 1258 as devastating, with cold temperatures, relentless rainfall, and widespread flooding. Crops failed, and famine spread.
Scientists cannot definitively confirm whether the thousands of deaths in London were directly caused by the eruption. However, Professor Franck Lavigne of Université Paris 1 Panthéon-Sorbonne, one of the study’s authors, noted that “the population at the time must have been under severe stress.”
The sulfur injected into the stratosphere formed an aerosol veil that reflected sunlight and significantly lowered global temperatures. This mechanism is widely believed to have triggered the onset of what is known as the Little Ice Age, a prolonged cooling period lasting roughly from 1250 to 1850.
A study published in Geophysical Research Letters in 2012 suggests that a series of volcanic eruptions, with Samalas as the initial trigger, played a key role in the beginning of this extended cold period.
The impacts were not uniform across the world. In some regions, the cooling created new opportunities. In Arctic North America, shifting weather patterns produced ideal conditions for salmon spawning, leading to food surpluses for coastal communities.
In Hawaii, changes in rainfall patterns are believed to have supported agricultural expansion and accelerated political transformation from tribal systems into more centralized states. Meanwhile, in Central and South America, the Little Ice Age brought droughts, floods, and social pressures that led to large-scale migrations and conflict.
Tracing the “Fingerprint” of a 13th-Century Eruption
Identifying Samalas as the source of the 1257 eruption was far from straightforward. For decades, volcanologists knew that a massive eruption had occurred, but they did not know its origin.
Early candidates were spread across four countries: Okataina in New Zealand, El Chichón in Mexico, Quilotoa in Ecuador, and Samalas in Indonesia.
Professor Franck Lavigne and his team approached the mystery like a criminal investigation. “We did not know the culprit at the start, but we had the timing of the घटना and a fingerprint in the form of geochemical signals in ice cores, and that is what allowed us to trace the responsible volcano,” Lavigne explained.
The team combined multiple lines of evidence, including radiocarbon dating, geochemical analysis of volcanic ash, data on the distribution of pyroclastic material, tree-ring records, and local historical accounts from Babad Lombok, a palm-leaf manuscript written in Old Javanese that describes the collapse of the Lombok Kingdom.
Babad Lombok recounts the destruction of Pamatan, the royal capital, which was buried by the eruption. Scientists believe the ruins of this ancient city may still lie beneath layers of ash and pumice today, a kind of undiscovered “Pompeii” on Lombok.
Other candidates failed to meet the criteria for dating or geochemical matching. Only Samalas, as the researchers concluded, was able to “tick all the boxes.”
