In 1258, London had a problem that seemed to have little to do with a tropical island thousands of kilometres away. The harvest failed, grain became expensive, and hungry people began arriving in the city looking for food.
Centuries later, archaeologists found some of the victims of that crisis at Spitalfields in East London. Excavations carried out by the Museum of London Archaeology between 1991 and 2007 uncovered more than 10,500 human skeletons from nearly two millennia of burials.
Around 3,000 dated to the 13th century, including 2,323 people buried in dense mass graves. Some pits contained 20 to 40 bodies.
The burials clustered around 1258, the same year contemporary sources associated with a devastating food crisis. Estimates suggest that between 15,000 and 20,000 people may have died across London that year.
For a long time, historians knew what happened but could not fully explain why. The missing piece was not in London, or even in Europe. It was in Lombok, where a volcano had exploded the year before.
A Mountain That Disappeared
Between May and October 1257, Mount Samalas erupted on Lombok. It was an eruption on a scale rarely seen in the last 10,000 years.
A 2013 study led by volcanologist Franck Lavigne and involving 15 international scientists, including Indonesian researchers Surono and Indyo Pratomo, reconstructed the event and classified it as VEI 7. That puts Samalas in the same broad category as Mount Tambora's 1815 eruption, one of the most powerful eruptions in recorded history.
Samalas sent at least 40 cubic kilometres of material into the atmosphere, including around 29 cubic kilometres of pyroclastic material. Its eruption column rose as high as 38 to 43 kilometres, well into the stratosphere.
The mountain itself could not withstand the explosion. Much of Samalas collapsed into a massive caldera measuring roughly 6 by 8.5 kilometres. The depression eventually filled with water, creating the 11.3-square-kilometre Lake Segara Anak that sits inside Mount Rinjani today.
The landscape now attracts hikers. In 1257, it was the centre of a disaster that would reach far beyond Lombok.
When the Sky Changed
Ash was only part of the problem. The eruption also injected enormous quantities of sulfur dioxide and other gases into the stratosphere, where they formed aerosols capable of reflecting sunlight back into space.
Scientists still debate exactly how much sulfur Samalas released. One 2016 analysis estimated around 158 ± 12 million tonnes of sulfur dioxide, while other reconstructions based on volcanic material and ice cores produced lower estimates of roughly 119 to 120 million tonnes of stratospheric SO₂ equivalent.
The numbers differ, but the signal left behind does not. Sulfate from the eruption appears among the largest volcanic signals recorded in Greenland and Antarctic ice cores over the past two millennia. Material from an eruption on Lombok had travelled far enough to leave evidence in both hemispheres.
The climate responded. Tree-ring evidence suggests that Northern Hemisphere summers cooled by roughly 0.8 to 1.2°C around 1258 and 1259. Climate models give somewhat different estimates, and researchers continue to debate the exact magnitude and duration of the cooling. The effects nevertheless lasted for several years.
Europe was among the regions that felt the disruption.
Rain arrived when farmers needed a productive growing season. Crops failed across parts of Europe and North Africa, grain prices rose sharply in England, France, and Italy, and England had to import wheat from Germany and the Netherlands to compensate for shortages.
People began moving in search of food. Some made their way to London, where hunger and disease compounded the crisis. Centuries later, many of the people who died would be found together in the mass graves of Spitalfields.
Lombok Had Its Own Lost City
While Europe was struggling with the consequences, Lombok had already suffered a catastrophe of its own.
The Babad Lombok, an old palm-leaf manuscript written in the Sasak script and Javanese language, tells of Pamatan, a kingdom destroyed by a great eruption. The manuscript describes a city of roughly 10,000 people, with defensive walls, broad roads, gardens, meeting halls, productive farmland, and access to the sea.
For centuries, Pamatan was difficult to separate from legend. Then the physical evidence began to line up with the story.
In 2013, researchers compared radiocarbon dates from trees buried by volcanic material on Lombok with the chronology described in the Babad Lombok. The dates pointed to the same period as the Samalas eruption.
Pamatan itself has never been conclusively located. Archaeological work around Tanak Beak and Aik Berik has uncovered artefacts that support parts of the manuscript's account, but researchers still need broader archaeological and geophysical surveys to establish where the city once stood.
That leaves an unusual historical gap. We know the volcano, we know the approximate date, and we have a written account of a kingdom destroyed by an eruption. The city itself, however, remains somewhere beneath the landscape.
How Scientists Found the Connection
The eruption was not identified immediately. For decades, scientists knew that an enormous volcanic event had occurred around 1257 because sulfate deposits in polar ice cores preserved its chemical signature. They simply did not know which volcano had produced it.
The mystery was finally solved by bringing together evidence from places that had never seemed connected.
Ice cores in Greenland and Antarctica recorded the atmospheric aftermath. Volcanic deposits and radiocarbon dates on Lombok pointed to Samalas. The Babad Lombok supplied a historical account of a catastrophic eruption around the same period.
Together, they turned a mysterious signal in polar ice into a specific volcano in Indonesia.
The physical evidence shows just how far the eruption reached. Ash deposits have been traced westward from Lombok across Java, measuring about 22 centimetres at Ijen, around 240 kilometres away, and 15 centimetres at Bromo, roughly 380 kilometres away. At Mount Merapi, around 660 kilometres from Lombok, deposits were still detectable at 2 to 3 centimetres.
More than seven centuries ago, there was no way for anyone in London to know what had happened on Lombok. They could only see the consequences: rain that would not stop, crops that would not grow, grain that became harder to afford, and people who began dying from hunger and disease.
Today, the story can be read in two very different places. At Spitalfields, thousands of skeletons preserve the human cost of the crisis. Inside Rinjani, Lake Segara Anak occupies the caldera left behind by the volcano that helped set it in motion.
The two landscapes are separated by thousands of kilometres. The eruption of Samalas is what connects them.
References:
- Lavigne, F., et al. (2013). Source of the great A.D. 1257 mystery eruption unveiled, Samalas volcano, Rinjani Volcanic Complex, Indonesia. Proceedings of the National Academy of Sciences, 110(42), 16742–16747. https://doi.org/10.1073/pnas.1307520110
- Guillet, S., et al. (2016). Climate response to the Samalas volcanic eruption in 1257 revealed by proxy records. Scientific Reports (Nature), 6, 34868. https://www.nature.com/articles/srep34868
- Vidal, C.M., et al. Archaeological implications of a widespread 13th Century tephra marker across the central Indonesian Archipelago. ScienceDirect. https://www.sciencedirect.com/science/article/abs/pii/S0277379116305510
