The first telegram arrived in Singapore on a Monday, sent from the city of Batavia in the Dutch East Indies. “Terrific detonations from Krakatau,” it reported. Soon afterward: “Stones falling. Village near Anjer washed away.” The wires continued clattering out news of bridges destroyed, boats smashed, lighthouses “disappeared.” By noon on Tuesday, the scope of the natural disaster was clear: “Where once Mount Krakatau stood the sea now plays.”
Within days, the source of the destruction was known worldwide. On the morning of August 27, 1883, a volcanic eruption had obliterated two islands in the strait between Java and Sumatra, and most of a third. More than 36,000 people perished, the majority in devastating tsunamis that raced outward from the colossal explosion.
Thanks to Victorian-era telecommunications, it was the first time in history that people around the globe could begin to document the immediate and long-term effects of a catastrophic volcanic eruption. This event laid the foundations for the modern science of volcanology. The biggest eruptions can influence climate, agriculture, and even the course of human history.
In the months after Krakatau, drifting volcanic particles high in the atmosphere circled the globe, causing violently colored sunsets that contemporary artists captured in paintings, likely including the psychedelic background of Edvard Munch’s The Scream.
The key climate-driving component of the volcano’s emissions was sulfur from the molten rock that fed Krakatau. Once sulfur erupts into the atmosphere, it can form particles called aerosols that reflect sunlight and cool Earth. In the months and years after the eruption, average summer temperatures fell 0.6° Celsius in the non-tropical regions of the Northern Hemisphere.
Researchers now understand that climate changes, especially rapid ones, have transformed societies by affecting agriculture, public health, and living conditions. With what they’ve learned from Krakatau and other eruptions, volcanologists today are identifying past catastrophic blasts that may have contributed to historic events like droughts, famines, epidemics and societal unrest.
Katrin Kleemann, an environmental historian at the German Maritime Museum in Bremerhaven, says societies were affected in many different ways, including a failure in harvest or flooding or a cold summer or a really cold winter.
Volcanologists have uncovered some intriguing links, including some that could inform our understanding of how today’s society might react to a rapidly changing climate. They can’t prove an eruption caused the demise of a regime, but they have found connections between volcanic activity and human events.
The first challenge in making volcano-society connections is to find physical fingerprints of past eruptions. In the year 536, scribes in Europe, the Middle East, and Asia wrote about bizarre weather, including a haze that shrouded the sun for 18 months. Temperatures plummeted, harvests failed, and within a few years, the first documented global plague began.
Scientists can infer that big eruptions happened at certain times in the past by looking for sulfur and ash deposits in ice cores from Greenland and Antarctica. It turns out that polar ice cores do contain large amounts of sulfur dating to 536, a distinct signal of a major eruption.
Some researchers have speculated that it was the Samalas eruption that helped seal the fate of the Mongol Empire, which ended after its last ruler perished in a 1259 epidemic in China that could have been linked with the eruption-caused climate changes.
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A century after Samalas, there was yet another intriguing eruption-disease connection. Between 1346 and 1352, perhaps half of Europe’s population died in the Black Death plague, from infection by the flea-borne bacterium Yersinia pestis.
Historical records from Europe and Asia suggest that skies were darker than usual around that time, perhaps because of a volcanic haze. Ice-core records support that interpretation, documenting a big eruption, or perhaps several, around the year 1345—though the location remains unknown.
Ulf Büntgen, a tree-ring specialist at the University of Cambridge, used tree-ring data to confirm that the summers of 1345, 1346, and 1347 were unusually cold and wet in southern Europe. Büntgen and his colleagues note that as crops failed in the bad weather, Europeans imported grain from farther east, which arrived with rats harboring Y. pestis.
Connecting volcanoes to human events may be a challenge even today, but in 1784 an American ambassador to France named Benjamin Franklin was astute enough to link a strange haze that rolled across the countryside in the previous year to a distant eruption. The source turns out to be Laki, an Icelandic fissure that spewed lava for eight months starting in June 1783.
Though it happened just a few decades after Laki, one of the largest eruptions in recorded human history offers a much more detailed picture of how a volcanic climate shock can change history. In 1815, a mountain in Indonesia named Tambora exploded, sending sulfur into the upper atmosphere and triggering broad climatic changes.
Tambora’s eruption caused cooling across much of Europe and North America, where crops failed and 1816 was dubbed the “year without a summer.” The volcanic weather that year kept the writer Mary Shelley cooped up while traveling in Switzerland, where she wrote the novel Frankenstein.
The bad weather brought famine to Switzerland, Ireland, and elsewhere; grain prices and malnutrition soared in parts of Europe, prompting tens of thousands of people to emigrate to North America. Clive Oppenheimer, a volcanologist at the University of Cambridge, says human society has a lot of susceptibilities and vulnerabilities.
Some climate shocks will come and go, while at other times, the climate shock will come when there are greater societal vulnerabilities. These lessons may hold particular relevance today, because researchers see the historical fallout of past eruptions as a clue to how humanity might respond to present-day climate change.
Big volcanic eruptions cool the planet rather than warm it, but they represent the same sort of rapid planetwide shocks that societies are coping with now as Earth heats up. It is only a matter of time before the next big blast, and in the era of satellites and social media saturation, the whole world will know the moment it happens.
By studying past events like Krakatau and Tambora, we can have an idea of what will happen next, and prepare for the potential consequences of a large volcanic eruption on human society and the environment, including the potential for climate-related disasters.