The Lost Supervolcano: Was This the Biggest Eruption in Human History?

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Intro

This is the story of an extraordinary scientific quest: the search for a mysterious volcano that once erupted in the 13th century with extreme violence—one of the biggest eruptions in 10,000 years. Scientists believe the repercussions of the eruption were significant, possibly disrupting the entire planet’s climate at the time and causing a major impact on human society. But where is this mysterious volcano hiding? For 30 years, scientists the world over tried to locate it in vain. Yet finding the volcano is crucial; we rarely have the chance to study how large eruptions created climate change in the past and how they could very well do it again in the future. Today, an international team of scientists has taken up the search, determined to solve the mystery. They’re leading a large-scale investigation, traveling across the globe in search of clues, and they’ve discovered a prime suspect: a monster in hiding. But is it the volcano that erupted all those years ago? [Music]

Main Part: The Volcano of the Middle Ages

It was during a polar expedition that a surprising discovery took place. The story begins in Greenland, as scientists in the late 1970s were drilling into the ice on the plateau of Greenland and looking back into past climate on the Earth. This was a multinational project; there were French, US, Danish, and Swiss scientists involved. Two of the pioneering scientists who were leading this project were a Danish scientist named Hammer and a scientist from the US named Langway. The glaciologists planned to analyze the traces of atmospheric gas and particles that had been trapped in the layers of ice year after year over several millennia. By boring into the ice, the researchers could reveal the climate of the past, and they quickly found astonishing amounts of sulfates. When scientists first started working on the chemistry of the Greenland ice core, they noticed big sulfate spikes in the core that corresponded to major global volcanic eruptions. Some of these include the eruption of Vesuvius, the eruption of Aang volcano, the eruption of Tambora, and the eruption of Laki volcano. The scientists believe that the high quantities of sulfates were the result of a volcanic eruption. Large volcanic eruptions will pump so much dust and sulfur into the atmosphere that they will eventually rain out over the polar regions, and so you can find a record of past volcanism in the ice, as ice is really a fantastic repository of information about volcanoes. The sulfur that’s erupted from the volcanoes is trapped in the ice, so a single ice core can give you information about volcanic eruptions happening all over the world.

Of all the sulfate spikes the team discovered, one had exceptionally high levels; it could well be from the most colossal eruption of the past 10,000 years. The most prominent of these markers dated to 1259, and the only way to explain this was that there had to have been a phenomenally large volcanic eruption. However, we knew of no volcanic events from that time period. In 1259, this massive sulfate spike occurred in the heart of the Middle Ages. The problem was that no eruption had ever been recorded that year—a true mystery. Where could it have taken place? Since the traces were found in Greenland, glaciologists suspected the Northern Hemisphere. But a few years later, in the early ‘80s, other climate-related drillings were completed on the other side of the planet in Antarctica.

Once again, the scientists discovered something shocking. Glaciologists Joel Saverino and Jean Rer Pati, who work on climate reconstruction, are repeating the experiment conducted by their counterparts in the 1980s. The scientists passed an electrical current through an ice core that was collected in the South Pole, 79 meters below the surface. The ice contains atmospheric particles from 800 years ago, in the 13th century, which fell to the ground and were trapped in the ice. Wow! The same sulfate spike dating from 1259 was found in ice from both the North Pole and the South Pole. Such symmetry is truly exceptional. The scientists are intrigued: are they traces of the same eruption, or were there several eruptions that took place simultaneously in both hemispheres? The mid-13th century mystery layer was phenomenal for the amount of sulfur in it. Unfortunately, sulfur doesn’t tell us anything really about which volcano produced it; sulfur is sulfur. But there was something else in the layer that was much more valuable as a clue to finding the volcano, and that was very fine particles of ash. The ash proves to be very important because the ash can carry a unique fingerprint of the magma, the molten rock from the source volcano. To determine if it was a single eruption or several, the scientists conducted a side-by-side comparison of the tiny particles of volcanic ash trapped in the two poles. Their shapes and geochemical compositions are identical. The ashes thus came from the same eruption—one that must have been gigantic to have generated the massive sulfate spike of 1259. This information gives the scientists new leads in their search. The fact that you had the event recorded in both polar regions suggested that the eruption had to be somewhere in the tropics; a very high latitude eruption couldn’t get its dust into the opposing hemisphere, not so far north or south. So that was a clue, but it was still a huge challenge to identify the volcano responsible because there are so many volcanoes. Although locating the volcano is a challenge, researchers now have a lead: such an eruption must have left traces elsewhere. But where?

In Northern Quebec, spruces that have been dead for thousands of years are found at the bottom of lakes. Like polar ice, these trees bear witness to the climate of the past. Buried deep beneath the sediment, they were spared decomposition. Using carbon dating, the researchers are able to isolate specimens that grew in the 13th century. Studying the shape and size of the tree rings may reveal important clues about the climate of the time. Here in this sample, we can see a crack that corresponds to a light ring, which formed during a short summer. In the lab, we will polish the sample, and the end result is something like that. These rings represent the years from 1240 to 1258, where you can see an abrupt decrease in tree growth. We have sampled more than 2,000 trees in six lakes, and when we analyze all this data, we noticed some abrupt changes in tree growth, and the most significant was in 1258. It’s not just here in North America, because we know from other evidence that this was also a cold year in Mongolia, for example, and thus it was probably a global event. The trees have revealed their secret: a sudden planet-wide cooling took place in 1258. Was it connected to the mysterious eruption?

In Paris, at the Laboratory of Oceanography and Climate, climatologist Miriam Cadre is looking for the answer. She and her team studied the impact of the most powerful eruption of the 20th century, Mount Pinatubo in the Philippines, in 1991. Their modeling helps them understand how a stratospheric eruption can affect the climate of the entire planet. In the stratosphere, sulfur dioxide molecules mix with water to form a suspension of billions of microdroplets of sulfuric acid aerosols. This gigantic mirror effect diminishes sunshine, thus cooling the average temperature on Earth. But that’s not all; up in the stratosphere, aerosols absorb the infrared rays emitted by the sun and the Earth. This heats up the stratosphere, which in turn upsets the trajectories of the planet’s strongest air currents and creates meteorological chaos on Earth.

In modeling the Pinatubo eruption, Miriam discovered an unexpected clue: the date of the mysterious eruption. This means three years passed between the mysterious eruption in 1257 and its ashes falling on the poles in 1259. Using the year 1257 and the characteristics of the enormous sulfate spike, Miriam modeled the climate effects of the mysterious eruption.

Climate Effects

Latitude, a rapid planet-wide cooling of even 1°C over a few months, would have dramatic consequences. Researchers believe it would have devastated the medieval societies of the time. But where’s the proof? It’s in the heart of London that an extraordinary discovery would reignite the case.

Excavation Findings

In 1999, a market construction site in Spitalfields unearthed a large cemetery that contained hundreds of mass graves. Archaeologists dug up over 10,000 skeletons that dated back to the Middle Ages—a truly exceptional find. Osteologist Don Walker participated in the excavations.

“Mary Spital really is unique. Some sort of catastrophic episode has killed a lot of people in a very short space of time. In some circumstances, we found 20 or even up to about 40-45 individuals just in one single pit, and it was a real surprise. What we wanted to do was find out what’s going on here.”

Possible Causes of Death

Researchers explored several possible causes of death, starting with the Black Death in 1348. “We looked at this; we did radiocarbon dating to check the dating of the cemetery, and we actually found that most of them came out about 100 years earlier, in the mid-13th century. The Black Death was ruled out.”

Scientists explored the possibility of the graves being from a military battle, but of the 10,500 exhumed skeletons, only one showed signs of a fatal blow. Scientists also found proof of something else: half of the people in the mass burial pits were females. In a battle grave, you’d expect to find mostly males. So, in the absence of this kind of injury in the mass burial pits, we have to say that they are not from battle.

Health and Nutrition

So, what could have killed all these people? The only thing we could really find in the mass burial pits that was different was that they had lesions on the teeth, which suggests that the people who were dying were those who were weakest, who had suffered malnutrition in the past, and they were more vulnerable to disease. In later life, their immune systems were not working properly. You get opportunistic infections such as influenza or measles that go through a population very quickly. A terrible famine would have therefore struck London in the middle of the 13th century. Was it somehow connected to the mysterious eruption?

Historical Accounts

Writing being well-developed in the Middle Ages, Don Walker headed to the British Library for clues and focused on one particular manuscript from the middle of the 13th century: The Chronicum Maiorum. “From about that time till the end of March, the north wind blew without intermission. A continued frost prevailed, accompanied by snow and such unendurable cold that it bound up in the face of the Earth, and that led to the deaths of many animals and the failure of crops.”

This is a very important manuscript for us because it’s written by Matthew Paris, a monk who lived in St. Albans in the 13th century, and he described basically what was going on in London, especially in 1257-1258. So that’s key for our investigations.

Matthew Paris described what happened in the summer of 1258: “Owing to the scarcity of wheat, a large number of poor people died, and dead bodies were found in all directions, swollen and livid in the muddy streets. When several corpses were found, large and spacious holes were dug in the cemeteries, and a great many bodies were laid in them together.” This is exactly what we’d expect in times of famine. When, in fact, it’s not the food shortage itself that kills people; it’s the fact that infectious disease runs rife. All they want to do is bury them as soon as possible to prevent this disease from spreading, and so they have to dig these huge pits.

Impact of the Eruption

The population of London was hit hard by the effects of the eruption. The famine of 1258 was one of the worst ever recorded in England. Matthew Paris mentioned 15,000 deaths, which means 30% of the British capital’s inhabitants disappeared that fateful summer. If London wasn’t spared, could other places in the world have experienced such loss of life?

Further Research

Historian Sebastian Guier has visited numerous monasteries and libraries across Europe. Here too, it’s thanks to accounts recorded in monk manuscripts from the 13th century that he found precious clues. Among the most significant texts found by the historian was this inscription in the Annals of Spire in Germany: “Maxim atatus to text.” This dark year didn’t only concern the European continent; other accounts prove it affected the rest of the world as well.

Mysterious Eruption Analysis

Following the traces of the mysterious eruption revealed that from Europe to Asia, the eruption caused total climactic chaos and took tens of thousands of lives, but the mystery still lingered. Which volcano? With all the evidence that was amassing from the ice cores, from the tree rings, and from the chronicles, all points to a large explosive eruption that should have left a large crater behind. The culit hint looks like a giant crater and is equidistant from both poles in the tropics. That means it’s hidden among hundreds of other volcanoes over thousands of square kilometers. It’s a needle in a haystack. Yet, starting in the 1980s, the search for the mysterious volcano galvanized the scientific community. Multiple volcanoes were declared suspects, like Kilauea in Ecuador, but another name also came up: the terrifying El Chichón in Mexico. Its monster eruption in 1982 was both explosive and stratospheric. El Chichón became a really good candidate because when it erupted in the 80s, it was a very sulfur-rich eruption, and the sulfur from that eruption circled the globe. Also, El Chichón was known to have erupted more or less in the right time frame.

Looking at the intensity of the 1259 sulfate spike, volcanologists estimated that the mysterious eruption ejected around 40 cubic kilometers of magma. That’s around 40 times more than the terrifying El Chichón. The Mexican volcano was officially off the suspect list. The wanted monster was much, much larger. Over the next 20 years, the search seemed to reach a stalemate. That is until two researchers, Frank LaVine and Jean Kristoff Kovski, decided to reopen the case in the early 2010s. By combining these two clues—the crater size and the pumice stone sediments resulting from a massive explosive eruption—the two scientists started their search by exploring satellite images.

The Indonesian archipelago is home to 129 active volcanoes, including the illustrious Marapi and others known for past eruptions: Katoa, Toba, and Tambora. What’s unique about this archipelago is that it was formed by a highly active subduction process. The southern Indo-Australian plate still descends 7 cm a year beneath the northern Eurasian plate. Far below the surface, the Earth’s water-laden crust melts, generating large pockets of molten rock called magma. It then rises to the Earth’s surface in magma chambers, powering eruptions in the Indonesian archipelago. The volcano we seek could very well be hidden in the middle of this cluster.

Frank and Jean Kristoff prepared a list of suspect volcanoes that have both a large crater and pumice stone sediments. These are yet unexplored and undated, nor have they been geochemically analyzed. Additional suspects have been eliminated, but one island neighboring Bali has caught the researchers’ attention: the island of Lambok. Doubtful of the volcano’s dating, Frank and Jean Kristoff decided to follow their intuition. They headed to Lambok, accompanied by Indonesian scientists. Their goal is to explore the volcano that overlooks the island, Mount Rani, searching for clues that would allow them to date the eruption and quantify the volume of its sediments. Is this mysterious crater where the 40 cubic kilometers of mysterious volcanic material came from?

The original volcano no longer exists; nothing remains but this enormous caldera. What led to this incredible transformation? Several kilometers beneath the volcano, magma accumulated in the magma chamber. The gases dissolved in the magma put immense pressure on the entire structure. The volcano began to erupt; gases and magma were freed in an immense rising column that partially emptied the magma chamber and weakened the walls of the volcano. It collapsed over itself. Millions of tons of rock fell into the magma chamber, leaving in their wake a giant open crater: the caldera.

Jean Kristoff goes into the caldera to take a site reading. He meets up with Debbie Camille Cabana and his Indonesian volcanology team, who are responsible for observing all the volcanoes in eastern Indonesia. Debbie and his team closely monitor Mount Rani, its immense caldera, and its two other craters: an extinct volcano at an altitude of 3,726 m and the Baru Jari, a very active young volcano at the very center of the caldera. Mount Baru Jari is like a window into the magma chamber located 4 km beneath the surface of the caldera. To measure its evolution, volcanologists take gas and lava samples from the Baru Jari’s most recent flow. All signs indicate the magma chamber is filling up. This is confirmed by another clue: the water temperature of the lake that formed over the caldera. Normally, for a lake at an altitude of 2,000 m above sea level, we would have around 14 to 15°C, but here at Tarak Lake, we have 20 to 22°C, which indicates very strong magmatic activity beneath the caldera. A considerable amount of energy is still accumulating beneath the caldera, putting the young Baru Jari under constant pressure. Jean Kristoff is convinced that the Rani caldera is the remains of a gigantic eruption, just like the one they’ve been searching for. Could it be from the eruption of 1257?

To find out, the scientists decide to examine the very thing that could help them understand more about the volume of the eruption: the pumice stone sediments. The satellite images seem to indicate sizable sediments in the area, but Frank and Jean Kristoff didn’t expect to find such a large one more than 25 km from the volcano.

Volcanic Eruptions and Their Impact

Pyroclastic flows are an extremely destructive volcanic phenomenon that’s characteristic of explosive eruptions. These avalanches of gas and smoldering volcanic debris, including pumice, hurtled down the volcano sides for dozens of kilometers. These lithic sediments are the remains of the pyroclastic flow. Studying them reveals another precious clue about the date of the eruption.

[Music]

The discovery of charred tree trunks in the pyroclastic flow confirms the scientists’ initial impressions. Their carbon dating indicates a time frame between 1163 and 1264. Lithic sediments as remains of a gigantic explosive eruption, carbon dating confirming a 13th-century time frame, and a huge and still active caldera—all these signs make Lambach seem exceptionally promising. Jean Kristoff and Fran decide to go deeper into their investigation, accompanied by their colleague Indio Prao, an Indonesian volcanologist.

On the north side of the island, 30 km from the volcano, a 35 m high pumice cliff has caught their eyes. They want to know if the global volume of the pyroclastic flows could match the 40 cubic kilometers of material previously estimated. Lithic fragments are rocks from the volcano’s walls; their high concentration in the sediment reveals a clue. This flow formed towards the end of the eruption when the volcano was collapsing and becoming the caldera. This eruption created enormous quantities of pyroclastic flows until the end, but figuring out their overall volume will be an extra tricky part. Part of the pyroclastic flows disappeared into the sea. A map of their spread over the island confirms the magnitude of the eruption. But how can they calculate the overall volume of all the pyroclastic flows?

The answer is back in Paris at the Department of Geosciences at the University of Paris Sud, where geomorphologist Pierre Leit made a 3D model of the volcano before it collapsed over itself. The mathematical modeling proves there was actually not one but two volcanoes. After accounting for the water volume of Lake Cigara Anak, the volume of the young Barari, and that of the collapsed Rani in the caldera, Pierre Leit calculated that this great volcano lost 2,800 m in height and ejected 40 cubic kilometers of material during its eruption—a mind-boggling quantity that means this eruption was one of the most violent ever, a magnitude 7 equivalent to 100 times the strength of the Pompeii eruption. The computer profile confirms that the volume of a Lambok eruption matches the mystery eruption, but this new evidence reveals another problem: there’s a second volcano, one that isn’t on any map, which scientists now need to study.

Thanks to his Indonesian contacts, Frank Lavine learns that the museum in the capital of Mataram houses some precious texts, the Babad. These historical and legendary texts carved into palm leaves and written in Old Javanese are many centuries old. Among the 1,300 Babad preserved at the museum, one is particularly intriguing.

[Music]

Thanks to the Babad, scientists are finally able to name their primary suspect: the Samalas. But that’s not all. Fantastic archaeologists may someday find the remains of Patan, believed to be the Pompeii of Southeast Asia. But in the meantime, a third clue has caught the geographers’ attention. A tsunami of volcanic origin can be extremely destructive. If they can prove it took place, the scientists will have an even deeper understanding of the eruptions’ local and regional impacts. This task fell to Patrick Vosmer, a worldwide expert on tsunamis, accompanied by Indonesian oceanographer Baktiar Muttakin from Gadjah Mada University in Java. He began searching for clues on the west coast of the neighboring island Sumbawa. This area is directly across from the point of impact of the pyroclastic flows that occurred east of Lombok. Here, the two islands are separated by a mere 15 km.

Does any trace remain of the tsunami that would have surged towards the local coastlines hundreds of years ago? It’s at an abandoned shrimp farm that the scientists finally find an exposed outcrop. The eruption led to three waves that submerged the Sumbawa coastline, but using a simulation, the scientists discover another tsunami of much greater scope. When it uses North Lambok as the location where the pyroclastic flows entered the sea, the simulation reveals that other waves would have devastated the coasts of Bali and all surrounding islands for thousands of kilometers, taking many lives with them. The ideal predator is slowly revealing its secrets, but the scientists still need to prove that the Samalas eruption was what caused the enormous sulfate spike of 1259. To do so, they must prove the eruption reached the stratosphere and formed a giant global aerosol suspension.

It’s now the volcanologists’ turn to study the outcropping on Sumbawa Island. They’re looking for materials that were projected to far distances. Their inventory of pumice and lithic fragments found far from the volcano allows them to map the spread and the thickness of the eruption’s airfall. The affected area is enormous; the pyroclastic falls would have covered thousands of square kilometers around the volcano, perhaps even more than 600 km west of Java, where on the edges of the Mori, a 2 cm pumice layer was identified as being from the Samalas. But what will really determine whether the eruption column reached the stratosphere or not will be the size of the fragments found on the ground.

Did the Samalas plume reach the stratosphere? Based on the fragments that were found in the area, the height of the smoke plume was absolutely stupendous: 43 km. That’s the highest plume of smoke ever recorded. The eruption of the Samalas was clearly stratospheric, but did it inject enough sulfur dioxide into the atmosphere to have created the large sulfate spike of 1259? The problem is that all the gases vanished during the eruption. How can one quantify something that no longer exists? It’s at the Institute de Physique du Globe de Paris that researchers found the answer in the tiny crystals encrusted in the very heart of the pumice stones. Once cut into thin slices, these crystals revealed their treasures: melt inclusions. These are tiny drops of magma trapped within the crystals, which retained their gases in spite of the eruption.

By cross-referencing the 40 cubic kilometers of projected magma with the concentration of sulfur present in the crystals, the scientists are able to calculate the total amount of sulfur dioxide emitted by the Samalas: 158 million tons of sulfur dioxide, nearly two times the volume emitted by the eruption of Tambora in 1815, which up until now had been considered the largest eruption of the last few millennia. This volume corresponds to the intensity of the sulfate spike of 1259. All evidence points to the Samalas as the source of the mysterious eruption, and yet one final obstacle could still change everything.

In the laboratory of glaciology in Granola, the ash microparticles found in the South Pole have been carefully prepared so they can be compared to those from the Samalas. These microparticles are so fine that handling them requires an environment completely free of any outside dust. It’s a delicate operation. The micro ashes must be separated from the aerosols present in the sulfate spike of 1259 and from every other speck of dust that was present in the atmosphere at that time. The final step is carried out at the Institute de Physique du Globe de Paris. Compared side by side under an electronic microscope, the two samples found thousands of kilometers away from one another will reveal that they share the same origin: on the right, the ash from the South Pole; on the left, the ash from the Samalas.

The shapes match. Now for the last and final comparison: geochemical fingerprinting. The chemical composition of the Samalas ashes appears in blue; the two diagrams are identical. The many different clues are finally all coming together. The Samalas is definitely the volcano responsible for the giant eruption of 1257.

[Music]

In the field, Jean Kristoff Karski even found a wall that displays the entire eruption process. From here on to about the top of this cliff is the 36-hour eruption sequence summarized. This brown layer here is the ground layer at the time of the eruption in 1257, where people were farming and living. Walking in 1257 under massive pressure from the gas accumulated in its magma chamber, the Samalas exploded. The first phase of the eruption is basically an intense rain of pumice for 6 to 7 hours from a very tall eruption plume, similar to the Pompeii eruption but on a much larger scale. Then you notice here a second layer formed by a turbulent pyroclastic flow—an avalanche of incandescent fragments and gases, very turbulent, perhaps 200 to 300 km per hour, sweeping down the flanks of the volcano, reaching this location at 25 km from the volcano. And then we have the third phase of the eruption. Again, we get about 6 to 8 hours of continuous rain down of pumice fragments, and then we get the fourth phase, the final climactic phase of the eruption. You get such a high flux of material coming out that it cannot sustain the column, and yet the volcano is collapsing on itself, and it continues to erupt for several hours—a sequence of these pyroclastic flows devastating the whole area.

It only took this enormous volcano a few hours to radically change the course of the world, and it was thanks to great persistence that scientists were able to solve one of the greatest mysteries our planet has ever known. The Samalas is now a part of history. It took so long to solve this mystery, and I’m not that surprised it took so long. In fact, I’m surprised that we eventually found it because there are so many volcanoes around the world. There are even ones with calderas that are hidden beneath the sea that could be responsible for some very big events in the past. So I think we were actually quite lucky to find out that Samalas was responsible for this huge event in the mid-13th century. Yet the Samalas still harbors many secrets.

Could Patan be the Pompeii of Southeast Asia? Answering will be one of the next challenges. With their Indonesian physicist colleagues, Frank Lavine and his team have already discovered that 760 years ago, the shoreline was more than 2 km back from the current coastline, right in the middle of the old Mataram Airport runway. In the meantime, the clues gathered about the Samalas eruption could help envision the future.

[Music]

This could impact the global food distribution system. There will be winners and losers. There will be parts of the world which are very reliant on imports of grain that might be very severely hit. There will be huge disruption to global aviation—something, of course, that didn’t exist in the 13th century. There will be disruption of shipping. There will be huge regional impacts wherever this next event of this scale happens, which could have a huge impact on markets that could trigger another global economic crisis. Only after a global study that began more than 30 years ago did the Samalas finally reveal its secrets. This discovery gives us an exceptional opportunity—a chance to better understand the impacts of large-scale eruptions on the entire planet’s ecosystem. How would we deal with one today? Because an eruption like the Samalas could happen sooner than we think.

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