Eruption of Samalas in 1257

Traces in the ice cores

The ice caps are a unique source of information about the planet’s past: each winter, a layer of ice is added to the top of the cap, trapping air bubbles. By analyzing the air trapped in the ice, one can thus reconstruct very precise time series on the composition of the atmosphere over the past centuries. The Greenland Ice Sheet Project is an international project ( US , Denmark , Switzerland ) to take the harp of ice cores and use the information. The drilling begins in 1971 ² .

The measurement of sulfate over 2000 years shows peaks corresponding to volcanic eruptions: eruptions historically well known as that of Vesuvius in 79 or that of Tambora in 1815 , the plume reaches the stratosphere , are in the measurement. However other peaks do not correspond to any known eruption, and this is the case of the most important of all, located in the late 1250s. However, the measure in Greenland alone does not allow to determine if the we are dealing with an eruption of planetary importance, or a more modest event but located near the place of measurement. A few years later, similar measures in Antarcticashow a peak at the same time, reinforcing the idea of a rash that impacted the planet (although the assumption of simultaneous events in both polar regions can not be ruled out completely) ¹ .

In the early 1990s , the comparison between the volcanic ash (also trapped in the ice) collected in both polar regions shows a great similarity in appearance and Geochemistry , confirming a common origin. Moreover, the fallout is about the same amplitude in the two polar areas, which points to a volcano located in the intertropical zone ³ .

Volcano identification

The volcanologists have researched for thirty years volcanoes candidates to the eruption proved by circumstantial evidence ⁴ . In 2000, the date of the eruption and the magnitude of its consequences are well identified, but its location remains a mystery, several volcanoes like El Chichón in Mexico , the Quilotoa in Ecuador and a Saudi volcano have been implicated ^5 , 6 . El Chichón attracted a lot of intention: his geochemistry seemed to correspond to the ashes found in the ice, he had a sulfur emitting eruption in 1982and traces of an eruption around 1250 were found. However, the study on the site showed that this eruption was much too small to explain the observed sulfate peak, with an estimated VEI 4 ^7 , 6 .

At the beginning of the 2010s, French (Franck Lavigne, Paris 1 ) and Indonesian teams reviewed dozens of little-studied volcanoes in the Indonesian archipelago in search of traces of a corresponding eruption. Their work helped to identify almost certainly the eruption of 1257 with a caldera present on the island of Lombok near Bali , the Segara Anak Caldeira . The site is of a size compatible with the scale of the event 1257. The Carbon dating 14 twenty-one samples of trees buried in the pyroclastic deposits is perfectly consistent with an eruption in 1257 ⁶. The last doubts were raised with the geochemical identification of the ash to those found in the ice cores, and the modeling of the volcano which allowed to evaluate the volume of ejecta in the range 33-40 km³, consistent with the evaluations based on measurements of ice cores ⁸ .

The study of an ancient Javanese manuscript , Babad Lombok ( babad meaning ” Chronicle “) written on palm leaves and kept at the National Museum of Indonesia in Jakarta , provided historical evidence of the event, and put a local name on the volcano: the Samalas . This narrative indicates that a city named Pamatan, which was the capital of Lombok Kingdom (on which there is virtually no other source), was buried during the eruption by what evokes fiery clouds . of excavationson the site could thus give rise to a major archaeological discovery that has been compared to an ” Asian Pompeii ” ^6 , 9 .

Sequence of the eruption

The Samalas culminated at about 4,200 meters above sea level and was 8 to 9 kilometers in diameter ^10 , 6 . This cone had formed “well before 12,000 BC. AD “. The “new” Rinjani , much more recent, which still flanked the old volcano east ¹¹ .

The original volcano disappeared during the eruption. The gas pressure in the magma chamber caused the eruption of the volcano. In this type of volcano ( gray volcano ), the lava is too viscous to be evacuated easily, but a riser eventually establishes itself. The magma chamber is depressurized, and the whole edifice collapses on itself, forming a huge crater of 6 km by 8.

The eruption would have produced a volcanic plume reaching 43 kilometers altitude ¹⁰ . With a volcanic explosive index of 7, it is called “mega-colossal” and seems to have been the most violent of the last 10,000 years ¹² . Of volcanic clouds have descended the slopes of the mountain, a distance of 25 km to the coast in three directions, leaving up to 35 meters of pyroclastic deposits ^6 , 10 .

The caldera resulting from the eruption was then filled with water. The level of the lake is 2000 meters above sea level. Three smaller volcanic cones have formed in the caldera ¹¹ . One of them, Barujari , is always very active.

In a publication in 2017, a Chinese team found in sediment lake on one of the Paracel islands traces of volcanic material likely coming from Samalas ¹³

Consequences of the eruption

Local

The eruption has undoubtedly devastated, and made partially uninhabitable for decades, the island of Lombok, as well as Bali and western Sumbawa . The king Javanese Kertanagara annexed in 1284 the island of Bali to his own kingdom, without encountering strong resistance. This could be explained by the fact that the island has been permanently depopulated and disorganized by the eruption ⁶ .

Winter volcanic

The Samalas eruption has caused, according to a recent study based on geochemical traces, the most important release of gas (notably sulfur dioxide and chlorine gases ) in the stratosphere of the common era , before the eruption of Tambora in 1815. , much better documented. The release is estimated at 158 ​​million tonnes of sulfur dioxide, 227 million tonnes of chlorine, and 1.3 million tonnes of bromine ¹⁴ Such a release of gas has a significant effect on climate, through a phenomenon known as global darkening name .

Thus, the years immediately following the eruption were colder than normal in many parts of the world. This cold period, evidenced both by paleoclimatic traces such as dendrochronology ^15 , 16 and by direct historical evidence, led to poor harvests.

Thus England suffered a serious famine in 1258, and some researchers now make a connection with the eruption. This episode is related in the Chronica Majora ¹⁷ . A common grave containing 10 to 15,000 skeletons was discovered in the eastern part of London in the late 1990s . First attributed to the Great Plague , it eventually turned out to have been built for the victims of the 1258-59 famine. The population of London at the time was around 50 000, which gives an idea of the scale of human losses ¹⁸ .

Abnormally high food prices have also been reported in several European countries, causing social unrest and perhaps the emergence of the flagellants’ movement in Italy ⁵ . In Japan , the Azuma Kagami reports a cold and rainy summer and poor harvests causing starvation ¹⁶ .

However, a research article published in January 2017 ¹⁶ relativizes this effect on the climate, noting that North America does not seem to have been affected by this cooling and suggests that the food situation in England and Japan was already difficult before the eruption, which would have only aggravated an existing crisis.

Link with the Little Ice Age

A question that remains to be debated is whether this effect on the climate was only transient or whether the eruption was a cause of the switch from the medieval climatic optimum to the Little Ice Age ¹⁴ . If the direct effect of aerosols on the climate is brief, because they are rapidly disappearing from the atmosphere, volcanic winter may have triggered feedbacks (changes in ocean currents , progression of ice-covered surfaces) with long-term influence on the climate. Recent modeling work ¹⁹ of the transition to the Little Ice Age incorporates volcanic forcing (including the eruption of samalas, but that of Kuwaeparticular) among the causes taken into account. The experience of one-to-one removal of model forcings (volcanoes, changes in Earth’s orbit, variation of greenhouse gases, and variation in solar radiation) shows a significant influence of volcanism.

References