In 934 AD, the Volcano of Eldgjá in Iceland erupted. The eruption lasted a long time, bringing about widespread cooling around 939, causing severe climate change, and even China was deeply affected by the eruption.
In the middle of summer 939, snow fell in southeastern Inner Mongolia. In the winter of that year, near the capital of the Later Jin Dynasty, that is, in the area of Kaifeng, "heavy snow harmed the people and did not stop in fifties."
In addition, from 942 onwards, the Yellow River Basin began to experience uninterrupted drought, followed by locust plagues in the summer, crop failures, and deteriorating livelihood.
The Later Jin dynasty was severely damaged as a result, and was later attacked by the Khitan army, which was finally overthrown in 947.
On November 29, 2020, the volcano of La Palma Island in Spain continued to erupt | Emilio Morenatti/AP
The volcanic eruptions in Iceland could have affected the demise of Chinese dynasties. But is this case just an isolated case? What is the relationship between volcanoes and the fall of dynasties?
Recently, a research team from Zhejiang University and Trinity College jointly published a study on the relationship between volcanic eruptions and the collapse of Chinese dynasties, and found that volcanic eruptions will affect the general environment and climate, affect people's livelihood, economy, and political power from the bottom up, resulting in the collapse of dynasties. In the event of war and unrest, volcanic eruptions can also indirectly affect the demise of dynasties. The findings were published in the journal Communications Earth & Environment.
Volcanoes erupted and food production fell
The most direct effect of the volcanic eruption is to make the climate cold and dry, resulting in a reduction in food production.
The gases from the volcano erupt into the atmosphere are oxidized and form sulfuric acid aerosols. Aerosols absorb radiation on one side and reflect solar radiation on the other. Absorbing radiation raises atmospheric stratospheric temperatures; reflected solar radiation lowers surface temperatures. Coupled with the diffusion of atmospheric circulation, the range of aerosol-affected areas is expanded. For example, low-latitude volcanic eruptions may extend to the whole world.
When the temperature drops, the evaporation of water decreases, the monsoon weakens, and the cold, dry climate causes crop failures.
In a society dominated by agriculture as an economy, the stability of agriculture was crucial to the continuation of the dynasty. Sudden climate change will lead to a reduction in food production, which in turn will affect the stability of social indicators, and the impact may be as small as the people becoming rogue thieves, to the rise of the masses and the chaos of the world.
In pre-industrial times, volcanic eruptions were one of the most important drivers of short-term climate change. The volcano erupted suddenly, causing a cold and dry climate that affected agriculture. For example, the Tang Dynasty ended in 907 AD and the Ming Dynasty ended in 1644, and both ended with many periods of cold and drought.
How sudden disasters systematically affect the fall of dynasties
While volcanic eruptions affect climate change, what role does this sudden climate change shock play in social collapse? One difficulty in this type of research is how to establish the systemic effects of sudden, short-term climate fluctuations on social collapse.
China's long history offers an excellent research opportunity. The researchers obtained from the database a correlation between 68 dynastic overthrow years over two millennia, 156 volcanic eruption points in the northern hemisphere volcanic activity record, and the scale of post-eruptive aerosol releases recorded in polar ice cores, as well as the number of wars before the collapse in history.
Using ice core data, the researchers reconstructed the time series of volcanic aerosols in the Northern and Southern Hemispheres and global stratospheres over the past 1500 years. Ice cores were chosen because of their low human disturbance in their environment and a longer time series, making them suitable for reconstruction work. After the volcanic aerosol spreads, it is deposited at the north and south poles and gradually becomes part of the ice sheet. By measuring the conductivity or chemical composition in the ice core, past volcanic activity can be reconstructed.
References to the relationship between the fall of dynasties, volcanic eruptions and the frequency of wars in China| references[1]
The study found that of the 68 dynastic downfalls, 62 occurred before the fall of volcanic eruptions. Researchers believe that over the past nearly 2,000 years, volcanic eruptions have systematically affected the fall of dynasties.
At the same time, they hypothesized that the impact of the eruption might be inversely proportional to the social pressures before the collapse. For example, a small volcanic eruption can trigger a collapse when social pressure is high and social instability is high; even when social pressure is not great, a violent volcanic eruption can trigger a dynastic collapse.
However, the study also pointed out that the factors that caused the collapse of dynasties are complex and cannot be judged solely by the correlation shown in the data, which highlights the complexity of the causes of dynastic collapse.
In addition, the belief system of the time may also have had an impact on the fall of dynasties, especially the concept of "Mandate of Heaven". The researchers pointed out that at the time of the fall of the dynasty, because volcanic eruptions affected the monsoon, tides, climate, etc., there will be some special celestial phenomena, that is, celestial anomalies described in ancient texts. Some rebels may claim that the current dynasty has failed the people and lost its legitimacy, and that anomalous natural phenomena are proof of this. This religious discontent, combined with the social unrest caused by the volcanic eruption, could well overthrow the dynasty. By giving the next ruler the "Mandate of Heaven", stability after the collapse of the dynasty can be facilitated.
In modern society, vulnerable areas are more vulnerable to volcanic eruptions
Historically, climate change such as volcanic eruptions has had an important impact on the fall of dynasties, so in modern society, people need to be more prepared for future volcanic eruptions.
For residents living at the junction of the plates, it is particularly important to pay attention to the direct impact of volcanic eruptions, such as abnormal climatic reactions such as earthquakes and tsunamis before the eruption, forming a set of emergency measures to face natural disasters.
On December 23, 2018, the Krakatau volcano in the Sunda Strait caused a tsunami that, according to scientists, was about 100 meters/AFP high
The study points out that the eruptions of the twentieth and twenty-first centuries were smaller than those experienced in China over the past two thousand years. Even so, this relatively small eruption could cause major droughts in some regions, such as those experienced in Africa's Sahel region in the 1970s and 1990s.
Therefore, researchers believe that areas with fragile economies or poor resource management should be more prepared for future volcanic eruptions. If there are major eruptions in the future, it could affect agriculture in some of the most marginalized and densely populated areas.
bibliography
[1] Gao, C., Ludlow, F., Matthews, J. A., Stine, A. R., Robock, A., Pan, Y., ... & Sigl, M. (2021). Volcanic climate impacts can act as ultimate and proximate causes of Chinese dynastic collapse. Communications earth & environment, 2(1), 1-11.
[2] Gao, C., Ludlow, F., Matthews, J. A., Stine, A. R., Robock, A., Pan, Y., ... & Sigl, M. (2021). Volcanic climate impacts can act as ultimate and proximate causes of Chinese dynastic collapse. Communications earth & environment, 2(1), 1-11. https://www.sciencedaily.com/releases/2021/11/211111214623.htm
[3] What are the reasons for the fall of dynasties? The Zhejiang team looked for answers from volcanic eruptions over the past two thousand years https://news.sciencenet.cn/htmlnews/2021/11/468925.shtm
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[5] Zhou, Jie, and Fei. (2016). The drought and locust plague of 942-944 AD in the Yellow River Basin, China. Quaternary international 394, 115-122.
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