The sun was dark for 18 months: what we can learn from history's worst volcanic eruptions

Europe was plunged into darkness and suffered from intense crop failures and famines in the years A.D. 536 and A.D. 1258, after massive volcanic eruptions.

When many people think of  volcanic eruptions , they envisage deadly lava flows and suffocating  ash fall . The fate of the inhabitants of  Pompeii  after the eruption of Mount Vesuvius in the year A.D. 79 still resonates today. Yet, volcanic eruptions have more wide-ranging consequences than is often realised, and this is recorded in historical accounts.

Large volcanic eruptions emit gases and ash particles into the atmosphere. Although the ash itself settles within weeks, the aerosols spread around the planet and can remain suspended in the atmosphere for years.  Ice cores  – long cylindrical samples drilled from glaciers – reveal these past sediment layers over hundreds of thousands of years.

What we can see from studying historic records is that volcanic eruptions can produce climatic changes, and rapid spread of disease such as plague. They can also affect weather systems far beyond the immediate vicinity of the volcano itself.

'The worst year to be alive'

A massive volcanic eruption in A.D. 536 has led historians to describe it as the  "worst year to be alive." Its exact location is unknown, though it might have been in Iceland. Europe, the Middle East and parts of Asia were plunged into darkness for 18 months. Temperatures in the summer months fell by 1.5˚C to 2.5˚C, initiating one of the coldest decades in the past two millennia.

Procopius , a Byzantine historian who lived in Rome, wrote that "the Sun gave forth its light without brightness, like the Moon, during this whole year, and it seemed exceedingly like the Sun in eclipse."

From Constantinople,  John Lydus , a Byzantine administrator and writer, reported that "the Sun became dim … for nearly a whole year." Another contemporary writer (thought to be John of Ephesus) noted that "the Sun was dark and its darkness lasted for eighteen months; each day it shone for about four hours, and still this light was only a feeble shadow."

Crop failures followed. The  Annals of Ulster and of Inisfallen , two contemporary chronicles, reported a "failure of bread" in Ireland in A.D. 536.

The eruption of A.D. 536 was then followed by two more eruptions, in A.D. 540 and A.D. 547. These, in turn, were followed by a period of sustained cooling known as the Late Antique Little Ice Age.  Researchers  have suggested this cold period contributed to the emergence of the Justinianic plague (A.D. 541–49), one of the worst outbreaks of bubonic plague in history. This was partly driven by migration, food shortages and the importation of grain shipments carrying infected rats and fleas.

'There was no summer during summer'

The eruption of Samalas in Indonesia in A.D. 1257 ranks as one of the most  significant volcanic eruptions  of the past two millennia. It produced twice the volume of sulphur deposits in ice cores compared to the Tambora eruption of A.D. 1815, famous for causing the year without summer in A.D. 1816.

Northern Europe  was already experiencing hardships caused by heavy rain and poor weather. The volcanic eruption exacerbated this further, causing widespread crop failures and famine in A.D. 1258.

Jean d'Essey, bishop of  Coutances in Normandy , reported that "there was no summer during summer. The weather was very rainy and cold at harvest time; neither the crop harvest nor the grape harvest were good."

The contemporary monk and chronicler  Richer of Senones  in France recorded that the warmth of the Sun was hardly able to reach the Earth. He noted that "so great a thickness of clouds covered the sky throughout that whole summer that hardly anyone could tell whether it was summer or autumn."

The effects are particularly well attested to in England. When summarising the year A.D. 1257, the English Benedictine monk,  Matthew Paris , described it as a "barren and wretched year." He continued that "a great multitude of people died from hunger". Paris thought it had produced "chronic illnesses," scarcely allowing "one already afflicted to breathe at all."

He continued that England experienced particularly cold weather during April, May and June, which did not allow crops to grow. "Owing to the scarcity of wheat, a very large number of poor people died; and dead bodies were found in all directions, swollen and livid … in pigsties, on dunghills and in the muddy streets."

The large number of deaths in medieval England overwhelmed  coroners . Coroners were supposed to hold an inquest to establish the causes of a person's death. Yet, there were so many paupers "dying of starvation" that officials could not attend to them all.  King Henry III  sent word in April to suspend them where no foul play was suspected.

The contemporary  Annals of Burton  similarly recorded a high number of vagrants who died "of hunger and starvation" because of the "dearth of the times." Many were drawn to towns and cities in hope of charitable alms. London drew in many such desperate paupers, exacerbating the situation there.

The  Chronicles of the Mayors and Sheriffs  of London, for example, recorded that: "In this year, there was a failure of the crops; upon which failure, a famine ensued, to such a degree that the people from the villages resorted to the City for food; and there, upon the famine waxing still greater, many thousand persons perished; many thousands more too would have died of hunger, had not corn just then arrived from Germany."

The  Tewkesbury Annals , a contemporary chronicle written by the monks of Tewkesbury Abbey, placed the number of dead from the famine at 20,000.

Death and mass burials

Such was the scale of mortality that  Paris  reported: "when several corpses were found, large and spacious holes were dug in cemeteries, and a great many bodies were laid in them together."

These "large and spacious holes" have since been found at the hospital of St Mary Spital in London.  The Spitalfields  site contains some 2,300 skeletons from the 1250s, connected to both the  drought of 1252  and the famine of A.D. 1257-58.

Volcanic eruptions have global consequences, shaping lives far beyond their immediate vicinity.

Volcanoes, even on the other side of the world, had the power to plunge medieval Europe into darkness, destroying crops and lives in the process, and that should not be ignored today.

This story was originally published by The Conversation. Alex Brown is an associate professor of medieval history at Durham University.