Did scurvy exacerbate the plague?

Plague, the dreaded infectious disease, that decimated the populations of cities, countries and empires. It is caused by the bacterium Yersinia pestis. The plague is generally spread by rats that carry infected fleas.
Several pandemics are known to have ravaged the historic world. Three main Yersinia pestis strains are recognised: (1) Yersinia pestis Antiqua, which caused the Justinian Plague (541–544 AD), but continued intermittently until ∼750 AD; (2) Yersinia pestis Medievalis, which caused the Black Death in Europe (1347–1351 AD) and included successive waves, such as the Great Plague (1665–1666 AD), until the 18th century; and (3) Yersinia pestis Orientalis, which emerged in China in the 1850s and erupted there in a major epidemic in 1894 before spreading across the world as a series of epidemics until the middle of the 20th century.

Plague outbreaks appear to be related to increased abundance of rodents and other mammals that serve as hosts for the fleas that then transmit the disease to humans. We know that the plague is partially seasonal: at the end of the harvesting season, rat populations drop because they don't have enough to eat[1][2]. As a result, fleas start looking for new hosts to bite, and so begin targeting humans.

Most plague pandemics are preceeded by dramatic weather events, causing misery and crop failures. The result was famine.
But in times of famine, there is hardly any food for both humans and rats. As prolonged bad weather was seen over entire continents, rat populations dwindle accordingly over these continents, explaining the extremely fast expansion of the plague.

The population was already weakened by famine, but the prolonged lack of fresh fruits and vegetables meant that Vitamin C deficiency would be astonishingly common and that would undoubtedly lead to rampant scurvy. Remember, it was not uncommon for over 80% of sailors to die from scurvy during long voyages, with a total of an estimated two million succumbing to it between 1500 and 1800.

It's a deadly combination: famine, scurvy and the plague. No wonder then that the Black Death is estimated to have killed 30–60% of Europe's total population. The plague was somewhat less common in parts of Europe that probably had some alternative vitamin C-rich food supplies, such as seeweeds[3] (...vitamins such as vitamin C are present in large amounts in Ulva lactuca (sea lettuce).... That means that the majority of the Basque Country, isolated parts of Belgium and the Netherlands would have a highter chance to survive.

[1] Eckert: Seasonality of plague in early modern Europe: Swiss epidemic of 1628—1630 in Reviews of Infectious Diseases – 1980
[2] Bacaër: The model of Kermack and McKendrick for the plague epidemic in Bombay and the type reproduction number with seasonality in Journal of Mathematical Biology – 2012
[3] MacArtain et al: Nutritional value of edible seaweeds in Nutrition Reviews - 2007

When was Thera cq Atlantis destroyed?

New analyses that use tree rings could settle the long-standing debate about when the volcano Thea on Santorini erupted by resolving still existing discrepancies between archaeological and radiocarbon methods of dating the eruption[1].
[Santorini's craters]

Thera’s explosive eruption on Santorini more than 3,400 years ago buried the Minoan settlement on the island in a layer of ash and pumice more than 40 meters deep. The effects of the eruption were felt as far away as Egypt and it heralded the end of the Minoan civilisation. It is now understood that the explosive eruption of Thea was the basis of the story of Atlantis.

Archaeologists have estimated the eruption as occurring sometime between 1570 and 1500 BC by using human artifacts such as written records and pottery. Other researchers estimate the date of the eruption to about 1600 BC using carbon-14 measurements from organic matterial found just below the layer of volcanic ash.

“The volcanic eruption represents one short moment in time,” Charlotte Pearson, an assistant professor of dendrochronology said. “If you can date precisely when that moment is, then whenever you find evidence of that moment at any archaeological site, you suddenly have a very precise marker point in time.”

By counting annual rings of trees that lived at the time of the eruption, the team dates the eruption to someplace between 1600 and 1525 BC, a time period which overlaps with the 1570-1500 date range from the archaeological evidence.

Pearson and her colleagues used two different tree-ring chronologies from long-lived trees that were alive at the time of the Thera eruption. Salzer’s extensive work on long-lived bristlecone pines living in California and Nevada provided the 200 tree-ring samples representing each year from 1700 to 1500 BC. Brown provided 85 Irish oak annual tree-ring samples that spanned the same years.

Because Irish oaks and bristlecone pines add a growth ring every year, the rings laid down year-by-year represent an environmental history going back thousands of years in time.

A massive volcano such as Thera ejects so much material into the atmosphere that it cools the earth. For cold-climate trees such as Irish oaks and bristlecones, that exceptionally cold year shows up as a much narrower tree ring. Salzer’s work reveals at least four different years within the new radiocarbon age range for Thera where the bristlecone pines had exceptionally narrow rings that might indicate a huge volcanic eruption.

[1] Pearson et al: Annual radiocarbon record indicates 16th century BCE date for the Thera eruption in ScienceAdvances - 2018

Did Tambora eruption help defeat Napoleon at Waterloo?

On April 5 1815, Mount Tambora erupted on the Indonesian island of Sumbawa, killing some 100,000 people. The next year, 1816, became widely known as 'the year without a summer', as gases, ashes and dust drifted over the entire globe, reaching the stratosphere, where they remained long enough to create 'an enormous sun filter'.
The summer-less summer of 1816 even inspired writers, such as Mary Shelley who wrote Frankenstein, a gothic novel set in often stormy environments and gloomy weather conditions ('Yet I did not heed the bleakness of the weather').

Now, research seems to indicate that the effects of the eruption of Mount Tamboro were having a detrimental effect on the weather much quicker[1]. The eruptions can hurl this electrified ash much higher than previously thought into the atmosphere – up to 100 kilometres above ground. Very small electrified volcanic particles from eruptions can 'short-circuit' the electrical current of the ionosphere – the upper level of the atmosphere that is responsible for cloud formation. This ultimately leads to sudden formation of clouds.

These clouds brought heavy rains across Europe that contributed to Napoleon Bonaparte’s defeat at the Battle of Waterloo from 16 to 18 June 1815.

Author of the research, Dr Matthew Genge, explained: “Vigo Hugo in the novel 'Les Miserables' said of the Battle of Waterloo: "Had it not rained on the night of 17th/18th June 1815, the future of Europe would have been different …an unseasonably clouded sky sufficed to bring about the collapse of a World.”[2].’

[1] Genge: Electrostatic levitation of volcanic ash into the ionosphere and its abrupt effect on climate in Geology - 2018. See here.
[2] Wheeler, Demarée: The weather of the Waterloo campaign 16 to 18 June 1815: Did it change the course of history? in Royal Meteorological Society – 2005. See here.

Volcanic eruptions and the fall of the Roman Empire

Dendrochronology (or tree-ring dating) of the northern hemisphere now spans the past 7,600 years. Adverse weather conditions cause trees to grow slowly and that results in small tree rings. Various historical events, like volcanic eruptions, can be observed in those tree rings.

Vulcanic eruptions of AD 536 and 540 led to climate cooling and contributed to hardships of Late Antiquity societies throughout Eurasia, and triggered a major environmental event in the historical Roman Empire[1]. The period is known as Late Antique Little Ice Age (AD 536 – 660. Documents of that time describe the veiling of the solar radiation during and after AD 536, the sun was observed blue-colored, without brightness, spring without mildness and summer without heat[2].

A group of researchers has proposed the possibility of El Salvador's Ilopango, which is known to have erupted around 540 AD, but others think that there were two seperate erupting volcanoes.
[Ilopango - El Salvador]
What followed after these eruptions was a persistently low solar radiation in the entire northern hemnisphere that contributed to remarkably simultaneous outbreaks of famine and Justinianic plague in the eastern Roman Empire. An extended period of little light may make it difficult for humans to survive. The level of production of plants is dependent on the amount of available sunlight. Food production, i.e, farming and animal husbandry, rely on the same solar energy. Humans, meanwhile, become more prone to disease if they are not exposed to enough sunlight to produce vitamin D.

The new study tracks the correlation of carbon isotope variation and volcanic eruptions from the 19th century until recent years, and shows the dramatic reduction in available sunlight in AD 536 as well as between 541 and 544 AD. The unusually poor years coincide with the bubonic plague epidemic that devastated the Roman Empire. The epidemic caused by the Yersinia pestis bacterium began in 542 AD and killed approximately half of the inhabitants of what was then considered the Eastern Roman Empire. The plague spread through Europe, from the Mediterranean, possibly as far north as Finland, and had killed tens of millions of people by the 8th century.

Recent research shows that a vitamin D deficiency correlates with various infectious diseases[3]. Like Influenza or the plague.

[1] Helama et al: Volcanic dust veils from sixth century tree-ring isotopes linked to reduced irradiance, primary production and human health in Scientific Reports – 2018. See here.
[2] Stathakopoulos: Reconstructing the climate of the Byzantine world: State of the problem and case studies in People and Nature in Historical Perspective (pages 247–261) – 2003
[3] Gios et al: Vitamin D and Infectious Diseases: Simple Bystander or Contributing Factor? In Nutrients – 2017. See here.

Mount Etna is sliding towards the sea

Mount Etna is Europe's most active volcano, but it harbours an unexpected danger. Scientists have recently established that the whole structure on the Italian island of Sicily is edging in the direction of the Mediterranean at a rate of on average 14 millimeters per year. The volcano is sliding down a very gentle slope of 1-3 degrees[1]. This is possible because it is sitting on an underlying platform of weak, pliable sediments.
Lead author Dr John Murray and his team have placed a network of GPS stations around the mountain to monitor its behaviour. This instrumentation is so sensitive that it can detect millimetric changes in the shape of the volcanic cone. It has detected that the mountain is moving in an east-south-easterly direction, on a general track towards the coastal town of Giarre, which is about 15 kilometers away. At the current rate of speed, it will take Mount Etna roughly 100 million years to reach Giarre.

14 millimeters per year may seem small, that is 14 meters per century, but geological investigations elsewhere in the world have shown that extinct volcanoes that display this kind of trend can suffer catastrophic failures on their leading flank as they drift downslope. Stresses can build up that lead eventually to devastating landslides.

"I would say there is currently no cause for alarm, unless there is an acceleration in this motion," Murray said. "The thing to watch I guess is if in ten years' time the rate of movement has doubled - that would be a warning. If it's halved, I'd say there really is nothing to worry about."

[1] Murray et al: Gravitational sliding of the Mt. Etna massif along a sloping basement in Bulletin of Volcanology - 2018

Justinian Plague: Volcanic Winter or Comet Impact?

The Justinian Plague (541–542), named after emperor Justinian I (527-565), was a pandemic that afflicted the Byzantine Empire. The pandemic resulted in an estimated 25 to 50 million deaths in two centuries of its recurrence.
[Rabaul Volcano]
A global cooling in 536 AD, that preceded the plague, was possibly triggered by a major volcanic eruption that released immense amounts of ash and sulphur into the atmosphere. Two different volcanos are thought to be the culprit: Rabaul volcano (Papua New Guinea) and Lake Ilopango (El Salvador). Another theory is that the dust veil was due to a comet impact. Ice-core analysis of Greenland ice from between 533 and 540 AD do show high levels of tin, nickel and iron oxides from an extraterrestrial source in the dust layer[1].

The appearance of the dust veil in 536 AD had a major impact. Global cooling and colder summers caused crops to wither. Widespread famine ensued and this subsequently made the people of the time more susceptible to disease.

In 541 AD a mysterious illness began to appear on the outskirts of the Byzantine Empire. Victims were described as suffering from delusions, nightmares, fevers and swellings in the groin, armpits and behind their ears. The plague arrived in Constantinople, the capital of the empire, the following year. At its peak the plague was supposedly killing 10,000 people in Constantinople a day.

It had long been suspected that the Plague of Justinian was in fact bubonic plague, the cause of the infamous Black Death that also occurred in the 14th century. In 2012 it was finally confirmed that this was the case. A team of researchers analysed human remains from gravesites from the period and found the presence of Yersinia Pestis[1].

The Black Death was carried by rat fleas living on black rats. The infected rats and fleas travelled around the ports and trade routes of the Mediterranean via merchant ships.

The outbreak lasted less than 6 months in Constantinople but it is estimated that 40% of those living there died in that time period. The plague would reappear at periodic intervals over the next 300 years and it would eventually claim the lives of 25% of people living in the Mediterranean region. It is estimated that somewhere in the range of 25-50 million people died in total as a consequence of this catastrophic illness. The last recorded recurrence was in 750 AD, but by this time the outbreaks had become less virulent. The plague would then disappear from Europe completely until the 14th Century.

Whatever the cause of the Justinian Plague, be it volcanic or extraterrestrial, the course of human history was changed forever and Europe would not fully recover until the rise of the Renaissance.

[1] Rigby et al: A comet impact in AD 536? in News and Reviews in Astronomy and Geophysics - 2004. See here.
[2] Bos et al: Yersinia pestis: New Evidence for an Old Infection in PloS One - 201. See here.

Mount Toba eruption (~74.000 years ago) and southern Africa

Mount Tambora erupted in 1815 and has been responsible for a year without summer in 1816. The impact on the human population was dire – crop failures in Eurasia and North America, famine and mass migrations.

The eruption of Mount Toba, some 47.000 years ago, was a hundred times more massive than that of Mount Tambora[1]. The effects would have had a much larger, and longer-felt, impact on people around the globe.
The scale of the ash-fall alone attests to the magnitude of the environmental disaster. Huge quantities of aerosols injected high into the atmosphere would have severely diminished sunlight – with estimates ranging from a 25 to 90 percent reduction in light. Under these conditions, plants die-off, large herbivores starved and provided little sustenance to the predators, both carnivores and humans, that depended on them. The cycle repeated itself, year after year.

Recently archaeologists discovered microscopic glass shards (cryptotephra) characteristic of the ashfall from the Toba eruption in two sites (the Pinnacle Point rockshelter and an open air site some 10 kilometers away called Vleesbaai) on the south coast of South Africa[2]. The study also shows that along the food-rich coastline of southern Africa, humans thrived through this mega-eruption, perhaps because of the uniquely rich food regime on this coastline. Around 'neighbouring' Lake Malawi humans also thrived[3].

In the 1990s, scientists began arguing that this eruption of Mount Toba, the most powerful in the last two million years, caused a long-lived volcanic winter that may have devastated the ecosystems of the world and caused widespread population crashes, perhaps even a near-extinction event in our own lineage, a so-called bottleneck.

[1] Williams: The ∼73 ka Toba super-eruption and its impact: history of a debate in Quaternary International – 2012
[2] Smith et al: Humans thrived in South Africa through the Toba eruption about 74,000 years ago in Nature – 2018
[3] Lane et al: Ash from the Toba supereruption in Lake Malawi shows no volcanic winter in East Africa at 75 ka in Proceedings of the National Academy of Sciences of the United States of America - 2013

Third orangutan species developed near Mount Toba

Until very recently everybody thought that there were only two species of orangutan: the Bornean orangutan (Pongo pygmaeus) and the Sumatran orangutan (Pongo abelii). The Bornean species is divided into three subspecies.

But now, scientists have discovered that a group of orangutans, living in a high-elevation forest called Batang Toru in the mountainous region of Tapanuli on Sumatra, is in fact a seperate species[1].
Their DNA showed that Bornean orangutans, Sumatran orangutans, and the new species, Tapanula orangutan (Pongo tapanuliensis), comprise three distinct evolutionary lineages. Further analysis revealed that the oldest lineage belongs to the newest species. The Tapanula orangutan is more closely related to its counterparts from Borneo, across the sea, than to other orangutans living on the same island.

The genetic work suggests that several million years ago, orangutans moved from the South Asian mainland onto what is now Sumatra and occupied an area south of the Toba caldera. Around 3.3 million years ago, a group of them moved north to colonize the area north of Toba. While the two groups did interbreed from time to time, they would remain largely distinct.
Then, some 600,000 years ago, a second split occurred—this time between the original population south of Toba and the orangutans that went on to settle in Borneo. As ice ages progressed and sea levels changed, orangutans moved effortlessly between landmasses—which explains how the Batang Toru orangutans could be more closely related to those from Borneo.

Around 75,000 years ago, Mount Toba erupted, causing widespread destruction Perhaps not coincidentally, the genomic data indicates a population crash of orangutans around 75,000 years ago as well. Because the lava destroyed the surrounding rain forest, the orangutans living on either side of the volcano were permanently separated.

[1] Nater et al: Morphometric, Behavioral, and Genomic Evidence for a New Orangutan Species in Current Biology - 2017

Did volcanic eruptions spark revolts in Ancient Egypt?

The Ptolemaic Kingdom was a prosperous time in Egypt’s ancient history, nearly three centuries from 305 BC to 30 BC that for all intent and purposes ended with the reign of Queen Cleopatra VII (69-30 BC). Yes, I know, her son Caesarion ruled Egypt for two weeks before he was murdered by the Romans.
[Yearly flooding of the Nile]
But during that Ptolemaic Kingdom there were several bloody Egyptian revolts against the ruling Greeks. A team of historians and climate scientists say that the unrest and uprisings may have been tied to volcanic eruptions that triggered climatic changes[1].

When large volcanoes erupt, they spew large quantities of ash and sulfur high into the stratosphere. There, the sulfur oxidizes into sulfate aerosols that reflect sunlight back to space, reducing evaporation on the planet’s surface. This in turn may suppress monsoons, diminishing the annual floods of the river Nile and leading to food shortages in Egypt.
[Variation in water levels of the Nile]
But to establish a connection between volcanoes and revolts in ancient Egypt, the team first had to determine the dates for when the volcanoes erupted.

They began by looking at ice core data from Greenland and Antarctica, which contain trapped sulfur from ancient volcanic eruptions. The scientists then turned to papyrus records to figure out when the Nile River failed to flood as usual. But these records from the Ptolemaic period were all qualitative, not quantitative. So the team turned to the Nilometer record, which contains measurements taken by large instruments built during Egypt’s early Islamic period to monitor the Nile River’s annual flood level.
The Islamic Nilometer was constructed in 622 AD. In 1902 the Nilometer became obsolete because of the completion of Aswan Low Dam. The scientists identified 61 eruptions between those years. On average the Nile flood level was nearly 22 centimeters lower during eruption years, the team discovered.

After confirming a link between volcanic eruptions and poor Nile flooding, the team then matched the dates of Ptolemaic eruptions with papyrus records of well-known rebellions. They found that eight out of ten large uprisings happened within two years of a volcanic eruption.

[1] Manning et al: Volcanic suppression of Nile summer flooding triggers revolt and constrains interstate conflict in ancient Egypt in Nature Communications -2017

Eruption of Toba (74,000 BC) and humans in India

The eruption of Mount Toba, in what is now Indonesia, was the largest volcanic event of the last two million years. Mount Toba spewed as much as 3,000 cubic kilometers of magma, rained sulfuric acid down as far away as Greenland, and sent the world into a volcanic winter followed by a severe ice age.
As described here, the 'Toba catastrophe theory' claims that the Toba eruption is linked to a genetic bottleneck in human evolution about 50,000 years ago, which may have resulted from a severe reduction in the size of the total (world-wide) human population due to the effects of the eruption on the global climate. According to the genetic bottleneck theory, between 50,000 and 100,000 years ago, human populations sharply decreased to just 3,000–10,000 surviving individuals.

At a more local level, the eruption showered all of India with levels of of volcanic ash that could reach two meters in height and which acts as a marker of age in Earth's strata today.

Anthropologist Michael Petraglia and his colleagues unearthed stone tool assemblages from above and below the Toba ash deposit in India's Jwalapuram Valley[1].
Because these stone tools were found both above and below a layer of ash left behind by a volcanic supereruption 74,000 years ago, the discovery hints that humans in the region survived the blast's devastating effects.

The tools the team found resemble those made by modern humans in Africa, suggesting that the Indian ones could have been made by humans too, Petraglia said.

"The fact that we have this ash is just icing on the cake, because it tells us that if it's modern humans, then they were able to persist through a major eruptive event," he said. "But they would have had a very, very difficult time."

[1] Petraglia et al: Middle Paleolithic assemblages from the Indian subcontinent before and after the Toba super-eruption in Science - 2007

North Korea's nuclear tests could trigger supervolcano eruption

North Korea is not a tranquil country by any measure. Situated on the very border of North Korea and China lies Mount Paektu (Baekdusan in Korean or Changbaishan in Chinese), an active volcano. At 2,744 meters it is the highest mountain on the Korean Peninsula and of Northeast China. Both North and South Koreans consider the volcano and its caldera lake to be their countries' spiritual home.
A large crater lake, called Heaven Lake, lies in the caldera atop the mountain. The caldera was formed in 946 AD by a 'super-colossal' VEI-7 eruption, which erupted about 100–120 km3 of tephra. It was one of the largest and most violent eruptions in the last 5000 years and can be compared by the eruption of Tambora in 1815. It other words, this volcano can pack quite a powerful punch. Luckily, one might say, the volcano is dormant since its last eruption in 1903[1].

The North Korea’s latest nuclear test at its northerly nuclear test site Punggye-ri on September 3, 2017 was estimated at some 250 kilotons or nearly 17 times more powerful than the bomb that devastated Hiroshima. It was powerful enough to sink an area of roughly .34 square kilometers on the peak of a mountain above the tunnels where the test took place. After the test, scientists were worried that more underground explosions in the isolated country’s north could result in a deadly volcanic eruption from Mount Paektu[2]. Punggye-ri is located just 114 kilometers southeast of Mount Paektu.

A blast from such a super volcano could be catastrophic, with ash traveling thousands of miles and, depending on the direction of the wind, potentially causing hundreds of thousands of casualties.

So, North Korean's erratic leadership might strive for nuclear equilibrium with the USA, but it might unwittingly create their own Armageddon.

Update September 23, 2017: A (probably natural) earthquake of magnitude 3.4 rattled the North Korean area where they detonated their latest nuclear device. Is nature fighting back?

[1] Wei, H. et al. Three active volcanoes in China and their hazards in Journal of Asian Earth Sciences - 2003
[2] Hong et al: Prediction of ground motion and dynamic stress change in Baekdusan (Changbaishan) volcano caused by a North Korean nuclear explosion in Scientific Reports – 2017. See here.

Graham Island: The rise and fall of an island

On June 28, 1831, a small earthquake hit the west coast of the Mediterranean island of Sicily. At sea, one mariner felt the shock and thought his vessel had struck a sandbank. For days afterward, the waters off the coast of Sicily continued to boil. Dead fish floated on the surface. The air stank of sulfur. Pumice stones washed up on beaches.

On July 10, Giovanni Corrao, captain of the Neapolitan brigantine 'Teresina', was sailing in the Mediterranean when he saw a huge column of water and smoke that roared up to 20 meters above sea level. “A great noise like thunder” was also heard.
Ferdinand II, King of the Two Sicilies, ordered the warship 'Etna' to investigate. News also reached Malta, then under British rule. Sir Henry Hotham, British vice admiral on the island, likewise dispatched ships “to determine the exact position on the charts, and to make every other observation on the nature of the phenomenon.”

By July 19, 1831, some 30 kilometers south of Sicily, a new island could be seen — spawned by an eruption of the underwater volcano Empedocles. Charles Swinburne, commander of the British sloop 'Rapid', saw a high, irregular column of very white smoke or steam. As night fell, brilliant flashes mingled with the smoke, which remained clearly visible even by moonlight. Eruptions of lurid fire arose in its midst. At daybreak, when the smoke cleared a bit, he could see “a small hillock of a dark colour a few feet above the sea.”

Within a month the island stood some 65 meters high and had a circumference of about 3.5 kilometers.

Captain Humphrey Le Fleming Senhouse, landed on the island on August 2 and planted the British Union Jack. He named the island Graham Island, in honor of Sir James Graham, first lord of the Admiralty. Italy, not to be outdone, sent Carlo Gemellaro, professor of natural history, to the island. He named it Ferdinandea, after Ferdinand II. Unimpressed by the news of the flag already flying over it, Ferdinand formally declared the island to be part of his kingdom, even though it lay outside the territorial waters of Sicily.

As always, the French were last to arrive: Geologist Constant Prévost named the island Julia, as it had appeared during the month of July. He too raised his country’s flag over the isle. A potential conflict between England, Italy and France was born.
But as quickly as it had appeared, Graham Island also disappeared. By December the island had collapsed and was reduced to a hazardous reef a few feet below sea level. Studies later revealed that the entire island had been composed of a volcanic rock called tephra, known for its susceptibility to erosion.

Yellowstone Supervolcano waking up?

A swarm of over 1100 earthquakes recorded in the Yellowstone caldera over the past month prompted scientists to quell concerns about a dormant Yellowstone 'Supervolcano' slowly waking up.
Experts at the US Geological Survey say the risk of the Yellowstone Supervolcano erupting is quite low (the probability is calculated at one in 730,000). There have been three major 'caldera-forming eruptions' in Yellowstone in the last 2.1 million years, the last occurring 640,000 years ago. Since then, there have been a number of smaller erurptions, with the last one emitting rhyolite lava, causing the Pitchstone Plateau flow some 70,000 years ago, the UUSS wrote.

However, concerns escalated on July 6, 2017 after a strong Magnitude 5.8 earthquake hit western Montana - the strongest quake to hit the area in the past 20 years - the U.S. Geological Survey reported.

Mike Stickney, seismologist, found the location 'not surprising'. 'It’s right along the axis of the intermountain seismic belt.'. He said the quake occurred on a strike/slip fault, a vertical fault where one side moves horizontally against the other, similar to the kind of movement experienced along the San Andreas Fault in California.
That said, he said he 'does not believe' the quake is seismically tied to the recent 'swarm' of smaller earthquakes in the Yellowstone National Park.

But even if the Yellowstone Supervolcano would erupt, 'it's most likely to be a lava flow, as occurred in nearly all the 80 eruptions since the last 'supereruption' 640,000 years ago,' said Jacob Lowenstern from Yellowstone Volcano Observatory (YVO). 'A lava flow would be a big deal at Yellowstone, but would have very little regional or continental effect.'

Still, his own research paints a different picture: The last full-scale eruption of the Yellowstone Supervolcano, the Lava Creek eruption which happened approximately 640,000 years ago, ejected approximately 1,000 cubic kilometers of rock, dust and volcanic ash into the sky[1]. Ash spread over many tens of thousands of square kilometers[2].

Scientists believe that three super-eruptions have occurred in the past on a 600,000-700,000 year cycle, starting around 2.1 million years ago. The last huge eruption is thought to have occurred around 640,000 years ago. Do the math yourself.

Sleep well Americans. Nothing to worry about.

[1] Lowenstern et al: Steam Explosions, Earthquakes, and Volcanic Eruptions—What’s in Yellowstone’s Future? in U.S. Geological Survey: Fact Sheet – 2005
[2] Mastin et al: Modeling ash fall distribution from a Yellowstone supereruption in G3 - Geochemistry, Geophysics, Geosystems - 2014

Tree rings help dating eruption of Icelandic volcano

Iceland is now mostly treeless and barren, but there was a time when the island was covered with forests. Early settlers, who arrived in the late 9th century, harvested most of the trees they found on the island to establish an agricultural-based society.
In 2003, a spring flood of the Thverá River exposed hundreds of birch trees which had been buried for centuries beneath layers of volcanic sediment. The so-called Drumbabót forest is the best-preserved prehistoric forest in Iceland, and had been buried by an eruption of the nearby Katla volcano.

Large volcanic eruptions can be the cause of prolonged lower temperatures, but only with a precise date of eruption can researchers definitively account for the variability in climate. Thee rings contain information which can be used to reconstruct past climate conditions,
The trees that were uncovered in 2003 were studied by a team of researchers[1]. They were able to pinpoint the eruption date of the Katla volcano between late 822 and early 823, decades before the earliest settlers arrived.

The same team have previously confirmed that in 775 a large solar flare caused a spike in radiocarbon levels in the Earth’s atmosphere, which would be stored in the wood of trees that were alive at the time[2]. By measuring the radiocarbon levels in one of the Drumbabót trees, Ulf Büntgen and his colleagues were able to pinpoint the year 775 in the tree rings, and measure outward to the bark to count the number of years to the Katla eruption, when the tree died. The outermost tree ring had completely formed and a new one had not yet started, meaning that the eruption occurred after autumn 822 and before spring 823, before the next year’s growth had begun. Iceland was not settled until around 870, so this particular forest was destroyed almost half a century before humans arrived.

The unique tree ring results were then linked with those of co-authors Professors Christine Lane and Clive Oppenheimer. Lane and Oppenheimer used independent lines of ash (tephra) and ice core evidence to detect fingerprints of the Katla eruption.

The team also involved historians who analysed written documentary evidence from Europe and Asia, and found that there was a severe cold spell consistent with the timing of the reconstructed Katla eruption.

[1] Büntgen et al: Multi-proxy dating of Iceland’s major pre-settlement Katla eruption to 822-823 CE in Geology – 2017
[2] Büntgen et al: Extraterrestrial confirmation of tree-ring dating in Nature Climate Change - 2014

The Moon and Earthquakes

We all known that the moon is responsible for the Earth's  tides, which are strongest when the sun and moon are aligned, during a full moon or a new moon. That same pull of the moon is also affecting the earths crust.
[Foto: Nicolette van Berkel]
For years, scientists have speculated whether the moon might play a role in earthquakes. It would make sense that the moon’s gravity could tug at a fault in the crust, especially one that is already close to failing and slipping. But nobody had demonstrated firm evidence for this.

Studying data from the past two decades, researchers measured the timing of high tides and reconstructed the amplitude of the moon’s pull at those times, focusing on the two weeks prior to large earthquakes[1]. They measured the amplitude of the tides against the timing of those quakes, and found some of the largest and most devastating earthquakes in recent memory happened when the Earth’s crust was under the highest tidal stress. They found that very large earthquakes, including the 2004 Indian Ocean (magnitude 9,3 with tsunami), 2010 Maule earthquake in Chile (magnitude 8.8) and the 2011 Tohoku-Oki earthquake in Japan (magnitude 9.1 with tsunami), tend to occur near the time of maximum tidal stress amplitude.

The mechanisms underlying this connection are not entirely clear. The moon’s pull causes tidal disruptions that are far lower than those experienced in an earthquake. And not every change in tide comes with an earthquake and not every earthquake comes with a change in tide. Part of the problem is that scientists still don’t know exactly what causes a major earthquake. But one theory is that they begin as smaller fractures that build up via a cascading process, where the moon is constantly pulling.

Research also found that both small and major earthquakes are not always triggered by the moon[2]. But some of them might be, and so we’d do well to pay closer attention to the subtle yet powerful ways in which the moon exerts its influence on our planet.

[1] Ide et al: Earthquake potential revealed by tidal influence on earthquake size–frequency statistics in Nature – 2016. See here.
[2] Van der Elst et al: Fortnightly modulation of San Andreas tremor and low-frequency earthquakes in PNAS - 2016

Fossilised tree helps date volcanic eruption 1,000 years ago

The ‘Millennium Eruption’ of Changbaishan (also known as Mount Paektu). The volcano is located on the border between China and North Korea. The eruption ranks among the largest medieval volcanic eruptions. It produced a widely-dispersed tephra layer. It was however unknown when this eruption precisely occured, with estimates spanning at least the tenth century CE.
Now, a team of scientists has analysed the partly fossilised remains of a tree killed by the eruption[1]. The tree was 264 years old when it was killed and buried by a flow of larva, hot ashand pumice. They knew that the tree must have been standing in 775 AD – a year that was marked by a burst of cosmic rays reaching the Earth – and this event was detected in the tree rings. Correlating ice core data made it certain that the eruption occurred in the last two or three months of 946 AD.

This secure date rules out the possibility that the 'Millennium Eruption' contributed to the collapse of the Bohai Kingdom (Manchuria/Korea) in 926 AD, as has previously been hypothesised. Further, despite the magnitude of the eruption, the data did not show a consequent cooling signal in tree-ring-based reconstructions of Northern Hemisphere summer temperatures.

Lead author, Clive Oppenheimer says: "The Millennium eruption has fascinated scientists and historians for decades because of its size, potential worldwide impacts, and the mystery surrounding when it actually happened. Lacking a clear historical record of the event, there have been dozens of attempts to date the eruption using conventional tree ring techniques. We got lucky thanks to the burst of cosmic radiation that bathed the Earth in the year 775. It was only recently recognised that this left a worldwide signature in trees alive at the time. Now we have a secure date for the eruption at last, we can be more confident in investigating the effects it has on the climate, environment and society."
The new date focuses attention on a chronicle from a temple in Japan that reports "white ash falling like snow" on the 3rd November 946 AD. This site is not near any of Japan's active volcanoes, and is close to where ash from the Millennium eruption has recently been identified in lake sediments. It may well pinpoint the actual date of the eruption since it would only have taken the ash clouds a day or so to reach Japan.

Changbaishan is a site revered by the Koreans. It is steeped in folklore and Koreans see it as their spiritual and ancestral home. Its eruption in 946 AD was one of the most violent of the last two thousand years and is thought to have discharged around 100 cubic kilometers of ash and pumice into the atmosphere - enough to bury the entire UK knee deep.

[1] Oppenheimer et al: Multi-proxy dating the ‘Millennium Eruption’ of Changbaishan to late 946 CE in Quaternary Science Reviews – 2017

[Review] Classical Traditions in Science Fiction

'Classical Traditions in Science Fiction' (edited by Brett M. Rogers and Benjamin Eldon Stevens) is a book that contains 14 essays by scholars of the classics, Greek, English, and philosophy. The essays explore connections between Jules Verne and the Greek satirist Lucian; Dune and the Iliad; Alien Resurrection and the Odyssey; antiquity and Western identity in Battlestar Galactica; the Iliad and Dan Simmons’ Ilium; The Hunger Games and the Roman Empire; and the graphic novel Pax Romana, which explores the transition from antiquity to a Christian world.

The term 'science fiction' is inherently vague and finding an all encompassing definition proves surprisingly elusive. Adam Roberts’ dictum that science fiction is 'premised on a material, instrumental version of the cosmos,' in contrast to its close ally, fantasy, which concerns 'magic, the supernatural, the spiritual.' Alternately, Susan Sontag summed up the whole genre as consisting of the 'imagination of disaster,' a fascination with dread of irresistible destruction.

At first science fiction did keep itself busy with 'novel ideas' about a possible future as dictated by Adam Roberts. Yet, the next wave of SF consisted of visions of a drab and depressing future as summed up by Susan Sontag. During the Victorian era, the world was changing fast, for some too fast. When extrapolated, the rapid industralisation with its smog and crumbling institutions, could herald an apocalypse in the future.

To be literature, one school of thought goes, a science fiction novel must be depressing, ginging an account of hubris and failure, such as George Orwell’s 1984. Some consider Mary Shelley’s Frankenstein the first science fiction: the optimism that drives scientific advance is thwarted by that unreliable factor, the human element.

Jesse Weiner’s essay “Lucretius, Lucian, and Mary Shelley’s Frankenstein” gives a thorough account of the book’s debate with the ancients, its later influence, and Shelley’s ambivalence about scientific progress.

But Frankenstein is subtitled The Modern Prometheus. Shelley drew upon the myth of Prometheus, who steals fire from the gods and is condemned to eternal damnation. Dr. Frankenstein is seeking higher human knowledge, the secret to the spark of life, and pays dearly for it.

'Classical Traditions in Science Fiction' is a book that contains a fascinating collection of essays that gives readers a new understanding of the place of science fiction within the Western literary tradition. Science fiction certainly harks its history back to classical Greek literature. Well worth your time. 

Largest impact crater near Falklands Islands?

Some 66 million years ago a comet struck the earth near Yucatan in modern day Mexico. The impact was so devastating that it heralded the end of the dinosaur. Evidence of that impact is the 200-kilometer diameter Chicxulub impact crater discovered in and near the Yucatan in the late 1970s.

But the earth has witnessed many more mass extinctions, the largest of them being the Permian–Triassic (P–Tr) extinction event, which occurred about 252 million years ago. It formed the boundary between the Permian and Triassic geologic periods, as well as the Paleozoic and Mesozoic eras. This mass extinction killed 90% to 96% of all species.

So, the question is: where is that impact crater?

A very large 250 to 300 kilometers wide circular geophysical anomaly (visible both in gravity and magnetic maps) is has been discovered on the Falkland Plateau to the northwest of West Falkland Island in the southern Atlantic Ocean[1][2].
The scientists point to specific features that indicate the basin is an impact crater. They note that it is completely buried by sediments from more recent eras, which indicates it was formed long before its surroundings, and that it has no topographic expression on the present sea floor. Key to the basin’s identification as a potential impact crater are the decrease in the strength of Earth’s gravity over the site, indicating a large basin filled with younger low-density sediments and a strong increase in the strength of Earth’s magnetism at the site. The latter is characteristic of large impact structures, such as the Chicxulub impact crater discovered in the Yucatan.

If the Falklands basin is really an impact crater, and it has some of the most telling features, then it is one of the largest known. The scientists estimate the age of the basin to be from the late Paleozoic Era–approximately 270 to 250 million years ago.

[1] Rocca, Presser: A possible new very large impact crater in Malvina Islands in Historia Natural – 2015
[2] Rocca et al: Geophysical evidence for a large impact structure on the Falkland (Malvinas) Plateau in Terra Nova - 2017

Mount Etna had glaciers during last Ice Age

The Mediterranean mountains were repeatedly glaciated during the last Ice Age which ended around 11,500 years ago[1]. Glaciers were present in most of the major mountainous areas from Morocco in the west to the Black Sea coast of Turkey in the east.

Some mountains supported extensive ice caps and ice fields with valley glaciers tens of kilometers long. Other massifs sustained only small-scale ice masses, although this was the exception rather than the norm. Glaciers still exist today and there is evidence that small glaciers were a common sight in many regions during the Little Ice Age.
The Mediterranean mountains are important for palaeoclimate research because of their position in the mid-latitudes and sensitivity to changes in the climate regimes of adjacent areas including the North Atlantic. These mountains are also important areas of biodiversity and long-term biological change through the Quaternary ice age.

Mount Etna (3329 meters) on Sicily is by far the highest mountain on the Mediterranean islands and one of the highest mountains in the entire region, yet clear evidence of glaciation has been buried by lava flows or obliterated by explosive volcanic activity, perhaps most recently in the Late glacial[2].
[U-shaped valley on the slope of Mt. Etna]

However, this volcano would have certainly been glaciated[3][4]. Researchers estimated a Pleistocene snowline of circa 2500 meter and other scientists have identified morphological evidence of a glacial valley on the northeastern flank of mount Etna[5]. They think it is reasonable to hypothesize that, during the Quaternary glaciation, a portion of the volcanic edifice could have been covered by thick ice sheets that excavated U-shaped valleys along their pathway. They have found this kind of evidence only in a small valley located in this area, that the scientists interpret to be of glacial origin.

[1] Hughes, Woodward (eds): Quaternary Glaciation in the Mediterranean Mountains – 2017
[2] Albert et al: Late glacial explosive activity on Mount Etna: Implications for proximal–distal tephra correlations and the synchronisation of Mediterranean archives in Journal of Volcanology and Geothermal Research - 2013
[3] Neri et al: Incidenza dei ghiaccia pleistocenici nell’evoluzione morfo-strutturale del Vulcano Etna (Sicilia, Italia) in Terra Glacialis - 2002
[4] Neri et al: Ghiacciai pleistocenici dell’Etna: un problema aperto in Istituto Lombardo, Accademia di Scienze e Lettere (Rendiconti Scienze) - 1994
[5] Carveni et al: First finding of glacial morphology on Mt. Etna volcano north-eastern flank (Sicily) in Geoitalia - 2007

When did humans first alter the global climate?

Palaeoclimatologist Professor William Ruddiman has been working on a hypothesis that posits that pre-industrial age humans raised greenhouse gas levels in the atmosphere. Looking back seven thousand years into the Holocene - the current 11,500-year-old geological epoch - Ruddiman has proposed that early agriculture emitted enough methane and carbon dioxide to offset what would have been a global cold cycle[1].
He began his thinking about early agriculture and greenhouse gases in the late 1990s when new data from Greenland and Antarctic ice cores was made public. Examining the data, Ruddiman was puzzled by the rise of atmospheric methane around 3000 BC.

In the glacial cycles of the past four hundred thousand years, this natural methane emissions rate is linked with the earth’s approximate 22,000 years precession cycle, the orbital cycle in which the earth shifts its axis of orbit. When the northern hemisphere summer is closest to the sun via precession, the highest amount of global methane is emitted. In the current interglacial precessional cycle, the methane maximum occurred eleven thousand years ago, at which there was the expected 700 parts per billion (ppb) methane concentration in the atmosphere—expected because comparable interglacial periods have that methane level.
However, at around five thousand years ago, Ruddiman noted that instead of continuing downward to a 450 ppb level, the methane leveled off at 560 ppb, and, reversing course, rose to around 660 ppb by one thousand years ago. Ruddiman correlated the methane trajectory reversal with rice paddy agriculture in Asia, which intensified roughly around the same time, five thousand years ago. After harvesting, the rice paddy areas emit methane in a similar manner to that of natural wetlands’ organic decomposition.

Ruddiman says that in contrast to the familiar view that human-caused greenhouse gases began with the industrial revolution, “the baseline of human effects on climate started earlier and that the total effect is larger.”

He is arguing that the significant footprint of human add-on to climate began thousands of years ago and not just 150 years or so, which is still the conventional view[2]. Even today climate scientists are not in total agreement as to whether early agriculture had a significant impact on global climate. Nonetheless, support for Ruddiman’s hypothesis has broadened in recent years [3].

Ruddiman: How Did Humans First Alter Global Climate? in Scientific American – 2005
Ruddiman et al: Does Pre-industrial Warming Double the Anthropogenic Total? in Anthropocene Review -2014
Ruddiman et al: Late Holocene climate: Natural or anthropogenic? in Reviews of Geophysics – 2016

Famine in Switzerland during 1816 and 1817

The aftermath of the 1815 eruption of Mount Tambora caused widespread famine during 1816 and 1817. Studies often look at rising mortality rates and declining birth rates to measure famine. While it is an indirect indicator, it does convey a sense of the intensity of the hardship[1]. Switzerland has been the subject of several studies on the subject.
A decreasing number of baptisms in Switzerland showed the severity of the crisis. During famines, a scissor-like demographic change could be observed in the rising mortality rate and decreasing number of baptisms. Over a long-term perspective, annual birth rates do not fluctuate as strongly as annual mortality rates, and researchers therefore regard birth rates as the more reliable indicator. A cohort census from the year of 1860 enabled the reconstruction of the development of the cohort at a district level in the entire nation.

Vulnerability in the famine years proved to be dynamic rather than static: in the first year of the crisis, the climate-sensitive wine-growing regions by the large lakes of the Swiss Plateau, the cities, and the canton of Bern were particularly vulnerable. In the second year, the crisis moved to eastern Switzerland and the valleys of the Jura, where the jewelry and watchmaking industry had expanded. Statistically seen, while only sufficient food was lacking in western Switzerland, a true famine prevailed in eastern Switzerland.

Single communities lost around one ninth of their population, not even counting emigration. It was very likely “the worst demographic crisis since the pest of 1629”[2].
The famine also affected the development of the average body height. The body is very sensitive to crises during its growth phase, since the uptake of nutrients was still very dependent on the economic conditions during the beginning of the 19th century. The average body height of persons born between 1800 and 1809 decreased significantly in parts of Switzerland. They suffered from both the previous Napoleonic Wars (1803-1815) as well as the famine (1816-1817).

Surprisingly, the average body height of the middle class decreased more than that of the lower class. It is possible that they were less likely to request help in overcoming the crisis than members of the lower classes, due to a fear of social stigmas. A similar scenario occurred in Swiss cities a good hundred years later during the First World War[3].

The crisis of 1817 had considerable demographic effects. On the one hand, the mortality rate increased, on the other hand the birth rate decreased. Some communities lost up to one ninth of their population.

[1] Krämer: Menschen grasten nun mit dem Vieh: Die letzte grosse Hungerkrise der Schweiz 1816/17 – 2015
[2] Schürmann: Bevölkerung, Wirtschaft, und Gesellschaft in Appenzell Innerrhoden im 18. und frühen 19. Jahrhundert. Appenzell – 1974
[3] Staub: Der vermessene menschliche Körper als Spiegel der Ernährungs- und Gesundheitsverhältnisse am Ende des Ersten Weltkrieges - 2016

Tambora and 'Darkness'

Tambora, on the island of Sumbawa, Indonesia—then the Dutch East Indies—began its week-long eruption on April 5, 1815. Volcanic ash circulated in the upper atmosphere for years after the event, blocking out sunlight and lowering averages surface temperatures globally and 1816 became known as the 'Year without Summer'.
In 1816, there was snow in New England in July and dark rain clouds swept over Europe throughout the summer months. Hungary reported brown snowfall, tainted by volcanic ash. With the cold came crop failures and famine. Food shortages compounded those already in place in the wake of the Napoleonic wars after retreating armies had helped themselves to whole harvests Leo Tolstoy in 'War and Peace' (1869), offers an vivid image of “... a splendid field of oats in which a camp had been pitched and which was being mown down by the soldiers, evidently for fodder.”.

But these bleak circumstances hit hardest in and around the Alpine regions of France, Germany, Austria, and Switzerland.

In April 1816, Mary Shelley traveled to Geneva, accompanied by her half sister, Claire Clairmont and her lover, Percy Shelley. Claire was eager to rekindle a romance with another British literary exile, Lord Byron.
The perpetual gloominess of what should have been summer skies inspired Byron to compose his miserable poem “Darkness,” in which the sun is permanently extinguished, and mankind dies:
I had a dream, which was not all a dream.
The bright sun was extinguish'd, and the stars
Did wander darkling in the eternal space,
Rayless, and pathless, and the icy earth
Swung blind and blackening in the moonless air;
Morn came and went and came, and brought no day,

During that same sunless summer Byron wrote another grim poem, “Prisoner of Chillon”. It delivered the same depressing feeling:
First came the loss of light, and air,
And then of darkness too:
For all was blank, and bleak, and grey;
It was not night it was not day;

Volcanism in Ethiopia speeded early human evolution

The Ethiopian Rift Valley hosts the longest record of human co-existence with volcanoes on Earth. Dramatic and rapid changes from volcanic activity in Ethiopia appear to have set the stage for the emergence of Homo sapiens around 200,000 years ago. According to new research, the first known fossil evidence for our species was unearthed there, where explosive volcanic activity was dramatically changing the landscape and environment[1].
"Pyroclastic flows -- hot currents of gas, ash and rock -- would have inundated large tracts of the rift floor while ash and pumice fallout from larger plumes are likely to have covered regions to at least 100 kilometers from the vent," commented lead author William Hutchison of the University of Oxford's Department of Earth Sciences.

The earliest humanoid fossils date to 195,000 years ago, so early humans likely witnessed the eruptions. Hutchison said that the volcanic eruptions occurred along the entire East African Rift System, which is a still-active continental rift where Africa is slowly being pulled apart. One segment runs through Ethiopia. Hutchison and his team reconstructed the eruptive history of a 124-mile-long segment of the rift in Ethiopia by studying the Aluto and Corbetti volcanoes. The researchers tried to determine the dates of erupted rocks. They also analyzed the sizes of eruptions along the rift over time.
"We suggest that an increased flux of melt from the mantle into the crust generated the large magma chambers that over-pressured and erupted 320,000–170,000 years ago," Hutchison said. "These events are called flare-ups."

“Major volcanic eruptions and the environmental devastation that followed might have greatly reduced hominid populations living in the rift zone," Hutchison said. "The eruptions themselves would have made certain sections of the rift uninhabitable, potentially for many thousands of years. These mechanisms provide a means of reducing and isolating certain populations which might have promoted human adaptation and evolution at this time."

"This suggests," he added, "that our earliest ancestors not only had to deal with changing climate but also with the environmental devastation caused by major explosive eruptions."

Earlier research supports that the region was already heavily populated with hominins long before our species emerged on the scene. Lucy (Australopithecus afarensis) was the only potential human ancestor species that roamed in what is now the Afar region of Ethiopia.

[1] Hutchison et al: A pulse of mid-Pleistocene rift volcanism in Ethiopia at the dawn of modern humans in Nature Communications – 2016

Africa's Deadly Lakes

Let us start with a definition: a limnic eruption is a rare event in which dissolved carbon dioxide (CO2) suddenly erupts from deep lake waters, forming a cloud of exsolved gas that can suffocate wildlife, livestock and humans. Scientists believe earthquakes or volcanic activity can trigger for such phenomenon.
To date, this phenomenon has been observed only twice. The first was in 1984 at Lake Monoun (Cameroon), causing the asphyxiation and death of 37 people living nearby[1]. The event was associated with a landslide from the eastern crater rim, which slumped into deep water. A second, decidedly deadlier eruption happened in 1986 at neighbouring Lake Nyos, a deep lake high on the flank of an inactive volcano. This time the eruption released over 80 million cubic meters of CO2 and killing around 1,746 people and 3,500 livestock, again by asphyxiation[2].

While data indicate a volcanic source of the carbon dioxide, the gas is probably gradually build-up and not able to rise to the surface because of thermal layers in the water. The carbon dioxide is hovering near saturation and an earthquake or volcanic activity may suddenly alter the status quo. The thermal layers of cold and warmer waters are disturbed and the dissolved carbon dioxide is released.

Lake Monoun and Lake Nyos are relatively small lakes but other much larger density-stratified equatorial lakes might potentially harbour much more danger. Lake Kivu in east Africa, has a methane and carbon dioxide gas content that is higher by two to four orders of magnitude than that of the Cameroon lakes.
A gas burst from Lake Kivu in Rwanda - with two million people living nearby - would form a carbon dioxide and methane cloud up to 340 cubic kilometers in volume and expansion of the exsolving gas from deep water to atmospheric pressure would correspond to an energy release equivalent to 8 megatons of explosive[3]. Which is quite a large explosion.

[1] Sigurdsson et al: Origin of the lethal gas burst from Lake Monoun, Cameroun in Journal of Volcanology and Geothermal Research – 1987
[2] Kling et al: The 1986 Lake Nyos Gas Disaster in Cameroon, West Africa in Science – 1987
[3] Sigurdsson: Gas bursts from Cameroon crater lakes: a new natural hazard in Disasters - 1988

The eruption of Laki (1783)

Laki or more correct Lakagígar (Craters of Laki) is a volcanic fissure in the south of Iceland. On 8 June 1783, a fissure with 130 craters opened with earthquakes and explosions when groundwater interacted with the rising basalt magma. The eight-month emission of sulfuric aerosols resulted in one of the most dramatic climatic and societal events in historic times[1].

The eruption produced huge amounts of basalt and tephra. Gases were climbing to altitudes of about 15 km. These gasses, including millions of tons of hydrogen fluoride and sulfur dioxide, gave rise to what has since become known as the 'Laki haze' across Europe.
For two years following the initial explosions, Europe, North America and north Africa experienced bizarre weather phenomena. Within days, the haze produced by ash and smoke from Laki turned the sun blood red across Iceland. By June 10, ash was falling in Norway that withered tree leaves and grass in Bergen on the southwestern coast. That same day, in Denmark black ash discolored the sails and decks of ships as they approached the harbor.

Meanwhile, the haze – also referred to as 'dry fog' – spread swiftly across Europe. It arrived in Prague on June 16. On the 17th, the sun turned blood red in Berlin and on June 18, the haze appeared in Lyon, France:

“The fog was cold and humid, with the wind coming from the south and one could with eye look at the sun with a telescope without a blackened lens. The fog was such as the oldest men here have not seen before…”

That same day the haze covered Padua, Italy. Clearly, it was quite different from the ordinary fog the locals were used to. They wrote that it smelled of sulfur and that it withered the grass. In England, on June 23, a clergyman in Hampshire noted that the vegetation was yellow and looked “as if scorched with frost.” All of this makes it clear that the fog carried with it sulfur dioxide from Laki’s eruption.

By the end of June, the haze covered virtually all of Europe. In St. Petersburg, people recorded the dry fog on June 26. By June 30, it had reached Moscow. In central Asia, visitors reported unseasonable frosts throughout the summer as the haze kept the sun from warming the earth.
North Africans were also taking notice of the odd “cloud.” By the end of June it arrived in Tripoli, then in Syria. By July, the haze extended into Baghdad and the Altai Mountains.

In Egypt, it was noticed that the summer of 1783 was radically different from most summers in Egypt. Every spring the Nile River flooded, leaving behind wet, fertile soil in which the Egyptians grew their crops. However, that year the inundation was not sufficient. With no flood, the crops failed, with drastic consequences for the Egyptians.

The bizarre weather patterns triggered by Laki’s explosion meant that the monsoon that year was abnormally weak. In turn, this led to a severe droughts in India and Egypt. As a result of that drought, the Nile didn’t flood.

Egypt, so distant from Iceland, suffered the largest number of deaths in the wake of Laki’s eruption. Historians estimate that the population of Egypt was reduced by one sixth in the resulting famine.

The effects of the eruption lingered across North America and Europe as well. Parish records in England show a large increase in the number of deaths in July and August of 1783, presumably from respiratory illnesses caused by the haze.

In North America, the winter following the eruption was extremely cold and very long. The harbour in Charleston, North Carolina froze so hard that men and women could skate across it. In February 1784, ice floated down the Mississippi River to New Orleans and out into the Gulf of Mexico where it lingered, not melting.

In Iceland, a disease that caused the skin and flesh to rot off the living animals as they grazed in the fields. The symptoms were those of chronic fluorosis: the grazing livestock were poisoned because they ate vegetation that had been contaminated with fluorine as a result of the volcanic fallout.

Within days, the animals most severely affected were dead. Within a few months over 60% of all livestock in Iceland died, leaving the Icelanders to face the winter of 1783-84 without a proper food supply. The ongoing eruption, the colder than usual summer and the fallout of ash and poisonous haze meant that few if any crops could be saved. As a result, between 1783 and 1786 approximately 20% of the population of Iceland died of starvation and disease. This period is known in Icelandic as moðuharðindin, the 'Mist Hardships'.

[1] Thordarson and Self: Atmospheric and environmental effects of the 1783–1784 Laki eruption: A review and reassessment in Journal of Geophysical Research - 2003