̽��ֱ�� of Cambridge - Clive Oppenheimer

Medieval monks accidentally recorded some of history’s biggest volcanic eruptions

sc604 — Wed, 05 Apr 2023 14:58:42 +0000

An international team, including researchers from the ̽��ֱ�� of Cambridge, drew on readings of medieval texts, along with ice core and tree ring data, to accurately date some of the biggest volcanic eruptions the world has ever seen. Their results, reported in the journal Nature, uncover new information about one of the most volcanically active periods in Earth’s history, which some think helped to trigger the Little Ice Age, a long interval of cooling that saw the advance of European glaciers.

It took the researchers, led by the ̽��ֱ�� of Geneva (UNIGE), almost five years to examine hundreds of annals and chronicles from across Europe and the Middle East, in search of references to total lunar eclipses and their colouration.

Total lunar eclipses occur when the moon passes into the Earth’s shadow. Typically, the moon remains visible as a reddish orb because it is still bathed in sunlight bent round the Earth by its atmosphere. But after a very large volcanic eruption, there can be so much dust in the stratosphere – the middle part of the atmosphere starting roughly where commercial aircraft fly – that the eclipsed moon almost disappears.

Medieval chroniclers recorded and described all kinds of historical events, including the deeds of kings and popes, important battles, and natural disasters and famines. Just as noteworthy were the celestial phenomena that, to the chroniclers, might foretell such calamities. Mindful of the Book of Revelation, a vision of the end times that speaks of a blood-red moon, the monks were especially careful to take note of the moon’s colouration.

Of the 64 total lunar eclipses that occurred in Europe between 1100 and 1300, the chroniclers had faithfully documented 51. In five of these cases, they also reported that the moon was exceptionally dark.

Asked what made him connect the monks’ records of the brightness and colour of the eclipsed moon with volcanic gloom, the lead author of the work, UNIGE’s Sébastien Guillet said: “I was listening to Pink Floyd's Dark Side of the Moon album when I realised that the darkest lunar eclipses all occurred within a year or so of major volcanic eruptions. Since we know the exact days of the eclipses, it opened the possibility of using the sightings to narrow down when the eruptions must have happened.”

̽��ֱ��researchers found that scribes in Japan took equal note of lunar eclipses. One of the best known, Fujiwara no Teika, wrote of an unprecedented dark eclipse observed on 2 December 1229: ‘the old folk had never seen it like this time, with the location of the disk of the Moon not visible, just as if it had disappeared during the eclipse... It was truly something to fear.’

̽��ֱ��stratospheric dust from large volcanic eruptions was not only responsible for the vanishing moon. It also cooled summer temperatures by limiting the sunlight reaching the Earth’s surface. This in turn could bring ruin to agricultural crops.

“We know from previous work that strong tropical eruptions can induce global cooling on the order of roughly 1°C over a few years,” said Markus Stoffel from the ̽��ֱ�� of Geneva, a specialist in converting measurements of tree rings into climate data, who co-designed the study. “They can also lead to rainfall anomalies with droughts in one place and floods in another.”

Despite these effects, people at the time could not have imagined that the poor harvests or the unusual lunar eclipses had anything to do with volcanoes – the eruptions themselves were all but one undocumented.

“We only knew about these eruptions because they left traces in the ice of Antarctica and Greenland,” said co-author Professor Clive Oppenheimer from Cambridge’s Department of Geography. “By putting together the information from ice cores and the descriptions from medieval texts we can now make better estimates of when and where some of the biggest eruptions of this period occurred.”

To make the most of this integration, Guillet worked with climate modellers to compute the most likely timing of the eruptions. “Knowing the season when the volcanoes erupted is essential, as it influences the spread of the volcanic dust and the cooling and other climate anomalies associated with these eruptions,” he said.

As well as helping to narrow down the timing and intensity of these events, what makes the findings significant is that the interval from 1100 to 1300 is known from ice core evidence to be one of the most volcanically active periods in history. Of the 15 eruptions considered in the new study, one in the mid-13th century rivals the famous 1815 eruption of Tambora that brought on ‘the year without a summer’ of 1816. ̽��ֱ��collective effect of the medieval eruptions on Earth’s climate may have led to the Little Ice Age, when winter ice fairs were held on the frozen rivers of Europe.

“Improving our knowledge of these otherwise mysterious eruptions, is crucial to understanding whether and how past volcanism affected not only climate but also society during the Middle Ages,” said Guillet.

̽��ֱ��research was supported in part by the Swiss National Science Foundation.

Reference:
Sébastien Guillet et al. ‘Lunar eclipses illuminate timing and climate impact of medieval volcanism.’ Nature (2023). DOI: 10.1038/s41586-023-05751-z

By observing the night sky, medieval monks unwittingly recorded some of history’s largest volcanic eruptions, according to a new analysis of 12th and 13th century European and Middle Eastern chronicles.

Recueil de poésies françaises. Consolation de Boèce, Ms. 822, fol. 61v, Bibliothèque Municipale de Toulouse /Gallica, BnF

An illuminated manuscript from the late 14th to the early 15th century, depicting two individuals observing a lunar eclipse

̽��ֱ��text in this work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

Yes

Lava from 2021 Icelandic eruption gives rare view of deep churnings beneath volcano

cmm201 — Fri, 16 Sep 2022 14:30:00 +0000

̽��ֱ��study, published in the journal Nature and led by the ̽��ֱ�� of Iceland, reports that the eruption was unusual because it was supplied by a particularly deep reservoir of magma originating around 15 kilometres beneath the surface, at the base of Earth’s crust.

Their results also show that volcanoes like this can be fed by complex plumbing systems, where different batches of magma can mix and travel to the surface in just a matter of days or weeks.

̽��ֱ��researchers took measurements of lava and volcanic gases during the first 50 days of the eruption — giving them a near-real time report on the changing magma supply.

“I never expected to see the chemical composition of erupting lava change this quickly, showing us just how fast things can change in the depths beneath volcanoes,” said Simon Matthews from the ̽��ֱ�� of Iceland.

̽��ֱ��chemical fingerprint of lavas and the crystals inside them — together with the volcanic gases erupted — helped the researchers decode where the magma originated from and its journey to the surface. Until now, there has been a lack of information about the deepest parts of magmatic systems.

̽��ֱ��results showed that, during the initial phases of the eruption, the lava was predominately coming from around the boundary between the crust and underlying mantle – the thick, rocky layer that makes up most of Earth’s interior. But over the following weeks, the composition of the lava changed, indicating the eruption was directly tapping magma from greater depths.

“Ever since Enlightenment thinkers started writing about volcanoes, scientists have drawn cross-sections to visualise how they might work below ground,” said co-author Professor Clive Oppenheimer from Cambridge’s Department of Geography. “This study draws together different strands of information from monitoring the chemistry of lava and gas emissions to describe what is happening up to 20 kilometres down.”

They used indicators including the magnesium contents of the lava and carbon dioxide levels in the volcanic gases as barometers to gauge how hot and deep the magma feeding the eruption was. They suggest that, for the magma to come from 15 kilometres below the surface, the eruption was fed by something like a high-speed train direct to the mantle.

“We’ve known for a while that magma coming from the mantle is variable,” said co-author Professor John Maclennan from Cambridge’s Department of Earth Sciences, “But we’ve had to work hard to find clues as to how this complex mixing happens.”

̽��ֱ��authors point out that it has long been argued that different kinds of magma can mix deep in magmatic systems before an eruption. ̽��ֱ��new research shows that new magma can flow into a deep reservoir and mix with existing magma rapidly, in as little as 20 days.

Normally scientists use lavas erupted from old or extinct volcanoes to get a below ground view of volcanoes. But these samples are often too old to unravel processes happening over the course of a few days, “I’ve looked at hundreds of samples from dead volcanoes, but never had the chance to observe such a spectacular example of magma mixing in real-time,” said Maclennan.

Magma mixing has been shown to be an important process in triggering volcanic eruptions, so the study findings could have implications for understanding what drove the eruption and for future monitoring of volcanic activity in Iceland and at similar volcanoes.

Reference:
Sæmundur A. Halldórsson et al. ‘Rapid shifting of a deep magmatic source at Fagradalsfjall volcano, Iceland.’ Nature (2022). DOI: 10.1038/s41586-022-04981-x.

After centuries without volcanic activity, Iceland’s Reykjanes peninsula sprang to life in 2021 when lava erupted from the Fagradalsfjall volcano. New research involving the ̽��ֱ�� of Cambridge helps us see what is going on deep beneath the volcano by reading the chemistry of lavas and volcanic gases almost as they were erupted.

I’ve looked at hundreds of samples from dead volcanoes, but never had the chance to observe such a spectacular example of magma mixing in real-time

John Maclennan

Fagradalsfjall volcano

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

Yes

Earliest human remains in eastern Africa dated to more than 230,000 years ago

sc604 — Wed, 12 Jan 2022 15:28:02 +0000

̽��ֱ��age of the oldest fossils in eastern Africa widely recognised as representing our species, Homo sapiens, has long been uncertain. Now, dating of a massive volcanic eruption in Ethiopia reveals they are much older than previously thought.

̽��ֱ��testimony of trees: how volcanic eruptions shaped 2000 years of world history

sc604 — Mon, 28 Sep 2020 03:00:00 +0000

̽��ֱ��researchers, led by the ̽��ֱ�� of Cambridge, used samples from more than 9000 living and dead trees to obtain a precise yearly record of summer temperatures in North America and Eurasia, dating back to the year 1 CE. This revealed colder and warmer periods that they then compared with records for very large volcanic eruptions as well as major historical events.

Crucial to the accuracy of the dataset was the use of the same number of data points across the entire 2000 years. Previous reconstructions of climate over this extended period have been biased by over-representation of trees from more recent times.

̽��ֱ��results, reported in the journal Dendrochronologia, show that the effect of volcanoes on global temperature changes is even greater than had been recognised, although the researchers stress that their work in no way diminishes the significance of human-caused climate change.

Instead, the researchers say, the study contributes to our understanding of the natural causes and societal consequences of summer temperature changes over the past two thousand years.

“There is so much we can determine about past climate conditions from the information in tree rings, but we have far more information from newer trees than we do for trees which lived a thousand years or more ago,” said Professor Ulf Büntgen from Cambridge’s Department of Geography, the study’s lead author. “Removing some of the data from the more recent past levels the playing field for the whole 2000-year period we’re looking at, so in the end, we gain a more accurate understanding of natural versus anthropogenic climate change.”

Comparing the data from tree rings against evidence from ice cores, the researchers were able to identify the effect of past volcanic eruptions on summer temperatures.

Large volcanic eruptions can lower global average temperatures by fractions of a degree Celsius, with strongest effects in parts of North America and Eurasia. ̽��ֱ��main factor is the amount of sulphur emitted during the eruption that reaches the stratosphere, where it forms minute particles that block some sunlight from reaching the surface. This can result in shorter growing seasons and cooler temperatures, that lead in turn to reduced harvests. Conversely, in periods when fewer large eruptions occurred, the Earth is able to absorb more heat from the Sun and temperatures rise.

“Some climate models assume that the effect of volcanoes is punctuated and short,” said Büntgen. “However, if you look at the cumulative effect over a whole century, this effect can be much longer. In part, we can explain warm conditions during the 3^rd, 10^th and 11^th centuries through a comparative lack of eruptions.”

Reconstructed summer temperatures in the 280s, 990s and 1020s, when volcanic forcing was low, were comparable to modern conditions until 2010.

Compared with existing large-scale temperature reconstructions of the past 1200–2000 years, the study reveals a greater pre-industrial summer temperature variability, including strong evidence for the Late Antique Little Ice Age (LALIA) in the 6^th and 7^th centuries.

Then, working with historians, the scientists found that relatively constant warmth during Roman and medieval periods, when large volcanic eruptions were less frequent, often coincided with societal prosperity and political stability in Europe and China. However, the periods characterised by more prolific volcanism often coincided with times of conflict and economic decline.

“Interpreting history is always challenging,” said Dr Clive Oppenheimer, the lead volcanologist of the study. “So many factors come into play – politics, economics, culture. But a big eruption that leads to widespread declines in grain production can hurt millions of people. Hunger can lead to famine, disease, conflict and migration. We see much evidence of this in the historical record.

“We knew that large eruptions could have these effects, especially when societies were already stressed, but I was surprised to see the opposite effect so clearly in our data – that centuries with rather few eruptions had warmer summers than the long-term average.”

̽��ֱ��new temperature reconstructions provide deeper insights into historical periods in which climactic changes, and their associated environmental responses, have had an outsized impact on human history. This has clear implications for our present and future. As climate change accelerates, extreme events, such as floods, drought, storms and wildfires, will become more frequent.

“Humans have no effect on whether or not a volcano erupts, but the warming trend we are seeing right now is certainly related to human activity,” said Büntgen. “While nothing about the future is certain, we would do well to learn how climate change has affected human civilisation in the past.”

Reference:
Ulf Büntgen et al. ‘Prominent role of volcanism in Common Era climate variability and human history.’ Dendrochronologia (2020). DOI: 10.1016/j.dendro.2020.125757

Researchers have shown that over the past two thousand years, volcanoes have played a larger role in natural temperature variability than previously thought, and their climatic effects may have contributed to past societal and economic change.

Some climate models assume that the effect of volcanoes is punctuated and short. However, if you look at the cumulative effect over a whole century, this effect can be much longer.

Ulf Büntgen

Clive Oppenheimer

Driftwood in Siberia

Yes

Cambridge Science Festival returns for milestone 25th year

Anonymous — Fri, 25 Jan 2019 15:48:27 +0000

Celebrating its 25th year, the Festival runs for two weeks from 11-24 March and explores the theme of ‘discoveries’. An impressive line-up of acclaimed scientists includes microscopist Professor Dame Pratibha Gai, Astronomer Royal Professor Lord Martin Rees, 2018 Nobel prize winner Sir Gregory Winter, geneticist Dr Giles Yeo, statistician Professor David Spiegelhalter, engineer Dr Hugh Hunt, marine biologist and author Helen Scales, THIS Institute Director Professor Mary Dixon-Woods, futurist Mark Stevenson, and science presenter Steve Mould.

̽��ֱ��full programme is teeming with events ranging from debates, talks, exhibitions, workshops and interactive activities to films, comedy and performances, held in lecture theatres, museums, cafes and galleries around Cambridge. There are events for all ages and most are free.
With so many events on offer, audiences will be spoilt for choice. Some of the biggest events in week one include:

Is technology making us miserable? (11 March). Virtually every interaction we have is mediated through technology. Despite being ‘always-on’, are we any better off? Are we better connected? Or is technology making us miserable?
Putting radioactivity in perspective (12 March). Following a renewal of electricity generated by nuclear power, Professors Ian Farnan and Gerry Thomas, Imperial College London, discuss radioactivity in the natural world and the outcomes of decades of study on the health effects of radiation. Could these research outcomes reset attitudes towards radiation and the risks?
̽��ֱ��universe of black holes (13 March). Christopher Reynolds, Plumian Professor of Astronomy, describes how future research into black holes may yet again change our view of reality.
̽��ֱ��long-term perspective of climate change (14 March). Professors Ulf Büntgen, Mike Hulme, Christine Lane, Hans W Linderholm, Clive Oppenheimer, Baskar Vira, and Paul J Krusic discuss how we investigate past climate and the challenges we face in applying this to the policy-making process.
Catalytic activation of renewable resources to make polymers and fuels (15 March). Professor Charlotte Williams, ̽��ֱ�� of Oxford, discusses the development of catalysts able to transform carbon dioxide into methanol, a process which may deliver more sustainable liquid transport fuels in the future.
Does the mother ever reject the fetus? (15 March). Professor Ashley Moffett discusses fetal rejection and explores new discoveries that show that there are multiple mechanisms to ensure there is a peaceful environment in the uterus, where the placenta is allowed to grow and develop to support the fetus.

Top picks for the second week include:

Cambridge gravity lecture: Sir Gregory Winter (18 March). Sir Gregory is a molecular biologist and 2018 Nobel Laureate best known for his work on developing technologies to make therapeutic monoclonal antibodies. His research has led to antibody therapies for cancer, rheumatoid arthritis and multiple sclerosis.
Discoveries leading to new treatments for dementia (18 March). Professor of Clinical Neurosciences and Associate Director of the UK Dementia Research Institute, Giovanna Mallucci discusses how new research leading to insights into dementia and degenerative brain diseases may lead to new treatments.
Improving quality and safety in healthcare (19 March). THIS Institute Director Professor Mary Dixon-Woods looks at the challenges to improving quality and safety in healthcare and considers why it’s so hard to answer the question: Does quality improvement actually improve quality? With Dr Fiona Godlee, Editor in Chief of ̽��ֱ��BMJ.
Immunology: the future of medicine? (19 March) Professor Clare Bryant and a panel of Cambridge immunologists discuss how understanding disease triggers may enable entirely new approaches to treating and potentially preventing disease.
Polar ocean: the dead end of plastic debris (19 March). An estimated 80% of all the litter in our oceans is plastic, and a significant concentration of plastics debris is found in both polar oceans. ̽��ֱ��impact of this debris on the sensitive polar ecosystem could be profound. Pelagic marine ecologist Dr Clara Manno, British Antarctic Survey, explores the current research and existing situation in the polar regions.
Reluctant futurist (19 March). Old models for healthcare, education, food production, energy supply and government are creaking under the weight of modern challenges. Futurist Mark Stevenson looks at the next 30 years and asks, how can we re-invent ourselves for the future?
Adolescent mental health: resilience after childhood adversity (20 March). Adolescence is characterised by huge physiological changes as well as a rapid rise in mental health disorders. Around 45% of adolescent mental health problems are caused by childhood difficulties but fortunately not all who experience difficulties develop mental health disorders. Dr Anne-Laura van Harmelen discusses mechanisms that may help adolescents with a history of childhood difficulty to become more resilient.
Making algorithms trustworthy (21 March). Increasingly, algorithms are being used to make judgements about sensitive parts of our lives. How do we check how their conclusions were arrived at, and if they are valid and fair? Professor David Spiegelhalter looks at efforts to make algorithms transparent and trustworthy, using systems that make predictions for people with cancer as an example.
On the future: prospects for humanity (22 March). Professor Lord Martin Rees argues that humanity’s prospects on Earth and in space depend on our taking a different approach to planning for tomorrow.

This year’s Cambridge Science Festival also celebrates significant milestones in science, including the 200th anniversary of Cambridge Philosophical Society, Cambridge’s oldest scientific society, and 150 years since the publication of the modern Periodic Table.

Speaking ahead of the Festival, Dr Lucinda Spokes, Festival Manager, said: “We are tremendously proud of this year’s programme due to the variety of events and the calibre of our speakers from a range of institutions and industries.

“Alongside the meatier topics we have an array of events for all ages and interests across both weekends. We have everything from the science of perfumery and how your mood affects your taste, to a science version of 'Would I Lie to You?'

“One of my personal top picks are the open days at the various institutes and departments based at the West Cambridge site on Saturday 23 March. As always, the site is hosting some truly fascinating events, everything from the future of construction and how to make Alexa smarter, to how nanotechnology is opening up new routes in healthcare, and state-of-the-art approaches to low-cost solar energy and high-efficiency lighting solutions.

“A Festival of this magnitude would not be possible without the help from many people; we thank all our scientists, supporters, partners and sponsors, without whom the Festival would not happen. Most of all, we thank the audiences – there are more than 60,000 visits to the Festival events every year. We very much look forward to welcoming everyone from all ages to join us in March to explore the fabulous world of science.”

You can download the full programme here.

Bookings open on Monday 11 February at 11am.

This year’s Festival sponsors and partners are Cambridge ̽��ֱ�� Press, AstraZeneca, MedImmune, Illumina, TTP Group, Science AAAS, Anglia Ruskin ̽��ֱ��, Astex Pharmaceuticals, Cambridge Science Centre, Cambridge Junction, IET, Hills Road 6th Form College, British Science Week, Cambridge ̽��ֱ�� Health Partners, Cambridge Academy for Science and Technology, and Walters Kundert Charitable Trust. Media Partners: BBC Radio Cambridgeshire and Cambridge Independent.

̽��ֱ��2019 Cambridge Science Festival is set to host more than 350 events as it explores a range of issues that affect today’s world, from challenges around climate change policy, improving safety and quality in healthcare, and adolescent mental health, to looking at what the next 25 years holds for us and whether quantum computers can change the world.

We have everything from the science of perfumery and how your mood affects your taste, to a science version of 'Would I Lie to You?'

Dr Lucinda Spokes

Yes

Size matters: if you are a bubble of volcanic gas

sc604 — Mon, 06 Aug 2018 11:13:18 +0000

A team of scientists, including a volcanologist and mathematician from the ̽��ֱ�� of Cambridge, discovered the phenomenon through detailed observations of gas emissions from Kīlauea volcano in Hawaii.

At many volcanoes around the world, gas emissions are monitored routinely to help with forecasting eruptions. Changes in the output or proportions of different gases - such as carbon dioxide and sulphur dioxide – can herald shifts in the activity of a volcano. Volcanologists have considered that these chemical changes reflect the rise and fall of magma in the Earth’s crust but the new research reveals that the composition of volcanic gases depends also on the size of the gas bubbles rising up to the surface.

Until the latest spectacular eruption opened up fissures on the flank of the volcano, Kīlauea held a vast lava lake in its summit crater. ̽��ֱ��behaviour of this lava lake alternated between phases of fiery ‘spattering’ powered by large gas bubbles bursting through the magma, and more gentle gas release, accompanied by slow and steady motion of the lava.

In the past, volcanic gases have been sampled directly from steaming vents and openings called fumaroles. But this is not possible for the emissions from a lava lake, 200 metres across, and at the bottom of a steep-sided crater. Instead, the team used an infrared spectrometer, which is employed for routine volcano monitoring by co-authors of the study, Jeff Sutton and Tamar Elias from the Hawaiian Volcano Observatory (US Geological Survey).

̽��ֱ��device was located on the edge of the crater, pointed at the lava lake, and recorded gas compositions in the atmosphere every few seconds. ̽��ֱ��emissions of carbon- and sulphur-bearing gases were measured during both the vigorous and mild phases of activity.

Each individual measurement was used to compute the temperature of the volcanic gas. What immediately struck the scientists was that the gas temperatures ranged from 1150 degrees Celsius – the temperature of the lava – down to around 900 degrees Celsius. “At this temperature, the lava would freeze,” said lead author Dr Clive Oppenheimer, from Cambridge’s Department of Geography. “At first, we couldn’t understand how the gases could emerge much colder than the molten lava sloshing in the lake.”

̽��ֱ��clue to this puzzle came from the variation in calculated gas temperatures – they were high when the lava lake was placid, and low when it was bubbling furiously. “We realised it could be because of the size of the gas bubbles,” said co-author Professor Andy Woods, Director of Cambridge’s BP Institute. “Larger bubbles rise faster through the magma and expand rapidly as the pressure reduces, just like bubbles rising in a glass of fizzy drink; the gas cools down because of the expansion.” Larger bubbles form when smaller bubbles bump into each other and merge.

Woods and Oppenheimer developed a mathematical model to account for the process, which showed a very good fit with the observations.

But there was yet another surprising finding from the gas observations from Hawaii. As well as being cooler, the emissions from the large gas bubbles were more oxidised than expected – they had higher proportions of carbon dioxide to carbon monoxide.

̽��ֱ��chemical balance of volcanic gases such as carbon dioxide and carbon monoxide (or sulphur dioxide and hydrogen sulphide) is generally thought to be controlled by the chemistry of the surrounding liquid magma but what the new findings showed is that when bubbles get large enough, most of the gas inside follows its own chemical pathway as the gas cools.

̽��ֱ��ratio of carbon dioxide to carbon monoxide when the lava lake was in its most energetic state was six times higher than during the most stable phase. ̽��ֱ��scientists suggest this effect should be taken into account when gas measurements are being used to forecast major changes in volcanic activity.

“Gas measurements are critical to our monitoring and hazard assessment; refining our understanding of how magma behaves beneath the volcano allows us to better interpret our observations,” said co-author Tamar Elias from the Hawaiian Volcano Observatory.

And there is another implication of this discovery – not for eruptions today but for the evolution of the Earth’s atmosphere billions of years ago. “Volcanic emissions in Earth’s deep past may have made the atmosphere more oxidising than we thought,” said co-author Bruno Scaillet. “A more oxygen-rich atmosphere would have facilitated the emergence and viability of life on land, by generating an ozone layer, which shields against harmful ultraviolet rays from the sun.”

Reference:
Clive Oppenheimer et al “Influence of eruptive style on volcanic gas emission chemistry and temperature” Nature Geoscience (2018). DOI: 10.1038/s41561-018-0194-5

Inset image: Clive Oppenheimer in Hawaii. Credit: Clive Oppenheimer

̽��ֱ��chemical composition of gases emitted from volcanoes – which are used to monitor changes in volcanic activity – can change depending on the size of gas bubbles rising to the surface, and relate to the way in which they erupt. ̽��ֱ��results, published in the journal Nature Geoscience, could be used to improve the forecasting of threats posed by certain volcanoes.

At first, we couldn’t understand how the gases could emerge much colder than the molten lava sloshing in the lake.

Clive Oppenheimer

Kīlauea eruption, 2018

Yes

Volcanic eruption influenced Iceland’s conversion to Christianity

sc604 — Mon, 19 Mar 2018 00:48:16 +0000

A team of scientists and medieval historians, led by the ̽��ֱ�� of Cambridge, has used information contained within ice cores and tree rings to accurately date a massive volcanic eruption, which took place soon after the island was first settled.

Having dated the eruption, the researchers found that Iceland’s most celebrated medieval poem, which describes the end of the pagan gods and the coming of a new, singular god, describes the eruption and uses memories of it to stimulate the Christianisation of Iceland. ̽��ֱ��results are reported in the journal Climatic Change.

̽��ֱ��eruption of the Eldgjá in the tenth century is known as a lava flood: a rare type of prolonged volcanic eruption in which huge flows of lava engulf the landscape, accompanied by a haze of sulphurous gases. Iceland specialises in this type of eruption – the last example occurred in 2015, and it affected air quality 1400 kilometres away in Ireland.

̽��ֱ��Eldgjá lava flood affected southern Iceland within a century of the island’s settlement by Vikings and Celts around 874, but until now the date of the eruption has been uncertain, hindering investigation of its likely impacts. It was a colossal event with around 20 cubic kilometres of lava erupted – enough to cover all of England up to the ankles.

̽��ֱ��Cambridge-led team pinpointed the date of the eruption using ice core records from Greenland that preserve the volcanic fallout from Eldgjá. Using the clues contained within the ice cores, the researchers found that the eruption began around the spring of 939 and continued at least through the autumn of 940.

“This places the eruption squarely within the experience of the first two or three generations of Iceland’s settlers,” said first author Dr Clive Oppenheimer of Cambridge’s Department of Geography. “Some of the first wave of migrants to Iceland, brought over as children, may well have witnessed the eruption.”

Once they had a date for the Eldgjá eruption, the team then investigated its consequences. First, a haze of sulphurous dust spread across Europe, recorded as sightings of an exceptionally blood-red and weakened Sun in Irish, German and Italian chronicles from the same period.

Then the climate cooled as the dust layer reduced the amount of sunlight reaching the surface, which is evident from tree rings from across the Northern Hemisphere. ̽��ֱ��evidence contained in the tree rings suggests the eruption triggered one of the coolest summers of the last 1500 years. “In 940, summer cooling was most pronounced in Central Europe, Scandinavia, the Canadian Rockies, Alaska and Central Asia, with summer average temperatures 2°C lower,” said co-author Professor Markus Stoffel from the ̽��ֱ�� of Geneva’s Department of Earth Sciences.

̽��ֱ��team then looked at medieval chronicles to see how the cooling climate impacted society. “It was a massive eruption, but we were still amazed just how abundant the historical evidence is for the eruption’s consequences,” said co-author Dr Tim Newfield, from Georgetown ̽��ֱ��’s Departments of History and Biology. “Human suffering in the wake of Eldgjá was widespread. From northern Europe to northern China, people experienced long, hard winters and severe spring-summer drought. Locust infestations and livestock mortalities occurred. Famine did not set in everywhere, but in the early 940s we read of starvation and vast mortality in parts of Germany, Iraq and China.”

“ ̽��ֱ��effects of the Eldgjá eruption must have been devastating for the young colony on Iceland – very likely, land was abandoned and famine severe,” said co-author Professor Andy Orchard from the ̽��ֱ�� of Oxford’s Faculty of English. “However, there are no surviving texts from Iceland itself during this time that provide us with direct accounts of the eruption.”

But Iceland’s most celebrated medieval poem, Vǫluspá (‘ ̽��ֱ��prophecy of the seeress’) does appear to give an impression of what the eruption was like. ̽��ֱ��poem, which can be dated as far back as 961, foretells the end of Iceland’s pagan gods and the coming of a new, singular god: in other words, the conversion of Iceland to Christianity, which was formalised around the turn of the eleventh century.

Part of the poem describes a terrible eruption with fiery explosions lighting up the sky, and the Sun obscured by thick clouds of ash and steam:

“ ̽��ֱ��sun starts to turn black, land sinks into sea; the bright stars scatter from the sky.
Steam spurts up with what nourishes life, flame flies high against heaven itself.”

̽��ֱ��poem also depicts cold summers that would be expected after a massive eruption, and the researchers link these descriptions to the spectacle and impacts of the Eldgjá eruption, the largest in Iceland since its settlement.

̽��ֱ��poem’s apocalyptic imagery marks the fiery end to the world of the old gods. ̽��ֱ��researchers suggest that these lines in the poem may have been intended to rekindle harrowing memories of the eruption to stimulate the massive religious and cultural shift taking place in Iceland in the last decades of the tenth century.

“With a firm date for the eruption, many entries in medieval chronicles snap into place as likely consequences – sightings in Europe of an extraordinary atmospheric haze; severe winters; and cold summers, poor harvests; and food shortages,” said Oppenheimer. “But most striking is the almost eyewitness style in which the eruption is depicted in Vǫluspá. ̽��ֱ��poem’s interpretation as a prophecy of the end of the pagan gods and their replacement by the one, singular god, suggests that memories of this terrible volcanic eruption were purposefully provoked to stimulate the Christianisation of Iceland.”

Reference:
Clive Oppenheimer et al “ ̽��ֱ��Eldgjá eruption: timing, long-range impacts and influence on the Christianisation of Iceland.” Climatic Change (2018). DOI: 10.1007/s10584-018-2171-9

Inset image: Codex Regius, which contains a version of the Vǫluspá.

Memories of the largest lava flood in the history of Iceland, recorded in an apocalyptic medieval poem, were used to drive the island’s conversion to Christianity, new research suggests.

With a firm date for the eruption, many entries in medieval chronicles snap into place as likely consequences.

Clive Oppenheimer

Eldgjá fissure in southern Iceland

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

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Tree rings pinpoint eruption of Icelandic volcano to half a century before human settlement

sc604 — Thu, 29 Jun 2017 16:21:01 +0000

̽��ֱ��team, which included volcanologists, climatologists, geographers and historians among others, used a combination of scientific and historical evidence to pinpoint the eruption date of the Katla volcano between late 822 CE and early 823 CE, decades before the earliest settlers arrived. Their results are reported in the journal Geology.

In a similar way to how fossils can be used to understand the development and evolution of life on Earth, different types of environmental evidence can be used to understand what the Earth’s climate was like in the past and why. ̽��ֱ��‘fingerprints’ contained in tree rings and ice cores help scientists to estimate past climatic conditions and extend our understanding of the interaction between humans and the environment hundreds and thousands of years back in time.

“In our work, we’re trying to reconstruct past natural temperature and precipitation variability from tree rings – trying to reveal when it was cold and wet or warm and dry for instance,” said Professor Ulf Büntgen of Cambridge’s Department of Geography, the paper’s lead author. “We’re also interested in detecting and understanding key drivers of the Earth’s climate dynamics and their possible linkages with changes in human history.”

Currently, Iceland is for the most part treeless. However, before the first permanent settlers arrived in the late 9^th century, it was most likely covered by extensive woodland. Early settlers harvested most of the trees they found on the island to establish an agricultural-based society, and the trees never recovered.

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. ̽��ֱ��so-called Drumbabót forest is the best-preserved prehistoric forest in Iceland, and had been buried by an eruption of the nearby Katla volcano, Iceland’s most active volcanic system.

Volcanic eruptions are often responsible for an abrupt period of cooling, but only with a precise date of eruption can researchers definitively account for the variability in climate. Büntgen, who uses the information locked within tree rings to reconstruct past climate conditions, used the trees exposed by the 2003 flood to pinpoint when this particular eruption took place.

̽��ֱ��team behind the current work have previously confirmed that in 775 CE, 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. By measuring the radiocarbon levels in one of the Drumbabót trees, 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. ̽��ֱ��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.

̽��ֱ��unique tree ring results were then linked with those of co-authors Professors Christine Lane and Clive Oppenheimer, also from Cambridge’s Department of Geography. Lane and Oppenheimer used independent lines of ash (tephra) and ice core evidence to detect fingerprints of the Katla eruption.

In addition to the scientific results, 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.

“It was a happy coincidence that we were able to use all these different archives and techniques to date this eruption,” said Büntgen. “Data and methods we are using are constantly getting better, and by building more links with the humanities, we can see the real effects volcanoes have on human society.”

Reference
Büntgen et al. ‘Multi-proxy dating of Iceland’s major pre-settlement Katla eruption to 822-823 CE.’ Geology (2017). DOI: 10.1130/G39269.1

An international group of researchers has dated a large volcanic eruption in Iceland to within a few months. ̽��ֱ��eruption, which is the oldest volcanic eruption to be precisely dated at high northern latitudes, occurred shortly before the first permanent human settlements were established, when parts of the now mostly treeless island were still covered with forest.

It was a happy coincidence that we were able to use all these different archives and techniques to date this eruption.

Ulf Büntgen

Drumbabót forest in Iceland

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

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