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Metals mark magma for life

From Department of Earth Sciences. Published on Sep 03, 2018.

Gases erupted by volcanoes contain various volatile metal products. New research by Marie Edmonds and Emma Liu in Cambridge and Tamsin Mather in Oxford has discovered that different kinds of volcanoes have distinctive metal ‘signatures’, which reflect differences in how their magma forms.

Size matters: if you are a bubble of volcanic gas

By sc604 from University of Cambridge - Department of Earth Sciences. Published on Aug 06, 2018.

A team of scientists, including a volcanologist and mathematician from the University 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. The 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).

The device was located on the edge of the crater, pointed at the lava lake, and recorded gas compositions in the atmosphere every few seconds. The 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.”

The 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.

The 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.

The 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. The 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

 

The 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. The 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

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Scientists measure severity of drought during the Maya collapse

By sc604 from University of Cambridge - Department of Earth Sciences. Published on Aug 02, 2018.

Researchers from the University of Cambridge and the University of Florida developed a method to measure the different isotopes of water trapped in gypsum, a mineral that forms during times of drought when the water level is lowered, in Lake Chichancanab in Mexico’s Yucatán Peninsula where the Maya were based.

Based on these measurements, the researchers found that annual precipitation decreased between 41% and 54% relative to today during the period of the Maya civilisation’s collapse, with periods of up to 70% rainfall reduction during peak drought conditions, and that relative humidity declined by 2% to 7% relative to today. The results are reported in the journal Science.

“The role of climate change in the collapse of Classic Maya civilisation is somewhat controversial, partly because previous records are limited to qualitative reconstructions, for example whether conditions were wetter or drier,” said Nick Evans, a PhD student in Cambridge’s Department of Earth Sciences and the paper’s first author. “Our study represents a substantial advance as it provides statistically robust estimates of rainfall and humidity levels during the Maya downfall.”

Maya civilisation is divided into four main periods: the Preclassic (2000 BCE – 250 CE), Classic (250 CE – 800 CE), terminal Classic (800 - 1000 CE) and Postclassic (1000 CE – 1539 CE). The Classic period was marked by the construction of monumental architecture, intellectual and artistic development, and the growth of large city-states.

During the 9th century however, there was a major political collapse in the central Maya region: their famous limestone cities were abandoned and dynasties ended. And while the Maya people survived beyond this period, their political and economic power was depleted.

There are multiple theories as to what caused the collapse of the Maya civilisation, such as invasion, war, environmental degradation and collapsing trade routes. In the 1990s, however, researchers were able to piece together climate records for the period of the Maya collapse and found that it correlated with an extended period of extreme drought.

Professor David Hodell, Director of Cambridge’s Godwin Laboratory for Palaeoclimate Research and the senior author of the current paper, provided the first physical evidence of a correlation between this period of drought at Lake Chichancanab and the downfall of the Classic Maya civilisation in a paper published in 1995.

Now, Hodell and his colleagues have applied a new method and estimated the extent of this drought. Using a new geochemical method to measure the water locked within gypsum from Chichancanab, the researchers have built a complete model of hydrological conditions during the terminal Classic Period when the Maya collapsed.

The researchers analysed the different isotopes of water trapped within the crystal structure of the gypsum to determine changes in rainfall and relative humidity during the Maya downfall.

They measured three oxygen and two hydrogen isotopes to reconstruct the history of the lake water between 800 and 1000 CE. When gypsum forms, water molecules are incorporated directly into its crystalline structure, and this water records the different isotopes that were present in the ancient lake water at the time of its formation. “This method is highly accurate and is almost like measuring the water itself,” said Evans.

In periods of drought, more water evaporates from lakes such as Chichancanab, and because the lighter isotopes of water evaporate faster, the water becomes heavier. A higher proportion of the heavier isotopes, such as oxygen-18 and hydrogen-2 (deuterium), would indicate drought conditions. By mapping the proportion of the different isotopes contained within each layer of gypsum, the researchers were able to build a model to estimate past changes in rainfall and relative humidity over the period of the Maya collapse.

This quantitative climate data can be used to better predict how these drought conditions may have affected agriculture, including yields of the Maya’s staple crops, such as maize.

The research was supported by the European Research Council.

Reference:
Nicholas P. Evans et al. ‘Quantification of Drought During the Collapse of the Classic Maya Civilization.’ Science (2018). DOI: 10.1126/science.aas9871

Inset image: Lake Chichancanab, the site of the study. Chichancanab means “Little Sea” in Yucatec Maya, reflecting its relatively salty water composed dominantly of calcium and sulfate. (Credit: Mark Brenner)

The severity of drought conditions during the demise of the Maya civilisation about 1,000 years ago has been quantified, representing another piece of evidence that could be used to solve the longstanding mystery of what caused the downfall of one of the ancient world’s great civilisations. 

The role of climate change in the collapse of Classic Maya civilisation is somewhat controversial, partly because previous records are limited to qualitative reconstructions.
Nick Evans
Edzná ruins, Campeche

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The text in this work is licensed under a Creative Commons Attribution 4.0 International License. Images, including our videos, are Copyright ©University 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.

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Lessons about a future warmer world using data from the past

From Department of Earth Sciences. Published on Jun 25, 2018.

Selected intervals in the past that were as warm or warmer than today can help us understand what the Earth may be like under future global warming. A latest assessment of past warm periods, by an international team of 59 scientists from 17 nations including Cambridge Earth Sciences' Professor Eric Wolff, shows that in response to the warming ecosystems and climate zones will spatially shift and on millennial time scales ice sheets will substantially shrink.

Why life on Earth first got big

By sc604 from University of Cambridge - Department of Earth Sciences. Published on Jun 25, 2018.

The research, led by the University of Cambridge, found that the most successful organisms living in the oceans more than half a billion years ago were the ones that were able to ‘throw’ their offspring the farthest, thereby colonising their surroundings. The results are reported in the journal Nature Ecology and Evolution.

Prior to the Ediacaran period, between 635 and 541 million years ago, life forms were microscopic in size, but during the Ediacaran, large, complex organisms first appeared, some of which – such as a type of organism known as rangeomorphs – grew as tall as two metres. These organisms were some of the first complex organisms on Earth, and although they look like ferns, they may have been some of the first animals to exist – although it’s difficult for scientists to be entirely sure. Ediacaran organisms do not appear to have mouths, organs or means of moving, so they are thought to have absorbed nutrients from the water around them.

As Ediacaran organisms got taller, their body shapes diversified, and some developed stem-like structures to support their height.

In modern environments, such as forests, there is intense competition between organisms for resources such as light, so taller trees and plants have an obvious advantage over their shorter neighbours. “We wanted to know whether there were similar drivers for organisms during the Ediacaran period,” said Dr Emily Mitchell of Cambridge’s Department of Earth Sciences, the paper’s lead author. “Did life on Earth get big as a result of competition?”

Mitchell and her co-author Dr Charlotte Kenchington from Memorial University of Newfoundland in Canada examined fossils from Mistaken Point in south-eastern Newfoundland, one of the richest sites of Ediacaran fossils in the world.

Earlier research hypothesised that increased size was driven by the competition for nutrients at different water depths. However, the current work shows that the Ediacaran oceans were more like an all-you-can-eat buffet.

“The oceans at the time were very rich in nutrients, so there wasn’t much competition for resources, and predators did not yet exist,” said Mitchell, who is a Henslow Research Fellow at Murray Edwards College. “So there must have been another reason why life forms got so big during this period.”

Since Ediacaran organisms were not mobile and were preserved where they lived, it’s possible to analyse whole populations from the fossil record. Using spatial analysis techniques, Mitchell and Kenchington found that there was no correlation between height and competition for food. Different types of organisms did not occupy different parts of the water column to avoid competing for resources – a process known as tiering.

“If they were competing for food, then we would expect to find that the organisms with stems were highly tiered,” said Kenchington. “But we found the opposite: the organisms without stems were actually more tiered than those with stems, so the stems probably served another function.”

According to the researchers, one likely function of stems would be to enable the greater dispersion of offspring, which rangeomorphs produced by expelling small propagules. The tallest organisms were surrounded by the largest clusters of offspring, suggesting that the benefit of height was not more food, but a greater chance of colonising an area.

“While taller organisms would have been in faster-flowing water, the lack of tiering within these communities shows that their height didn’t give them any distinct advantages in terms of nutrient uptake,” said Mitchell. “Instead, reproduction appears to have been the main reason that life on Earth got big when it did.”

Despite their success, rangeomorphs and other Ediacaran organisms disappeared at the beginning of the Cambrian period about 540 million years ago, a period of rapid evolutionary development when most major animal groups first appear in the fossil record.

The research was funded by the Natural Environment Research Council, the Cambridge Philosophical Society, Murray Edwards College and Newnham College, Cambridge.

Reference
Emily G. Mitchell and Charlotte G. Kenchington. ‘The utility of height for the Ediacaran organisms of Mistaken Point.’ Nature Ecology and Evolution (2018). DOI: 10.1038/s41559-018-0591-6

Inset image: 
A close-up view of the Mistaken Point ‘E’ surface community. Credit: Emily Mitchell. 

Some of the earliest complex organisms on Earth – possibly some of the earliest animals to exist – got big not to compete for food, but to spread their offspring as far as possible. 

Reproduction appears to have been the main reason that life on Earth got big when it did.
Emily Mitchell
Artist’s reconstruction of the community at Lower Mistaken Point

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The text in this work is licensed under a Creative Commons Attribution 4.0 International License. Images, including our videos, are Copyright ©University 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.

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Dating the emplacement of the Shap granite using zircon

From Department of Earth Sciences. Published on Jun 07, 2018.

G5a - the distinctive coarse-grained, pink granite exposed at Shap in Cumbria - has long been a favourite igneous hand specimen for Earth Sciences teaching in Cambridge. New research uses the age of zircon crystal formation to suggest a long gestation period in the mid-crust before its final emplacement 405 million years ago.

Sedgwick’s paper time machines

By Guest from Cambridge Earth Sciences blog. Published on Jun 06, 2018.

21 May 2018 marked two hundred years since Adam Sedgwick (1785-1873) became the Woodwardian Professor of Geology in Cambridge. Staff at the Sedgwick Museum have organised events and displays to celebrate this special anniversary. In this blog we look at the Archive – beginning with Sedgwick’s early journals. There are more than 60 journals and …

L'Oréal UNESCO For Women in Science award for Dr Emma Liu

From Department of Earth Sciences. Published on Jun 04, 2018.

Congratulations to Dr Emma Liu, Leverhulme Research Fellow in Volcanology, who has been awarded a 2018 L’Oreal UNESCO For Women In Science fellowship to support her postdoctoral research.

Major shift in marine life occurred 33 million years later in the South

From Department of Earth Sciences. Published on May 17, 2018.

A new study of marine fossils from Antarctica, Australia, New Zealand and South America reveals that one of the greatest changes to the evolution of life in our oceans occurred more recently in the Southern Hemisphere than previously thought.

Deploying nBOSS: the North Borneo Orogeny Seismic Survey

By Guest from Cambridge Earth Sciences blog. Published on May 04, 2018.

Bye bye “Beast from the East”. We couldn’t have chosen a better time (and location!) for some fieldwork as we left behind an extreme cold snap that froze the UK and dumped fresh snow on Cambridge. In March a team of seismologists from the University of Cambridge and University of Aberdeen boarded a plane for …

A musical, an opera and stand-up comedy: sharing Earth Sciences with the public

By Matthew Kemp from Cambridge Earth Sciences blog. Published on Apr 27, 2018.

Making science – with all its complexities, uncertainties and nuances – palatable for the general public presents many challenges, and what better place to try this out than the Cambridge Science Festival. As a Research Assistant at the Department of Earth Sciences, I communicate science all the time. Whether discussing my work with colleagues, writing …

Cambridge Earth Sciences once again top amongst UK geology departments in the Complete University Guide

From Department of Earth Sciences. Published on Apr 25, 2018.

The Department is delighted to be placed first amongst UK geology departments once again.

Gender inequality is ‘drowning out’ the voices of women scientists

By ed515 from University of Cambridge - Department of Earth Sciences. Published on Apr 24, 2018.

Dr Heather Ford and her colleagues analysed data from the American Geophysical Union (AGU) Fall Meeting and found that, overall; female scientists are offered fewer opportunities than men to present their research.

The team examined the gender, career stage and type of presentation delivered by each participant from 2014 to 2016. They found that female members are at a disadvantage because the majority of them are students or in the early stages of their careers, groups whose members are typically given fewer chances to present their research. The results are reported in the journal Nature Communications.

Conference speakers are often at more senior stages of their careers, where there are usually fewer women in Science, Technology, Engineering and Maths (STEM) fields. A further problem is that men are more likely to provide speaking opportunities to other men, potentially limiting women’s career prospects.

“The burden of representation often falls on under-represented groups. We need the majority groups to think about representation, otherwise minority voices will continue to be drowned out,” said Ford, who is a NERC Independent Research Fellow in Cambridge’s Department of Earth Sciences.

However, the research showed some positive signs, as women were invited at a much higher rate than men in the early and mid- career stages.

The researchers are calling for more students and early career researchers to have opportunities to speak at future conferences, in a bid to help some of the many female members who are at the beginning of their careers. They also want to see more women selecting the conference speakers, and suggest that all members may benefit from diversity training before they can invite speakers and assign conference presentations.

Attending and presenting at conferences helps academics at every stage of their careers to build their network, meet potential collaborators and share their research. Conferences are important for career progression, and can be key in helping researchers to find funding and receive job offers. Presenting at academic conferences can also help researchers to gain recognition and awards for their work. 

Ford says she and her co-author Petra Dekens from San Francisco State University were motivated to look into this topic after sitting in “too many conference sessions” with either no female speakers, or a single female speaker.

The global context is also an important issue for Ford, particular the ongoing campaign for gender equality. She said; “A lot of women have been motivated to speak out about gender inequality in the past year – people are much more vocal about how they’ve been treated. I wanted to find a productive way to channel my frustrations.”

The AGU Fall Meeting is the world’s largest geoscience conference, with more than 22,000 presentation proposals each year. The AGU has more than 60,000 members in 137 countries, and around a third of its members are women. Geoscience is one of the least diverse STEM fields.

Reference:  
Heather L. Ford et al. ‘'Gender inequity in speaking opportunities at the American Geophysical Union Fall Meeting.’ Nature Communications (2018). DOI: 10.1038/s41467-018-03809-5

A University of Cambridge researcher is calling for the voices of women to be given a fairer platform at a leading scientific conference.

We need the majority groups to think about representation, otherwise minority voices will continue to be drowned out.
Heather L. Ford
Margaret Leinen at the 2012 AGU Fall Meeting

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1000 km down: seismologists probe the mid-mantle

From Department of Earth Sciences. Published on Apr 24, 2018.

Many questions remain unanswered about the mid-mantle, 600 to 1200 km below Earth’s surface. Does this layer decouple convection between the upper and lower mantle? How are processes here linked to plate tectonics and volcanism? Cambridge Earth Scientists are using seismic constraints to determine the compositional heterogeneity in the mid-mantle. They hope to identify processes which could obstruct or divert convection 1000 km down.

Brachiopods prove tougher than previously thought

From Department of Earth Sciences. Published on Apr 18, 2018.

A remarkable 120-year record of resilience to environmental change in the world’s oceans has been uncovered within a group of marine organisms called brachiopods. Although they are not well known today, brachiopods have had considerable importance in the evolution of seabed life.

Hot, warm or cold?: new insight into how columnar jointing forms

From Department of Earth Sciences. Published on Apr 13, 2018.

A new study by researchers at the University of Liverpool, with contributions from Cambridge Earth Sciences PhD student Fiona Iddon, has identified the temperature at which cooling magma cracks to form geometric columns such as those found at the Giants Causeway in Northern Ireland.

Two billion year old salt rock reveals rise of oxygen in ancient atmosphere

From Department of Earth Sciences. Published on Apr 12, 2018.

A two billion year old chunk of sea salt provides new evidence for the transformation of Earth's atmosphere into an oxygenated environment capable of supporting life as we know it.

A day in the field: geological mapping of Northern Baffin Island

By Owen Weller from Cambridge Earth Sciences blog. Published on Apr 10, 2018.

The Archean Eon (4–2.5 billion years ago) is one of the last great frontiers in our knowledge of the Earth. Plate tectonics is considered to have initiated during this time period, and large volumes of the continental crust formed, but fundamental questions remain regarding the timing, mechanisms and drivers of these transitions. Central to these …

Behind the scenes at the Sedgwick Club Conference

By Sean Herron from Cambridge Earth Sciences blog. Published on Mar 29, 2018.

It began with coffee. Like so many things in life, the Sedgwick Club Conference 2018 started with a healthy dose of caffeine. The doors to the Cambridge Earth Sciences department were nearly ready to be opened and the masses allowed to flood in for the annual speakers’ event. All that was left to do was …

Observing deep carbon with an Icelandic volcano

From Department of Earth Sciences. Published on Mar 23, 2018.

An important new chemical dataset from the basalt lavas of the Icelandic Borgarhraun volcano is helping Cambridge Earth Scientists John Maclennan and Dan McKenzie with colleagues from the US and Iceland estimate the carbon dioxide content of Earth’s mantle. Borgarhraun is one of the few places in the world from where it is possible to probe the mantle CO2. This new data, published in the latest issue of Geology will improve understanding of the link between volcanism and long-term climate change.

"We all need to press for progress, in science and beyond"

By ed515 from University of Cambridge - Department of Earth Sciences. Published on Mar 08, 2018.

Read more about the female scientists at Cambridge taking their fields by storm - and using International Women's Day to encourage others to do the same. 

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In conversation with Nick Rawlinson

By Greg Palmer from Cambridge Earth Sciences blog. Published on Mar 03, 2018.

Geophysicist Professor Nick Rawlinson recently moved to Cambridge to take up the BP McKenzie Chair in Earth Sciences. During a career in Australia and the UK he has specialised in observational and theoretical seismology. Nick discussed his life and work with Greg Palmer. How did you get in to Earth Sciences? When I finished high …

Evolution of land plants transformed sedimentation on Earth

From Department of Earth Sciences. Published on Mar 01, 2018.

The vegetation of our planet irrevocably changed surface processes on Earth. New research suggests the evolution of land plants in the Ordovician caused an increase in the volume of mud preserved on the continents. This marked a change in global sedimentation, with implications for the study of sedimentary processes on our planet and beyond.

Investigating the warm climate stability of the West Antarctic ice sheet

From Department of Earth Sciences. Published on Feb 19, 2018.

Recent modelling studies predict that anthropogenic warming could lead to the loss of the West Antarctic Ice Sheet (WAIS) in the next few centuries, and a big rise in sea level.

Life in Ice Age Cambridgeshire – a new exhibit in the Sedgwick Museum

By Douglas Palmer from Cambridge Earth Sciences blog. Published on Feb 19, 2018.

Hippos from Barrington, woolly mammoths from Barnwell and beavers from Burwell Fen help tell the remarkable story of Late Ice Age Cambridgeshire. A new ‘Ice Age’ exhibit in the Sedgwick Museum displays spectacular fossil finds from local villages that show how life, climate and the environment of the region have changed dramatically over the last …

Blue mussel shape is a powerful indicator of environmental change

From Department of Earth Sciences. Published on Feb 12, 2018.

Scientists at the University of Cambridge and British Antarctic Survey have developed a new method to identify natural patterns of shell shape variation in common blue mussels.

Pteropods tougher than thought

From Department of Earth Sciences. Published on Jan 29, 2018.

Elegant little sea butterflies, more technically known as pteropods, are important members of the marine ecosystem because they are so abundant and are a food source for other marine organisms, especially whales.

Investigating Ethiopian volcanism: RiftVolc fieldwork in East Africa

By Guest from Cambridge Earth Sciences blog. Published on Jan 23, 2018.

Last year I travelled out to Ethiopia for fieldwork twice, quite a feat considering it had taken two years of broken limbs and civil unrest causing setbacks. Avoiding the rains and unseasonably hot conditions of the summer (although I didn’t quite manage to avoid the heatstroke) I visited the Butajira volcanic field in April and …

RAS Gold Medal for Professor Robert White

From Department of Earth Sciences. Published on Jan 22, 2018.

Congratulations to Robert (Bob) White, Professor of Geophysics and Fellow of St Edmund’s College, who has been awarded the Royal Astronomical Society's Gold Medal for a lifetime of distinguished achievement in solid Earth geophysics.

The beginnings of communal life – 565 million years ago

From Department of Earth Sciences. Published on Jan 18, 2018.

Ancient rock strata exposed within the World Heritage Site of Mistaken Point Ecological Reserve, Newfoundland, record one of Life's very first communities of seabed dwelling macro-organisms. Known as the Ediacaran biota, it is around 565 million years old.

Cambridge Earth Sciences at AGU 2017

By Gautier Nicoli from Cambridge Earth Sciences blog. Published on Dec 28, 2017.

This year, in a rare turn of events, the AGU Fall Meeting took place far away from the West coast of the USA. The Golden Gate Bridge and steep streets of San Francisco were replaced with alligator-filled swamps and Creole cottages. The 2017 conference was held from 11-15 December in New Orleans, at the Ernest …

Himalayan Hydrogeology: an ICIMOD internship in Nepal

By Matthew Lees from Cambridge Earth Sciences blog. Published on Dec 24, 2017.

The Earth is a very blue planet, with almost three quarters of the surface covered in water. It seems perverse, then, that there should ever be water shortages. However, only 4% of Earth’s water is freshwater, and there are seven billion people dependent on this resource for domestic, agricultural and industrial use. Hence, the apparent …

Going underground: Cambridge digs into the history of geology with landmark exhibition

From Department of Earth Sciences. Published on Dec 20, 2017.

A box full of diamonds, volcanic rock from Mount Vesuvius, and the geology guide that Darwin packed for his epic voyage on the Beagle are on display at the Cambridge University Library as part of the first major exhibition to celebrate geological map-making.

A scientific voyage in Galápagos

By Michael Stock from Cambridge Earth Sciences blog. Published on Dec 19, 2017.

Almost 200 years ago, the young Charles Darwin came up to Christ’s College to begin a comprehensive theological education. In what could be considered the most productive procrastination in history, he instead spent much of his time in Cambridge attending lectures in the natural sciences, under the mentorship of John Stevens Henslow and Adam Sedgwick. …

Thomas McKenny Hughes: one hundred years on

By Douglas Palmer from Cambridge Earth Sciences blog. Published on Dec 14, 2017.

A hundred years ago Thomas McKenny Hughes (1832-1917) died. He was Adam Sedgwick’s successor as eighth Woodwardian Professor and his biographer. Today, although few geologists, even in Cambridge, will have heard of McKenny Hughes, he made his mark on British geology. It was McKenny Hughes who managed the planning and building of the Sedgwick Museum …

Is there life beyond Earth (Sciences)?

By Kevin Wong from Cambridge Earth Sciences blog. Published on Nov 27, 2017.

Poster boards stand tall in a crowded room. Friendly, familiar faces exchange advice over a generous keg. Curious minds eagerly watch and listen, before collecting free pens from a nearby table. The Department of Earth Sciences’ careers event near the end of Michaelmas term invites alumni and industry representatives to speak to new generations of …

Enhancing the growth of plants on inhospitable land using a biological fertiliser

From Department of Earth Sciences. Published on Nov 20, 2017.

A simple mixture of organic waste, such as chicken manure and zeolite, a porous volcanic mineral, has been developed into a powerful bio-fertiliser which can also reclaim semi-arid and contaminated land.

Collaborating on carbon capture and storage

From Department of Earth Sciences. Published on Oct 25, 2017.

Cambridge Earth Sciences is part of a global project researching new sites for carbon capture and storage (CCS), supported by leading multinational minerals and energy company BHP.

Carbon capture: universities and industry work together to tackle emissions

By sc604 from University of Cambridge - Department of Earth Sciences. Published on Oct 25, 2017.

The world is not going carbon-free any time soon: that much is clear. Developed and developing countries alike rely on fossil fuels for transport, industry and power, all of which release CO2 into the atmosphere. But as sea levels rise, ‘unprecedented’ weather events become commonplace and the polar ice caps melt, how can we balance our use of fossil fuels with the imperative to combat the catastrophic effects of climate change?

“Everything suggests that we won’t be able to stop burning carbon-based fuels, particularly in rapidly developing countries like India and China,” says Professor Mike Bickle of Cambridge’s Department of Earth Sciences. “Along with increasing use of renewable energy and improved energy efficiency, one way to cope with that is to use carbon capture and storage – and there is no technical reason why it can’t be deployed right now.”

Carbon capture and storage (CCS) is a promising and practical solution to drastically reducing carbon emissions, but it has had a stilted development pathway to date. In 2015, the UK government cancelled a £1 billion competition for CCS technology six months before it was due to be awarded, citing high costs. Just one year later, a high-level advisory group appointed by ministers recommended that establishing a CCS industry in the UK now could save the government and consumers billions per year from the cost of meeting climate change targets.

CCS is the only way of mitigating the 20% of CO2 emissions from industrial processes – such as cement manufacturing and steel making, for which there is no obvious alternative – to help meet the world’s commitments to limit warming to below 2oC. It works by trapping the CO2 emitted from burning fossil fuels, which is then cooled, liquefied and pumped deep underground into geological formations, saline aquifers or disused oil and gas fields. Results from lab-based tests, and from working CCS sites such as Sleipner in the North Sea, suggest that carbon can be safely stored underground in this way for 10,000 years or more.

“The big companies understand the science of climate change, and they understand that we’ve got to invest in technologies like CCS now, before it’s too late,” says Dr Jerome Neufeld of Cambridge’s Department of Applied Mathematics and Theoretical Physics, and Department of Earth Sciences. “But it’s a tricky business running an industry where nobody is charging for carbon.”

“Everyone always wants the cheapest option, so without some form of carbon tax, it’s going to be difficult to get CCS off the ground at the scale that’s needed,” says Bickle. “But if you look at the cost of electricity produced from gas or coal with CCS added, it’s very similar to the cost of electricity from solar or wind. So if governments put a proper carbon charge in place, renewables and CCS would compete with each other on a relatively even playing field, and companies would have the economic incentive to invest in CCS.”

Bickle and Neufeld are following discussions about CCS closely because, along with collaborators from Stanford and Melbourne Universities, they have recently started a new CCS project with the support of BHP, one of the world’s largest mining and materials companies.

The three-year project will develop and improve methods for the long-term storage of CO2, and will test them at Otway in southern Australia, one of the largest CCS test sites in the world. Using a mix of theoretical modelling and small-, medium- and large-scale experiments, the researchers hope to significantly increase the types of sites where CCS is possible, including in China and developing economies.

In most current CCS schemes, CO2 is stored in porous underground rock formations with a thick layer of non-porous rock, such as shale, on top. The top layer provides extra insurance that the relatively light CO2 will not escape.

The new research, which will support future large-scale CO2 storage, will consider whether CO2 could be effectively trapped without the top seal of impermeable rock, meaning that CCS could be deployed in a wider range of environments. Their research findings will be made publicly available to accelerate the broader deployment of CCS.

“We are seeing a growing acknowledgement from industry, governments and society that to meet emissions reductions targets we are going to need to accelerate the use of this technology – we simply can’t do it quickly enough without CCS across both power generation and industry,” says BHP Vice President of Sustainability and Climate Change, Dr Fiona Wild. “We know CCS technology works and is proven. Our focus at BHP is on how we can help make sure the world has access to the information required to make it work at scale in a cost effective and timely way.”

During the project, Stanford researchers will measure the rate at which porous rock can trap CO2 using small-scale experiments on rock samples at reservoir conditions, while the Cambridge researchers will be using larger analogue models, in the order of metres or tens of metres. The Melbourne-based researchers will use large-scale numerical simulations of complex geological settings.

“One of the things this collaboration will really open up is the ability to deploy CCS almost anywhere,” says Neufeld, who is also affiliated with Cambridge’s Department of Earth Sciences and the BP Institute. “We know that CO2 can be safely trapped in porous rock with a seal of shale on top, but the early results from Otway have shown that even without the impenetrable seal, CO2 can be trapped just as effectively.”

When CO2 is pumped into underground saline aquifers, it is in a ‘super-critical’ phase: not quite a liquid and not quite a gas. The super-critical CO2 is less dense than the salt water, and so has a tendency to run uphill, but it’s been found that surface tension between the salt water and the rock is quite effective at pinning the CO2 in place so that it can’t escape. This phenomenon, known as capillary trapping, is also observed when water is held in a sponge.

“The results from Otway show that if you inject CO2 into a heterogeneous reservoir, it will mix with the salt water and capillary trapping will pin it there quite effectively, so it opens up a much broader range of potential carbon storage sites,” says Bickle.

“However, we need to start deploying CCS now, and the biggest challenges we face are economics and policy. If these prevent us from doing anything until it’s too late, and we’re at a stage when we’d have to start capturing carbon directly from the atmosphere, it will be far more expensive. By not starting CCS now, we’re building false economies.”

An international collaboration between universities and industry will further develop carbon capture and storage technology – one of the best hopes for drastically reducing carbon emissions – so that it can be deployed in a wider range of sites around the world.

We need to start deploying CCS now, and the biggest challenges we face are economics and policy. If we’re at a stage when we’d have to start capturing carbon directly from the atmosphere, it will be far more expensive.
Mike Bickle
Modelling CCS

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Award winning researchers in Earth Sciences

From Department of Earth Sciences. Published on Oct 18, 2017.

Congratulations to our researchers who have recently won awards.

Acting Director of the Sedgwick Museum appointed

From Department of Earth Sciences. Published on Oct 17, 2017.

Dr Elizabeth Harper has been appointed Acting Director of the Sedgwick Museum following the retirement of Dr Ken McNamara.

100 years since John E Marr elected Woodwardian Professor

From Department of Earth Sciences. Published on Oct 17, 2017.

To mark 100 years since John E Marr became Woodwardian Professor, on 30 October 1917, a selection of documents have been digitised and will be available to view on the Sedgwick Museum website from 30 October.

Arctic adventures: fieldwork on the Skaergaard intrusion, Greenland

By Victoria Honour from Cambridge Earth Sciences blog. Published on Oct 09, 2017.

Skaergaard is a classic example of a layered intrusion. It is a wonderful natural laboratory for geologists and highly photogenic, with its striking igneous layering. There is near 100% surface exposure as not much grows there; an advantage of its location at 68°N. We have just returned from a six week expedition, studying this fascinating …

Plate Tectonics at 50

From Department of Earth Sciences. Published on Oct 06, 2017.

The Geological Society of London has launched its new archive of Emeritus Professor Dan McKenzie’s work.

Exploring the igneous geology of Rum

By Carrie Soderman from Cambridge Earth Sciences blog. Published on Sep 28, 2017.

In July 2017, I found myself on my first non-compulsory fieldtrip as an undergraduate, in a group of 5 with two academic staff members and two PhD students heading to the Isle of Rum in the Scottish Inner Hebrides. The trip had been planned initially for my Masters project, but with Rum such a famous …

‘Mysterious’ ancient creature was definitely an animal, research confirms

By sc604 from University of Cambridge - Department of Earth Sciences. Published on Sep 15, 2017.

A new study by researchers at the universities of Cambridge, Oxford, Bristol, and the British Geological Survey provides strong proof that Dickinsonia was an animal, confirming recent findings suggesting that animals evolved millions of years before the so-called Cambrian Explosion of animal life. The study is published in the journal Proceedings of the Royal Society B.

Lead author on the paper is Dr Renee Hoekzema, a PhD candidate at Oxford who carried out this research while completing a previous PhD in Oxford’s Department of Earth Sciences. She said: ‘Dickinsonia belongs to the Ediacaran biota – a collection of mostly soft-bodied organisms that lived in the global oceans between roughly 580 and 540 million years ago. They are mysterious because despite there being around 200 different species, very few of them resemble any living or extinct organism, and therefore what they were, and how they relate to modern organisms, has been a long-standing palaeontological mystery.’

In 1947, Dickinsonia became one of the first described Ediacaran fossils and was initially thought to be an organism similar to a jellyfish. Since then, its strange body plan has been compared to that of a worm, a placozoan, a bilaterian and several non-animals including fungi, lichens and even entirely extinct groups.

Co-author Dr Alex Liu, from Cambridge's Department of Earth Sciences, said: ‘Discriminating between these different hypotheses has been difficult, as there are so few morphological features in Dickinsonia to compare to modern organisms. In this study we took the approach of looking at populations of this organism, including assumed juvenile and adult individuals, to assess how it grew and to try to work out how to classify it from a developmental perspective.’

The research was carried out on the basis of a widely held assumption that growth and development are ‘conserved’ within lineages – in other words, the way a group of organisms grows today would not have changed significantly from the way its ancestors grew millions of years ago.

Dickinsonia is composed of multiple ‘units’ that run down the length of its body. The researchers counted the number of these units in multiple specimens, measured their lengths and plotted these against the relative ‘age’ of the unit, assuming growth from a particular end of the organism. This data produced a plot with a series of curves, each of which tracked how the organism changed in the size and number of units with age, enabling the researchers to produce a computer model to replicate growth in the organism and test previous hypotheses about where and how growth occurred.

Dr Hoekzema said: ‘We were able to confirm that Dickinsonia grows by both adding and inflating discrete units to its body along its central axis. But we also recognised that there is a switch in the rate of unit addition versus inflation at a certain point in its life cycle. All previous studies have assumed that it grew from the end where each “unit” is smallest, and was therefore considered to be youngest. We tested this assumption and interpreted our data with growth assumed from both ends, eventually coming to the conclusion that people have been interpreting Dickinsonia as having grown at the wrong end for the past 70 years.

‘When we combined this growth data with previously obtained information on how Dickinsonia moved, as well as some of its morphological features, we were able to reject all non-animal possibilities for its original biological affinity and show that it was an early animal, belonging to either the Placozoa or the Eumetazoa.

‘This is one of the first times that a member of the Ediacaran biota has been identified as an animal on the basis of positive evidence.’

Dr Liu added: ‘This finding demonstrates that animals were present among the Ediacaran biota and importantly confirms a number of recent findings that suggest animals had evolved several million years before the “Cambrian Explosion” that has been the focus of attention for studies into animal evolution for so long.

‘It also allows Dickinsonia to be considered in debates surrounding the evolution and development of key animal traits such as bilateral symmetry, segmentation and the development of body axes, which will ultimately improve our knowledge of how the earliest animals made the transition from simple forms to the diverse range of body plans we see today.’

Reference:
Renee S. Hoekzema et al. ‘Quantitative study of developmental biology confirms Dickinsonia as a metazoan’. Proceedings of the Royal Society B (2017). DOI: 10.1098/rspb.2017.1348

Adapted from a University of Oxford press release

It lived well over 550 million years ago, is known only through fossils and has variously been described as looking a bit like a jellyfish, a worm, a fungus and lichen. But was the ‘mysterious’ Dickinsonia an animal, or was it something else?

Recent findings suggest animals had evolved several million years before the 'Cambrian Explosion' that has been the focus of attention for studies into animal evolution for so long.
Alex Liu
The Ediacaran fossil Dickinsonia costata, specimen P40135 from the collections of the South Australia Museum, Adelaide

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Christine Kelsey (1931-2017)

From Department of Earth Sciences. Published on Aug 31, 2017.

We are very sad to announce the death of Christine Kelsey on Wednesday 23 August.

Study identifies dinosaur ‘missing link’

By sc604 from University of Cambridge - Department of Earth Sciences. Published on Aug 16, 2017.

A bizarre dinosaur which looked like a raptor but was in fact a vegetarian may be the missing link between plant-eating dinosaurs and theropods, the group that includes carnivores such as Tyrannosaurus rex and Velociraptor.

Researchers from the University of Cambridge and the Natural History Museum used a comprehensive dataset to analyse more than 450 anatomical characteristics of early dinosaurs and correctly place the creature, known as Chilesaurus, in the dinosaur family tree. Their results, reported in the journal Biology Letters, suggest that Chilesaurus effectively fills a large gap between two of the major dinosaur groups, and shows how the divide between them may have happened.

Chilesaurus, which was discovered in southern Chile, was first described in 2015. It lived during the Late Jurassic period, about 150 million years ago, and has an odd collection of physical characteristics, which made it difficult to classify. For example, its head resembles that of a carnivore, but it has flat teeth for grinding up plant matter.

Chilesaurus almost looks like it was stitched together from different animals, which is why it baffled everybody,” said Matthew Baron, a PhD student in Cambridge’s Department of Earth Sciences and the paper’s joint first author.

Earlier research suggested that this peculiar dinosaur belonging to the group Theropoda, the ‘lizard-hipped’ group of dinosaurs that includes Tyrannosaurus, but the new study suggests that it was probably a very early member of a completely different group, called Ornithischia. This shuffling of the dinosaur family tree has major implications for understanding the origins of Ornithischia, the ‘bird-hipped’ group of dinosaurs that includes Stegosaurus, Triceratops and Iguanodon.

The bird-hipped dinosaurs have several common physical traits: the two most notable of these are an inverted, bird-like hip structure and a beak-like structure for eating. The inverted hips allowed for bigger, more complex digestive systems, which in turn allowed larger plant-eaters to evolve.

While Chilesaurus has a bird-like hip structure, and has flat teeth for grinding up plants, it does not possess the distinctive ‘beak’ of many other bird-hipped dinosaurs, which is what makes it such an important find.

“Before this, there were no transitional specimens – we didn’t know what order these characteristics evolved in,” said Baron. “This shows that in bird-hipped dinosaurs, the gut evolved first, and the jaws evolved later – it fills the gap quite nicely.”

Chilesaurus is one of the most puzzling and intriguing dinosaurs ever discovered,” said co-author Professor Paul Barrett of the Natural History Museum. “Its weird mix of features places it in a key position in dinosaur evolution and helps to show how some of the really big splits between the major groups might have come about.”

“There was a split in the dinosaur family tree, and the two branches took different evolutionary directions,” said Baron. “This seems to have happened because of change in diet for Chilesaurus. It seems it became more advantageous for some of the meat eating dinosaurs to start eating plants, possibly even out of necessity.”

Earlier this year, the same group of researchers argued that dinosaur family groupings need to be rearranged, re-defined and re-named. In a study published in Nature, the researchers suggested that bird-hipped dinosaurs and lizard-hipped dinosaurs such as Tyrannosaurus evolved from a common ancestor, potentially overturning more than a century of theory about the evolutionary history of dinosaurs.

Although their dataset has already thrown up some surprising results, the researchers say that as it currently analyses only early dinosaurs, there are probably many more surprises about dinosaur evolution to be found, once characteristics of later dinosaurs are added.

The research was funded by the Natural Environment Research Council (NERC).

Reference:
Matthew G. Baron and Paul M. Barrett. ‘A dinosaur missing-link? Chilesaurus and the early evolution of ornithischian dinosaurs.’ Biology Letters (2017). DOI: 10.1098/rsbl.2017.0220

A ‘Frankenstein’s monster’ dinosaur may be the missing link between two major dinosaur groups, plugging what was previously a big gap between them. 

Chilesaurus almost looks like it was stitched together from different animals, which is why it baffled everybody.
Matthew Baron
Life reconstruction of Chilesaurus diegosuarezi

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Alan Smith (1937-2017)

From Department of Earth Sciences. Published on Aug 14, 2017.

We were very sad to announce the death of Alan Smith on Sunday 13th August.

Meadow of dancing brittle stars shows evolution at work

By sc604 from University of Cambridge - Department of Earth Sciences. Published on Aug 14, 2017.

Researchers have described a new species of brittle star, which are closely related to starfish, and showed how these sea creatures evolved in response to the rise of shell-crushing predators during the late Palaeozoic Era. The results, reported in the Journal of Systematic Palaeontology, also suggest that brittle stars evolved new traits before the largest mass extinction event in Earth’s history, and not after, as was the case with many other forms of life.

A fossilised ‘meadow’ of dancing brittle stars – frozen in time in the very spot that they lived – was found in Western Australia and dates from 275 million years ago. It contains several remarkably preserved ‘archaic’ brittle stars, a newly-described genus and species called Teleosaster creasyi. They are the last known complete brittle stars of their kind, an evolutionary hangover pushed to the margins of the world’s oceans by the threat from predators.

The researchers, from the University of Cambridge, suggest that while other species of brittle stars evolved in response to predators such as early forms of rays and crabs, these archaic forms simply moved to where the predators weren’t – namely the seas around Australia, which during the Palaeozoic era was pushed up against Antarctica. In these cold, predator-free waters, the archaic forms were able to grow much larger, and lived at the same time as the modern forms of brittle star, which still exist today.

Brittle stars consist of a central disc and five whip-like appendages, which are used for locomotion. They first appear in the fossil record about 500 million years ago, in the Ordovician Period, and today there are about 2,100 different species, mostly found in the deep ocean.

Early brittle stars were just that: brittle. During the Palaeozoic Era, when early shell-crushing predators first appeared, brittle stars made for easy prey. At this point, a split in the evolutionary tree appears to have occurred: the archaic, clunky brittle stars moved south to polar waters, while the modern form first began to emerge in response to the threat from predators, and was able to continue to live in the warmer waters closer to the equator. Both forms existed at the same time, but in different parts of the ocean.

“The threat from predation is an under-appreciated driver of evolutionary change,” said study co-author Dr Kenneth McNamara of Cambridge’s Department of Earth Sciences. “As more predators began to appear, the brittle stars started to evolve more flexible bodies, which enabled them to either burrow into the sediment, or to move more rapidly to escape.”

About 250 million years ago, the greatest mass extinction in Earth’s history – the Permian-Triassic extinction event, or the “Great Dying” – occurred. More than 90% of marine species and 70% of terrestrial species went extinct, and as a result, most surviving species underwent major evolutionary changes as a result.

“Brittle stars appear to have bucked this trend, however,” said co-author Dr Aaron Hunter, a visiting postdoctoral researcher in the Department of Earth Sciences. “They seem to have evolved before the Great Dying, into a form which we still see today.”

Meadows of brittle stars and other invertebrates such as sea urchins and starfish can still be seen today in the seas around Antarctica. As was the case during the Palaeozoic, the threat from predators is fairly low, although the warming of the Antarctic seas due to climate change has been linked to the recent arrival of armies of king crabs, which represent a real threat to these star-filled meadows.

Reference:
Aaron W. Hunter and Kenneth J. McNamara. ‘Prolonged co-existence of “Archaic” and “Modern” Palaeozoic ophiuroids – evidence from the early Permian, Southern Carnarvon Basin, Western Australia.’ Journal of Systematic Palaeontology (2017). DOI: 10.1080/14772019.2017.1353549

Inset image: Brittle stars, by Ratha Grimes.

Newly-described fossil shows how brittle stars evolved in response to pressure from predators, and how an ‘evolutionary hangover’ managed to escape them. 

The threat from predation is an under-appreciated driver of evolutionary change.
Kenneth McNamara
Fossilised Teleosaster creasyi, from the Cundlefo Formation, Gascoyne Junction, Western Australia

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Volcanic arcs recycle crustal carbon

From Department of Earth Sciences. Published on Jul 20, 2017.

New research by Cambridge scientists is helping answer a key question about the origin of carbon emitted from Earth’s volcanoes.

Link identified between continental breakup, volcanic carbon emissions and evolution

By sc604 from University of Cambridge - Department of Earth Sciences. Published on Jul 20, 2017.

The researchers, from the University of Cambridge, used existing measurements of carbon and helium from more than 80 volcanoes around the world in order to determine its origin. Carbon and helium coming out of volcanoes can either come from deep within the Earth or be recycled near the surface, and measuring the chemical fingerprint of these elements can pinpoint their source. When the team analysed the data, they found that most of the carbon coming out of volcanoes is recycled near the surface, in contrast with earlier assumptions that the carbon came from deep in the Earth’s interior. “This is an essential piece of geological carbon cycle puzzle,” said Dr Marie Edmonds, the senior author of the study.

Over millions of years, carbon cycles back and forth between Earth’s deep interior and its surface. Carbon is removed from the surface from processes such as the formation of limestone and the burial and decay of plants and animals, which allows atmospheric oxygen to grow at the surface. Volcanoes are one way that carbon is returned to the surface, although the amount they produce is less than a hundredth of the amount of carbon emissions caused by human activity. Today, the majority of carbon from volcanoes is recycled near the surface, but it is unlikely that this was always the case.

Volcanoes form along large island or continental arcs where tectonic plates collide and one plate slides under the other, such as the Aleutian Islands between Alaska and Russia, the Andes of South America, the volcanoes throughout Italy, and the Mariana Islands in the western Pacific. These volcanoes have different chemical fingerprints: the ‘island arc’ volcanoes emit less carbon which comes from deep in the mantle, while the ‘continental arc’ volcanoes emit far more carbon which comes from closer to the surface.

Over hundreds of millions of years, the Earth has cycled between periods of continents coming together and breaking apart. During periods when continents come together, volcanic activity was dominated by island arc volcanoes; and when continents break apart, continental volcano arcs dominate. This back and forth changes the chemical fingerprint of carbon coming to Earth’s surface systematically over geological time, and can be measured through the different isotopes of carbon and helium.

Variations in the isotope ratio, or chemical fingerprint, of carbon are commonly measured in limestone. Researchers had previously thought that the only thing that could change the carbon fingerprint in limestone was the production of atmospheric oxygen. As such, the carbon isotope fingerprint in limestone was used to interpret the evolution of habitability of Earth’s surface. The results of the Cambridge team suggest that volcanoes played a larger role in the carbon cycle than had previously been understood, and that earlier assumptions need to be reconsidered.

“This makes us fundamentally re-evaluate the evolution of the carbon cycle,” said Edmonds. “Our results suggest that the limestone record must be completely reinterpreted if the volcanic carbon coming to the surface can change its carbon isotope composition.”

A great example of this is in the Cretaceous Period, 144 to 65 million years ago. During this time period there was a major increase in the carbon isotope ratio found in limestone, which has been interpreted as an increase in atmospheric oxygen concentration. This increase in atmospheric oxygen was causally linked to the proliferation of mammals in the late Cretaceous. However, the results of the Cambridge team suggest that the increase in the carbon isotope ratio in the limestones could be almost entirely due to changes in the types of volcanoes at the surface.

“The link between oxygen levels and the burial of organic material allowed life on Earth as we know it to evolve, but our geological record of this link needs to be re-evaluated,” said co-author Dr Alexandra Turchyn, also from the Department of Earth Sciences.

The research was funded by the Alfred P. Sloan Foundation, the Deep Carbon Observatory and the European Research Council.

Reference:
Emily Mason, Marie Edmonds, Alexandra V. Turchyn. ‘Remobilization of crustal carbon may dominate volcanic arc emissions.’ Science (2017). DOI: 10.1126/science.aan5049.

Inset Image: Schematic diagram to show the possible sources of carbon in a subduction zone volcanic system.

Researchers have found that the formation and breakup of supercontinents over hundreds of millions of years controls volcanic carbon emissions. The results, reported in the journal Science, could lead to a reinterpretation of how the carbon cycle has evolved over Earth’s history, and how this has impacted the evolution of Earth’s habitability. 

The link between oxygen levels and the burial of organic material allowed life on Earth as we know it to evolve, but our geological record of this link needs to be re-evaluated.
Alexandra Turchyn
ISS013-E-24184 (23 May 2006) --- Eruption of Cleveland Volcano, Aleutian Islands, Alaska is featured in this image photographed by an Expedition 13 crewmember on the International Space Station.

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Global cooling from a less leaky Ice Age Ocean

From Department of Earth Sciences. Published on Jul 13, 2017.

A new survey and analysis of global radiocarbon dates derived from ocean-dwelling micro-organisms is providing important new measures of the difference between the ocean today and 20,000 years ago, at the height of the last Ice Age.

Shape-shifting rangeomorphs cut fractal frills to grow and grow

From Department of Earth Sciences. Published on Jul 10, 2017.

Around 571 million years ago life first made a grade-change from organisms that were only a few centimetres in size to those that grew to two metres or so high. The organisms that were able to take off in this way were the extinct rangeomorphs, softbodied frondose organisms that grew rooted in the seabed of late Precambrian times.

Don’s Diary

From Department of Earth Sciences. Published on Jul 05, 2017.

This article first appeared in CAM - the Cambridge Alumni Magazine – Issue 81 Easter 2017. Professor Marian Holness is Professor of Petrology and a Fellow of Trinity College.

Unravelling the tectonic regime: Almeria, Spain

By Charlotte Jackson from Cambridge Earth Sciences blog. Published on May 24, 2017.

Early Sunday morning the department was full of life as bleary eyed finalists arrived eager for their final field trip. The Spanish coastline would not disappoint, a week of beautiful sunshine and exciting, challenging geology lay ahead. With the aim to unravel the tectonic regime that has dominated this region we started off on Monday …

A journey across the equator: Arran 2017

By Victoria Honour from Cambridge Earth Sciences blog. Published on May 24, 2017.

The end of Lent term brings with it the start of the undergrad fieldtrip season. The first group of 1A’s left bright and early on Thursday morning for the Ayrshire coast in Scotland, ready for their first proper fieldtrip away from Cambridgeshire. The coach journey was very long, but we eventually made it to the …

Impressions from ‘not a geologist’ – the Dorset section of the 1B South West Trip

By Sarah Humbert from Cambridge Earth Sciences blog. Published on Oct 17, 2016.

Day 1 – Off we go! I’d never been to any part of the southwest so I was very much looking forward to my second Earth Sciences Department field trip – third if we count an afternoon at Ketton Quarry. My first big trip had been to Arran the previous year, to my mind it …

Sun, sea and subduction: Spain 2016

By Clare Donaldson from Cambridge Earth Sciences blog. Published on May 26, 2016.

Spain 2016 outshone Spain 2015 the moment the plane took off from Gatwick Airport. David Hodell, our mighty leader, breathed a sigh of relief when French Air Traffic Control decided not to strike at the same time as the Cambridge fourth-year Earth Sciences fieldtrip. 29 students and 8 demonstrators left the drizzle behind us and …

Greece 2015: faults, fissures, footwalls and more

By Greg Palmer from Cambridge Earth Sciences blog. Published on Jan 12, 2016.

The end of Michaelmas had arrived and it was time for 21 Part IIs and 8 demonstrators to head for Greece. By coach and plane we travelled to Athens, where we picked up our minibuses (without telling the hire company how much off-roading we had planned!) and headed for Loutraki… Woken by birdsong and lure …