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Living in a new Age

Living in a new Age

If you were suddenly told you were living in a different time period, what would your immediate reaction be? Changes in the calendar – even if it’s just terminology – have proven emotive in the past. In 1752, when England shifted from the Julian to Gregorian calendars, and 11 days were cut from 1752 to catch up, there are suggestions that civil unrest ensued.

Once again, the name of the period in which we live has recently changed; the Holocene is now subdivided into three parts, and we’re now living in the Meghalayan age, according to the International Commission on Stratigraphy (ICS). While there weren’t riots in the streets this time, it has proved controversial for some researchers.

The division of time into different epochs and eras is an important part of stratigraphy. While time marches on, ignorant of the names humans give to its divisions, defining periods like the Cretaceous and Jurassic helps scientists compare results from around the world, even where the fossil and sedimentary records differ. It also draws into sharp focus the globally significant differences between each period, often including the devastating mass-extinctions that mark the boundaries of a handful of these periods.

The Holocene has been for at least a century the term favoured to describe the period in which we live, with its beginning marked by the end of the last ice age. The date at which the Holocene began has been more and more closely defined by experts over time, to the now accepted value of approximately 11,650 calendar years before present. The Holocene period encompasses the emergence of human civilisation, and represents a period of relatively warmer, somewhat stable climate in comparison with the prior ice age.

After considerable debate, however, the ICS has decided that the Holocene should be further subdivided; now, the period from 11,650 and 8,200 years before present is the Greenlandian; the Northgrippian stretches from 8,200 to 4,200 years before present, and the Meghalayan defines the time between then and the present. Why did the Holocene need to be divided up as such? If it wasn’t broken, why fix it?

The International Commission on Stratigraphy (ICS) has updated the timeline for the earth’s full geologic history, dividing the Holocene into three distinct periods. What does that mean for the Anthropocene? (Credit: International Commission on Stratigraphy)

The distinctions between an ice age and a warmer period, also known as an interglacial period, are globally significant, and a good place to start when describing how Earth’s climate has changed over the past few hundred thousand years. The swings in global temperature and ice extent are large enough that we often ignore the subtler climate changes that occur within an interglacial or glacial period. However, sediment and fossil records from more recent eras are relatively well preserved (simply because those records have had less chance to be destroyed by other geological processes), and this enables us to explore more recent periods in finer detail. Looking within the Holocene, the transition between the Greenlandian and Northgrippian is marked by a dramatic cooling of the climate, while the Northgrippian – Meghalayan by an abrupt ‘mega-drought’ and cooling that affected the nascent agricultural societies developing at that time.

By dividing the Holocene into these bite-sized chunks, the ICS has drawn attention to these changes in the earth’s geological system and provided a global context to the climatic shifts of the last ten thousand years. It also helps emphasise that climate can and does change on timescales more abrupt that glacial-interglacial periods – something we need to remember when considering the likely effects of anthropogenic climate change.

So far, so scientific. So why have the changes upset some people? Well, there’s an elephant in the stratigraphic room that looms larger now that these changes have been officially ratified. If there’s anything that has marked out the Holocene as fundamentally different from other historical ages, it’s the growth of human society. In particular, we are now at a point in history where the actions of a specific species – humans – can have global effects on the stratigraphic record.

Humans have added large quantities of carbon dioxide to the atmosphere, sown radioactive isotopes across the oceans from nuclear bomb testing, and left waste deposits in environments from the top of Mt Everest to the middle of the Pacific Ocean. Many of these impacts could leave lasting traces in the sedimentary and fossil records, leading to some scientists calling for a new period of time – the Anthropocene. And this may not fit well with the ICS changes.

I spoke with Helmut Weissert, President of the EGU Stratigraphy, Sedimentology and Palaeontology Division about these changes, and he suggested that the new changes devised by the ICS might shift the debate over the Anthropocene, at least in the short term:

I am quite worried. After the introduction of the new subdivisions I cannot see how the Holocene working group soon will vote for a further subdivision of the Holocene. The Anthropocene working group is confronted with a difficult task. I can envisage that the Anthropocene will be used as an informal term, not officially defined and introduced into the Stratigraphic Chart. I use the term regularly in my writing and in talks, everybody understands the term, I can explain how man is a geological agent. So, we may have to continue using an excellent term which is not yet properly defined, but most people do not care about the definition.

The Anthropocene is certainly an effective term to draw the attention of the wider public to the impact of society on global geological cycles. But from a stratigraphic perspective, it offers a number of challenges. Where and when, for example, should the beginning of the period be set? Changes in geological periods require specific chemical changes that can be identified globally and an internationally agreed upon reference point – a physical location – that defines the base of the section. There are many potential examples that could be chosen to define the beginning of human interference in the natural system; ice cores showing the uptick in carbon dioxide at the industrial revolution, or ocean sediments attesting to nuclear bomb tests in the 1950s. But the choice of which section to pick is fraught.

Each stratigraphic division needs a reference point that defines the split between the prior time period and the one in question. Here, a ‘golden spike’ defines the base of the Ediacaran period (635 million years ago) in the Flinders Ranges of South Australia. (Credit: Bahudhara via Wikimedia Commons)

Moreover, preservation is a crucial part of stratigraphy; how much of human impact will in fact be preserved, especially after further anthropogenic changes? What if we clean up the environment? What if we dredge the ocean floor for rare metals, and, in doing so, extirpate the signal of the 1950s nuclear bomb tests? What if we melt the ice caps that record the incipient CO2 increases from the industrial revolution? Sure, these changes may be recorded elsewhere, but how can we be sure a reference stratigraphic section will remain intact?

And this brings us to a perhaps more philosophical point: what if the human impact on the natural system we see today is only a fraction of what is to come? Any Anthropocene we define now would be based only upon the impact to date, but future changes may make these seem small in comparison. What would come after the Anthropocene? The question echoes that of 20th century philosophers, asking what comes after Post-Modernism? Perhaps instead of stratigraphy, we should look to written history and recorded data to better contextualise our impact.

Whether we end up defining our current era as the Meghalayan, the Anthropocene, or something else, it seems clear that the debate has drawn increased attention to the short-term climate changes – and in particular those driven by human intervention. A better public appreciation of our role within the natural system is a vital step in limiting damaging future climate change.

by Robert Emberson

Robert Emberson is a Postdoctoral Fellow at NASA Goddard Space Flight Center, and a science writer when possible. He can be contacted either on Twitter (@RobertEmberson) or via his website (www.robertemberson.com)

Imaggeo on Mondays: A Colombian myth with geologic origins

Imaggeo on Mondays: A Colombian myth with geologic origins

This photograph shows El salto del Tequendama, a natural waterfall of Colombia, located in the Department of Cundinamarca at an altitude of 2400 metres above sea level and approximately 30 kilometres southwest of the country’s capital, Bogotá.

The Salto del Tequendama is a space of transit and connectivity between the warm lands of the Magdalena river basin and the cold lands of the Sumapaz paramo, a Neotropical alpine tundra located at 4,000 metres above sea level.

Dutch-Colombian geologist Thomas Van der Hammen concluded that approximately 60,000 years ago the entire savannah of Bogota (populated today by 9 million people) was covered by a large lake, known as the Humboldt Lake, and the associated wetland plants instead of the paramo vegetation seen today.

Over time, the climate became warmer and the bottom of the Humboldt Lake began to rise. 30,000 years ago, the lake’s waters were channelled through the Bogota River and led to the Salto del Tequendama, a real climate event that we Colombians received through the myth of Bochica, a legendary hero to the Colombian indigenous group the Muisca. Here is the summarised myth of Bochica and the Tequendama jump:

“… As the Muiscas had lost respect for the gods, they offended Chibchacum, who had previously been the most beloved of their gods. He decided to punish them by flooding the savanna, for which he gave birth to the Sopo and Tivito rivers, which joined their rivers to the Funza (former name of the Bogotá River). The flood ended with many crops and human lives, until the people clamored with fasting and sacrifices to Bochica to free them from that calamity. The sage Bochica appeared on the rainbow and with his golden scepter, hit the rocks allowing the water to form a gigantic waterfall. So Bochica created the Tequendama jump.”

The large lake was partially dried and separated into smaller wetlands, where Andean plants, deer, foxes, weasels and more than 100 bird species made their home.

The waterfall, famous for its size, surrounding vegetation and vapourous waters, has been widely studied since 1668, when the Bishop of Panamá, Lucas Fernández de Piedrahíta made the first written record of its mythical origin story.

During the 18th and 19th centuries in particular, the Salto was one of the most famous natural attractions both locally and worldwide, due to the waterfall’s 157-metre drop onto a circular rocky abyss in a wooded region of permanent haze.

In the 19th century, large estates, also known as haciendas, were built on the region’s wetlands, and the natural environment was converted into places for fishing, hunting and logging. Through drainage channels, communities dried up the land to establish livestock and agricultural systems. In the last century, as the city of Bogota grew in population and size, the wetlands were filled to build neighborhoods, streets and avenues.

Like many Bogotanos, on a family weekend trip to relieve the stress generated by the chaos of the city and in search of clean air, I took this picture. The Salto was and always has been a fundamental part of the Bogota family mythology.

By Maria Cristina Arenas Bautista, National University of Colombia, Department of Civil Engineering and Agricultural (Bogotá)

Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submit their photographs and videos to this repository and, since it is open access, these images can be used for free by scientists for their presentations or publications, by educators and the general public, and some images can even be used freely for commercial purposes. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. Submit your photos at http://imaggeo.egu.eu/upload/.

Imaggeo on Mondays: Probing the Pliocene

Imaggeo on Mondays: Probing the Pliocene

The heights we go to for science…

This photograph shows a member of our team preparing to abseil down a cliff in the Charyn Canyon, in the Ili River basin of southeast Kazakhstan. The Charyn River and its tributaries, a branch of the Ili River north of the Tien Shan Mountains, have cut canyons up to 300 metres deep, carving through rocks of different geologic ages, some as old as 540 million years.

The name “Charyn” may derive from local Uighur or Turkic words for “ash tree” or “precipice” respectively, both of which are common in the area.

Charyn Canyon is presently characterized by a cold semi-arid climate, with dry summers and cold winters. However, these conditions are likely to have varied through time, becoming wetter, drier, warmer and cooler in response to major climate systems’ changing intensity and influence over the region.

Our research team investigates the past and present climate systems of the Cenozoic era, our current geological era which began 66 million years ago; the most recent 2.6 million years have been characterised by alternating ice ages and warmer so-called “interglacial” phases, and saw the evolution of humans. More specifically, we study climate systems in one of the most remote regions of Central Asia, known as the Eurasian Continental Pole of Inaccessibility. The area is a challenging place for climate research since it has no marine or ice core records, the most common calendars of ancient climate.

This region is poorly understood yet important within the global climate system, since it lies at the boundaries of the major northern hemispheric climate systems. These systems, such as the Siberian high pressure system and Asian monsoons, are likely to have shifted, expanded and contracted over time. These changes occur in response to factors like mountain uplift, and changes in the Earth’s orbital patterns and incoming solar radiation.

The aim of our study is to reconstruct climatic change over this period. By analysing various chemical and physical characteristics of the sediments, such as their age, magnetism, grain size and chemistry, we can reconstruct quantitative palaeoclimatic variability through time.

Here we focus on an 80-metre thick layer of sediment, which alternates between layers of river-transported gravels and wind-blown dust deposits, known as loess. Younger sedimentary layers have thicker dust deposits, reflecting a long-term aridification trend in the Ili Basin and, more broadly, Central Asia.

Our preliminary results from our fieldwork indicate that the canyon’s sediments represent an uninterrupted representation of the region’s climate from the Pliocene to early Pleistocene (from approximately 4.5 to 1 million years ago).

Achieving a comprehensive geological sampling of the Charyn Canyon was only possible by abseil. Our fieldwork, undertaken from May to June 2017, was a hot and dusty business, but ultimately a lot of fun. Definitely not for those with a fear of heights!

By Kathryn Fitzsimmons, Max Planck Institute for Chemistry, Germany and Giancarlo Scardia, São Paulo State University, Brazil

GeoTalk: How will large Icelandic eruptions affect us and our environment?

GeoTalk: How will large Icelandic eruptions affect us and our environment?

Geotalk is a regular feature highlighting early career researchers and their work. In this interview we speak to Anja Schmidt, an interdisciplinary researcher at the University of Cambridge who draws from atmospheric science, climate modelling, and volcanology to better understand the environmental impact of volcanic eruptions. She is also the winner of a 2018 Arne Richter Award for Outstanding Early Career Scientists. You can find her on twitter at @volcanofile. 

Thank you for talking to us today! Could you introduce yourself and tell us a little more about your career path so far?

I was born and raised in Leipzig, Germany. I started my career completing an apprenticeship as an IT system engineer with the engineering company Siemens. I then decided to combine my interests in geology and IT by studying geology and palaeontology (with minors in Computing/IT and Geophysics) at the University of Leipzig in Germany. As part of my degree programme, I also studied at the University of Leeds’ School of Earth and Environment as an exchange student. I liked studying there so much I ended up returning to Leeds for a PhD.

My PhD on the atmospheric and environmental impacts of tropospheric volcanic aerosol again combined my interests in computing and volcanology, although I had to educate myself in atmospheric physics and chemistry, which wasn’t easy to begin with. However, I was embedded in a diverse,   supportive research group with excellent supervision, which eased the transition from being a geologist to becoming a cross between an atmospheric scientist and a volcanologist.

Initially, being neither one nor the other made me nervous. My supervisors and mentors all had rather straightforward career paths, whereas I was thought of as an atmospheric scientist when I presented my research in front of volcanologists and as a volcanologist when I presented to atmospheric scientists.

After my PhD, I spent just under 2 years at one post-doc before securing an independent research fellowship at the University of Leeds. The first year of total independence and responsibility as principle investigator was very challenging, but after a while I began to appreciate the benefits of the situation. I also really started to embrace the fact that I would always sit between the disciplines. I spent my summers in the United States at the National Centre for Atmospheric Research, helping them to build up their capability to simulate volcanic eruptions in their climate model. These research visits had a major impact on my career as they generated a lot of new research ideas, opened up opportunities and strengthened my network of collaborators greatly.

I considered myself settled when, shortly before the end of my fellowship, a lectureship came up. It had the word ‘interdisciplinary’ in its title and I simply couldn’t resist. Since September 2017, I have been an interdisciplinary lecturer at the University of Cambridge in the UK.

At this year’s General Assembly, you will receive an Arne Richter Award for Outstanding Early Career Scientists for your work on the environmental impacts of volcanic eruptions. What brought you to study this particular field?

I have always been fascinated by volcanic eruptions, but my first active volcano viewing wasn’t until college, where I had to chance to travel to Stromboli, a volcanic island off the coast of Sicily. While studying at the University of Leipzig, I used every opportunity to join field trips to volcanoes. I ended up spending 10 weeks in Naples, Italy to work with Giovanni Chiodini, a researcher from the National Institute of Geophysics and Volcanology in Rome, and his team on CO2 degassing from soils at the Solfatara volcano. Later on I was awarded a scholarship from the University of Leeds, which allowed me to delve deeper into the subject, although I ended up learning as much about atmospheric science and computer modelling as about volcanology.

Anja in front of the 2010 Fimmvörðuháls eruption in Iceland. Fimmvörðuháls was the pre-cursor eruption to Eyjafjallajökull. Credit: Anja Schmidt.

My PhD work focused on Icelandic volcanism and its potential effects on the atmosphere as well as society. In 2010, during the 3rd year of my PhD studies, Eyjafjallajökull erupted in Iceland. While an eruption like this and its impacts did not really come as a surprise to a volcanologist, I personally considered it a game-changer for my career. I had an opportunity to witness the pre-cursor eruption in Iceland and present my research. Within a matter of months, interest in my work increased. I even started to advise UK government officials on the risks and hazards of volcanic eruptions in Iceland.

In August 2014, an effusive eruption started at the Holuhraun lava field in Iceland. To this date, analysing field measurements and satellite data of the site and modelling simulations keeps me busy. Many of my senior colleagues told me that there is one event or eruption that defined their careers; for me that’s the 2014-2015 Holuhraun eruption.

At the General Assembly you also plan to talk about your work on volcanic sulphur emissions and how these emissions can alter our atmosphere as well as potentially affect human health in Europe. Could you tell us a little more about this research?

On average, there is one volcanic eruption every three to five years in Iceland. The geological record in Iceland also reveals that sulphur-rich and long-lasting volcanic eruptions, similar to Iceland’s Laki eruption in 1783-1784, occur once every 200 to 500 years. Sulphur dioxide and sulphate particles produced by volcanic eruptions can have detrimental effects on air quality and human health. Historical records from the 1780s imply that the Laki eruption caused severe environmental stress and contributed to spikes in mortality rates far beyond the shores of Iceland. While these long-lasting eruptions occur much less frequently than more typical short-duration explosive eruptions (like Grímsvötn 2011), they are classified as ‘high-impact’ events.

I was always interested in investigating how a similar magnitude eruption like Laki’s would affect modern society. By combining a global aerosol microphysics model with volcanological datasets and epidemiological evidence, I led a cross-disciplinary study to quantify the impact that a future Laki-type eruption would have on air quality and human health in Europe today.

Our work suggests that such an eruption could significantly degrade air quality over Europe for up to 12 months, effectively doubling the concentrations of small-sized airborne particles in the atmosphere during the first three months of the eruption. Drawing from the epidemiological literature on human response to air pollution, I showed that up to 140,000 cardiopulmonary fatalities could occur across Europe due to such an eruption, a figure that exceeds the annual mortality from seasonal influenza in Europe.

In January 2012, this discovery was used by the UK government as contributing evidence for including large-magnitude effusive Icelandic eruptions to the UK National Risk Register. This will help to mitigate the societal impacts of future eruptions through contingency planning.

Anja and her colleague Evgenia Ilyinskaya from the University of Leeds carrying out measurements during the 2014-2015 Holuhraun eruption in Iceland. Credit: Njáll Fannar Reynisson.

Since then, we have done more work on smaller-magnitude effusive eruptions such as the 2014-2015 Holuhraun eruption in Iceland, showing that this eruption resulted in short-lived volcanic air pollution episodes across central and northern Europe and longer-lasting and more complex pollution episodes in Iceland itself.

Something that you’ve touched on throughout this interview are the challenges of ‘sitting between the disciplines.’ From your experience, what has helped you address these issues throughout your career?

Indeed, it is often challenging to sit between the disciplines, but it can also be very rewarding. It helps to ignore boundaries between disciplines. I also tend to read a lot and very widely to get an idea of key concepts and issues in specific fields. In addition, I think collaboration and a willingness to challenge yourself are key if you want to make progress and break traditional disciplinary boundaries.

Anja, thank you so much for speaking to us about your research and career path. Before I let you go, what advice do you have for aspiring scientists? 

Be curious and never hesitate to ask a lot questions, no matter how ‘stupid’ or basic they may seem to you. The latter is particularly true when it comes to cross-disciplinary collaboration and work.  I also didn’t always follow the conventional route most people would advise you to take to achieve something. Never be afraid to take a chance or work with some level of risk.

I also have two or three close mentors that I can approach whenever I require some advice or feedback. No matter what career stage you are at, I think it almost always helps to get an outsider’s perspective and insight not only when there are problems.

Finally, never forget to have fun. Some of my best pieces of work were done when I was surrounded by collaborators that are really fun to be with and work with!

Interview by Olivia Trani, EGU Communications Officer.

References: 

Ilyinskaya, E., et al.: Understanding the environmental impacts of large fissure eruptions: Aerosol and gas emissions from the 2014–2015 Holuhraun eruption (Iceland), Earth and Planetary Science Letters, 472, 309-322, 2017

Schmidt, A., et al.: Satellite detection, long-range transport, and air quality impacts of volcanic sulfur dioxide from the 2014–2015 flood lava eruption at Bárðarbunga (Iceland)Journal of Geophysical Research: Atmospheres12097399757, 2015

Schmidt, et al.: Excess mortality in Europe following a future Laki-style Icelandic eruption, Proceedings of the National Academy of Sciences, 108(38), 15710-15715, 2011