Imaggeo on Mondays: Ice forming on Chesapeake Bay

Imaggeo on Mondays: Ice forming on Chesapeake Bay

Sandwiched between the U.S states of Mayland, Delaware, Pennsylvania, New York State, the District of Columbia and Virginia, lies Chesapeake Bay, the largest estuary in North America. It is of huge ecological importance: “the bay, its rivers, wetlands and forests provide homes, food and protection for countless animals and plants”, says the Chesapeake Bay Program. Up to 150 major rivers and streams feed into the bay’s watershed.

Geologically speaking, Chesapeake Bay isn’t very old. As recently as 18,000 years ago the bay was covered by dry land. Global sea levels were up to 200m lower than they are at present and the last of the great ice sheets to cover America was at its peak. The rivers which flowed along the east of the continent had to cut valleys in what is now the bay bottom, to reach the continental shelf, and drain out to sea.

Fast forward 8,000 years and rising global temperatures caused the ice sheets to melt rapidly. Global sea levels started to rise, flooding the continental shelf and coastal areas, which now make up the modern-day estuary.

The process was helped along by a remarkable, much older geological feature. During the late Eocene, 35 million years ago, the Atlantic margin of the U.S was struck by a 3.5 km bolide (an asteroid or meteorite). The impact crater is located about 200 km south of Washington D.C., buried below 300 -500 m of sediments in Chesapeake Bay. Though the crater didn’t form the estuary, it did create a long-lasting depression in the area which helped determine the location of the bay.

Landsat satellite picture of Chesapeake Bay (centre) and Delaware Bay (upper right) – and Atlantic coast of the central-eastern United States. Credit: Landsat/NASA. Distributed by Wikimedia Commons.

Further reading

The Chesapeake Bay Bolide Impact: A New View of Coastal Plain Evolution: USGS Fact Sheet 049-98.

Chesapeake Bay Program

Landsat Images Offer Clearer Picture of Changes in Chesapeake Watershed (Nasa Landsat Science)

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

GeoTalk: Hellishly hot period contributed to one of the most catastrophic mass extinctions of Earth’s history

GeoTalk: Hellishly hot period contributed to one of the most catastrophic mass extinctions of Earth’s history

Geotalk is a regular feature highlighting early career researchers and their work. Following the EGU General Assembly, we spoke to Yadong Sun, the winner of a 2017 Arne Richter Award for Outstanding Early Career Scientists, about his work on understanding mass-extinctions. Using a unique combination of sedimentological, palaeontological and geochemical techniques Yadong was able to identify some of the causes of the end-Permian mass extinction, which saw the most catastrophic diversity loss of the Phanerozoic. 

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

Many thanks for inviting me here. I am currently working at the GeoZentrum Nordbayern, University of Erlangen-Nuremberg as a post-doc researcher.

I grew up in a small coastal town called Haiyang, east to the major city Tsingtao in North China. I moved to central China for university and majored in Geology at the China University of Geosciences (Wuhan) in 2004-2008.

This was followed by an exciting, 5 years split-site PhD program in which I spent two and a half years in China for field work and palaeontological training; half a year at Erlangen Germany for stable isotope and geochemical studies and the final 2 years at the University of Leeds, UK for training in sedimentology.

After my PhD, I successfully applied a fellowship from the Alexander von Humboldt Foundation and become an honourable Humboldtian.

In late 2015, two years after my PhD, I had 31 peer-reviewed papers including two in Science but was not fully prepared for the job market. It was already near the end of my fellowship. I only applied for one job—the O.K. Earl postdoc fellowship at the California Institute of Technology, US, but I didn’t get it. Completely unprepared for the situation, I was unemployed for about half a year.

I considered this the first setback in my early career. It taught me a valuable lesson; since I applied various research funding and fellowships and have never failed.

In early 2016, I was offered a postdoc position in a big project from the German Science Foundation (DFG forschergruppe) at Erlangen. I am very happy to be involved in the project and work again with many German and European colleagues.

Meet Yadong, pictured on fieldwork in the Himalayas. Credit: Yadong Sun.

During EGU 2017, you received an Arne Richter Award for Outstanding Early Career Scientists for your work understanding the end-Permian mass extinction. Could you tell us a little bit more about this period during Earth’s history?

The end-Permian mass extinction, which happened 252 million years ago, is the most devastating crisis seen in the Phanerozoic (the period of time during which there has seen life on Earth). However, the ultimate killing (or triggering) mechanism of this mass extinction is not fully understood and has been intensely debated for years.

Many fossil groups, in the ocean and on land were completely wiped out. The end-Permian mass extinction had profound influence on the evolution of life on Earth; such was the scale of the dying at this time. Extinction losses appear non-selective; virtually no groups escaped unscathed.

In the oceans some of the most abundant organisms such as the brachiopods (two-shelled organisms), radiolaria and foraminifera were almost (but not quite) eliminated whilst the rugose corals, tabulate corals, goniatites and trilobites were forever lost.

On land, the dominant herbivorous animals, the pareiasaurs, together with the gorgonopsids, the top predators, were lost. They lived in a world in which the dominant trees were the seed-bearing gymnosperms (e.g. glossopterids, gigantopterids, cordaites). All these groups, together with many other animals, including diverse insect groups, failed to survive the extinction.

After the mass extinction, the Early Triassic world was a time of extraordinary low diversity with the same monotonous communities found everywhere. For example, there is a 5 million year gap during which corals are not found in the rock record.

On land this included assemblages dominated by a shrub-like tree fern called Dicroidium, whilst the dominant animal was Lystrosaurus a pig-sized herbivore, belonging to a group called the dicynodonts.

In the world’s oceans, in the immediate aftermath of the extinction, it was the mollusks which occurred in the greatest numbers; a bivalve called Claraia was prolifically abundant just about everywhere.

It took an unusually long time (around 4-5 million years) for the biosphere to start recovering from the end-Permian mass extinction. This is much longer than after other mass extinctions and has lead scientists to speculate that the harsh conditions, responsible for the extinction in the first place, may have persisted for long afterwards.

At the same time, ocean chemistry was probably very different to modern day Earth. The oxygen levels in seawater were very low.

Despite the debate, what do scientists know about the causes of the end-Permian extinction?

The causes of the end-Permian mass extinction are, as a matter of fact, not perfectly understood. There are many different hypotheses. The key is to test the different hypotheses.

At the moment, we know with quite some certainty that anoxia (no free oxygen in seawater) and high temperatures both likely contributed to the end-Permian mass extinction.

Around the time of the extinction, there was massive volcanic activity in present day Siberia, known as the Siberian Traps. The lavas they left behind are known as the Siberian flood basalts. The eruption of the super volcano triggered global warming, voluminous volcanic CO2 inject to the atmosphere could lead to ocean acidification. This is because CO2 reacts with water and becomes carbonic acid (CO2 + H2O ↔ H2CO3). This is a very new and popular hypothesis to explain the mass extinction.

However, I myself am not fully convinced by the ocean acidification theory for the end-Permian mass extinction because there is a lot of evidence for carbonate over-saturated conditions at this time too. Carbonate saturated conditions mean that seawater contains very high concentrations of species such as CO32- and HCO3. They easily combine with Ca2+ and precipice as limestone and calcite cements. High concentrations CO32- and HCO3 have a buffering effect which inhibit the reaction forming carbonic acid. Therefore, it is not really possible to have ocean acidification and carbonate over-saturation at the same time. More detailed studies are needed to investigate this paradox.

In the past, some scientists proposed a sudden cooling or bolide impact as potential causes for the extinction, but these theories are no longer popular because of a lack of evidence.

In your presentation at EGU 2017 you spoke about how the extinction was accompanied by a rapid temperature rise, from 25 °C to 32 °C. How were you able to establish that such a significant temperature rise occurred?

I use oxygen isotope thermometry from conodonts: an extinct eel-like creature. Oxygen has two isotopes—18O and 16O. The ratio of the two isotopes in an animal is proportional to temperature from the oxygen isotope ratio of the water they ingest.

Reconstruction of temperatures for the end-Permian mass extinction is not easy since most shelly fossils died out. Those preserved are often subject to burial changes and therefore no longer preserve the original environmental information.

On the other hand, conodonts survived the end-Permian mass-extinction and are ideal for oxygen isotope analyses. They are very tiny (typically ~300 micro meter long) and consist of biogenic apatite. Apatite has 4 very robust P-O chemical bonds and very difficult to be altered after burial. Therefore, measuring oxygen isotope ratio of conodonts could help solved the problem.

However, because conodonts are so small and rare in rocks, I had to collect 2 tons of carbonate rocks dissolve the rock in acetic acid and pick the conodonts one by one under a binocular microscope, to get a big enough sample! It was a lot of work and required a lot of patience.

A Triassic conodont from south China. Credit: Yadong Sun.

That certainly sounds like painstaking work! Once the tedious task was completed, how were you able to link the temperature records you deciphered from the conodonts with the mass extinction?

All living creatures have a thermal threshold, also called thermal tolerance – the temperature range which they are able to tolerate to survive. It varies significantly amongst different groups. Most animals, on land or in the oceans, cannot live in environments that are consistently hotter than 47 °C. However, certain groups of desert ants and scorpions have developed special mechanisms and can survive 53 °C for a very brief time. Another example is the elevated seawater temperatures which contribute to high death rates of corals.

High temperatures supress photosynthesis. In most C3 plants, at temperatures above 35°C, photorespiration exceeds photosynthesis, wasting the energy generated by the plants.  in most C3 plants. Under such circumstances, C3 plants will stop growing and probably die shortly after. Maximum growth rates of single-celled algae in the ocean are normally achieved below 40°C.

A significant rise in seawater temperatures has many negative effects. One of them is that the amount of oxygen dissolved in seawater decreases as temperature rises, while animals use up more energy to perform even the simplest tasks. . This is one reason for which most marine groups prefer environments < 35°C.

These observations tie mass extinctions with temperature increase.

For our study, once the oxygen isotope ratios of conodonts are measured, we can use it in an equation to calculate the absolute temperature of the seawater at the time. The results show significantly higher ocean temperatures than today. We know the equation explains the relationship accurately because it was established in aquariums where scientists raise fishes in controlled temperatures. As temperatures are known, they measure the oxygen isotope of the water and fish teeth and established the oxygen isotope—temperature equation.

What do your findings mean for the current understanding of the causes of the mass-extinction?

This is an excellent question. There are quite some studies which postulate global warming as a potential killing mechanism for the end-Permian mass extinction. There is a link between the timing of the massive eruptions of the Siberia Large Igneous Province and the end-Permian mass extinction, which has led scientists to propose different warming scenarios. They are all correct, but they are not able to show direct evidence for their hypotheses or quantify the temperature change.

Our data show the worst-case scenario in terms of temperature rise and the mass mortality of species. This does not necessarily imply high temperatures killed everything because many adverse environmental conditions could trigger synergetic effects (for example low oxygen levels). Our study set an example for comparison.

Our results mean that rapid warming, such as what we are encountering at present, is truly worrying.

Yadong, thank you for speaking to me about your reasearch. As an award winner with an impressive career so far, what advice do you have for early career scientists?

Europe is probably the best place in the world for young scientists. It provides considerable fair funding opportunities and many possibilities to work with other scientists in the EU.

However, it is undeniable that fixed positions in academia are rare and highly competitive. It is always the best to go to meetings/conferences at least once a year to showcase your research, meet colleagues and seek collaboration opportunities.

Research projects nowadays are much more complex. Many tasks cannot be done by one person or one team. The success of a young scientist cannot be achieved without the support of senior scientists as well as the community.

Also don’t be shy to contact people and always be prepared for the job market. In the post-doc stage, if your project is very challenging, the best strategy is to work on some small projects on the side and keep publishing.

Interview by Laura Roberts Artal (EGU Communications Officer)


Sun, Y. Climate warming during and in the aftermath of the End-Permian mass extinction, Geophysical Research Abstracts, Vol. 19, EGU2017-2304, 2017, EGU General Assembly, 2017

Geoscience communication: A smart investment

Geoscience communication: A smart investment

In this post, originally published in June 2017 on the blog of the Geological Society of America (GSA), Terri Cook, a science and travel writer and former winner of the EGU’s Science Journalism Fellowship, argues the importance of quality science communication as a means for scientists to make their research accessible to a broad audience. One way to achieve this is working with a science journalist who can help researchers bring their work to life. To facilitate this partnership and to encourage science journalists to develop an in-depth understanding of the research questions, approaches, findings and motivation which drives geoscientists, the EGU launched the Science Journalism Fellowship. Now in its 7th edition, the 2018 competition opens today. The fellowships enable journalists to report on ongoing research in the Earth, planetary or space sciences, with successful applicants receiving up to €5000 to cover expenses related to their projects. The deadline for applications is 5th December 2017.

The dissemination of new knowledge is an integral part of the scientific enterprise; regular publication of high-impact, peer-reviewed articles is one of the most important metrics for measuring a scientist’s success. Due to the technical nature of these manuscripts, however, such communication does not typically boost the public’s understanding of the specific study results — or of science in general.

Yet, according to the Science Literacy Project, scientific research and novel technologies “play a major role in key political, economic, cultural and social policy discussions, as well as in public dialogue.” In an age of “alternative facts” and shrinking science budgets, and a time when the U.S. risks losing its edge in research and development, advocating for an evidence-based approach to decision making, which is independent of political views, has become crucial. So too has successfully reaching policymakers and the public, who must wrestle with the science underpinning a host of geoscience-related issues with important societal ramifications, from energy development to procuring mineral resources vital to our national security, in order to make informed decisions.

While there is much that individual scientists can do to disseminate their research and promote civil discourse, including holding public talks, harnessing social media, and writing for popular audiences, these are time-consuming endeavors. In addition, communicating with a lay audience is a skill; it’s easy to become mired in jargon, and there may be gaps between what scientists assume the public knows and what it actually does, according to a 2013 article in the Journal of Undergraduate Neuroscience Education. Plus most scientists, according to that same article, don’t receive any formal training on how to communicate scientific topics to the public, and there is often little incentive to prioritize this.

Science journalists like myself arguably serve an important societal role by disseminating the results of rigorous, peer-reviewed research to broader audiences.

“Our common mission,” writes Alison Fromme in The Science Writers’ Handbook, “is to explain very complicated things with both maximum simplicity and maximum accuracy.” A significant part of our job is to ask tough questions. “This critical questioning is important, and what it needs more than anything else is experience,” said BBC News Correspondent Pallab Ghosh in a 2013 panel discussion.

But even as the need for experienced science journalists continues to rise, the number of full-time jobs in this field, as well as the pay rate for freelancers, continues to decrease while the workload has generally increased, according to a 2009 Nature survey. This has led to some alarm.

“Independent science coverage is not just endangered, it’s dying,” said science journalist Robert Lee Hotz of the Wall Street Journal.

What then can geoscientists do to help avert what Gosh has called “a crisis in science journalism”? Journalists need honest answers from scientists, including an assessment of a study’s limitations and flaws, as well as its significance, in order to provide a balanced assessment of the research. We also need quotations to help us communicate the relevance and impact of scientists’ findings. One of the easiest ways to acquire the insight and capture the myriad details necessary to write an informative and captivating article is to visit a researcher onsite. In the geosciences, this is often in the field. Yet there is little support for science journalists to do this; few outlets will pay such expenses, especially for freelancers, who account for roughly half the number of science journalists.

To encourage the in-depth understanding of geoscientists’ approaches, research questions, motivations, and findings, the European Geosciences Union (EGU) has established an annual Science Journalism Fellowship that provides funding specifically intended for journalists to visit geoscientists in the field. The annual award of €5000 is typically split between two recipients each year, so since its inception in 2012 a dozen journalists, including myself, have received awards.

While the journalists benefit, so too do the scientists; their research receives wide exposure in prestigious publications, and they are given the luxury of being able to explain the intricacies of their work, such as dating previous motion along major faults in Nepal, and its implications first-hand and directly answering journalists’ questions as they arise.

But I would argue that it’s the general public who benefits the most. During the fellowship’s first four years, the seven recipients produced 18 pieces of science reporting, ranging from blog articles to a book, in a wide variety of outlets that included Nature, Science, Der Tagesspiegel, and EGU’s GeoLog blog. The topics, which are proposed by the journalists, have covered a broad range of geoscience disciplines, from the disastrous historic eruption of Iceland’s Laki volcano and fracking in Europe to my proposal about using dams to unleash artificial floods in order to restore rivers’ ecological integrity.

Recognizing the many potential benefits of better communicating the value of geoscience, the Geological Society of America (with the help of several generous donors) also recently established an annual Science Communication Fellowship.  The intent of this ten-month position is to help improve communication of geoscience knowledge between the members of GSA and the non-scientific community. I hope that other societies will soon follow suit. We are living in a period of unprecedented human influence on climate and the environment; establishing these awards sends a strong signal that geoscience communication is a priority — as well as a smart investment.

Terri Cook is a freelance science and travel writer based in Boulder, Colorado. 

Imaggeo on Mondays: One of the oldest evergreen rainforests in the world

Imaggeo on Mondays: One of the oldest evergreen rainforests in the world

A blazing sky and shimmers cast by water ripples frame the spectacular beauty of one of the world’s oldest treasures: an evergreen rainforest in Thailand. Today’s featured image was captured by Frederik Tack, of the Institute for Space Aeronomy in Brussels.

This picture was taken during sunset between the limestone mountains with the sunlight reflecting on beautiful Ratchaprapha lake in Khao Sok National Park.

Khao Sok National Park is one of the oldest evergreen rainforests in the world since Thailand has remained in a similar equatorial position throughout the last 160 million years. The climate in the area has been relatively unaffected by ice ages, as the landmass is relatively small and has seas on both sides. Even whilst other places on the planet were suffering droughts, the Khao Sok region still received enough rainfall to sustain the forest.

Khao Sok is also famous for its vertiginous limestone cliffs or ‘karst’ mountains. In most of the region, ground level is about 200m above sea level with the average mountain heights around 400m. The tallest peak in the National Park is 960m high. The national park area is inhabited by a large range of mammals such as tigers, elephants, tapirs and many monkey species. Birds such as hornbills, banded pittas and great argus are as well forest residents. Less commonly seen reptiles include the king cobra, reticulated python, and flying lizards.

One of the most interesting areas is stunningly beautiful Cheow Lan or Ratchaprapha Lake in the heart of the National Park. It is an 165-square-kilometre artificial lake, created in 1982, by the construction of Ratchaprapha Dam as a source of electricity.

By Frederik Tack, of the Institute for Space Aeronomy in Brussels

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