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This guest post was contributed by a scientist, student or a professional in the Earth, planetary or space sciences. The EGU blogs welcome guest contributions, so if you've got a great idea for a post or fancy trying your hand at science communication, please contact the blog editor or the EGU Communications Officer Laura Roberts Artal to pitch your idea.

Imaggeo on Mondays: Moulin on the Athabasca Glacier

Moulin . Credit: Stephanie Grand (distributed via  imaggeo.egu.eu)

Moulin . Credit: Stephanie Grand (distributed via imaggeo.egu.eu)

The Athabasca Glacier is located in Jasper National Park, in the Canadian Rockies. It is the largest of seven named distributary glaciers carrying ice away from the Columbia Icefield, the largest icefield in the Rocky Mountains. This picture shows a summer meltwater stream running on the surface of the ice disappear in a moulin – a vertical shaft forming part of the glacier’s internal plumbing system. After entering the moulin, the meltwater may flow through englacial streams before reaching the bottom of the glacier, where it forms a glacial deposit known as a kame (see this video for a description of kame formation processes filmed on location at the Athabasca glacier).

Easily accessible from the highway, the Athabasca glacier is one of the most striking places to observe first-hand the effects of climate change. Warmer temperatures have caused an acceleration of ablation processes such as surface melting and erosion, as shown in this picture. The toe of the glacier is currently retreating between 10 and 25 m each summer and the surface of the glacier is dropping down by more than 5 meters per year. It is expected that the Athabasca glacier will disappear completely within a generation.

Collectively, glaciers in Western Canada and Alaska are estimated to lose 20 to 30 per cent as much as what is melting annually from the Greenland Ice Sheet, compounding disruptions in ocean circulation patterns and global sea levels. The disappearance of these mountain glaciers also has implications for hydropower generation capacity and fisheries.  ​

By Stéphanie Grand, Lecturer at the Institute of Earth Surface Dynamics at the University of Lausanne

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: The organisation of a river system

Imaggeo on Mondays: The organisation of a river system

The picture shows the Elbe Rivervalley, one of the major rivers of Central Europe. It was taken from the Bastei Bridge close to Rathen, which towers 194 meters above the Elbe River in the state of Saxony in the south-eastern Germany. This region belongs to the national park known as Saxon Switzerland. Together with the Bohemian Switzerland in the Czech Republic, the Saxon Switzerland National Park forms the Elbe Sandstone Mountains, which represents the greatest cretaceous sandstone erosion complex in Europe and is popular with tourists and climbers.

The Elbe basin covers the largest area in Germany (65.5 %) and the Czech Republic (33.7 %). The smaller parts of the basin lie in the Austria (0.6 %) and Poland (0.2 %). It starts in the northern Czech Republic at an elevation of about about 1400 meters above sea level and flows via Bohemian, Germany, and into the North Sea at Cuxhaven. Therefore, the Elbe river system connects four countries as well as large German cities such as Dresden, Wittenberg, Magdeburg and Hamburg.

The sandstone of the Elbe Mountains was formed by accumulation of sands during a marine regression – a process where previously submerged seafloor becomes exposed due to receding ocean waters – (Cretaceous sea) millions of years ago. The varying sandstone formations that make up the mountains represent variations in pressure regime, horizontal structure and fossil content. After the marine regression, the developed sandstone formations were uplifted. The uplifted sandstone formations have been shaped by subsequent chemical and physical erosion and biological processes acting on the rocks. Moreover, the water masses of the Elbe River formed the valleys and streambeds. Therefore, the current state of the landscape of the Elbe Sandstone Mountains is characterised by the changes between plains, ravines, table mountains and rocky regions with undeveloped areas of forest. Human activity also plays an important role in the shaping of the highland region’s landscape as it is affected by settlements, tourisms and climbers.

The image illustrates how the interplay between long-term processes, such as geology, tectonic history, geomorphology, climate, biology and human influence shape landscapes.

By Tatiana Feskova, researcher at the Helmholtz Centre for Environmental Research.

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: Tombstones Mountains

Imaggeo on Mondays: Tombstones Mountains

This week’s Imaggeo image is brought to you by one of our network bloggers, Matt Herod. Of the image, Matt said ” this particular one is one of my all time favourites. I have even blown it up and hung it on my wall at home,” and we couldn’t agree more; this Canadian landscape is breathtaking. Dive into this post and let Matt take you on a tour of the hydrology, archaeology and volcanic history of the Tombstone Mountain Range.

The Yukon Territory in the fall is a wonderful place and may be among the most beautiful on Earth. As the days shorten the colours become more vibrant and the grasses and shrubs transform. Combine this with the stark and rugged nature of the landscape and you have a potent combination that begs to be explored and photographed.

The subject of this photo is the Tombstone Mountain Range just north of Dawson City, a world heritage site famous for its gold rush, the Sourtoe Cocktail and the funnest casino I have ever been to. The Tombstones constitute the headwaters of the North Klondike River which flows at the base of the valley in the photo and eventually meets up with the larger Klondike River and then joins with the Yukon River at Dawson. Hydrologically the Tombstones mark a continental divide and the transition from southern flowing rivers to northern ones takes place nearby as the many of the rivers just slightly to the north feed into the Peel River and eventually the mighty Mackenzie. A colleague of mine recently concluded a project on the North Klondike measuring the groundwater discharge and chemistry of the river over several years to understand the water sources and the effect of permafrost on the local hydrology.

Indeed, at the base of the valley there is a groundwater discharge point that builds up every winter into a large, layered sheet of ice called and aufeis. As the warmer groundwater continues to discharge throughout the winter it freezes when it meets the cold air forming the aufeis. These structures are often seen at groundwater discharge points in the far north.

The Tombstones themselves, named after the really pointy mountain in the background, are geologically very interesting. Indeed, this relief was created by igneous intrusions during the Cretaceous period. More recently, alpine glaciations shaped the terrain giving rise to a suite of interesting geomorphological and permafrost structures.

The region also has a fascinating archeological heritage and is home to over 70 sites dating back ~8000 years to the Holocene period and some of the earliest human incursions into North America via the Bering land bridge.

This photo was taken in August 2012 on my way up the Dempster Highway. I was collecting water samples for iodine-129 analysis and stopped off in the Tombstone Territorial Park for a sample.

By Matt Herod, researcher at Department of Earth Sciences at the University of Ottawa in Ontario, Canada.

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/.

Geosciences Column: The Oldest Eurypterid

Geosciences Column: The Oldest Eurypterid

The name of a newly found fossil of sea scorpion draws inspiration from ancient Greece warships and is a unique example of exceptional preservation, shedding light on the rich life of this bygone sea critter, explains David Marshall of Palaeocast fame. To learn more about the importance of giving new fossils names and what Pentecopterus decorahensis (as the new fossil is formally called) teaches us about a crucial time for biodiversification, read on!

It is considered best-practice that organisms, extinct or extant, be given a descriptive name. Triceratops, or ‘three horned-face’, is a perfect example of this. However scientists have often utilised some poetic license with this: Tyrannosaurus rex translates as ‘tyrant lizard king’, referring to its unrivalled size and ferocity, and Brontosaurus as ‘thunder lizard’, envisioning the noise produced by the placement of one of its gigantic legs. Recently the etymology of some names has become somewhat less poetically-descriptive and more, shall we say, ‘tabloid-newspaper-friendly’. The publication of names such as Dracorex hogwartsia, translating as ‘dragon king of Hogwarts’, do conjure images, even if it is done with a lot of artistic license. One animal with an equally abstract, but appropriate, name is described in BMC Evolutionary Biology today as Pentecopterus decorahensis.

Pentecopterus is a newly identified species of eurypterid, or ‘sea scorpion’. Eurypterids are an extinct group of chelicerates, the group containing the terrestrial arachnids (such as spiders and scorpions) and the aquatic ‘merostomes’ (represented today solely by the horseshoe crabs). The sea scorpions bear a close morphological resemblance to their namesakes, but perhaps may have been more closely related to horseshoe crabs. They were active predators or scavengers in the Paleozoic seas, between the Ordovician and Permian periods, approximately 460 – 250 million years ago. Some crawled along the ocean floor, whilst others were capable of limited swimming. Some reached incredible size, with the largest arthropod yet discovered, Jaekelopterus, estimated to have measured up to 2.5m.

Whilst most were quite small and generally unremarkable to look at, some eurypterids were truly the things of nightmares. Pentecopterus was a megalograptid: a particularly large and well-armed eurypterid family, typically measuring between 0.75 and 1.5m. Their appendages bore an array of inward-facing spikes, perfect for ambush, but without jaws, teeth or the sophisticated injection of enzymes, they (as with all eurypterids) would have simply shredded their prey into small enough pieces to eat. These were undoubtedly active predators, built as if solely for offence.

Results of the phylogenetic analysis plotted as an evolutionary tree. All of the branches of the tree leading to Pentecopterus must have occurred before we see our first Pentecopterus specimen (solid box). We can therefore infer ‘ghost ranges’ (dashed lines) for many eurypterid species and groups, where we believe they existed, but haven’t found fossils yet. Examination of rocks within the ghost ranges may yield new finds.

Results of the phylogenetic analysis plotted as an evolutionary tree. All of the branches of the tree leading to Pentecopterus must have occurred before we see our first Pentecopterus specimen (solid box). We can therefore infer ‘ghost ranges’ (dashed lines) for many eurypterid species and groups, where we believe they existed, but haven’t found fossils yet. Examination of rocks within the ghost ranges may yield new finds. Image credit: James C. Lamsdell et al / BMC Evolutionary Biology

Pentecopterus was discovered close to Decorah, Iowa, (hence the species name decorahensis) and is the oldest eurypterid yet described, hailing from the Darriwilian Stage of the Ordovician Period, some 467.3 – 458.4 million years old. This was a time of great change; the Ordovician biosphere underwent an explosion of species, form and ecology, in what is now dubbed the ‘Great Ordovician Biodiversification Event’. Organisms, previously confined to in and around the sea floor in the Cambrian period, began inhabiting the whole water column. Photosynthesising plankton took off (figuratively and literally) and the oceans were filled with new food webs based on this primary productivity. Sitting close to the top of the pile was Pentecopterus, a new kind of predator: large, armour-clad and armed to the teeth.

The genus name Pentecopterus is derived from marriage of the Greek words Πεντηκόντορος (Penteconter) with φτερός (–pterus, meaning wing) as the standard suffix for eurypterid genera. The Penteconter is a ship from the Archaic Period of Ancient Greece. This period saw the rapid expansion of the population of Greece, the formation of the city-state and founding of colonies. The Archaic period was a time of great social, political and economic change. This was primarily facilitated by the relationship the Ancient Greeks had with sea. But up until this time, there was little diversity in form of vessels; form did not necessarily follow function.

The Penteconter changed this. A vessel powered by 50 men (the name translating as fifty-oared), it was fast, manoeuvrable and built solely for aggression. It is considered to be the world’s first warship.

But far beyond the tabloid media coverage of ‘Oldest killer sea scorpion found’, and even my fondness for its poetical name, Pentecopterus is quite a remarkable specimen for our understanding of eurypterids.

Reconstruction: Scientific reconstruction of Pentecopterus. A, Dorsal view of a complete specimen. B, Genital segment. C, Ventral view of headshield. The semi-circular area is where the appendages would have inserted. D, Ventral view of prosoma with appendages in place. Scale 10cm.

Reconstruction: Scientific reconstruction of Pentecopterus. A, Dorsal view of a complete specimen. B, Genital segment. C, Ventral view of headshield. The semi-circular area is where the appendages would have inserted. D, Ventral view of prosoma with appendages in place. Scale 10cm. Image credit: James C. Lamsdell et al / BMC Evolutionary Biology

Despite most of the Pentecopterus specimens being disarticulated or fragmentary, with parts of the animal still yet to be discovered, there are enough pieces to put together a very good picture of its external anatomy. From the presence or absence of spines on certain parts of its appendages, this new species can clearly be assigned to the megalograptid family. For various anatomical reasons, the megalograptids have long been considered to be one of the most primitive groups of eurypterids, placed right at the base of the eurypterid ‘family tree’, with Pentecopterus as the oldest yet found supporting this theory. However, a phylogenetic analysis (a hypothesis of likely relationship based on numbers of shared anatomical characteristics) conducted on the eurypterid group provided some interesting ramifications.

The analysis placed the megalograptids with some other families belonging to the larger group Carcinosomatoidea. The interesting thing is that all other carcinosomatoids are typically at the top-end of the eurypterid family tree. Moving the megalograptids up from the bottom to join them at the top now means that we have one of the highest branches of the tree appearing first in geological time. The implication of this is that the whole tree has to be moved back in time. All the branches and splits that happen before we get to our carcinosomatoid group have to have occurred earlier than the time at which we find Pentecopterus. Whilst Pentecopterus is the earliest and most ‘primitive’ member of the megalograptids and carcinosomatoids, it cannot be the first eurypterid.

So, a quick recap: we found the oldest-yet eurypterid, we figured out it can’t actually be the first and we named it after a boat. And yet, we still haven’t got to the most-significant details of Pentecopterus. This lies within the exquisite preservation of the fossils.

If you are familiar with palaeontology, you may understand the fossil record is biased towards the preservation of the hard parts of organisms. The hard parts are useful and can tell us a lot about organisms: how they walked, how they ate, how they protected themselves, but most of the important information is lost. Consider your own body and the importance of your soft tissues and organs. Your sight, your touch, your taste, your reproductive organs. None of these would be preserved under normal circumstances. Soft-body preservation is exceedingly rare, but can provide unparalleled insights into extinct organisms. We have skin impressions from dinosaurs, muscle fibres from worms and optical pigments in squid. Pentecopterus has no soft-body preservation, but then again, it doesn’t need it.

Arthropods subscribe to a different ethos of construction; they wear their hard parts on the outside. This means that all their interactions with the environment occurs through their exoskeleton. Their eyes are hard and both their touch and taste is conducted through sensory hairs projecting through the hard cuticle. In Pentecopterus we find exceptional hard-body preservation. The fossils, though incomplete and disarticulated yield a treasure-trove of ecological information. The ‘teeth’ of Pentecopterus come equipped with thick spinose hairs, the legs and body bear the insertion sockets of finer hairs and swimming paddles have rows of sockets along the edges. What we’re seeing is how this organism sensed its environment. Although this information isn’t unique within eurypterids, it is exceedingly rare and this new species provides an essential point of comparison which hopefully will allow us to distinguish the exact function of the different hair types.

The Great Ordovician Biodiversification Event went on to shape the biosphere. It was a time of great change and whilst we may not know all of the events that occurred at the time, we may at least be able to discover how Pentecopterus felt about it.

By David Marshall, PhD student at the University of Bristol.

Reference

J. C. Lamsdell, Briggs D.E.G, Liu H.P., et al.: The oldest described eurypterid: a giant Middle Ordovician (Darriwilian) megalograptid from the Winneshiek Lagerstätte of Iowa, BMC Evolutionary Biology, doi 10.1186/s12862-015-0443-9, 2015