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Imaggeo on Mondays: Decreasing Moon

Decreasing Moon Imaggeo

This picture shows the decreasing Moon on May 6, 2015, two days after the full Moon, as viewed from Hamburg, Germany. There are still 96.4% of the lunar front illuminated.

The Moon does not glow on its own, but its surface reflects the sunlight. The Sun always illuminates a complete half of our natural satellite, which, in its orbit around our planet, always turns its face (which we see at full Moon) toward the Earth.

As the Moon is in constant motion with respect to the Earth and the Sun, the angle of view of the Moon – and thus its phase – changes from day to day. The particular angle at which the illuminated, visible lunar surface appears depends on latitude. Near the equator, for example, the boundary between the light and shadow sides of the crescent is approximately horizontal. In the northern hemisphere, an increasing Moon is illuminated on the right, a waning Moon on the left. In the southern hemisphere, the phases of the moon appear reversed: the illuminated surface of the Moon increases from left to right.

Edited from the description by Wolfgang Fraedrich. Read more at imaggeo.egu.eu

If you pre-register for the 2018 General Assembly (Vienna, 08–13 April), you can take part in our annual photo competition! From 15 January until 15 February, every participant pre-registered for the General Assembly can submit up three original photos and one moving image related to the Earth, planetary, and space sciences in competition for free registration to next year’s General Assembly!  These can include fantastic field photos, a stunning shot of your favourite thin section, what you’ve captured out on holiday or under the electron microscope – if it’s geoscientific, it fits the bill. Find out more about how to take part at http://imaggeo.egu.eu/photo-contest/information/.

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: Glacier-fed rivers

Imaggeo on Mondays: Glacier-fed rivers

A view of the southern edge of the Ladebakte mountain in the Sarek national park in north Sweden.

At this place the rivers Rahpajaka and Sarvesjaka meet to form the biggest river of the Sarek national park, the Rahpaädno. The rivers are fed by glaciers and carry a lot of rock material which lead to a distinct sedimentation and a fascinating river delta for which the Sarek park laying west of the Kungsleden hiking trail is famous.

As the borders of this picture are not straight (due to lens-correction in GIMP) an edited version has been uploaded.

Description by Jakob Keck, as it first appeared on imaggeo.egu.eu.

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 hunt for Antarctica’s oldest time capsule

Geosciences Column: The hunt for Antarctica’s oldest time capsule

The thick packs of ice that pepper high peak of the world’s mountains and stretch far across the poles make an unusual time capsule. As it forms, air bubbles are trapped in the ice, allowing scientists to peer into the composition of the Earth’s atmosphere long ago. Today’s Geosciences Column is brought to you by PhD researcher Ruth Amey, who writes about recently published research which reveals how a team of scientists might have found the oldest ice yet, which has important implications for our understanding of how Earth’s environment has changed over time.

Ice cores give us a slice through the past. By analysing the composition of ice and gas bubbles trapped within it, we can find out information about temperature, atmospheric conditions, deposition and even the magnetic field strength of the past.

This helps us to understand past conditions on the Earth, but currently the longest record is ~800,000 years (800 kyrs) old. One phenomenon scientists hope to understand better is a change in glaciation cycles. During the Mid-Pleistocene Transition, glaciation cycles changed from 40,000 year cycles related to the obliquity periodicity of the Earth’s orbit to longer, stronger 100,000 year cycles. Scientists of the ice-core community have their eyes on finding out why this change happened, and for this they need data from the onset of the change, between 1250 and 700 kyrs ago.

Which means we need much, much older ice.

A new study, published in EGU’s open access journal The Cryosphere has pinned down two locations where they think the base of Antarica’s ice sheet is significantly older. In fact they believe the ice could be as old as 1.5 million years, which would extend the current ice core record by ~700,000 years: nearly doubling it.

A Treasure hunt – using airborne radar and some simple models

The group, led by Frederic Parrenin at University of Grenoble Alpes, France, went on the hunt for the oldest ice East Antarctica could give them. The survival of ice is an interplay between many factors: the ice acts a little bit like a conveyor belt, being fed by accumulation, with the oldest information lost off the end by basal melting. This means areas of thinner ice, where there is less basal heating, often has a higher likelihood of the old, information-rich ice surviving.

Figure 2: A cross-section of ice in East Antarctica, from surface to bedrock, with colour bar showing the modelled ice age. The model identifies two patches of ice older than 1.5 Myr (shown in white): North Patch and Little Dome D Patch. Adapted from Figure 3 of Parrenin et al 2017.

Airborne radar can ‘see’ into the top three-quarters of the East Antarctica ice sheet. By identifying reflections within it, isochrones of ice of the same age can be traced. Parrenin’s group exploited an area in East Antarctica known as ‘Dome C’ with rich record of radar investigations. Using information derived from the radar, they then created a mathematical model, which balanced accumulation rate, heat flow and melting to give a simple 1-D ice flow model. This helps locate areas of accumulation and melting, which gives an indication of where ice might be the oldest, beyond the sight of the airborne radar. A nearby ice-core, EDC, also provided corroboration of their model.

X Marks the Spot

The team located two sites where they believe the ice to be older than 1.5 million years old, named Little Dome C and North Patch. And fortunately these sites are within a few tens of kilometres from the Concordia research facility, meaning drilling them is a real possibility.

This ancient ice could give vital insight into what happened in the Mid-Pleistocene Transition. What caused the new glaciation cycle onset? Was it a change in sea ice extent? A change in atmospheric dust? Decrease in carbon dioxide concentrations? Changes in the Earth’s orbit? The answers may well be locked in the ice.

By Ruth Amey, Postgraduate Researcher at the University of Leeds

 

References and Resources

Parrenin, F., Cavitte, M. G. P., Blankenship, D. D., Chappellaz, J., Fischer, H., Gagliardini, O., Masson-Delmotte, V., Passalacqua, O., Ritz, C., Roberts, J., Siegert, M. J., and Young, D. A.: Is there 1.5-million-year-old ice near Dome C, Antarctica?, The Cryosphere, 11, 2427-2437, https://doi.org/10.5194/tc-11-2427-2017, 2017

Berger, A., Li, X. S., and Loutre, M. F.: Modelling northern hemisphere ice volume over the last 3 Ma, Quaternary Sci. Rev., 18, 1–11, https://doi.org/10.1016/S0277-3791(98)00033-X, 1999

Imbrie, J. Z., Imbrie-Moore, A., and Lisiecki, L. E.: A phase-space model for Pleistocene ice volume, Earth Planet. Sc. Lett., 307, 94–102, https://doi.org/10.1016/j.epsl.2011.04.018, 2011

Jean Jouzel, Valérie Masson-Delmotte, Deep ice cores: the need for going back in time, In Quaternary Science Reviews, Volume 29, Issues 27–28, Pages 3683-3689, ISSN 0277-3791, https://doi.org/10.1016/j.quascirev.2010.10.002, 2010

Martínez-Garcia, A., Rosell-Melé, A., Jaccard, S. L., Geibert, W., Sigman, D. M., and Haug, G. H.: Southern Ocean dust-climate coupling over the past four million years, Nature, 476, 312–315, doi:10.1038/nature10310, 2011

Tziperman, E., and H. Gildor, On the mid-Pleistocene transition to 100-kyr glacial cycles and the asymmetry between glaciation and deglaciation times, Paleoceanography, 18(1), 1001, doi:10.1029/2001PA000627, 2003

Wessel, P. and W. H. F. Smith, Free software helps map and display data, EOS Trans. AGU, 72, 441, 1991

Imaggeo on Mondays: The best of imaggeo in 2017

Imaggeo on Mondays: The best of imaggeo in 2017

Imaggeo, our open access image repository, is packed with beautiful images showcasing the best of the Earth, space and planetary sciences. Throughout the year we use the photographs submitted to the repository to illustrate our social media and blog posts.

For the past few years we’ve celebrated the end of the year by rounding-up some of the best Imaggeo images. But it’s no easy task to pick which of the featured images are the best! Instead, we turned the job over to you!  We compiled a Facebook album which included all the images we’ve used  as header images across our social media channels and on Imaggeo on Mondays blog post in 2017 an asked you to vote for your favourites.

Today’s blog post rounds-up the best 12 images of Imaggeo in 2017, as chosen by you, our readers.

Of course, these are only a few of the very special images we highlighted in 2017, but take a look at our image repository, Imaggeo, for many other spectacular geo-themed pictures, including the winning images of the 2017 Photo Contest. The competition will be running again this year, so if you’ve got a flare for photography or have managed to capture a unique field work moment, consider uploading your images to Imaggeo and entering the 2018 Photo Contest.

Alpine massifs above low level haze . Credit: Hans Volkert (distributed via imaggeo.egu.eu).

The forward scattering of sunlight, which is caused by a large number of aerosol particles (moist haze) in Alpine valleys, gives the mountain massifs a rather plastic appearance. The hazy area in the foreground lies above the Koenigsee lake; behind it the Watzmann, Hochkalter, Loferer Steinberge and Wilder Kaiser massifs loom up behind one other to the right of the centre line. Behind them is the wide Inn valley, which extends right across the picture.

A lava layer cake flowing . Credit: Timothée Duguet (distributed via imaggeo.egu.eu)

Check out a post from back in May to discover how layers of alternating black lavas and red soils built up to form a giant ‘mille feuilles’ cake at Hengifoss, Iceland’s third-highest waterfall.

Sediment makes the colour . Credit: Eva P.S. Eibl (distributed via imaggeo.egu.eu)

Earth is spectacularly beautiful, especially when seen from a bird’s eye view. This image, of a sweeping pattern made by a river in Iceland is testimony to it. Follow the link to learn more about river Leirá which drains sediment-loaded glacial water from the Myrdalsjökull glacier in Iceland.

Movement of ancient sand . Credit: Elizaveta Kovaleva (distributed via imaggeo.egu.eu).

Snippets of our planet’s ancient past are frozen in rocks around the world. By studying the information locked in formations across the globe, geoscientist unpick the history of Earth. The layers in one of the winning images of the 2017 photo contest may seem abstract to the untrained eye, but Elizaveta Kovaleva (a researcher at the University of the Free State in South Africa) describes how they reveal the secrets of ancient winds and past deserts in a blog post we published in November.

View of the Tuva River and central mountain range
. Credit: Lisa-Marie Shillito (distributed via imaggeo.egu.eu).

Initially, this photo may seem like any other tropical paradise: lush forests line a meandering river, but there is much more to the forests in the foreground than first meets the eye.

On the way back from Antarctica. Credit: Baptiste Gombert (distributed via imaggeo.egu.eu).

Our December 2017 header image – On the way back from Antarctica, by Baptiste Gombert – celebrated #AntarcticaDay.

Angular unconformity. Credit: André Cortesão (distributed via imaggeo.egu.eu).

It is not unusual to observe abrupt contacts between two, seemingly, contiguous rock layers, such as the one seen above. This type of contact is called an unconformity and marks two very distinct times periods, where the rocks formed under very different conditions.

Find a new way . Credit: Stefan Winkler (distributed via imaggeo.egu.eu)

Stephan Winkler’s 2017 Imaggeo Photo Contest finalist photo showcases an unusual weather phenomenon…find out more about this process in the post from last year.

On the way back from Antarctica. Credit: Alicia Correa Barahona (distributed via imaggeo.egu.eu).

August’s social media header image showcases how, in the altiplano of Bolivia, Andean ecosystems, life and the hydrological cycle come together.

Icelandic valley created during a volcanic eruption. Credit: Manuel Queisser (distributed via imaggeo.egu.eu).

The image shows a valley in the highland of Iceland carved out during a volcanic eruption with lava coming from the area visible in the upper right corner. The landscape is playing with the viewers sense of relation as there is no reference. The valley is approximately 1 km wide. The lower cascade of the water fall is ca. 30 m high. A person (ca. 3 pixels wide) is located near the base of the water fall about 50 m away. It was our October header image.

Despite being one of the driest regions on Earth, the Atacama desert is no stranger to catastrophic flood events. This post highlights how the sands, clays and muds left behind once the flood waters recede can hold the key to understanding this natural hazard.

The heart of the Canadian Rocky Mountains. Credit: Jennifer Ziesch (distributed via imaggeo.egu.eu).

“I saw one of the most beautiful place on earth: The glacially-fed Moraine Lake in the Banff National Park, Canada. The lake is situated in the Valley of the Ten Peaks. The beautiful blue colour is due to the mix of glacier water and rock flour,” says Jennifer, who took the photograph of this tranquil setting.

Symbiosis of fire, ice and water . Credit: Michael Grund (distributed via imaggeo.egu.eu)

This mesmerising photograph is another of the fabulous finalists (and winner) of the 2017 imaggeo photo contest. The picture, which you can learn more about in this blog post, was taken at Storforsen, an impressive rapid in the Pite River in northern Sweden, located close to the site of a temporary seismological recording station which is part of the international ScanArray project. The project focuses on mapping the crustal and mantle structure below Scandinavia using a dense temporary deployment of broadband seismometers.

f you pre-register for the 2018 General Assembly (Vienna, 08 – 13 April), you can take part in our annual photo competition! From 15 January up until 15 February, every participant pre-registered for the General Assembly can submit up three original photos and one moving image related to the Earth, planetary, and space sciences in competition for free registration to next year’s General Assembly!  These can include fantastic field photos, a stunning shot of your favourite thin section, what you’ve captured out on holiday or under the electron microscope – if it’s geoscientific, it fits the bill. Find out more about how to take part at http://imaggeo.egu.eu/photo-contest/information/.