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The explosive history of Hekla volcano a

4 Nov

The explosive history of Hekla volcano and an insight into Iceland’s activity in this week’s Imaggeo on Mondays: http://bit.ly/18CAIcb. Image: Wolfgang Schwanghart http://ow.ly/i/3zEP7

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We are moving!

13 Jul

As you can see from our updated header, from Monday 16 July 2012 onwards, we will be moving GeoLog to a new, simpler address: http://geolog.egu.eu/. The content and layout of the blog on our new page are exactly the same as on this one – only the address is changing.

If you subscribed to this blog via email, you will be automatically subscribed to the posts in the new address. If you subscribed to this blog via WordPress, please follow our new blog by clicking on the “Follow” button on the bottom right corner of the new website.

Geolog has a new URL, update your bookmarks!

Imaggeo on Mondays: Cordillera del Paine

9 Jul

Cordillera del Paine by Martin Mergili, distributed by EGU under a Creative Commons licence.

Images such as the one above inspire scientists and nature lovers alike. This photograph, showing a Chilean landscape with elements representative of various Earth-science disciplines, is simply stunning. In a beautiful mix of shapes and colours, a quiet lake with floating icebergs appears tucked in between a roughed mountain in the background and a colourful double rainbow in the foreground.

The photographer, Martin Mergili of the University of Natural Resources and Life Sciences in Vienna, captured this inspiring scenery during a holiday trip a few years ago. The photo shows the eastern edge of the southern part of Cordillera del Paine, a “small but spectacular” mountain group in the Torres del Paine National Park, which is located in Chilean Patagonia almost 2,000 kilometres south of Santiago de Chile.

“The prominent peaks visible in the left portion of the image are the Cuernos del Paine,” Martin explains. “The rainbow in the foreground is not just decoration, it reflects the ever-changing weather patterns characteristic of that area. Even though it is located in the rainshade of the Cordillera at the edge of the semi-arid Patagonian lowlands, the westerlies bring a lot of moist air from the Pacific Ocean. The icebergs in the lake in the foreground (Lago Grey) originate from the large Glaciar Grey calving into the lake.”

More stunning images of this and other landscapes are available from Martin’s website.

Imaggeo is the online open access geosciences image repository of the European Geosciences Union. Every geoscientist who is an amateur photographer (but also other people) can submit their images to this repository. Being open access, it can be used by scientists for their presentations or publications as well as by the press. If you submit your images to imaggeo, you retain full rights of use, since they are licenced and distributed by EGU under a Creative Commons licence.

Geosciences column: For permafrost, (sediment) size does matter

4 Jul

In this month’s Geosciences Column, David Bressan – now a regular EGU contributor – highlights a recent result published in The Cryosphere with implications on the occurrence and preservation of alpine permafrost.

The last 150 years saw an increase of 0.8°C in the Earth’s mean global temperature. In mountain ranges like the European Alps, however, this rising trend is even more pronounced with an increase of 1.5°C in temperature observed over the same period. This rise not only accelerates the retreat of the alpine glaciers, but also causes the slow degradation of alpine permafrost – solid material with temperatures well below the freezing point of water at 0°C – and rock glaciers – lobes composed of a mixture of ice and rock debris, covered by a few meters of ice-free debris.

On a superficial glimpse, the permafrost seems relatively well isolated from superficial changes due to the cover of ice-free soil and rocks. However, measurements in the past few years have shown that the melting rate of ice inside the rock glaciers significantly increased in the last decades, which could lead to the destabilization of mountain slopes and could influence the hydrology of nearby springs.

To understand the behavior of permafrost in a warmer future it is therefore essential to understand how the material (for example different rock types) and the texture (like grain size or distribution) of the layers covering the permafrost transport heat from the warming surface into the frozen underground. Heat transfer in these layers can occur in two ways: conduction trough the rocky material or convection by mobile phases, like air or water, in the voids and pores of the material.

Scientists first investigated the site of the Murtel rock glacier, located in the mountains of the Swiss canton of Engadin, in 1970. The area has since become one of the best documented sites for mountain permafrost in the world. Permafrost occurs here below very heterogenous substrate like barren bedrock, vegetated bedrock, debris of a talus slope, fine-grained and coarse-grained debris of two rock glaciers. In a long-term project, geographer Sina Schneider and her team analyzed the temperature profiles of these different substrates, recorded in five boreholes over a period of eight years (2002–2010). The study was published last year in The Cryosphere, an open access journal of the European Geosciences Union.

Photographs of the different surfaces at the borehole locations in the investigation area, taken in summer 2009 (from Schneider et al. 2012).

The results confirmed in part previous observations, but showed also new intriguing finds. Freezing during late autumn and early winter influences significantly the temperature profile in all boreholes, as without an impermeable snow cover cold air can penetrate into the pores of the material. A dry winter with lacking or thin snow cover and rare freezing can therefore be more important for thawing permafrost than a hot summer.

Also the covering material can influence the behavior of the subsurface permafrost. Sites covered with an isolating cover of soil and vegetation showed significantly fewer fluctuations in the temperatures between winter and summer.

Borehole temperature data from 2002–2010 compared to monthly mean air temperature and snow cover. In bedrock the superficial heat (red and green colours) is conducted deep into the underground. Coarse-grained debris (like found at the talus slope or at the rock glaciers) is a relative effective insulator; however in fine-grained debris heat penetrates deep into the underground, causing thawing of permafrost (from Schneider et al. 2012).

In coarse-grained material air circulation in the voids plays a major role, cooling the underground effectively. Both in the coarse-grained debris of the talus slope and in the rock glacier no significant increase of temperatures along the contact between cover and permafrost was observed in eight years. However, it was in fine-grained material that most permafrost thawing occurred. Numerous complex processes, like water infiltration, freezing and air circulation, seem to be especially effective in the small pores of fine-grained sediments and transport heat deep into the underground.

In computer models used to calculate the changes and future distribution of permafrost and permafrost-related natural hazards the composition of the surface is often neglected – in part due the difficulties to gain detailed information in rugged mountain terrains. However the study by Schneider et al. shows that sediment type and size does matter and detailed field survey and data collection play essential parts in understanding the reactions of the hidden permafrost in a warmer climate.

By David Bressan, freelance geologist based in Italy

Teachers at Sea: Farewell Marion!

2 Jul

In the last couple of weeks, GeoLog had the pleasure to host reports from Teachers at Sea. This educational programme, co-sponsored by the European Geosciences Union (EGU) and the French Polar Insitute (IPEV), gives school teachers the opportunity to take part in oceanographic cruises with scientists. This year, Sandrine Vivier and Ana Sánchez, teachers of Biology and Geology in Rodez (France) and Madrid (Spain), respectively, together with EGU’s Education Chair Carlo Laj, joined scientists on board of the Marion Dufresne. The research vessel navigated the South China Sea where teachers worked alongside scientists in collecting marine sediments to retrieve the secrets of deep ocean circulation and understand past variations of the Asian Monsoon. This is the last post of the series. Check out previous posts here.

Report 9: Farewell Marion!

As the Marion Dufresne heads back to Singapore, the cruise enters its last few days.

The scientific team on board has been very busy updating all measurements taken, storing them in different computers, writing the final cruise reports, cleaning all the equipment used, and packing some of the instruments used to send back home.

The cores in the refrigerated container (photo by Catherine Kissel)

The cores that will be shipped to France are now stored in a refrigerated (4°C) container, ready to transit first to the Réunion Island on the Marion, and from there to France in the same container but on a different vessel. They will be delivered at the Laboratoire des Sciences du Climat et de l’Environnement (LSCE) at Gif sur Yvette near Paris in early September. The cores for Tongji University will have a shorter journey: from Singapore, where they will be disembarked, they will be shipped directly to Shanghai.

During the short seven days of coring, much work was done. We have obtained 350 meters of cored sediments, collected water samples for measuring the pH (to study ocean acidification), obtained several CTD (Conductivity/Temperature/Depth) profiles, just to mention a few of our activities.

End of the cruise party in the forum of the Marion Dufresne (photo by Ana Sanchez)

End of the cruise barbecue dinner on the rear deck (photo by Ana Sanchez)

After all the work, we have had a well-deserved ‘end of the cruise party’ at the forum and an ‘end of the cruise barbecue’ on the back deck, now clean and free from the coring equipment. We have also taken the traditional group photo of all the scientists together with the crew of the Marion Dufresne.

The team on board of the Marion Dufresne

We express our deep thanks to the French Polar Institute (IPEV) and to the European Geosciences Union (EGU) for making it possible for us to participate in this session of the Teachers at Sea programme. Many thanks to the IPEV personnel on board who were always very patient with us. Special thanks also go to Bárbara Ferreira, for editing our texts and publishing them in such an attractive blog!

Thank you also to the crew of the Marion Dufresne, particularly to Captain Lassiette and Chief Engineer Rolland.

And of course, we wish to thank all the scientists on board, especially co-chief scientists Catherine Kissel and Zhimin Jian.

The Marion Dufresne from the Zodiac raft (photo by Hélène Léau)

Long live the Marion Dufresne!

By Carlo Laj (with Sandrine Vivier and Ana Sánchez)

Imaggeo on Mondays: Kerlingarfjöll

2 Jul

Kerlingarfjöll by János Kovács, distributed by EGU under a Creative Commons licence.

Iceland, with its stunning volcanic landscapes, is one of the world’s most geologically rich countries. Kerlingarfjöll, featured in this week’s image, is a prime example of that. This Icelandic mountain range, covering an area of 150 square kilometres, formed during a volcanic eruption in the Late Pleistocene – some 100 thousand years ago.

“Kerlingarfjöll is very different to the environment around, both in shape and colour. The mountains are mostly made out of rhyolite and both dark and bright tuff, and there is also a lot of volcanic glass,”  it is explained in the  Kerlingarfjöll official website. “When Kerlingarfjoll was being created, there was a glacier over the mid highlands, and in certain places it seems that pillars of tuff reached out of the melting glacier ice. That is why there are tuff pillars with a lava top.”

The mountains are located in central Iceland, in an area of stunning natural beauty. “I had the chance to visit this beautiful country several times in the last ten years,” the photographer János Kovács, a geologist based at the University of Pécs in Hungary, says. “If anyone wants to see the real Iceland, they should rent a big 4×4 and drive through the country.”

Imaggeo is the online open access geosciences image repository of the European Geosciences Union. Every geoscientist who is an amateur photographer (but also other people) can submit their images to this repository. Being open access, it can be used by scientists for their presentations or publications as well as by the press. If you submit your images to imaggeo, you retain full rights of use, since they are licenced and distributed by EGU under a Creative Commons licence.

Teachers at Sea: Learning physics and ocean science from high sea

29 Jun

Since last week, GeoLog has had the pleasure to host reports from Teachers at Sea. This educational programme, co-sponsored by the European Geosciences Union (EGU) and the French Polar Insitute (IPEV), gives school teachers the opportunity to take part in oceanographic cruises with scientists. This year, Sandrine Vivier and Ana Sánchez, teachers of Biology and Geology in Rodez (France) and Madrid (Spain), respectively, together with EGU’s Education Chair Carlo Laj, join scientists on board of the Marion Dufresne. The research vessel is navigating the South China Sea where teachers will work alongside scientists in collecting marine sediments to retrieve the secrets of deep ocean circulation and understand past variations of the Asian Monsoon. Check out previous posts in this series here.

Report 8: A student experiment enters a new stage

The last coring site, which we’ve reached earlier this week, appeared to be a good place to cast off ‘our’ buoy, Neptune. What is this, you may ask? Neptune is an oceanographic buoy made by students in Lycée Monteil in Rodez, France and by the CNES (Centre National d’Etudes Spatiales) as part of Argonautica, a project to educate students about the marine environment and the climate.

The device provides data through Argos, a system for worldwide tracking and environmental monitoring by satellite. The system receives messages from markers fixed on animals or on buoys all around the world.

Neptune’s instruments

This scientific adventure began in 2008 when Sandrine and her students decided to study marine currents in order to understand the link between the weather and the oceans. The first buoy they built in the remit of this project, named Venus, was cast off in the Mediterranean Sea in November 2009 at the 43rd parallel offshore. It contained sensors made by the Monteil students themselves, which were able to measure temperature and luminosity at different depths inside and outside the buoy.

Unfortunately, it worked for less than three days. But Sandrine and her students decided not to give up and built a new buoy to continue their marine-currents study. And, since then, the project has progressively gathered more supporters at the French high school: just in 2012, 50 students between 15 and 18 years old have worked on it.

On board of the Marion Dufresne, Sandrine has been testing the second buoy, Neptune, since the start of the cruise. The tests showed all sensors functioning correctly, and water tightness was checked in a swimming pool on board.

Students made Neptune’s temperature sensors

There are many components in Neptune, and all need to be carefully checked. The ‘Hera card’, supplied by CNES and the French society Tenum transmits data to a satellite, while specific sensors measure temperature and humidity inside the buoy. The device needs batteries to work, of course, and these are covered in resin in order to resist as long as possible in water.

A key Neptune instrument is the ‘stormeter’ (or storm-meter), which is able to measure the amplitude and frequency of waves. It contains an accelerometer to measure gravity, and the signal obtained in this way is then filtered and amplified. After filtering to eliminate high frequency results, a signal oscillates between a maximum and a minimum level thanks to an operational amplifier. Sandrine students will know that the difference between the maximum and minimum levels is proportional to the amplitude of the entry signal and to the wave amplitude via a calibration curve established in class in previous experiments. The buoy serves to teach physics as well as marine science!

Printed circuit and accelerometer in Neptune

Just before the coring in the last site, Hélène Leau, the Operations Manager of the French Polar Institute, allowed us to prepare the buoy. Members of the crew helped Sandrine fix a floating anchor to it and a weight at the end of the line of anchorage (a 40-metre electric cable under the buoy).

Then, the captain gave permission to Carlo to temporarily leave the Marion Dufresne on a small raft. He wanted to take pictures of Neptune in the water, and also to film a Casq coring from outside the ship!

The Marion Dufresne and Neptune on their way

Neptune had a successful 24 hours covering12.5 miles in the northwest direction. With all sensors functioning correctly, the buoy continues its path towards the north of the South China Sea. The students have reasons to be proud!

By Sandrine Vivier, Ana Sánchez, and Carlo Laj

Teachers at Sea: Working hard for science!

27 Jun

Since last week, GeoLog has had the pleasure to host reports from Teachers at Sea. This educational programme, co-sponsored by the European Geosciences Union (EGU) and the French Polar Insitute (IPEV), gives school teachers the opportunity to take part in oceanographic cruises with scientists. This year, Sandrine Vivier and Ana Sánchez, teachers of Biology and Geology in Rodez (France) and Madrid (Spain), respectively, together with EGU’s Education Chair Carlo Laj, join scientists on board of the Marion Dufresne. The research vessel is navigating the South China Sea where teachers will work alongside scientists in collecting marine sediments to retrieve the secrets of deep ocean circulation and understand past variations of the Asian Monsoon. Check out previous posts in this series here.

Report 7: Handling a core on board

When a corer arrives at the surface, the crew of the Marion Dufresne lifts it on to the deck. This is not a simple operation, especially considering the length of some of the Calypso cores recovered during this cruise. It involves separating the huge weight of about six or seven tons from the corer itself, and then laying down the core along the starboard corridor (if a Calypso) or on the rear deck (if a Casq). The crew also takes the plastic liner out of the metallic tube (Calypso) or unscrews the numerous bolts that seal the Casq core.

Measuring a Calypso core after being extracted from the corer

From then on, the scientists take over. For a Calypso core, as mentioned in a previous report, our duty is first to cut it into 1.5 meters sections and label it precisely. The plastic liner impresses a straight, longitudinal ‘fiducial line’ along the core, which is used later to split the core into two halves, one to work on and one to archive. The labelling is therefore done on both halves.

A typical label may seem rather complex to those not on the ship: ‘MD12-3432-X’ with additional labels ‘T-1350’ at the top and ‘B-1500’ at the bottom, is an example. But the letters and numbers have very precise meanings that later help to identify the core. ‘MD12’ indicates that it was taken by the Marion Dufresne in 2012 and ‘3421’ that it is the 3432th core taken by this vessel (!). The Latin character X labels the tenth section of the core, which extends from 1350 cm at the top (T) to 1500 cm at the bottom (B).

Labeling a Calypso core

For a Casq core, sampling is done differently, as there is no external plastic liner. Plastic liners, called D-tubes are pushed inside the sediment, labelled in a way identical to Calypso cores, and then extracted after cutting the sediment with a nylon string (a fishing line). The different D-tubes are then covered with a lid that fits tightly on them. Due to the large dimensions of a Casq core, we can obtain three different levels of D-tubes from it.

Sampling a Casq core

The team splits the Calypso core sections into two longitudinal splits along the fiducial line (so that their relative orientation is preserved) using an automated saw. The instrument used on the Marion Dufresne is affectionately called Georginette in honor of Georges Oggian, the engineer from the University of Bordeaux who designed it.

The Georginette

The scientific team immediately packs and stores the archive half, while the working half is submitted to some measurements (preliminary to the on shore laboratory studies). Done in the Mechanical Stability Testing or MST container, using a specific instrument, these include taking a photographic record of all the sections, measuring the magnetic susceptibility of the sediment, recording its optical reflectance (a first order measurement of its mineralogical composition), its density (via absorption of gamma rays), and the speed of sound in it via the velocity of seismic P-waves. These last two measurements are linked to the sediment density.

The team also does the sedimentological description of each section to characterise possible changes in the sediment. This would reflect changes in the paleoenvironmental conditions or, in other words, changes in the environment at a given period in the geologic past.

A first, very important, analysis is the microscopic observation of the foraminifera content in the part of the sediment present in the lowermost part of the core (the core catcher). The presence of a Globigerinoides ruber (pink) type of foraminifera at the bottom of the core indicates that this core has reached the ‘age’ of 130,000 years (more or less one climatic cycle). This analysis guides the choice of successive coring sites.

MST apparatus

As you can see, there is a lot of work involved in handling a core on board! Just the task prior to the analysis, sampling a Calypso or a Casq core, takes more than the four hours of a shift. Therefore, different shifts each do a part of the work.

Ana and Sandrine are in the 4-8 shift, meaning that they work from 4 to 8 in the morning, and again from 4 to 8 in the afternoon. They work under the direction of the experienced Aurélie Vantoer, who has participated in many Marion Dufresne cruises.

Carlo is not assigned to a specific shift. His job is to ‘spot’ suitable coring sites using the 3.5 KHz sub-bottom profiler – a sonar projected into the seafloor to see down into the sediment. He is active almost round the clock, together with our two co-chief scientists, Catherine and Zhimin.

It is hard work on board, but we are excited to see what the next coring operations will bring!

By Sandrine Vivier, Ana Sánchez, and Carlo Laj

Teachers at Sea: Bon Appétit

26 Jun

Since last week, GeoLog has had the pleasure to host reports from Teachers at Sea. This educational programme, co-sponsored by the European Geosciences Union (EGU) and the French Polar Insitute (IPEV), gives school teachers the opportunity to take part in oceanographic cruises with scientists. This year, Sandrine Vivier and Ana Sánchez, teachers of Biology and Geology in Rodez (France) and Madrid (Spain), respectively, together with EGU’s Education Chair Carlo Laj, join scientists on board of the Marion Dufresne. The research vessel is navigating the South China Sea where teachers will work alongside scientists in collecting marine sediments to retrieve the secrets of deep ocean circulation and understand past variations of the Asian Monsoon. Check out previous posts in this series here.

Report 6: the ‘Vatel des mers’

Our position today [25/06]

François Vatel, a 17th century cook, is the most famous of the great chefs of French cuisine, which has recently been distinguished as a world cultural heritage by UNESCO. Here, at the Marion Dufresne, we are lucky enough to enjoy meals prepared by a true ‘Vatel des Mers’ – Chef Claude Cornet!

At the vessel, is it easy to lose track of time, but we know when it’s Sunday because of the Marion Dufresne tradition of eating croissants for breakfast on this day of the week. On weekdays, on the other hand, Chef Claude bakes wonderful French baguettes for breakfast.

He also prepares delicious lunches and dinners, keeping with the theme of French cuisine. Assiette de crevettes with mayonnaise, tournedos bordelaise, coquille de poisson, entrecôte béarnaise are some of the dishes we’ve had the pleasure to eat for lunch. Mixed salads, lasagna, and fish fillets have been served at dinner time. And all the meals invariably end with a platter of French cheeses and fresh fruit!

Chef Claude Cornet

The starter for today’s lunch

Chef Claude welcomed us in his kitchen while preparing lunch. His job includes cooking as well as buying all sorts of ingredients beforehand. He gets the meat in Brazil, the rice in Malaysia, the alcohol in France, the fresh vegetables and fruits at every port call. These ingredients are then stored inside the different refrigerators and deep freezers of the Marion Dufresne: meat is kept up to 6 months, fresh vegetables for up to 3 weeks, and fruits for 5 weeks.

Claude can count with the much-needed help of three assistants. At times, when the Marion is used as a supply boat for the French territories in the Southern Ocean (Amsterdam Island, Crozet, Kerguelen archipelago) and Antarctica (Terre Adélie), the team of cooks prepares food for up to 140 people and the scientific party!

Chef Claude and one of his assistants preparing dessert

Thank you Claude and your team for making life on board all the more enjoyable!

By Sandrine Vivier, Ana Sánchez, and Carlo Laj

Teachers at Sea: the ‘brain’ of the Marion Dufresne

25 Jun

Since last week, GeoLog has had the pleasure to host reports from Teachers at Sea. This educational programme, co-sponsored by the European Geosciences Union (EGU) and the French Polar Insitute (IPEV), gives school teachers the opportunity to take part in oceanographic cruises with scientists. This year, Sandrine Vivier and Ana Sánchez, teachers of Biology and Geology in Rodez (France) and Madrid (Spain), respectively, together with EGU’s Education Chair Carlo Laj, join scientists on board of the Marion Dufresne. The research vessel is navigating the South China Sea where teachers will work alongside scientists in collecting marine sediments to retrieve the secrets of deep ocean circulation and understand past variations of the Asian Monsoon. Check out previous posts in this series here.

Report 5: At the controls of a research vessel

Inside the bridge of the vessel

The ‘brain’ of the Marion Dufresne, always alert during the oceanographic cruises, is located at the bridge – the room from where the vessel is commanded.

To navigate the oceans of the world, the Marion Dufresne uses three shipboard GPS satellite systems, as well as nautical charts. Weather reports and charts obtained daily from Bon Voyages Systems, a private company, are also used for navigation. We were a little worried in the first few days when, looking at the most recent weather chart, we realized that a rather severe tropical storm was sitting on the area where our coring sites were located! Luckily for us, the storm moved away from the zone and so far we have found only calm waters.

Forecast of stormy weather in the area of the core sites

Captain Bernard Lassiette and his officers showed us the different instruments present at the bridge of the vessel. We were first struck by the two radar screens, right in the centre, which operate at two different wavelengths, 3 cm and 10 cm. The one operating at the shortest wavelength yields very precise images but is sensitive to atmospheric phenomena such as rain, while the other one provides less precise images but is much less sensitive to these kind of atmospheric perturbations. Both detect other vessels or the coast at a distance of about 50 km.  Also in the centre is the rudder, which can be computer controlled or hand manoeuvred.

The two radars

On the port (left) side, there are two panels similar to those we saw in the machinery control room a few days ago. The commands originate from here and are reproduced in the ‘heart’ of the Marion Dufresne four decks below.

But the most spectacular feature in the bridge is the control station – the real ‘brain’ of the ship – on the starboard (right) side. This station is particularly important during the long coring sessions, when the Marion Dufresne cannot move by more than two or three meters during the entire operation.  To keep the vessel in the same position, it is important to take wind and surface current into account. The ‘brain’ does this (up to rather bad sea and weather conditions) and automatically controls the two propellers and the thruster to keep the Marion Dufresne stable. At times, however, man replaces the machine: the ship officers can control the boat manually using a ‘joy stick’.

The joy stick to control the boat

As for the ongoing coring operations, we obtained three new cores  (35, 49 and 52 meters long) with Casq and Calypso since our last report! The activities in the Marion Dufresne don’t stop: the team continues to work, preparing, labeling, and storing the cores. At the same time the scientists study the main characteristics of the samples: color, density, magnetism, foraminifers, and so on.

Ana and Sandrine packing a Casq core

There is much to discover on board of the vessel!

By Sandrine Vivier, Ana Sánchez, and Carlo Laj