Étretat is a coastal region in northern France, well known for its stunning geological landscape. Particularly the headland you see here.

“The chalk cliffs of Étretat” by Chiara Arrighi, distributed by the EGU under a Creative Commons licence.

Headland erosion is perhaps one of the best known processes in coastal erosion, where a crack in the headland is opened and enlarged by hydraulic abrasion. Continued wave action causes the widened crack or cave to break through the headland and form an arch. As erosion continues, the arch collapses, leaving behind a stack (or needle) that erodes down to its base to form a much smaller stump. There are some great examples of other coastal processes describes in The British Geographer.

How headlands form and coastal arches erode. Source: Sbsgeog’s Weblog.

But that’s not all there is to Étretat, the chalky cliffs are composed of several layers, clearly distinguishable in Arrighi’s photo. These chalk layers are of varying hardness and can be clustered into three main strata: the lowest is a light, fine, stratified chalk aggregate, rich in foraminifera; the middle stratum is a compact chalk layer with beds that are tens of metres thick, and the uppermost stratum is composed of chalk nodules that, like the lowest stratum, is rich in foraminifera.

These strata provide insight into how the chalk of the region was laid down: the fine strata would have been a calcareous ooze, deposited by gentle currents and the nodular material would have formed as small “bullets”, before accumulating more calcareous material as they are transported and redeposited elsewhere. The sediments that now make up the Étretat chalk sequences were subject to several episodes of deformation and slumping before cementing to form the layered cliffs you see above.

References:

Dercourt, J. and Paquet J. (1985). Sedimentary Facies. Geology Principles and Methods, pp. 195-206.

Bromley, R.G. and Ekdale A.A. (2006) Mass transport in European Cretaceous chalk; fabric criteria for its recognition. Vol. 34, pp.1079-1092.

Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submit their images to this repository and since it is open access, these photos can be used by scientists for their presentations or publications as well as by the press and public for educational purposes and otherwise. If you submit your images to Imaggeo, you retain full rights of use, since they are licensed and distributed by EGU under a Creative Commons licence.

“Rainbow in stone” by Marina Manea, distributed by the European Geosciences Union under a Creative Commons licence.

Nothing better characterises the wild US West than endless landscapes of red hoodoos, spires of rock protruding from the bottom of an arid drainage basin or badland. Found mainly in desert and dry, hot areas, hoodoos are distinctive from similarly-shaped formations, such as spires or pinnacles, because their profiles vary in thickness throughout their length. Their distinctive colour bands are the product of erosional patterns differentially affecting layers of harder and softer minerals.

Nowhere in the world are hoodoos as abundant as in the northern section of Bryce Canyon National Park in Utah, USA. There, these formations, also known as goblins or in French as demoiselles coiffées (“ladies with hairdos”), dominate the landscape.

At Bryce Canyon, hoodoos are formed by two continuously operating weathering processes. The first, frost wedging, occurs as a result of Bryce’s over 200 annual freeze/thaw cycles. In the same way potholes are formed on a paved road, water breaks open the rock when it seeps into cracks, freezes, and expands. Secondly, the hoodoos are also sculpted by rainfall, both physically, because it removes debris, and chemically, because its slightly acidic pH dissolves the limestone.

Marina Manea, who works in the Computational Geodynamics department of the Universidad Nacional Autonoma de Mexico, took this early-morning picture from a helicopter whilst on holiday in Utah in August 2010. She explains, “Bryce Canyon has a unique geology, with deposits from the late Cretaceous and early Cenozoic eras. It is not a classical canyon but, rather, a collection of amphitheaters modelled by the erosional force of frost-wedging and the dissolving power of rainwater acting on the colorful limestone rock of the Claron Formation. In this way, the spires, or ‘hoodoos,’ are formed. The rocks forming the hoodoos are limestone (sedimentary rocks) exhibiting beautiful colours (red, orange, or white). The entire geology of the Bryce Canyon is related to the geology of the Grand Staircase region and Black Mountains volcanic complex. It rained just before this picture was taken, which explains the exceptionally vivid colours on display here.”

The area around Bryce Canyon was originally settled by Native Americans and later by Mormon pioneers. The national park was established in 1928 and today around 1.3 million (2011) people annually travel to witness its wild terrain and spectacular sunset colours.

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.

“Ellesmere Island” by Jean-Daniel Champagnac, distributed by the European Geosciences Union under a Creative Commons licence.

Located within the Canadian Arctic Archipelago, Ellesmere Island is the world’s tenth largest island and features Canada’s most northerly point but little else apart from vast landscapes of pristine natural habitat. It is separated from Greenland only by the Nares Strait, a major pathway for sea ice flushing out of the High Arctic.

Belonging to the Canadian territory of Nunavut, Ellesmere’s permanent population is under 200, most of whom endure the hostile weather found at Grise Ford, where the annual temperature is a staggering -16.5°C.

It comes as no surprise, then, that this mosaic of colours was captured from high above Ellesmere’s unforgiving environment. Jean-Daniel Champagnac, of the Geological Institute of the Swiss Federal Institute of Technology, Zurich, explains, “This picture was taken through the window of an airplane cruising at around 10,000m en route between Frankfurt, Germany and Anchorage, Alaska. Here you can see the bare rock of Ellesmere Island, with presumably folded sedimentary rocks, and a frozen fjord being unglaciated. This picture, taken in June 2011, has been quite substantially modified from the raw initial picture.”

As with many untouched Arctic environments, it is thought Ellesmere may be rich in natural resources, specifically in thermal coal deposits used to produce heat and electricity. If confirmed, this finding could be pivotal for the future of Nunavut. Canada’s mostly-aboriginal territory (83.6% Inuit, according to the 2006 census) is currently experiencing an energy crisis.

About his picture, Champagnac concludes, “It is always worth having a camera along when you fly, especially on a clear day.” We couldn’t agree more and we encourage you to submit more of your aerial shots to Imaggeo.net.

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.

This week’s guest post introduces a book recently published by Cambridge University Press.

Written by William I. Newman, a Professor at the University of California, Los Angeles, Continuum Mechanics in the Earth Sciences provides an introduction to continuum mechanics and essential mathematical and physical approaches in the Earth sciences. It also contains problem sets and worked examples, altogether providing a valuable first step towards understanding continuum mechanics, related tensor notation, and mathematical-background concepts. Clearly structured and merging basic with advanced topics, this textbook will capture the attention of both expert researchers and beginners in the area.

Hardback; ISBN: 9780521562898; Publication date: March 2012; 194 pages; Price: £40 (~€50)

The text is divided into nine main chapters, with the first three covering geometrical definitions of the material body and the response of materials under different forces. These definitions start with a review of essential mathematics for continuum problems, with the purpose of their geometrical descriptions in addition to covering rotation, transformation, and kinematics. The text continues, mainly in Chapter 2, by covering the most important physical quantities in continuum mechanics, like temperature, force, and stress.

The fourth chapter is devoted to fundamental laws and equations. This part of the text starts by introducing new terminology and is followed by the derivation of conservation laws. The following subsections cover some well-known constitutive equations, describing the internal mechanical, thermal, and other properties, of the constitutive quantities of the continuum materials. These parts are followed by thermodynamic considerations, which play a key role in the geosciences, particularly in the context of flows in Earth materials where the temperature can undergo dramatic change.

Chapter 5 is dedicated to linear elastic solids. It defines a body of material as elastic if at each body point the strain is a one-to-one function of stress at that point regardless of its history of loading. This chapter continues with discussions on statics and dynamical equations of isotropic bodies, homogeneous deformation equations, and the role of temperature on body deformation. It ends with a quick review on microscopic structure of crystals and their behaviour.

The next two chapters, on classical fluids and geophysical fluid dynamics, discuss the motion of fluids and their behaviour under stationary and dynamic inertial environments. Examples include the interior of Earth as well as the motion of the oceans and atmospheres.

The book ends with two chapters covering computations in continuum mechanics and nonlinearity in the Earth. The first one deals with partial differential equations used in numerical methods with the purpose of solving complicated real-word problems of continuum bodies rather than using simplified and linearized solutions.

Finally, the last chapter starts with some comments on the role of nonlinearity and its manifestation in the Earth sciences and continues by reviewing both friction, as the oldest mechanical aspect, and fracture, as one of the most challenging aspects of continuum mechanics. The last subsections cover percolation models, used to demonstrate self-organization under specific conditions, as well as fractals, used for the generation of noticeably realistic details of the objects.

Although on the whole an informative volume, this book unfortunately does not provide sufficient rigorous examples to work with, as is common in other continuum mechanics books. In addition, more examples about applications of continuum mechanics into real life Earth science problems could have made the book a little more interesting for student readers even in other fields within engineering.

By Arash Maghsoudloo, Research Assistant at Middle East Technical University

Jointed Colorado Rockies by Will Gosnold, distributed by the EGU under a Creative Commons license

The Rocky Mountains, or Rockies, are a North American mountain system stretching around 5,000 km from northern British Columbia, Canada, to New Mexico in the southwestern United States. They are made up of a discontinuous series of mountain ranges with distinct geological origins, the last of which was formed during the Laramide orogeny (mountain formation event) 80–55 million years ago.

With a population of 568,158 (2011 estimate), Wyoming has the lowest population and second lowest population density of any US state, yet it has the 10th largest area. Its environment is defined by its geological history, lying at the intersection of the Rockies to the west and, to the east, the Great Plains, a broad expanse of flat land running north to south across North America.

The sheer size and distance covered by the Rockies, even through just the one state of Wyoming, is hard to imagine by European standards. At 253,348 sq km, Wyoming itself has a greater area, for example, than the UK, Romania, Belarus, Greece, or Bulgaria, just to name a few. Perhaps the best way to understand the scale of the Rockies is by experiencing them from above, an experience captured here by Will Gosnold through an aircraft window. Gosnold, a professor within the Department of Geology and Geological Engineering at the University of North Dakota, describes this photo opportunity, “I took the photo from the window of a Delta Airlines plane, over what is likely Wyoming, during a flight from San Francisco to Minneapolis while returning from the Fall Meeting of the American Geophysical Union on 9 December 2011.”

Apart from boasting the Rockies and its vast expanse of publicly owned land, including a section of Yellowstone National Park, Wyoming produces a broad array of mineral commodities. Apart from being the largest and second largest producer of coal and natural gas respectively in the US, it also produces coalbed methane, crude oil, uranium, and trona, an evaporite mineral used for the production of washing soda (sodium carbonate). Diamond and uranium mines have also recently operated in the state.

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.

Praia das Rodas by Jorge Mataix-Solera, distributed by EGU under a Creative Commons licence.

Often listed as one of the most beautiful beaches in the world, Praia das Rodas is located on the Isla do Faro, part of the three-island Cíes archipelago within the Atlantic Islands of Galicia National Park. The beach faces eastwards, towards Vigo and the Galician coast of northwestern Spain, its accumulation of sand forming a land-bridge between two islands during low tide. All three islands are the visible peaks of submerged granitic mountains.

Soil scientist Jorge Mataix-Solera visited Praia das Rodas in 2007. “The picture was taken when I arrived by boat to the island in the early morning, the day after I was on a PhD thesis evaluation committee at the University of Vigo. This beach is one of the most beautiful beaches in the world, composed of quartz sand from granitic material,” he explains.

Beaches form over thousands of years from the deposit of sediment and other materials that moves from land into the ocean and back again.

To view more from Jorge Mataix-Solera’s astounding collection of photos, please visit: http://www.jorgemataix.com.

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.

Abstract submission for the EGU General Assembly 2012 (EGU2012) is now open. The General Assembly is being held from Sunday 22 Apr 2012 to Friday 27 Apr 2012 at the Austria Center Vienna, Austria.

You can browse through the Sessions online.

Each Session shows the link Abstract Submission. Using this link you are asked to log in to the Copernicus Office Meeting Organizer. You may submit the text of your contribution as plain text, LaTeX, or MS Word content. Please pay attention to the First Author Rule.

The deadline for the receipt of Abstracts is 17 January 2012. In case you would like to apply for support, please submit no later than 15 December 2011. Information about the financial support available can be found on the Support and Distinction part of the EGU GA 2012 website.

Further information about the EGU General Assembly 2012 on it’s webpages. If you have any questions email the meeting organisers Copernicus.

Akutan Volcano, Alaska. Image by Michael Jackson, distributed by EGU under a Creative Commons License.

High winds create lenticular clouds off Shishaldin Volcano in the Aleutian Islands. UNAVCO staff installed 16 integrated geophysical instruments including GPS, seismic, tilt, meteorologic instruments on Unimak Island as part of the EarthScope Project.

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.

Oasis Valley, Nevada, USA. Image by Jean-Daniel Champagnac, distributed by EGU under a Creative Commons License.

This picture has been taken from the air (small plane) during fieldwork in Alaska during 2009. Oasis valley is located between frontal lobes of Fan and Bremner glaciers (143.57°W; 60.87°N). The orange colour is from sand that have been brought in by the glaciers, and carved by rivers.

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.