GeoLog

geomorphology

Imaggeo on Mondays: Finger Rock

Finger

Standing proud amongst the calm waters of Golovnina Bay is ‘The Devil’s Finger’, a sea stack composed of volcanic sediments. Located on the Pacific coast of Kunashir Island -which is controlled by Russia but claimed by Japan – the stack is testament to the volcanic nature of the region. The island itself is formed of four active volcanoes which are joined together by low-lying geothermally active regions.

Sea stacks, tall columns of rocks which jut out of the sea close to the shore, are common across the world, with famous examples found in the UK, Australia, Thailand, Ireland and elsewhere. Sea stacks are formed naturally by erosion processes. Headlands which protrude out towards the sea are subject to many years of battering by wild winds and seas. Slowly, the force of the wind and sea weakens, cracks and breaks up the rock and a cave is formed. The process continues, particularly during stormy weather spells, when eventually an arch is formed. Given more time, the arch too breaks away, leaving a solitary tower of rock, such as that seen in this week’s Imaggeo on Mondays picture. In case you are looking to expand your Russian vocabulary, it might be useful to know that Russian term for sea stack is ‘kekur’!

The known unknowns – the outstanding 49 questions in Earth Sciences (Part IV)

We are coming to the end of the known unknowns series and so far we have explored issues which mainly affect the inner workings of our planet. Today we’ll take a look at the surface expression of the geological processes which shape the Earth. Topography significantly affects our daily life and is formed via an interplay between primarily tectonics and climate, but it also affected by biological, mechanical and chemical processes at the Earth’s surface. We’ve  highlighted how advances in technology mean detailed study of previously inaccessible areas has now become possible, but that doesn’t mean there aren’t still plenty of questions left unanswered!

Earth’s landscape history and present environment

Drainage patterns in Yarlung Tsangpo River, China (Credit: NASA/GSFC/LaRC/JPL, MISR Team)

Drainage patterns in Yarlung Tsangpo River, China (Credit: NASA/GSFC/LaRC/JPL, MISR Team)

  • Can we use the increasing resolution of topographic and sedimentary data to derive past tectonic and climatic conditions? Will we ever know enough about the erosion and transport processes? Was also the stocasticity of meteorological and tectonic events relevant in the resulting landscape? And how much has life contributed to shape the Earth’s surface?
  • Can classical geomorphological concepts such as ‘peneplanation’ or ‘retrogressive erosion’ be understood quantitatively? Old mountain ranges such as the Appalachian or the Urals seem to retain relief for > 10^8 years, while fluvial valleys under the Antarctica are preserved under moving ice of kilometric thickness since the Neogene. What controls the time-scale of topographic decay? (Egholm, Nature, 2013)
  • What are the erosion and transport laws governing the evolution of the Earth’s Surface? (Willenbring et al., Geology, 2013) Rivers transport sediment particles that are at the same time the tools for erosion but also the shield protecting the bedrock. How important is this double role of sediment for the evolution of landscapes? (Sklar & Dietrich, Geology, 2011, tools and cover effect); (Cowie et al., Geology, 2008, a field example).
  • Can we predict sediment production and transport for hazard assessment and scientific purposes? (NAS SP report, 2010)
  • What do preserved 4D patterns of sediment flow tell us from the past of the Earth? Is it possible to quantitatively link past climatic and tectonic records to the present landforms? Is it possible to separate the signals of both processes? (e.g. Armitage et al., Nature Geosc, 2011).

    Smaller-scale patterns at the limit between river channels and hillslopes (Credit: Perron Group, MIT)

    Smaller-scale patterns at the limit
    between river channels and hillslopes (Credit: Perron Group, MIT)

  • Can we differentiate changes in the tectonic and climate regimes as recorded in sediment stratigraphy? Some think both signals are indeed distinguishable(Armitage et al., Nature Geosc, 2011). Others, (Jerolmack &Paola, GRL, 2010), argue that the dynamics intrinsic to the sediment transport system can be ‘noisy’ enough to drown out any signal of an external forcing.
  • Does surface erosion draw hot rock towards the Earth’s surface? Do tectonic folds grow preferentially where rivers cut down through them, causing them to look like up-turned boats with a deep transverse incision? (Simpson, Geology, 2004).
  • How resilient is the ocean to chemical perturbations? What caused the huge salt deposition in the Mediterranean known as the Messinian Salinity Crisis? Was the Mediterranean truly desiccated? What were the effects on climate and biology, and what can we learn from extreme salt giants like this? (e.g. Hsu, 1983; Clauzon et al., Geology, 1996; Krijgsman et al., Nature, 1999; Garcia-Castellanos & Villaseñor, Nature, 2011). Were the normal marine conditions truly reestablished by the largest flood documented on Earth, 5.3 million years ago? (Garcia-Castellanos et al., Nature, 2009).

The next post will be our final post in the series and we will list open questions on how climate has contributed to shape the surface of planet Earth, from its surface to the emergence of life and beyond.

Have you been enjoying the series so far? Let us know what you think in the comments section below, particularly if you think we’ve missed any fundamental questions.

By Laura Roberts Artal, EGU Communications Officer, based on the article previously posted on RetosTerricolas by Daniel Garcia-Castellanos, researcher at ICTJACSIC, Barcelona

Imaggeo on Mondays: A massive slump

One of the regions that has experienced most warming over the second half of the 20th century is the Potter Peninsula on King George Island in Antartica. It is here that Marc Oliva and his collaborators are studying what the effects of the warming conditions on the geomorphological processes prevailing in these environments.

“Permafrost is present almost down to sea level in the South Shetland Islands, in Maritime Antarctica” says Marc, “in some recent deglaciated environments in this archipelago, the presence of permafrost favours very active paraglacial processes”.

Permafrost is defined as the ground that remains frozen for periods longer than two consecutive years and constitutes a key component of the Cryosphere. However, it is not fully understood how it reacts to climate variability. In this sense, there is an on-going effort to improve our knowledge on these topics by carrying out long–term monitoring of permafrost, as well as of geomorphological processes, in order to better understand the response of the terrestrial ecosystems to recent warming trends.

This weeks’ Imaggeo on Mondays picture shows a massive slump and the exposed permafrost in the shoreline of a lake in Potter Peninsula (King George Island, Maritime Antarctica). Following the deglaciation of this ice-free area paraglacial processes are very active transferring unconsolidated sediments down-slope to the lake.

Slump-permafrost, Potter Peninsula, Antarctica. (Credit: Marc Oliva via imaggeo.egu.eu)

Slump-permafrost, Potter Peninsula, Antarctica. (Credit: Marc Oliva via imaggeo.egu.eu)

Imaggeo is the EGU’s open access geosciences image repository. Photos uploaded to Imaggeo can be used by scientists, the press and the public provided the original author is credited. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. You can submit your photos here.

GeoEd: Why fieldwork is essential to training the next generation of Geoscientists

Our latest GeoEd article is brought to you by Simon Jung, a lecturer and palaeoceanographer from the University of Edinburgh, who highlights what makes fieldwork a brilliant way to understand Earth processes…

Studying geosciences involves training across a broad range of natural sciences. Only equipped with such background knowledge will students be able to grasp key concepts in the various sub-disciplines that geosciences has to offer. So what’s the best way to get ahold of such knowledge?

A substantial part of the theoretical background in geosciences can be delivered via lectures and/or practicals. Using this standard teaching approach, for example, knowledge of the various rock types and the minerals they contain can be conveyed clearly and effectively. Background information on different soil types, or shapes of rivers, can also be passed on in this fashion.

For something more visual, geological or geomorphological maps can create a great 2D representation of a 3D structure, giving basic insights into the relationship between larger sets of strata or geomorphological features in a given region.

There are, however, important limitations as to the level of understanding students can possibly reach through a classroom-only approach. And these can only be overcome through field training.

Viewing a landscape from an elevated spot – or otherwise suitable location – in the field allows much better comprehension of the processes that have shaped a region. For the first time, truly understanding the nature of the succession of different rock types is an eye-opening and life changing event. Similarly, grasping the role of time in allowing long-term erosion to shape a region can only be attained in the field. A visit to the northwest of Scotland is one way to achieve these goals.

Studying an outcrop in northwest of Scotland. (Credit: Simon Jung)

Studying an outcrop in northwest of Scotland. (Credit: Simon Jung)

Geological and geomorphological research in northwest Scotland has been instrumental in laying the foundations of many crucial concepts in geosciences. The area offers easy access to a unique set of rock sequences documenting Scotland’s early geological history, the explosion of life on Earth, as well as how rivers and ice have shaped the modern landscape. Students from the University of Edinburgh are frequently taken out here, where they are exposed to a huge variety of geological and geomorphological phenomena.

The more specific learning outcomes center around three main areas:

  1. Hands on training in the field helps refining all aspects related to fieldwork (e.g. observational skills, mapping)
  2. Using self-generated field data regarding rock sequences and their 3D orientation allows students to comprehend the long-term geological history
  3. Students also obtain a greater understanding of the role of erosion in shaping the landscape in a region. How? By determining river runoff at a number of locations and making measurements of the sediments being transported

Such excursions allow students to develop an improved understanding of the local geological and geomorphological history of a region.  At a larger scale, they will also develop a more comprehensive view of the processes having shaped the Earth. As the video below documents, this journey is not only educating, but fun too!

By Simon Jung, Lecturer in Palaeoceanography, University of Edinburgh