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Geotalk: Steven Smith on fossil faults and fantastic faulting

24 Apr

This week in Geotalk, we’re talking to Steven Smith, a Lecturer from the University of Otago. Steven takes us on an Earth-shaking journey, explaining how ancient faults reveal what’s happening under the Earth’s surface and delving into the future of fault zone research.

First, could you introduce yourself and tell us a little about what you are currently working on?

Last September I started as a Lecturer at the University of Otago in New Zealand. My work focuses on understanding the structure and evolution of tectonic fault zones in the continental crust. I graduated from Durham University (England) back in 2005 and remained there to complete my PhD, studying a large fault zone exposed on Italy’s Island of Elba. My Italian connection continued as I then moved to Rome for 4 years to undertake a post-doc with Giulio Di Toro and Stefan Nielsen at the INGV (National Institute of Geophysics and Volcanology). In Rome I was working on a large group project funded by the European Union. The project involved integrating field and experimental work to better understand some of the extreme deformation processes that occur in fault zones during earthquakes. When my post-doc finished, I relocated to New Zealand, attracted by the research opportunities available here and the wonderful places waiting to be explored!

Steve on the summit of Lobbia Alta (3,195 m), a peak in the Adamello area of the Italian Alps. This area is part of a large Tertiary magmatic batholith that is cut by several fault zones Steve studied as part of his post-doc work. (Credit: Steven Smith)

Steve on the summit of Lobbia Alta (3,195 m), a peak in the Adamello area of the Italian Alps. This area is part of a large Tertiary magmatic batholith that is cut by several fault zones Steve studied as part of his post-doc work. (Credit: Steven Smith)

Last year, you received a Division Outstanding Young Scientists Award for your work on the structure of shear zones. Could you tell us a bit more about your research in this area?

I work mainly on so-called “exhumed” fault zones – those that were once active and have been brought to the surface of the Earth by millions of years of uplift and erosion. By studying the structure of exhumed fault zones we can understand a lot about the physical and chemical processes that are active when faults slip. I have worked on fault zones in Europe that were exhumed from both the middle and upper crust. I’m particularly interested in the crushed-up rocks in the cores of fault zones (better known as fault rocks) and what these can tell us about fault zone rheology and deformation processes.

In the last few years, we have identified a number of previously-unrecognised textures in the cores of large normal and thrust faults in Italy. These include faults with highly reflective “mirror-like” surfaces and small rounded grains resembling pellets. Our work focused on trying to understand the significance of these textures, and in doing so we had to develop new experimental methods to deform fault zone materials under more realistic conditions. By comparing our field observations to the experimental data, we realised that the textures we identified probably represent ancient “fossil” earthquakes preserved in the rock record.

When thinking of a fault zone, you don’t often think small. How can you scale down what’s going on to create a laboratory-sized experiment?

That’s a very good question, and something that experimentalists have to be aware of all the time. It’s generally not possible to reproduce in the laboratory all of the conditions that a natural fault enjoys, which is why laboratory work ideally has to be integrated with other data, such as field observations of natural faults and theoretical modelling. But it is possible to perform experiments at quite realistic pressures and temperatures, and some deformation apparatus can deform fault zone samples over a very wide range of slip velocities – the sort you would expect during the seismic cycle along natural faults.

Laboratory experiments allow us to produce data on rock strength and fault zone behaviour that simply wouldn’t be possible by any other means. At the same time, it’s important to bear in mind that a small laboratory experiment might represent the behaviour of only a single point on a much larger fault surface – that’s where complementary field and geophysical observations come in. Looking at fault geometry and fault zone evolution over time helps put lab studies into context.

Admiring the inner workings of a fantastic fault on the Italian Island of Elba. (Credit: Bob Holdsworth, Durham University)

Admiring the inner workings of a fantastic fault on the Italian Island of Elba. (Credit: Bob Holdsworth, Durham University)

How does deformation differ across the world’s fault zones?

In the last few years, seismologists have detected different types of slip behaviour along active faults, from those that creep along steadily at rates of a few millimetres per year to those that fail catastrophically in earthquakes. In between there are other types of slip behaviour seen in seismological signals (such as seismic waves) from the deeper parts of fault zones like the San Andreas fault and the Alpine fault in New Zealand. Understanding the basic controls of this rich variety in fault slip behaviour is one of the key goals of modern earthquake science. Geologists studying exhumed fault zones have also long recognised that fault zone structure in the crust is very complex and highly dependent on factors like the type of host rock, level of exhumation, availability of fluids and so on. A future goal for geologists like me is trying to understand whether different types of fault slip behaviour recognised in modern-day seismic signals are preserved in the structure of fault zones in some way. 

Is digital mapping an essential tool for the modern-day structural geologist? How does it help?

As in most branches of science, digital technologies are now increasingly used for geological mapping purposes, although a majority of universities still favour the traditional pen-and-paper approach to training students in geological mapping. In many mapping situations – ranging from reconnaissance-scale mapping to detailed surface topography measurements – there are a number of benefits to a digital approach, the main one being that field data are automatically located using GPS or laser-based technology. This opens up a range of possibilities to map and study 3D structures that would be difficult and time-consuming, if not impossible, using more traditional approaches.

I certainly think that digital technologies will play an increasingly important role in geological mapping and research in the future, and the technology will inevitably become more fit-for-purpose and affordable. I recently taught a short workshop on digital mapping to a group of 4th year students in Otago; after a few days they were all quite confident using handheld computers and GPS devices to map, and I think they were impressed by the ease with which the digital data could be analysed to better understand the inherent complexities of geological structure.

Finally, will you be working on faults in the future or moving on to pastures new?

I think there are a lot of important research problems to tackle in fault zones, so it’s likely I’ll continue working on faults in a broad sense in the future. The devastating Tohoku-oki earthquake and tsunami in Japan in 2011 highlighted that our understanding of fault zones is far from complete. My post-doc experience has convinced me that integrating field and experimental work is a promising way to understand fault zone processes. At the moment I’m particularly interested in the very-small scale frictional processes that occur on fault surfaces during earthquakes, and I’m currently using some of the analytical equipment here in Otago to study experimental samples that were deformed under earthquake-like conditions.

If you’d like to suggest a scientist for an interview, please contact Sara Mynott.

Imaggeo on Mondays: Exploring the East African Rift

10 Mar

This week’s Imaggeo on Mondays is brought to you by Alexis Merlaud, an atmospheric scientist from the Belgian Institute for Space Aeronomy. While the wonders of the African atmosphere feature in his photography, the East African Rift has a much bigger tale to tell. Drawing from all aspects of geoscience Alexis shares its story…

Kilimanjaro from Mount Meru. (Credit: Alexis Merlaud, distributed via imaggeo.egu.eu)

Kilimanjaro from Mount Meru. (Credit: Alexis Merlaud, distributed via imaggeo.egu.eu)

This picture shows Kilimanjaro, Africa’s highest mountain, at sunrise. It was taken from Socialist Peak, which marks the top of Mount Meru, some 70 km to the southwest. Both mountains are located in Tanzania and are among the largest stratovolcanoes of the East African Rift Zone. Unlike Kilimanjaro, Meru is active and its most recent eruption occurred in 1910.

Stratovolcanoes, also called composite cones, are built-up by alternating layers of lava flows, pyroclastic rocks, and volcanic ash. During a large eruption, huge quantities of ash and sulphur dioxide can reach the stratosphere, where they can affect the climate for several years, as did the eruptions of Krakatau in 1883 and Pinatubo in 1991. Sulphur dioxide is converted to sulphuric acid droplets, which spread with the ashes throughout the stratosphere. These aerosols screen some of the sunlight, decreasing the average surface temperature by about one degree. The temperature in the stratosphere simultaneously rises by a few degrees, due to the enhanced absorption of sunlight by aerosols.

There is a difference in the tectonic processes associated with these South East Asian volcanoes and the East African Rift: the former are located above a subduction zone while the rift is a divergent boundary.  An example of large volcanic eruption in a divergent zone is the Laki (Iceland) eruption in 1783, which yielded severe meteorological conditions and reduced harvests for several years in Europe. This eruption may have also helped trigger the French Revolution in 1789.

Plate tectonics in East Africa created Kilimajaro and have also played a role in early human evolution, by shaping the local landscape and the long-term climate, thus modifying the environment of our ancestors. East Africa is the area in the world where most of the hominid fossils have been discovered, including Homo sapiens – the oldest fossil record is 200,000 years old and started to move out from Africa 100,000 years ago!

A final thanks: thanks Cristina Brailescu for help climbing Meru and Emmanuel Dekemper for support on editing the picture. 

By Alexis Merlaud, Belgian Institute for Space Aeronomy

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.

Geoscience under the tree

18 Dec

In a festive-themed post, EGU Media and Communications Manager Bárbara Ferreira selects a plethora of geoscience-inspired Christmas presents, which you could give to your favourite researcher. Please note that, with the exception of the last one, the items listed below are not necessarily recommended or endorsed by the EGU.

For me Christmas is more about eating large amounts of food and celebrating with family and friends than it is about giving and receiving presents. But I am guessing many of the readers of this blog are still scratching their heads thinking what gifts to get to the geoscientists in their families, to their Earth or space science researcher friends or, why not, themselves. This, and the fact that Paleoseismicity posted about some beautiful geology shoes a few days ago, is why I’ve set out to discover the best geoscience-inspired gift items out there.

Compiling this list ended up being easier than I thought because a few people, such as Georneys’ Evelyn Mervine and Agile’s Matt Hall have written similar blog posts in the past. And also because I discovered that Etsy – the e-commerce website for all things handmade or vintage – has an impressive collection of geoscience-y items. So, brace yourselves for a link-rich post!

Solid Earth

I’ll start with a present idea for our crafty readers: if you are into knitting, or know someone who is, this book filled with knitted-dinosaur patterns might be for you. If you’re not crafty, you may prefer to gift this triceratops cup or a pair of agate bookends, or even this t-shirt with a different take on the Earth’s internal structure. The geomorphologist in your life might like this antique map illustrating the geomorphology of the Alpine region or this simple yet beautiful travel journal.

If, instead, volcanology is your thing, then you might like this awesome volcano woolly hat – and if you are looking for a gift for a little one, this wooden volcano stacker could be your choice. For soil scientists, Etsy has a collection of beautifully illustrated soil postcards, while tectonic scientists and seismologists, may find this t-shirt funny. This science kit would suit a young fan of rocks and minerals, while this tie with crystalline formations would be more appropriate for a grown up.

Volcano hat by MariaBjork

Volcano hat by MariaBjork

Soft Earth

Moving on to soft-Earth disciplines, atmospheric scientists might like this wonderful screen print of different types of clouds, or this original necklace representing the various layers of the Earth’s atmosphere. And there’s this rather neat calendar of the sky and sea, which may also please ocean scientists. These researchers might also like an ocean tide ceramic pot or a 19th century map of the Atlantic Ocean.

Budding hydrologists, on the other hand, may be fascinated by this hydropower kit, while older ones will likely appreciate this antique engraving of water engineering. On the topic of antiques, the climate scientist in your life may like this climate map of Europe or this beautifully illustrated book to teach kids about climate. When gifting biogeoscientists, you can’t go wrong with this fantastic diatoms t-shirt (available for men and women) or these seaweed magnets.

Diatoms t-shirt by vortextradingcompany

Diatoms t-shirt by vortextradingcompany

Space and planetary science

Moving up into the upper atmosphere, your favourite solar-terrestrial scientist might like to receive this rather cute card of aurora in the Arctic or, for something a bit different, this pair of Northern Lights leggings! Going further up into space, the Earth’s magnetosphere finds its way into this totebag/backpack while the solar corona is the star of this antique print.

Planetary scientists also have plenty to choose from, with a variety of art decals and solar system charts available on Etsy. There is even a seller who builds jewellery with photos from NASA missions, such as this Mars Curiosity Rover pendant. Budding space and planetary scientists will likely be happy with this space exploration kit from National Geographic.

Interdisciplinary areas

Moving on to the more interdisciplinary areas of the EGU, I couldn’t help but mention Slow Factory, who produce stunning (but expensive!) clothing items from satellite images: the Terra MODIS Greenland dress and this silk square with an image of phytoplankton from the Bay of Biscay are two of the highlights. For something a bit more affordable, you could gift this top to bottom poster from Our Amazing Planet (sadly, the original interactive infographic can’t be put up on the wall) or this carbon cycle t-shirt. If you are feeling crafty, you can get LEGOs to build this rather incredible LEGO globe. Energy, resources and the environment enthusiasts have plenty to choose from, from a sustainable Earth lab or a solar-powered night light to a pair of windmill earings or a wind-energy decal. If great waves are more your thing, you may be interested in this tsunami top or, if landslides are your natural-hazard of choice, in this interesting pendant.

If you, like me, prefer to give and receive an experience as a gift, then why not offer a geoscientific trip? Though I haven’t been on a trip of this kind myself, I found a few companies that organise geo-themed excursions, such as this one in Italy, this one in Iceland or this one for trips further afield.

Finally, I couldn’t finish this blog post without suggesting the best present of them all (OK, I’m biased!). This Christmas, why not gift EGU memberships to the Earth, planetary and space scientists in your life? It is very affordable and researchers will likely appreciate the discounted registration rate members receive to the EGU General Assembly!

By Bárbara Ferreira, EGU Media and Communications Manager

Imaggeo on Mondays: All kinds of exposure

2 Dec

This photo was taken by Grant Wilson at Arches National Park, Utah, USA. The park is home to more than 2,000 sandstone arches, exposed by years of weathering and the removal of softer rock. They are part of the Entrada Sandstone formation, which was deposited during the Jurassic. “The arches form as ice accumulated in fissures expands and breaks the rock forming fins. Wind and water eroded the fins, removing the less resistant material to form the arches,” Wilson explains.

“Star trails at arches” by Grant Wilson, distributed by the EGU under a Creative Commons licence.

“Star trails at arches” by Grant Wilson, distributed by the EGU under a Creative Commons licence.

The arch in this photo is called Broken Arch because it has a crack running through its apex. The arch itself is not the only exciting feature in this photo though. It was taken at night – and those streaks in the sky are stars. But if the photo wasn’t taken during the day, how is it so bright?

Exposure. Not rock exposure, but the time taken to take a photo – this image was captured with a 3 hour-long exposure, letting a lot of light into the camera. This also means we can see the stars tracking across the sky: “During this time the Earth rotates approximately 45 degrees, forming the star trails in the photo. At the time the moon was almost full, which lit up the arch allowing it to be seen in the middle of the night,” explains Wilson.

For more on the formation of Utah’s sandstone arches, see this short animation, which takes you from the formation of the Rocky Mountains some 300 million years ago, through to the final steps that expose the arches that stand there today:

Imaggeo is the EGU’s open access geosciences image repository. A new and improved Imaggeo site will be launching soon, so you will be able to peruse an even better database of visually stunning geoscience images. 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.

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