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Imaggeo on Mondays: Chilean relics of Earth’s past

Imaggeo on Mondays: Chilean relics of Earth’s past

As Earth’s environment changes, it leaves behind clues used by scientists to paint portraits of the past: scorched timber, water-weathered shores, hardened lava flows. Chile’s Conguillío National Park is teeming with these kind of geologic artifacts; some are only a few years old while others have existed for more than 30 million years. The photographer Anita Di Chiara, a researcher at Lancaster University in the UK, describes how she analyses ancient magnetic field records to learn about Earth’s changing crust.

Llaima Volcano, within the Conguillío National Park in Chile, is in the background of this image with its typical double-hump shape. The lake is called Lago Verde and the trunks sticking out are likely remnants from one of the many seasonal fires that have left their mark on this area (the last one was in 2015).

The lake sits on pyroclastic deposits that erupted from the Llaima Volcano. On these deposits, on the side of the lake, you can even track the geologic record of seasonal lake level changes, as the layers shown here mark the old (higher) level of the lake during heavy winter rains.

The lake also overlaps the Liquiñe-Ofqui Fault, which runs about 1000 kilometers along the North Patagonian Andes. The fault has been responsible for both volcanic and seismic activity in the region since the Oligocene (around 30 million years ago).

I was there as field assistant for Catalina Hernandez Moreno, a geoscientist at Italy’s National Institute of Geophysics and Volcanology, studying ancient magnetic field records imprinted on rocks. We examined the rocks’ magnetised minerals (aligned like a compass needle to the north pole) as a way to measure how fragmented blocks of the Earth’s crust have rotated over time along the fault.

From this fieldwork we were able to examine palaeomagnetic rotation patterns from 98 Oligocene-Pleistocene volcanic sites. Even more, we concluded that the lava flows from the Llaima Volcano’s 1958 eruption would be a suitable site for studying the evolution of the South Atlantic Anomaly, an area within the South Atlantic Ocean where the Earth’s magnetic field is mysteriously weaker than expected.

By Anita Di Chiara, a research technician at the Lancaster Environment Centre in the UK 

References

Hernandez-Moreno, C., Speranza, F., & Di Chiara, A.: Understanding kinematics of intra-arc transcurrent deformation: Paleomagnetic evidence from the Liquiñe-Ofqui fault zone (Chile, 38-41°S), Tectonics, https://doi.org/10.1002/2014TC003622, 2014.

Hernandez-Moreno, C., Speranza, F., & Di Chiara, A.: Paleomagnetic rotation pattern of the southern Chile fore-arc sliver (38°S-42°S): A new tool to evaluate plate locking along subduction zones. Journal of Geophysical Research: Solid Earth, 121(2), https://doi.org/10.1002/2015JB012382, 2016.

Di Chiara, A., Moncinhatto, T., Hernandez Moreno, C., Pavón-Carrasco, F. J., & Trindade, R. I. F.: Paleomagnetic study of an historical lava flow from the Llaima volcano, Chile. Journal of South American Earth Sciences, 77, https://doi.org/10.1016/j.jsames.2017.04.014, 2017.

 

Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submittheir 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/.

June GeoRoundUp: the best of the Earth sciences from around the web

June GeoRoundUp: the best of the Earth sciences from around the web

Drawing inspiration from popular stories on our social media channels, as well as unique and quirky research news, this monthly column aims to bring you the best of the Earth and planetary sciences from around the web.

Major Story

With June being the month when the world’s oceans are celebrated with World Ocean Day (8th June) and the month when the UN’s Ocean Conference took place, it seemed apt to dedicate our major story to this precious, diverse and remote landscape.

In fact, so remote and inaccessible are vast swathes of our oceans, that 95% of them are unseen (or unvisited) by human eyes. Despite their inaccessibility, humans are hugely reliant on the oceans.  According to The World Bank, the livelihoods of approximately 10 to 12% of the global population depends on healthy oceans and more than 90%of those employed by capture fisheries are working in small-scale operations in developing countries. Not only that, but the oceans trap vast amounts of heat from the atmosphere, limiting global temperature rise.

Yet we take this valuable and beautiful resource for granted.

As greenhouse gas emissions rise, the oceans must absorb more and more heat. The ocean is warmer today than it has been since recordkeeping began in 1880. Over the past two decades this has resulted in a significant change in the composition of the upper layer of water in our oceans. Research published this month confirms that ocean temperatures are rising at an alarming rate, with dire consequences.

Corals are highly sensitive to changes in ocean temperatures. The 2015 to 2016 El Niño was particularly powerful. As its effects faded, ocean temperatures in the Pacific, Atlantic and Indian oceans remained high, meaning 70 percent of corals were exposed to conditions that can cause bleaching. Almost all of the 29 coral reefs on the U.N. World Heritage list have now been damaged by bleaching.

This month, the National Oceanic and Atmospheric Administration (NOAA) declared that bleaching was subsiding for the first time in three years. Some of the affected corals are expected to take 10 to 15 years to recover, in stress-free conditions. But as global and ocean temperatures continue to rise, corals are being pushed closer to their limits.

Warmer ocean temperatures are also causing fish to travel to cooler waters, affecting the livelihoods of fishermen who depend on their daily catch to keep families afloat and changing marine ecosystems forever. And early this month, millions of sea-pickles – a mysterious warm water loving sea creature- washed up along the western coast of the U.S, from Oregon to Alaska. Though scientists aren’t quite sure what caused the bloom, speculation is focused on warming water temperatures.

It is not only warming waters which are threatening the world’s oceans. Our thirst for convenience means a million plastic bottles are bought around the world every minute. Campaigners believe that the environmental crisis brought about by the demand for disposable plastic products will soon rival climate change.

In 2015 researchers estimated that 5-13 million tonnes of plastics flow into the world’s oceans annually, much coming from developing Asian nations where waste management practices are poor and the culture for recycling is limited. To tackle the problem, China, Thailand, Indonesia and the Philippines vouched to try and keep more plastics out of ocean waters. And, with a plastic bottle taking up to 450 years to break down completely, what happens to it if you drop it in the ocean? Some of it, will likely find it’s way to the Arctic. Indeed, recent research suggests that there are roughly 300 billion pieces of floating plastic in the polar ocean alone.

A bottle dropped in the water off the coast of China is likely be carried eastward by the north Pacific gyre and end up a few hundred miles off the coast of the US. Photograph: Graphic. Credit: If you drop plastic in the ocean, where does it end up? The Guardian. Original Source: Plastic Adrift by oceanographer Erik van Sebille. Click to run.

And it’s not only the ocean waters that are feeling the heat. As the demand for resources increases, the need to find them does too. The sea floor is a treasure trove of mineral and geological resources, but deep-sea mining is not without environmental concerns. Despite the ethical unease, nations are rushing to buy up swathes of the ocean floor to ensure their right to mine them in the future. But to realise these deep-water mining dreams, advanced technological solutions are needed, such as the remote-controlled robots Nautilus Minerals will use to exploit the Bismarck Sea, off the coast of Papua New Guinea.

What you might have missed

Lightning reportedly ignited a deadly wildfire in Portugal, seen here by ESA’s Proba-V satellite on 18 June.

“On June 17, 2017, lightning reportedly ignited a deadly wildfire that spread across the mountainous areas of Pedrógão Grande—a municipality in central Portugal located about 160 kilometers (100 miles) northeast of Lisbon”, reported NASA – National Aeronautics and Space Administration. The death toll stands at 62 people (as reported by BBC News). The fires were seen from space by satellites of both NASA and ESA – European Space Agency satellites.

Large wildfires are also becoming increasing common and severe in boreal forests around the world. Natural-color images captured by NASA satellites on June 23rd, shows wildfires raging near Lake Baikal and the Angara River in Siberia. At the same time, a new study has found a link between lightning storms and boreal wildfires, with lightning strikes thought to be behind massive fire years in Alaska and northern Canada. This infographic further explores the link between wildfires triggered both by lightning and human activities.

Meanwhile, in the world’s southernmost continent the crack on the Larsen C ice-shelf continues its inexorable journey across the ice. The rift is set to create on of the largest iceberg ever recorded. Now plunged in the darkness of the Antarctic winter, obtaining images of the crack’s progress is becoming a little tricker. NASA used the Thermal Infrared Sensor (TIRS) on Landsat 8 to capture a false-color image of the crack. The new data, which shows an acceleration of the speed at which the crack is advancing, has lead scientists to believe that calving of the iceberg to the Weddell Sea is imminent.

Links we liked

The EGU story

This month saw the launch of two new division blogs over on the EGU Blogs: The Solar-Terrestrial Sciences and the Geodynamics Division Blogs. The EGU scientific divisions blogs share division-specific news, events, and activities, as well as updates on the latest research in their field.

And don’t forget! To stay abreast of all the EGU’s events and activities, from highlighting papers published in our open access journals to providing news relating to EGU’s scientific divisions and meetings, including the General Assembly, subscribe to receive our monthly newsletter.

It’s not my fault

A line on a map is important. In the Beverly Hills region of Los Angeles a series of mapped fault lines are now the cause of a major controversy. Communities have been alarmed, money has been lost and legal proceedings are ongoing.

It started in 1992. James Dolan and Kerry Sieh, two earthquake geologists at the California Institute of Technology, published a map in a field trip guidebook about the Los Angeles Basin. The map in question included suggestions of two potentially active earthquake faults in the north of the basin – the West Beverly Hills Lineament and the Santa Monica Fault – though neither of them had been confirmed by detailed study.

In the two decades since the situation has slowly spiralled out of control. Dolan and Sieh’s original map has been included in a whole series of academic papers and in 2005 the faults were added –as dotted lines – to an official map from the United States Geological Survey. Then, in 2010, the state published a map in which it labelled both faults as ‘active’.

Map released by the Los Angeles metro company at the press conference in 2011. Red lines show suggested active faults and BHHS is the Beverly Hills high school.

Map released by the Los Angeles metro company at the press conference in 2011. Red lines show suggested active faults and BHHS is the Beverly Hills high school.

Eldon Gath, from Earth Consultants International, has been reflecting on the escalating situation at the EGU General Assembly 2014. “What was a hypothesis,” explains Gath, “became a fact without any new information. Every subsequent map has reproduced these faults without even questioning whether they are right.”

These careless assumptions have now come back to haunt the people of Beverly Hills. Metro, the Los Angeles underground company, are proposing a new ‘Subway to the Sea’, an underground line from Los Angeles to the coast that would pass directly through Beverly Hills and Santa Monica. In 2011 they held a press conference to announce the results of some geotechnical surveys they had commissioned and duly claimed that a whole series of active earthquake faults ran through the proposed train route and, crucially, right under the local Beverly Hills high school. The metro company also proposed a new route for their underground line to avoid some of the faults.

Beverly Hills high school. (Credit: Eldon Gath)

Beverly Hills high school. (Credit: Eldon Gath)

“It came as a big shock to everyone,” says Gath, “this was dropped on the local community at a press conference and there was no advance notice that the map was going to be released. The high school found out about this fault map when the Los Angeles Times called them. That’s just not good public relations.”

Immediately after the press conference the school decided to launch its own investigations. It commissioned new boreholes and a trench that stretched from the front door of the school right across the proposed location of the fault. If the fault was there, then the trench would reveal layers of sediment that had been offset in previous earthquakes. But nothing was found; 50,000 year old sediments were entirely undisturbed. At a nearby location one fault was found, but the sediment ages revealed that it hadn’t moved for at least the last 200,000 years. After all the disruption, it appears that the faults don’t even exist.

Trench excavated in front of the school. No evidence of past earthquakes was found in the trench. (Credit: Eldon Gath)

Trench excavated in front of the school. No evidence of past earthquakes was found in the trench. (Credit: Eldon Gath)

To date the school has spent an estimated three million dollars on these studies and at least three other property owners in the vicinity have commissioned similar work. “It’s unfortunate that they had to spend so much money,” says Gath, “but the lawyers are now feasting at the trough.” Multiple lawsuits have been filed and a couple of cases have already been successful.

But why were these mistakes allowed to happen? “I think there was a paradigm-driven interpretation,” explains Gath. In the original work done by the metro company, “every kind of mismatch was interpreted as a fault. It was a fault-driven interpretation. But they didn’t pay any attention at all to the sediment ages.” It is also alleged that competing financial and political interests have played a role.

The current situation can hardly be blamed on Dolan and Sieh’s original map, but their initial tentativeness has been lost somewhere in the Chinese-whispers-style translation.

In the future, we must make sure that someone takes responsibility for the faults.

By Tim Middleton, University of Oxford

Reference:

Gath et al., 2014: The West Beverly Hills Lineament and Beverly Hills High School: Ethical Issues in Geo-Hazard Communication. Geophysical Research Abstracts, Vol. 16, EGU2014-1131-1

GeoTalk: Steven Smith on fossil faults and fantastic faulting

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.