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Weathering the storm from a research vessel

Weathering the storm from a research vessel

Fieldwork can take geoscientists to some of the most remote corners of the Earth in some of the harshest conditions imaginable, but stories from the field hardly make it into a published paper. In this blog post, Raffaele Bonadio, a PhD student in seismology at the Dublin Institute for Advanced Studies in Ireland, shares a particularly formidable experience in the field while aboard a research vessel in the North Atlantic Ocean.  

We knew it would be stormy that night. At the previous evening’s briefing, the captain of the ship, composed and collected, notified us that we needed to make a diversion from the planned route to avoid getting too close to the eye of the storm, “We’ll slow down the vessel…” “kind of five metres swell expected”. He was calm and comfortable. The crew members were calm and comfortable. We, the guest scientists, were not.

Why were we in the middle of the ocean?

I was part of a team of researchers from the Dublin Institute for Advanced Studies working on the project SEA-SEIS (Structure, Evolution and Seismicity of the Irish offshore). Our task was to deploy a suite of seismometers on the bottom of the North Atlantic Ocean from our research vessel, the RV Celtic Explorer, to investigate the geological evolution of the Irish offshore.

A map of the North Atlantic Ocean, showing the locations of seismometers deployed by the team’s research vessel, the RV Celtic Explorer. Credit: Raffaele Bonadio

Why study the Irish offshore?

The tectonic plate that Ireland sits on was deformed and stretched to form the deep basins offshore. The plate then broke, and its parts drifted away from each other, as the northern Atlantic Ocean opened. Hot currents in the convecting mantle of the Earth caused volcanic eruptions and rocks to melt 50-100 km below the Earth’s surface. These hot currents may have come from a spectacular hot plume rising all the way from the Earth’s core-mantle boundary (at 2891 km depth) to just beneath Iceland.

What do ocean bottom seismometers do?

Ocean bottom seismometers record the tiny vibrations of the Earth caused by seismic waves, generated by earthquakes and ocean waves. As the waves propagate through the Earth’s interior on their way to the seismic stations, they accumulate information on the structure of the Earth that they encounter. Seismologists know how to decode the wiggles on the seismograms to obtain this information. With this data, they can do a 3D scan (tomography) of what’s inside the Earth.

One of the research team’s seismometers being dropped into the North Atlantic Ocean. The instruments sink to the bottom of the ocean, where they measure the Earth’s movement. Credit: SEA-SEIS Team

In this project, we want to better understand how the structure of the tectonic plate varies from across the North Atlantic and what happens beneath the plates. And is there an enormous hot plume beneath Iceland, responsible for the country’s volcanoes today and the formation of Giant’s Causeway in Ireland? This is what we hope we will find out!

Experiencing an ocean storm

We were aboard the ship about 9 days and had just deployed “Ligea”, the 14th seismometer before the captain had notified us that a storm was heading our way.

While we were told in advance of the approaching storm, there was no way we could have imagined what it would be like to be in the middle of a stormy ocean. I had only heard some stories and I didn’t fully believe them…

I was awakened by the sound of my table lamp smashing on the ground, even the 15 cm protection edge around the table couldn’t help. The closet door opened and hit the wall. I managed not to fall off the bed, pointing my legs and make a crack with my back. I heard one of my colleagues laughing in the next cabin after a loud thud. “Did he just fall off the bed?” I thought to myself – his laugh did sound a bit of hysterical.

I realized a big wave had crashed on the side of the ship. I couldn’t believe that water and metal crashing together could make such a harsh bang. The previous evening was a continuation of bangs, splashes, sprinkles, bloops, clangs, and creaks … but even with all these noises and disturbances, I managed to sleep, exhausted from dizziness and sea-sickness.

I checked the clock on the wall: it was 3:20 in the morning. I looked at the porthole, due to the vertical movement my cabin was underwater half of the time. I walked through the cabin, trying to reach the toilet. “Oh, I wish they made the cabin smaller! I can’t reach both walls with my arms,” I said to myself. I opened the tap to refresh my face, the flowing water danced right and left across the basin. I then climbed up to the deck, I had to literally climb up the stairs. Up there I couldn’t see anything but darkness; I couldn’t see the boundary between the sky and the sea.

More than a week had passed since our departure, yet my body had still not adapted to this incessant movement. My eyes could not follow my body and my stomach did not react well, I couldn’t see anymore what was horizontal and what wasn’t. However, I wasn’t even scared, I believed nobody on the ship was (or is it only that I wanted to believe this?). It wasn’t fear, but rather an unceasing uncomfortable feeling: I knew I was more than 900 km from any dry land, in the middle of the North Atlantic Ocean, on a 66 m long vessel; I knew the captain and the crew were working hard to take us far from the storm. I was not scared…

In a few hours we were planning to deploy an ocean bottom seismometer, a very sophisticated device that is able to operate at huge pressures at the bottom of the ocean; released from the ship it would sink and install itself on the seafloor 4 km under the surface of the waves. In other words, a 200 kg ‘little orange elephant’, as the students who supported us from land every day liked to call it! “Will we be able to deploy? Will we be able not to crash the instrument on the sides? Will we instead be able to keep our balance and walk up to the deck?”

“Yes, we will.”

How did this look like? Find out more in this video:

 

So, what did we accomplish?

As part of the SEA-SEIS project, led by Dr. Sergei Lebedev, our research team successfully deployed 18 seismometers at the bottom of the North Atlantic Ocean. The network covers the entire Irish offshore, with a few sensors also in the UK and Iceland’s waters. The ocean-bottom seismometers were deployed between 17 September and 5 October, 2018, and will be retrieved in April of 2020.

To find out more about the SEA-SEIS Projects, have a look at SEA-SEIS or check out our introductory video.

By Raffaele Bonadio, Dublin Institute for Advanced Studies, Ireland

GeoTalk: The life and death of an ocean – is the Atlantic Ocean on its way to closing?

GeoTalk: The life and death of an ocean – is the Atlantic Ocean on its way to closing?

Geotalk is a regular feature highlighting early career researchers and their work. Following the EGU General Assembly, we spoke to João Duarte, the winner of a 2017 Arne Richter Award for Outstanding Early Career Scientists.  João is a pioneer in his field. He has innovatively combined tectonic, marine geology and analogue modelling techniques to further our understanding of subduction initiation and wrench tectonics. Not only that, he is a keen science communicator who believes in fostering the next generation of Earth scientists.

Thank you for talking to us today! Could you introduce yourself and tell us a little more about your career path so far?

I am a geologist by training. I gained my undergraduate degree from the University of Lisbon and I stayed there to research geodynamics as part of my PhD which I finished in 2012. As I was coming to the end of writing up my thesis I moved to Monash University, in 2011, to start a postdoc.

Yes! I worked on my PhD and a postdoc at the same time, but I was only really finishing up. My thesis was almost ready. When I moved to Australia the defence was outstanding, but otherwise I was almost done.

My PhD thesis focused on the reactivation of the SW Iberian margin. It was the very first time I came across the problem of subduction initiation and that has become a big focus of my career to date.

My postdoc came to an end in 2015 and I moved back to Portugal and took up a position at the Faculty of Sciences of the University of Lisbon where I’ve started building my own research group [more on that later on in the interview].

I’ve always been passionate about science. It started when I was a kid, I’ve always been interested in popular science. My favourite writers are Isaac Asimov and Carl Sagan.

During EGU 2017, you received an Arne Richter Award for Outstanding Young Scientists for your work on subduction initiation and wrench tectonics. What brought you to study this particular field?

On the morning of the 1st of November 1755, All Saints Day, when many Portuguese citizens found themselves at church attending mass, one of the most powerful earthquakes ever document struck off the coast of Portugal, close to Lisbon.

It was gigantic, with an estimated magnitude (Mw) 8.5 or 9. It triggered three tsunami waves which travelled up the Tagus River, flooding Lisbon harbour and the downtown area. The waves reached the United Kingdom and spread across the Atlantic towards North America too.

The combined death toll as a result of the ground shaking, tsunamis and associated fires may have exceeded 100,000 people.

The event happened during the Enlightenment period, so many philosophers and visionaries rushed to try and understand the earthquake. Their information gathering efforts are really the beginning of modern seismology.

But the 1755 event wasn’t an isolated one. There was another powerful earthquake off the coast of Portugal 200 years later, in 1969. It registered a magnitude (Mw) of 7.8.

This earthquake coincided with the development of the theory of plate tectonics. While Wegener proposed the idea of continental drift in 1912, it wasn’t until the mid-1960s that the theory really took hold.

People knew by then that the margins of the plates along the Pacific were active – the area is famous for its powerful earthquakes, explosive volcanoes and high mountain ranges. Both the 2004 Indian Ocean and 2011 Thoku (Japan) earthquakes and tsunamis were triggered at active margins.

But the margins of the Atlantic are passive [where the plates are not actively colliding with or sinking below one another, so tectonic activity – such as earthquakes and volcanoes – is minimal]. So, it was really strange that we could have such high magnitude quakes around Portugal.

A large European project was put together to produce a map of the SW Iberian margin and the Holy Grail would be to locate the source of the 1755 quake. The core of my PhD was to compile all the ocean floor and sub-seafloor data and produce a new map of the main tectonic structures of the margin.

Tectonic map of the SW Iberia margin. In grey the deformation front of the GibraltarArc, in white the strike-slip fault associated with the Azores-Gibraltar fracture zone, and in yellow the new set of thrust faults that mark the reactivation of the margin (Duarte et al., 2013, Geology)

What did the new map reveal?

Already in the 70s and later in the late 90s, researchers started to wonder if this margin could be in a transition between passive to active: could an old passive margin be reactivated? If so, could this mean a new subduction zone is starting somewhere offshore Portugal?

The processes which lead a passive margin to become active were unclear and controversial. All the places where subduction is starting are linked to locations where plates are known to be converging already.

The occurrence of the high magnitude earthquakes, along with the fact that there is structural evidence (folding, faulting and independent tectonic blocks) of a subduction zone in the western Mediterranean (the Gibraltar Arc) suggested that it was possible that a new subduction system was forming in the SW Iberian margin.

The new ocean floor and seismic data revealed three active tectonic systems, which were included in the map. The map shows the margin is being reactivated and allowed identifying the mechanism by which it could happen: ‘Subduction invasion’ or ‘subduction infection’ (a term first introduced by Mueller and Phillips, 1991).

I’d like to stress though, that the map and its findings are the culmination of many years of work and ideas, by many people. My work simply connected all the dots to try to build a bigger picture.

So, what does ‘subduction infection and invasion’ involve?

Subduction zones, probably, don’t start spontaneously, but rather they are induced from locations where another subduction system (or an external force, such as  a collisional belt) already exists.

For example, if a narrow bridge of land connects an ocean (as is often the case) where subduction is active to one where the margins are passive. The active subduction zones from one can invade the passive margins and activate them. You see this in the other side of the Atlantic (where subduction zones have migrated from the Pacific), in the Scotia and the Lesser Antilles arcs.

We also know this has happened in past. But Iberia might be the only place where it is happening currently. And that is fascinating!

Earlier on you said that the ‘Holy Grail’ moment of the map would be if you could find the source of the 1755 earthquake. Did you?

No. Not entirely. The source of the earthquake is probably a complex fault, where multiple faults ruptured to generate the quake, not just one (as is commonly thought).

In your medal lecture at the General Assembly in 2017 (and in your papers) you allude to the fact that the reactivation of the SW Iberian margin has even bigger implications. You suggest that staring of subduction process in the arcs of the Atlantic could ultimately lead to the ocean closing altogether?

The Wilson cycle defines the lifecycle of an ocean: first it opens and spreads, then its passive margins founder and new subduction zones develop; finally, it consumes itself and closes.

So, the question is: if subduction zones are starting in the Atlantic will it eventually close?

There are a few things to consider:

The ocean floor age is limited. It seems that it has to start to disappear after about ~ 200 million years (the oldest oceanic lithosphere is ~ 270 million years old). Passive margins in the Earth history also had life spans of the order of ~ 200 Ma, suggesting that this may not be a coincidence. I suspect that there is a dynamic reason for this…

Most researchers agree that the next major oceanic basin which is set to close is the Pacific. The Americas (to the east) are moving towards East Asia and Australia at a rate of 3-4 cm yr-1, so it should close in roughly 300 million years.

We also know that the Atlantic has been opening for 200 million years already. If you believe that the closing of the Pacific indicates that continental masses have been slowly gliding towards each other to form the next supercontinent (a theory know as extroversion); then the Atlantic has to continue to open until the Pacific closes. This would mean that ocean floor rocks in the Atlantic would be very old (up to 500 million years old!) – highly unlikely given the oldest existing oceanic rocks are 270 million years old.

The map I made during my PhD showed that the Atlantic oceanic lithosphere is already starting to break-up and is weakened.

All the pieces combined, I think the most likely outcome is that the Pacific and the Atlantic will close at the same time. This scenario would require other oceanic basins to form, and that’s possible in the existing Indian Ocean and/or the Southern Ocean. Present-day continents would be brought together to form a new supercontinent, which we called Aurica.

Aurica – the hypothetical future supercontinent formed as the result of the simultaneous closure of the Atlantic and the Pacific oceans (Duarte et al., 2016, Geological Magazine).

If you take into consideration present-day plate velocities the supercontinent could be fully formed in approximately 300 million years’ time. We expect Aurica to be centred slightly north of the equator, with Australia and the Americas forming the core of the landmass.

With those findings, it is obvious why subduction has been a recurring theme in your career as a researcher. But what sparked your initial interest in geology and then tectonics in general?

I spent a lot of time outdoors as a kid. I was always curious and fascinated by the outdoor world. I joined the scouts when I was eight. We used to camp and explore caves by candle-light!

When I was 14 I took up speleology; there are lots of caves in the region I grew up in, in Portugal. As amateurs, my speleology group participated in archaeological and palaeontological work. The rocks in the region are mainly of Jurassic age and contain lots of fossils (including some really nice dinosaurs).

The outdoors became part of me.

I knew early on that I didn’t want a boaring job with lots of routine. I wanted a career that would allow me to discover new things.

Geology was the most obvious choice when picking a degree. I felt it offered me a great way to stay in touch with the other sciences too – physics via geophysics and biology through palaeontology.

In my 2nd year at university, I was invited to help in an analogue lab looking at problems in structural geology and geodynamics.

I was always attracted to the bigger picture. Plate tectonics unifies everything. I like how by studying tectonics you can link a lot of little things and then bring them together to look at the bigger picture.

What advice do you have for early career scientists?

When I found out about the award I was shocked because I wasn’t expecting it at all.

I always felt I wasn’t doing enough [in terms of research output]. I think that early career scientists are being pushed to limits that are unreasonable; the competition is intense. It’s not always obvious, but there is a lot of pressure to publish. But there are also a lot of very good people whose publication record doesn’t necessarily reflect their skill as a scientist.

The award made me realise I was probably doing enough!

Moving to Australia was KEY. Moving and creating collaborations with different people will make you unique. You don’t want to stay in the same institution. [By doing so] you become very linear. There are a number of schemes available (like Marie Curie and Erasmus) which allow you to move. Use these to the fullest. Moving allows you to see problems from different perspectives. And you will become more unique as a scientist.

There a lot of bright young scientist – never have we had so many – we are all unique, but you have to find the uniqueness in yourself. Most of all have fun. Do science for the right reasons and remember that people still recognise honest hard work (the award showed me that).

Interview by Laura Roberts, EGU Communications Officer.

References

Duarte, J. C., Rosas, F, M., Terrinha, P., Schellart W, P., Boutelier, D., Gutscher, M-A., and Ribeiro, A.,: Are subduction zones invading the Atlantic? Evidence from the southwest Iberia margin, GEOLOGY, 41, 8, 839–842, https://

Duarte, J. C., and Schellart W, P.,: Plate Boundaries and Natural Hazards, Geophysical Monograph, 219 (First Edition), ISBN: 978-1-119-05397–2, 2016

Duarte, J., Schellart, W., & Rosas, F.,: The future of Earth’s oceans: Consequences of subduction initiation in the Atlantic and implications for supercontinent formation, Geological Magazine, 1–14,  https://doi.org/10.1017/S0016756816000716, 2016.

Purdy, G.M.,: The Eastern End of the Azores-Gibraltar Plate Boundary, GJI, 43, 3, 973–1000, https://doi.org/10.1111/j.1365-246X.1975.tb06206.x, 1975

Mueller, S., Phillips, R, J.,: On The initiation of subduction, JGR, 96, B1, 651-665, https://doi.org/10.1029/90JB02237, 1991

Ribeiro, A., Cabral, J., Baptista, R., and Matias, L.,: Stress pattern in Portugal mainland and the adjacent Atlantic region, West Iberia, Tectonics, 15, 3, 641–659, https://doi.org/10.1029/95TC03683, 1996

 

 

 

 

 

Imaggeo on Mondays: Lava highway in Kanaga Island

Imaggeo on Mondays: Lava highway in Kanaga Island

On a rare sunny day, Mattia Pistone (a researcher at the Smithsonian Institution in Washington DC) was able to capture this spectacular shot of Kanaga, a stratovolcano in the remote Western Aleutians, which is usually veiled by thick cloud.

The Western Aleutians form a chain of 14 large and 55 small volcanic islands, belonging to one of the most extended volcanic archipelagos on Earth (1900 km), stretching from Alaska across the northern Pacific towards the shores of Russia.

As part of a team of researchers, Mattia spent three grueling weeks in the isolated region. Being one of the most extended volcanic arc systems on Earth, the Aleutians can shed light on one of the most fundamental questions in the Earth sciences: how do continents form?

The Earth’s landmasses are made of continental crust, which is thought to be largely andesitic in composition. That could mean it is dominated by a silicon-rich rock, of magmatic origin, which is fine grained and usually light to dark grey in colour. However, basaltic magmas derived from the Earth’s upper mantle and erupted at active volcanoes contribute to chemistry of the continental crust. The fact that continental crust bears the chemical hallmarks of both suggests that the formation of new continents must somehow be linked to motion of magma and its chemistry.

Establishing the link between magma generation, transport, emplacement, and eruption can therefore significantly improve our understanding of crust-forming processes associated with plate tectonics, and, particularly, help determining the architecture and composition of the continental crust. The Alaska-Aleutian archipelago is a natural laboratory which offers a variable range of volcanic rocks. The islands present a perfect opportunity for scientists to try and understand the origin of continents.

By collecting samples of volcanic ash erupted at Kanaga and other volcanoes of the Aleutian arc, Mattia and his colleagues are currently investigating the origin of this volcanic ash. Understanding its chemistry allow the team to get a clearer idea of the conditions that were present while the magma was forming and ascending, for example, how much water and iron were present.

The team were based on the Maritime Maid research vessel, and hoped from island to island collecting samples and taking measurements of volcanic activity as part of a large research consortium called GeoPRISMS, funded by the National Science Foundation. The field work was supported by a Bell 407 helicopter and its crew.

Today’s featured image shows an andesitic lava flow erupted in 1906. The volcanic deposits were explored during the field geological mission by Mattia and the team. Kanaga last erupted in 1994. Ash from that eruption was found in the nearby island of Adak. Even at present, there is a highly active system of fumaroles at the summit of the volcano.

If you pre-register for the 2017 General Assembly (Vienna, 22 – 28 April), you can take part in our annual photo competition! From 1 February up until 1 March, every participant pre-registered for the General Assembly can submit up three original photos and one moving image related to the Earth, planetary, and space sciences in competition for free registration to next year’s General Assembly!  These can include fantastic field photos, a stunning shot of your favourite thin section, what you’ve captured out on holiday or under the electron microscope – if it’s geoscientific, it fits the bill. Find out more about how to take part at http://imaggeo.egu.eu/photo-contest/information/.