GeoLog

Svalbard

Volcanic ash layers in Svalbard hold clues to the formation of the North Atlantic

Volcanic ash layers in Svalbard hold clues to the formation of the North Atlantic

This guest post by Dr Morgan Jones (a Researcher in Volcanology at the Centre of Earth Evolution and Dynamics (CEED) at the University of Oslo, Norway) describes the latest findings of his multidisciplinary research into how the North Atlantic formed. His open access study, in collaboration with colleagues at CEED and the Massachusetts Institute of Technology (MIT) is published in the Nature Journal: Scientific Reports. This post is modified from a version which first appeared on John Stevenson’s blog, Volcan01010. Read the original post.

Summary

The Earth’s tectonic plates have pulled apart and come together multiple times during its long history. These processes leave hallmarks of the past layouts of continents, which allow scientists to reconstruct how the plates have moved through time. While we know from the geological record that these movements took place, it is sometimes difficult to work out when key events occurred and their correct order. One such example is just before the formation of the northeast Atlantic Ocean, around 62-55 million years ago, when there were several changes in the relative motions of North America, Greenland, and Eurasia (the combined landmass of Europe and Asia) in just a few million years.

A technique called radioisotopic dating allows us to determine the exact age of volcanic rocks. This study shows that the Greenland plate began to push against part of the Eurasian plate around 61.8 million years ago, leading to the formation of a mountain belt between Greenland and Svalbard. This precise age of first compression occurred at the same time as other changes around the edge of the Greenland plate. For the first time, this study provides evidence that these events are connected.

This gives scientists who work in plate tectonic reconstructions the ability to refine their models to understand how North America and Eurasia began to break apart.

Plate Tectonics in the Palaeocene

The Palaeocene epoch was between 66-55.8 million years ago, occurring after the Cretaceous period. The between the Cretaceous and the Palaeocene 66 million years ago is marked by the well-known catastrophe that led to the extinction of the dinosaurs.

The Palaeocene was also an important time period for plate tectonic motions in the northern hemisphere. At the time when dinosaurs became extinct, the North Atlantic Ocean was still in its infancy and seafloor spreading did not extend further north than Canada and Portugal. Over the course of the next few million years, North America and Eurasia began to break apart, which eventually resulted in a seaway that connected the Atlantic and Arctic Oceans.

However, the break up was a complicated process. As the Atlantic Ocean grew northward, branches opened on either side of southern Greenland (between Canada to the west and Scotland/Norway to the east). The western arm pulled apart first, but at some point both of these rift zones were active, and a mountain range was formed in what is now Svalbard. This meant that for a short period (geologically speaking) Greenland was its own tectonic plate, moving independently of both North America and Eurasia.

The aim of our study is to pinpoint exactly when Greenland and Svalbard began to push together, as this compression is directly related to the rifting further south. This means that understanding the geological history of Svalbard can shed light on when and why Greenland became its own tectonic plate.

The Geology of Svalbard

The rock outcrops in western Svalbard are intensely folded and cut by long faults. They were once part of a mountain chain that formed due to Greenland and Svalbard pushing together. This was followed later by sideways movement as the northeast Atlantic Ocean began to open; pulling Greenland and Svalbard apart.

The rocks in south-central Svalbard, adjacent to this ancient mountain range, are sedimentary deposits that were formed in deltas and shallow seas. Mountain ranges often have low-lying regions alongside them (called basins) where sediments accumulate. Modern examples include the Po Valley next to the Alps in Italy and the Ganges Basin next to the Himalayas in India.

Importantly, these basins form at the same time as the mountains grow, which means that techniques to work out the age of rock formations can be used to accurately date when both the basin and the mountains started to form.

Dating First Compression between Svalbard and Greenland

An important tool for working out the age of a rock is radioisotopic dating. Radioactive isotopes of elements are unstable, meaning that over time they will degrade from one form to another. The half-life (the rate at which radioactive decay occurs) of each system varies from milliseconds to billions of years, which means that different isotope systems can be used for dating, depending on how far back in time your interest lies.

This is an edited version of Figure 5 from the paper, created using the open source plate tectonics software GPlates by Grace Shephard and Morgan Jones. It shows a regional reconstruction of how the tectonic plates were 62 million years ago. The blacked dashed lines show where the plate boundaries between North America, Greenland, and Eurasia are predicted to have been. The light blue areas show the approximate extent of seafloor in the Labrador Sea and in Baffin Bay. The orange areas show the rifting zone to the east of Greenland where the northeast Atlantic would later open. The purple areas show the known extent of magma intrusions and volcanic deposits from the first pulse of the North Atlantic Igneous Province (NAIP). The purple star is where the centre of the mantle plume is predicted to be at this time. The red arrows show the onset of compression between Greenland and Svalbard, beginning at 61.8 million years ago. The volcano symbols mark where the ash layers in Svalbard came from.

When considering millions to billions of years in the past, uranium-lead (U-Pb) dating is used as 238U has a half-life of about 4.5 billion years. Zircon crystals are ideal for this method as they form in cooling magma chambers. Zircons can have a high uranium concentration, which means that if they are found in volcanic deposits such as lavas or volcanic ash layers, they can be used to accurately date those rocks.

The sediments in Svalbard have numerous volcanic ash layers preserved within them. These ash layers are likely to have originated from volcanoes in northern Greenland and Ellesmere Island, now over 1000 km away across the ocean.

Based on the dating of these ash layers it is possible to calculate when sedimentation first began in central Svalbard. This age of valley formation, and therefore the initiation of compression between Greenland and Svalbard, is predicted to be start around 61.8 million years ago.

This age is significant because it overlaps with key events further south. Around 61.6 million years ago there was a dramatic change in the sedimentation in the North Sea from limestone to sandstone and siltstone. The speed of seafloor spreading increased between Canada and Greenland, and many faults were active along the edges of eastern Greenland.

The synchronicity of these events strongly indicates a common driving force affecting all margins of Greenland.

Potential Causes

A remaining mystery is what caused Greenland to change direction.

There are several possible candidates that could have caused the shift, either individually or together.

The acceleration of seafloor spreading in the Labrador Sea has the potential to drive changes in relative plate motions. It is also plausible that events further afield may be important. Greenland was in between the North American and Eurasian plates, so the change in motion may be a result of forces acting on one of these much larger plates.

Another possibility is the arrival of a mantle plume at the base of the crust. Mantle plumes bring considerable heat from deep in the Earth, resulting in widespread crustal melting and volcanic activity. The North Atlantic Igneous Province (NAIP) is one such example. The first pulse of magma arrived at the surface around 62 million years ago and is still causing enhanced melting today to form Iceland.

The scale of volcanic and magmatic products from the NAIP is truly enormous. Current estimates put the total amount of magma at 6 to 10 million cubic kilometres. Much of this activity is still exposed along the edges of the northeast Atlantic, including the British Isles, Faroe Islands, and East Greenland. There are also considerable deposits found in West Greenland. It is therefore possible that the change in plate motions may be connected to this pulse of magma. However, further work is needed to test this hypothesis.

By Dr Morgan Jones, Researcher in Volcanology at the Centre of Earth Evolution and Dynamics (CEED) at the University of Oslo, Norway

Methane seeps – oases in the deep Arctic Ocean

Methane seeps – oases in the deep Arctic Ocean

The deep Arctic Ocean is not known for its wildlife. 1200 metres from the surface, well beyond where light penetrates the water and at temperatures below zero, it it’s a desolate, hostile environment. There are, however, exceptions to this, most notably around seeps in the seafloor that leak methane into the water above.

Here, methane is the fuel for life, not sunlight, creating oases in an otherwise barren landscape. On the Vestnesa Ridge, just off Svalbard, great plumes of methane stretch some 800 metres above the seabed. These seeps occur within pockmarks, depressions in the sea’s soft sediment, which span hundreds of metres across. At their base lies carbonate reefs, wide microbial mats and thriving meadows of tubeworms, which stretch out into the current. The microbes turn the methane into something much more valuable – carbon, and form the base of the deep Arctic food chain.

Emmelie Åström, a PhD student from the Centre for Arctic Gas Hydrate, Environment and Climate, has been using high definition seafloor images to work out what effect these seeps have on the surrounding biota. The images reveal that the carbonate rocks that form at the seep’s margins create a unique habitat in an otherwise featureless environment. These structures provide shelter for a huge variety of animals, which benefit from a food chain fuelled by methane. She presented her results at the EGU General Assembly this week.

Just some of the many marine animals found around methane seeps. Credit: CAGE

Just some of the many marine animals found around methane seeps. Credit: CAGE

The communities are totally different just tens of metres from the seep. Utterly dependent on the methane to survive, the animals of the deep Arctic Ocean stick close to their fuel.

“We took photos going from the outside of the pockmark inside and you can see how the seafloor is changing, also the animal distribution and aggregation. When you come inside a pockmark, the seafloor changes very dramatically,” explains Åström.

There are similarities between these seeps and others around the world, but none have been studied so high in the Arctic.

“The Arctic is a place where lots of things are happening right now and it’s important to understand what kind of animals are present here.”

By towing a camera across the sediment and taking samples to match, Åström was able to map out the marine life in these deep, dark oceans. “The typical view you have is that it’s very barren and that there’s not so many big animals here,” she says, but her images tell a different story. These vibrant patches may be separated by swathes of barren sediment, but they’re thriving, and may have an important role to play.

By Sara Mynott, EGU General Assembly Press Assistant and PhD Student at University of Exeter.

Sara is a science writer and marine science PhD candidate from the University of Exeter. She’s investigating the impact of climate change on predator-prey relationships in the ocean and is one of our Press Assistants this week at the Assembly.

The best of Imaggeo in 2015: in pictures

The best of Imaggeo in 2015: in pictures

Last year we prepared a round-up blog post of our favourite Imaggeo pictures, including header images from across our social media channels and Immageo on Mondays blog posts of 2014. This year, we want YOU to pick the best Imaggeo pictures of 2015, so we compiled an album on our Facebook page, which you can still see here, and asked you to cast your votes and pick your top images of 2015.

From the causes of colourful hydrovolcanism, to the stunning sedimentary layers of the Grand Canyon, through to the icy worlds of Svaalbard and southern Argentina, images from Imaggeo, the EGU’s open access geosciences image repository, have given us some stunning views of the geoscience of Planet Earth and beyond. In this post, we highlight the best images of 2015 as voted by our Facebook followers.

Of course, these are only a few of the very special images we highlighted in 2015, but take a look at our image repository, Imaggeo, for many other spectacular geo-themed pictures, including the winning images of the 2015 Photo Contest. The competition will be running again this year, so if you’ve got a flare for photography or have managed to capture a unique field work moment, consider uploading your images to Imaggeo and entering the 2016 Photo Contest.

Different degrees of oxidation during hydrovolcanism, followed by varying erosion rates on Lanzarote produce brilliant colour contrasts in the partially eroded cinder cone at El Golfo. Algae in the lagoon add their own colour contrast, whilst volcanic bedding and different degrees of welding in the cliff create interesting patterns.

 Grand Canyon . Credit: Credit: Paulina Cwik (distributed via imaggeo.egu.eu)

Grand Canyon . Credit: Credit: Paulina Cwik (distributed via imaggeo.egu.eu)

The Grand Canyon is 446 km long, up to 29 km wide and attains a depth of over a mile 1,800 meters. Nearly two billion years of Earth’s geological history have been exposed as the Colorado River and its tributaries cut their channels through layer after layer of rock while the Colorado Plateau was uplifted. This image was submitted to imaggeo as part of the 2015 photo competition and theme of the EGU 2015 General Assembly, A Voyage Through Scales.

Water reflection in Svalbard. Credit: Fabien Darrouzet (distributed via imaggeo.egu.eu)

Water reflection in Svalbard. Credit: Fabien Darrouzet (distributed via imaggeo.egu.eu)

Svalbard is dominated by glaciers (60% of all the surface), which are important indicators of global warming and can reveal possible answers as to what the climate was like up to several hundred thousand years ago. The glaciers are studied and analysed by scientists in order to better observe and understand the consequences of the global warming on Earth.

Waved rocks of Antelope slot canyon - Page, Arizona by Frederik Tack (distributed via imaggeo.egu.eu).

Waved rocks of Antelope slot canyon – Page, Arizona by Frederik Tack (distributed via imaggeo.egu.eu).

Antelope slot canyon is located on Navajo land east of Page, Arizona. The Navajo name for Upper Antelope Canyon is Tsé bighánílíní, which means “the place where water runs through rocks.”
Antelope Canyon was formed by erosion of Navajo Sandstone, primarily due to flash flooding and secondarily due to other sub-aerial processes. Rainwater runs into the extensive basin above the slot canyon sections, picking up speed and sand as it rushes into the narrow passageways. Over time the passageways eroded away, making the corridors deeper and smoothing hard edges in such a way as to form characteristic ‘flowing’ shapes in the rock.

 Just passing Just passing. Credit: Camille Clerc (distributed via imaggeo.egu.eu)

Just passing. Credit: Camille Clerc (distributed via imaggeo.egu.eu)

An archeological site near Illulissat, Western Greenland On the back ground 10 000 years old frozen water floats aside precambrian gneisses.

Sarez lake, born from an earthquake. Credit: Alexander Osadchiev (distributed via imaggeo.egu.eu)

Sarez lake, born from an earthquake. Credit: Alexander Osadchiev (distributed via imaggeo.egu.eu)

Beautiful Sarez lake was born in 1911 in Pamir Mountains. A landslide dam blocked the river valley after an earthquake and a blue-water lake appeared at more than 3000 m over sea level. However this beauty is dangerous: local seismicity can destroy the unstable dam and the following flood will be catastrophic for thousands Tajik, Afghan, and Uzbek people living near Mugrab, Panj and Amu Darya rivers below the lake.

Badlands national park, South Dakota, USA. Credit: Iain Willis (distributed via imaggeo.egu.eu)

Badlands national park, South Dakota, USA. Credit: Iain Willis (distributed via imaggeo.egu.eu)

Layer upon layer of sand, clay and silt, cemented together over time to form the sedimentary units of the Badlands National Park in South Dakota, USA. The sediments, delivered by rivers and streams that criss-crossed the landscape, accumulated over a period of millions of years, ranging from the late Cretaceous Period (67 to 75 million years ago) throughout to the Oligocene Epoch (26 to 34 million years ago). Interbedded greyish volcanic ash layers, sandstones deposited in ancient river channels, red fossil soils (palaeosols), and black muds deposited in shallow prehistoric seas are testament to an ever changing landscape.

Late Holocene Fever. Credit: Christian Massari (distributed via imaggeo.egu.eu)

Late Holocene Fever. Credit: Christian Massari (distributed via imaggeo.egu.eu)

Mountain glaciers are known for their high sensitivity to climate change. The ablation process depends directly on the energy balance at the surface where the processes of accumulation and ablation manifest the strict connection between glaciers and climate. In a recent interview in the Gaurdian, Bernard Francou, a famous French glaciologist, has explained that the glacier depletion in the Andes region has increased dramatically in the second half of the 20th century, especially after 1976 and in recent decades the glacier recession moved at a rate unprecedented for at least the last three centuries with a loss estimated between 35% and 50% of their area and volume. The picture shows a huge fall of an ice block of the Perito Moreno glacier, one of the most studied glaciers for its apparent insensitivity to the recent global warming.

 Nærøyfjord: The world’s most narrow fjord . Credit: Sarah Connors (distributed via imaggeo.egu.eu)

Nærøyfjord: The world’s most narrow fjord . Credit: Sarah Connors (distributed via imaggeo.egu.eu)

Feast your eyes on this Scandinavia scenic shot by Sarah Connors, the EGU Policy Fellow. While visiting Norway, Sarah, took a trip along the world famous fjords and was able to snap the epic beauty of this glacier shaped landscape. To find out more about how she captured the shot and the forces of nature which formed this region, be sure to delve into this Imaggeo on Mondays post.

The August 2015 header images was this stunning image by Kurt Stuewe, which shows the complex geology of the Helvetic Nappes of Switzerland. You can learn more about the tectonic history of The Alps by reading this blog post on the EGU Blogs.

 (A)Rising Stone. Credit: Marcus Herrmann (distributed via imaggeo.egu.eu)

(A)Rising Stone. Credit: Marcus Herrmann (distributed via imaggeo.egu.eu)

The September 2015 header images completes your picks of the best images of 2015. (A)Rising Stone by Marcus Herrmann,  pictures a chain of rocks that are part of the Schrammsteine—a long, rugged group of rocks in the Elbe Sandstone Mountains located in Saxon Switzerland, Germany.

If you pre-register for the 2016 General Assembly (Vienna, 17 – 22 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/.

Imaggeo on Mondays: Mirror Image

Imaggeo on Mondays: Mirror Image

This week’s Imaggeo on Mondays image is brought to you by Fabien Darrouzet, who visited the icy landscapes of Svalbard back in 2012. Whilst the aim of his trip was not to better understand the geology of the landscapes, his eyes were very much focused on goings on up, up in the sky, it didn’t stop him taking this still of the snow covered peaks.

This picture was taken in Svalbard (78° lat.) in June 2012. I was there for one week in order to observe the transit of the planet Venus in front of the Sun. I came here because at this time of the year, the Sun never sets, (midnight Sun), so it was possible to see Venus during most of the transit (for over six and a half hours!), and not only during its last minutes, as was the case for most parts of Europe.

During the day after the transit, I took a boat trip inside the fjords around Longyearbyen in order to discover the island and its local wildlife; I was interested in catching a glimpse of the elusive polar bears and hope to see seals too. We sailed in the Isfjorden, and in particular close to the southern border of a territory of Svalbard named Oscar II Land, where I took this picture from the deck of the boat. This area, and indeed all of Svalbard, is covered by snow most of the time, and just a few plants can germinate during July-August, when the average temperature is 5°C.

Svalbard is dominated by glaciers (60% of all the surface), which are important indicators of global warming and can reveal possible answers as to what the climate was like up to several hundred thousand years ago. The glaciers are studied and analysed by scientists in order to better observe and understand the consequences of the global warming on Earth.

 

By Fabien Darrouzet, Belgian Institute for Space Aeronomy

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

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