GeoLog

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Imaggeo on Mondays: Tones of sand

Tones of Sand

With rocks dating as far back as the Precambrian, mountain building events, violent volcanic eruptions and being covered, on and off, by shallow seas, Death Valley’s geological history is long and complex.

Back in the Cenozoic (65 to 30 million years ago), following a turbulent period which saw the eruption of volcanoes (which in time would form the Sierra Nevada of California) and regional uplift, Death Valley was a peaceful place. There was no deposition of sediments, nor emplacement of igneous rocks. The valley was being eroded, slowly.

Fast forward a few thousand years, to the Miocene (ca. 27 million years ago) and all that changed. New volcanic eruptions drove the onset of a major extensional event, which saw basins and ranges develop into Death Valley as we know it today.

The tectonics of the region were also complex: the North American plate was riding up and over the Pacific plate, but around the same time as the extension started in the basin, the spreading centre of the Pacific plate intersected with the Fallon Plate, splitting it in half. The northern section became the Juan de Fuca plate and the San Andreas Fault was created between the remnants of the subduction zone.

The Panamint Range – a fault-block mountain range on the edge of the Mojave Desert – formed as a result of the powerful tectonic events. Initially, it rode over and piggy backed on top of The Black Mountains, before sliding towards the west.  As the mountain ranges slid apart, the valleys lost height too and started receiving sediment.

The sediment influx happens to this day, as evidenced in today’s Imaggeo on Monday’s photograph, taken by Marc Girons Lopez, a hydrologist at Uppsala University (Sweden).

“The photograph was taken from Dante’s View viewpoint terrace and shows the Death Valley on the foreground and the Panamint Range on the background,” describes Marc.

At present, a series of alluvial fans drain the Panamint Range, forming triangle-shaped deposits of gravel, sand and silt. These fans are formed through the deposition of sediments eroded from the Panamint Range during flash flood events.

Marc says that “the colour of the sand forming the alluvial fans relates to their age; the clearer the tones the younger their age.”

The salt flats in the foreground, which are covered in salt and other minerals, are the remnants of Lake Manly, a landlocked lake system which drained to no other bodies of water such as rivers or oceans. The lake was present during the Pleistocene era (2.85 million years ago) and slowly evaporated as the region progressively desertified. The evaporitic salts have been exploited in modern times.

 

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/.

Shaking on Christmas Day: what we know about the 7.6 M Chile earthquake

Chile, Chiloe earthquake

While the majority of us were midway through our Christmas Day celebrations, a powerful 7.6 M earthquake struck off the western coast of the Chile. Natural hazards are not bound by time, location or festivities; an earthquake can happen at any time in any place, regardless of the significance of the day. As a result, in this earthquake prone region, raising awareness of the risk posed by natural hazards is vitally important.

The Christmas Day quake struck 42 km south west of the port city of Quellón, on the rural island of Chiloé at a depth of 34 km. Despite the powerful shaking, the tremor caused no casualties and damage to infrastructure was limited. For a time, services (such as water and power) to the southern tip of Chiloé were cut. Most affected were roads and bridges, particularly the recently renovated highway 5, which links Quellón with the fishing town of Chonchi.

The earthquake triggered a tsunami warning, leading to the evacuation of 4000 people in the coastal areas of Los Lagos Region, including the towns of Quellón and Chonchi. However, no tsunami waves were reported and the warning was lifted some 90 minutes after the temblor.

Chile’s long history of powerful earthquakes

As recently as September 2015, an 8.3 M tremor hit Illapel, causing 13 casualties, 6 missing and triggering a 4.5 m tsunami wave, with shaking felt as far as Bolivia and Argentina.

A powerful, and destructive, 8.8 M quake struck Maule in February 2010. On land, there was severe loss to infrastructure and housing, while a tsunami wave caused significant damage to coastal areas. Combined, the earthquake and tsunami resulted in the deaths of more than 500 people.

The most powerful tremor ever recorded, the estimated 9.5 M Valdivia earthquake, struck Chile in May 1960. More than 2,000 people were reported dead, a further 3,000 went missing and over 2,000,000 were left homeless. The damage in Southern Chile alone amounted to over $550 million. Tsunami waves generated by the quake struck Hawaii, Japan, the Philippines and the western USA coast, causing a further $50.5 million in damages and killing 231 people.

Damage to houses after the Valdivia earthquake, Chile

Damage to several houses in Chile after the earthquake. Credit: Pierre St. Amand – NGDC Natural Hazards Slides with Captions Header, Public Domain (distributed by Wikimedia Commons)

What causes earthquakes in Chile and what does the future hold?

Chile lies along the Pacific Ring of Fire, an area known for its high seismic and volcanic activity. Here, tectonic plates slide against each other, pull apart or converge and subduct under one another generating geologically active zones.

To understand why powerful earthquakes occur in Chile, we asked Cindy Mora Stock, a seismologist at the University of Concepción (Chile), to give us a more detailed insight into the tectonics of the region:

Earthquakes along the Chilean coast occur at the interface between the South American plate and the subducted Nazca plate. The rapid velocity between these plates (66 – 90 mm/yr) increases the potential for great earthquakes in the region, presenting on average an event of magnitude 8, or larger, every ten years. As a comparison, the Antarctic plate subducts under South American plate at a much slower rate (16 – 22 mm/yr).

The latest Mw 7.6 earthquake near Quellón on 25th of December [1], falls in the central part of the rupture zone (the portion of the fault which slipped during) of  the Valdivia earthquake – roughly 380 km south from Valdivia.

A study by Lange et al in 2007 showed a cluster of four main 4.0 < Ml < 4.4 events and their afteshocks, occurring at the interface between 12-30 km depth, beneath the western coast of Chiloe Island. Another study by Moreno et al in 2011 shows some patches at the interface that ruptured during the previous 1960 event, which are more stuck than other areas at the same interface.

Especially, computer simulations show the interface at the center part of the 1960’s rupture zone is fully locked, this means that part is “stuck”, not moving, and accumulating energy. Zones that present a high locking rate have shown to be prone areas for the nucleation of a great earthquake in the future. Although in all presented scenarios the Chiloe Island presents a high locking rate, this is not enough to state a range of time when an earthquake will occur at this patch.  Considering this, the previous seismicity, and the present Mw7.6 earthquake in the region it might seem like the interface might have ended its and it is starting to build up stress for a future earthquake.

By Laura Roberts, EGU Communications Officer, and Cindy Mora Stock, postdoctoral researcher at the University of Concepcion, Chile.

 

References and further reading

[1] Intensities of shaking felt after the 25 December earthquake (in Spanish): http://www.sismologia.cl/events/sensibles/2016/12/25-1422-28L.S201612.html

[2] Lange, D., Rietbrock, A., Haberland, E., et al.: Seismicity and geometry of the south Chilean subduction zone (41.5°S–43.5°S): Implications for controlling parameters, Geophysical Research Letters, 34, L06311, doi: 0.1029/2006GL029190, 2007

[3] Moreno, M., Melnick, D., Rosenau, M., et al.: Heterogeneous plate locking in the South–Central Chile subduction zone: Building up the next great earthquake, Earth and Planetary Research Letters, 305, 3-4, 413-424, doi: 10.1016/j.epsl.2011.03.025, 2011 (Paywalled)

USGS overview of M7.6 – 42km SW of Puerto Quellon, Chile (includes shake maps, regional tectonic information and moment tensor details): http://earthquake.usgs.gov/earthquakes/eventpage/us10007mn3#executive

Understanding Tectonic Processes Following Great Earthquakes (Eos: Earth & Space Science News)

25 December earthquake in the news:
·         Chile earthquake tsunami warning lifted (BBC News report)
·         Major quake jolts Chile tourist region on Christmas Day (Reuters in-depth news report)
·         Chile jolted by major 7.6-magnitude earthquake (Guardian News)
·         Imagenes del terremoto al sur de Chile (in Spanish: Images of the earthquake in Southern Chile – Gestión, diario de econimía y negocios de Perú)

The best of Imaggeo in 2016: in pictures

The best of Imaggeo in 2016: in pictures

Imaggeo, our open access image repository, is packed with beautiful images showcasing the best of the Earth, space and planetary sciences. Throughout the year we use the photographs submitted to the repository to illustrate our social media and blog posts.

For the past few years we’ve celebrated the end of the year by rounding-up some of the best Imaggeo images. But it’s no easy task to pick which of the featured images are the best! Instead, we turned the job over to you!  We compiled a Facebook album which included all the images we’ve used  as header images across our social media channels and on Imaggeo on Mondays blog post in 2016 an asked you to vote for your favourites.

Today’s blog post rounds-up the best 12 images of Imaggeo in 2016, as chosen by you, our readers.

Of course, these are only a few of the very special images we highlighted in 2016, but take a look at our image repository, Imaggeo, for many other spectacular geo-themed pictures, including the winning images of the 2016 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 2017 Photo Contest.

Blue Svartisen . Credit: Kay Helfricht (distributed via imaggeo.egu.eu)

When you think of a glacier the image you likely conjure up in your mind is that of bright white, icy body. So why do some glaciers, like Engabreen, a glacier in Norway, sometimes appear blue? Is it a trick of the light or some other phenomenon which causes this glacier to look so unusual?  You can learn all about it in this October post over on GeoLog.

 

‘There is never enough time to count all the stars that you want.’ . Credit: Vytas Huth (distributed via imaggeo.egu.eu). The centre of the Milky Way taken near Krakow am See, Germany. Some of the least light-polluted atmosphere of the northern german lowlands.

Among the winning images of our annual photo contest was a stunning night-sky panorama by Vytas Huth; we aren’t surprised it has been chosen as one of the most popular images of 2016 too. In this post, Vytas describes how he captured the image and how the remote location in Southern Germany is one of the few (in Europe) where it is still possible to, clearly, image the Milk Way.

 

“Above the foggy strip, this white arch was shining, covering one third of the visible sky in the direction of the ship's bow,” he explains. “It was a so-called white, or fog rainbow, which appears on the fog droplets, which are much smaller then rain droplets and cause different optic effects, which is a reason of its white colour.”

Gateway to the Arctic . Credit: Mikhail Varentsov (distributed via imaggeo.egu.eu)

“Above the foggy strip, this white arch was shining, covering one third of the visible sky in the direction of the ship’s bow,” describes Mikhail Varentsov, a climate and meteorology expert from the University of Moscow. “It was a so-called white, or fog rainbow, which appears on the fog droplets, which are much smaller then rain droplets and cause different optic effects, which is a reason of its white colour.” Mikhail captured the white rainbow while aboard the Akademik Tryoshnikov research vessel during its scientific cruise to study the effects of climate change on the Arctic.

 

History. Credit: Florian Fuchs (distributed via imaggeo.egu.eu)

The header image, History by Florian Fuchs, we used across our social media channels was popular with our Facebook followers, who chose it as one of the best of this year. The picture features La Tarta del Teide – a stratigraphic section through volcanic deposits of the Teide volcano on Tenerife, Canary Islands.

 

Find a new way . Credit: Wolfgang Fraedrich (distributed via imaggeo.egu.eu)

Lavas erupted into river waters, and as a result cooled very quickly, can give rise to fractures in volcanic rocks. They form prismatic structures which can be arranged in all kinds of patterns: horizontally (locally known as the woodpile), slightly arching (the harp) and in a radial configuration known as the rosette. The most common configuration is the ‘organ pile’ where vertical fractures form. These impressive structures are seen in the walls of the Gole dell ‘Alcantara, a system of gorges formed 8,000 years ago in the course of the river Alcantara in eastern Sicily.

 

Home Sweet Home . Credit: André Nuber (distributed via imaggeo.egu.eu)

Can you imagine camping atop some of the highest mountains in Europe and waking up to a view of snowcapped peaks, deep valleys and endless blue skies? This paints an idyllic picture; field work definitely takes Earth scientists to some of the most beautiful corners of the planet.

 

Isolated Storm . Credit: Peter Huber (distributed via imaggeo.egu.eu)

In November 2016 we featured this photograph of an isolated thunderstorm in the Weinviertel in April. The view is towards the Lower Carpathian Mountains and Bratislava about 50 kilometers from Vienna. Why do storms and isolated thunderstorms form? Find out in this post.

 

Glacial erratic rocks . Credit: Yuval Sadeh (distributed via imaggeo.egu.eu)

As glaciers move, they accumulate debris underneath their surface. As the vast frozen rivers advance, they carry the debris, which can range from pebble-sized rocks through to house-sized boulders, along with it. As the climate in the Yosemite region began to warm as the ice age came to an end, the glaciers slowly melted. Once all the ice was gone, the rocks and boulders, known as glacial erratics, were left behind.

 

Snow and ash in Iceland . Credit: Daniel Garcia Castellanos (distributed via imaggeo.egu.eu)

Icelandic snow-capped peaks are also sprinkled by a light dusting of volcanic ash in this photograph. Dive into this March 2016 post to find out the source of the ash and more detail about the striking peak.

 

Living Flows . Credit: Marc Girons Lopez (distributed via imaggeo.egu.eu)

There are handful true wildernesses left on the planet. Only a few, far flung corners, of the globe remain truly remote and unspoilt. To explore and experience untouched landscapes you might find yourself making the journey to the dunes in Sossuvlei in Namibia, or to the salty plain of the Salar Uyuni in Bolivia. But it’s not necessary to travel so far to discover an area where humans have, so far, left little mark. One of the last wilds is right here in Europe, in the northern territories of Sweden. This spectacular photograph of the Laitaure Delta is brought to you by Marc Girons Lopez, one of the winners of the 2016 edition of the EGU’s Photo Contest!

 


The power of ice. Credit: Romain Schläppy, (distributed via imaggeo.egu.eu).

The January 2016 header image across our social media was The Power of Ice, by Romain Schlappy. This vivid picture was captured from a helicopter by Romain Schläppy during a field trip in September 2011. You can learn more about this image by reading a previous imaggeo on mondays post.

 

Sea of Clouds over Uummannaq Fjord. Credit: Tun Jan Young (distributed via imaggeo.egu.eu)

The current header image, Sea of Clouds over Uummannaq Fjord by Tun Jan Young, is also a hit with our followers and the final most popular image from Imaggeo in 2016. A sudden change of pressure system caused clouds to form on the surface of the Uummannaq Fjord, Northwestern Greenland, shrouding the environment in mystery.

 

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/.

 

Looking back at the EGU Blogs in 2016: a competition

Looking back at the EGU Blogs in 2016: a competition

The past 12 months has seen an impressive 360 posts published across the EGU’s official blog, GeoLog, as well as the network and division blogs. From a lighthearted Aprils Fools’ Day post featuring an extreme chromatic phenomenon (otherwise known as FIB); through to how climate change is affecting mountain plant’s sex ratios; features on natural hazard events throughout the year and children’s disarming ability to ask really simple questions that demand straightforward answers, 2016 has been packed full of exciting, insightful and informative blog posts.

EGU Best Blog Post of 2016 Competition

To celebrate the excellent display of science writing across the network and division blogs, we are launching the EGU Blogs competition.

From now until Monday 16th January, we invite you, the EGU Blogs readers, to vote for your favourite post of 2016. Take a look at the poll below, click on each post to read it in full, and cast your vote for the one you think deserves the accolade of best post of 2016. The post with the most votes by will be crowned the winner.

New in 2016

Not only have the blogs seen some great writing throughout the year, they’ve also continued to keep readers up to date with news and information relevant to each of our scientific divisions.

With the addition of WaterUnderground, the network blogs now feature a groundwater nerd blog written by a global collective of hydrogeologic researchers. The new blog is for water resource professionals, academics and anyone interested in groundwater, research, teaching and supervision. Excitingly, it is also the first blog hosted jointly by the EGU Blogs and the AGU blogosphere.

The portfolio of division blogs was also expanded, with the addition of the Tectonics and Structural Geology (TS), Planetary and Solar System Sciences(PS) and Earth and Space Science Informatics (ESSI) blogs back in July. Since then they’ve featured posts on big data, a regular feature showcasing the variety of research methods used in tectonics and structural geology and research from the now iconic Rosetta Mission.

Fissure eruption at Bardabunga in 2014. Photo by Ragnar Th. Sigurdsson, as featured on the TS Blog.

Get involved

Are you a budding science writer, or want to try your hand at science communication? All the EGU Blogs, from GeoLog (the official EGU blog), through to the network and division blogs, welcome guest contributions from scientists, students and professionals in the Earth, planetary and space sciences.

It couldn’t be easier to get involved. Decide what you’d like to write about, find the blog that is the best fit for your post and contact the blog editor – you can find all editor details on the individual blog pages. If in doubt, you can submit your idea for a post via the Submit a Post page on GeoLog, or email the EGU Communications Officer, Laura Roberts, who can help with initial enquiries and introduce you to individual blog editors.

Don’t forget to a look at the blog pages for a flavour of the content you can expect from the new, and existing, blogs in 2017. The blogs are also a great place to learn about new opportunities, exciting fields of research and keep up to date with news relating to the upcoming 2017 General Assembly.

 

Editor’s note on the EGU Best Blog Post of 2016 Competition: The winning post will be that with the most votes on 15th January 2017. The winner will be announced on GeoLog shortly after voting closes. The winning post will take home an EGU goodie bag, as well as a book of the winners choice from the EGU library (there are up to 4 goodie bags and books available per blog. These are available for the blog editor(s) – where the winning post belongs to a multi-editor blog, and for the blog post author – where the author is a regular contributor or guest author and not the blog editor). In addition, a banner announcing the blog as the winner of the competition will be displayed on the blog’s landing page throughout 2017.

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