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Natural Hazards

Imaggeo on Mondays: Sedimentary record of catastrophic floods in the Atacama desert

Imaggeo on Mondays: Sedimentary record of catastrophic floods in the Atacama desert

Despite being one of the driest regions on Earth, the Atacama desert is no stranger to catastrophic flood events. Today’s post highlights how the sands, clays and muds left behind once the flood waters recede can hold the key to understanding this natural hazard.

During the severe rains that occurred between May 12 and 13, 2017 in the Atacama Region (Northern Chile) the usually dry Copiapó River experienced a fast increase in its runoff. It caused the historic center of the city of Copiapó to flood and resulted in thousands of affected buildings including the University of Atacama.

The city of Copiapó (~160,000 inhabitants) is the administrative capital of this Chilean Region and is built on the Copiapó River alluvial plain. As a result, and despite being located in one of the driest deserts of the world, it has been flooded several times during the 19th and 20th century. Floods back in 2015 were among the worst recorded.

The effects of the most recent events are, luckily, significantly milder than those of 2015 as no casualties occurred. However, more than 2,000 houses are affected and hundreds have been completely lost.

During this last event, the water height reached 75 cm over the river margins. Nearby streets where filled with torrents of mud- and sand-laden waters, with plant debris caught up in the mix too. Once the waters receded, a thick bed of randomly assorted grains of sand  was deposited over the river banks and urbanized areas.

Frozen in the body of the bed, the sand grains developed different forms and structures. A layer of only the finest grained sediments, silts and clays, bears the hallmark of the final stages of the flooding. As water speeds decrease, the finest particles are able to drop out of the water and settle over the coarser particles. Finally, a water saturated layer of mud, only a few centimeters thick, blanketed the sands, preserving the sand structures in 3D.

The presence of these unusual and enigmatic muddy bedforms has been scarcely described in the scientific literature. A new study and detailed analysis of the structures will help better understand the sedimentary record of catastrophic flooding and the occurrence of high-energy out-of-channel deposits in the geological record.

By Manuel Abad and Tatiana Izquierdo, Universidad de Atacama (Chile)

 

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

March 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

While the March headlines might not have been dominated by a particular story, the state of the Earth’s climate has definitely been the overarching theme of the month.

Ahead of World Meteorological Day (celebrate on the 23rd March) the World Meteorological Organization released its annual report on the State of Global Climate. Compiled from a broad range of sources, the report reiterates the findings of the US government agencies NASA and NOAA, who earlier this year declared that 2016 was the warmest year on record.

Not only were temperatures a remarkable 1.1 °C above the pre-industrial period and 0.06 °C above the previous record set in 2015, global sea ice extent dropped more than 4 million square kilometres below average in November. Boosted by a strong El Niño event global sea levels reached record highs too.

The report comes in the wake of US President Trump’s ‘blueprint’ budget for 2018, where he sets out his spending priorities for the year ahead. Nature put together a piece that highlights what US science would stand to lose if the budget is approved. NASA would experience a 0.8% cut from current levels, largely focused on Earth science missions, and future NOAA satellite programmes are also under threat. Worst hit by the cuts would be the Environment Protection Agency (EPA), with a proposed 31% cut in funding, which would “gut EPA programs tackling climate change and pollution”, according to The Guardian.

But the signals are clear: after the record warming in 2016, temperatures have continued to rise in 2017, affecting ecosystems around the world. An example are the corals of the Great Barrier Reef,  which have suffered from widespread bleaching – a situation where they expel their symbiotic algae, meaning they turn white and can die – for the third consecutive year. A new study on mass bleaching of corals was discouraging news: the only long-term solution to the problem is halting global warming. Improving water quality or enforcing fishing controls provides little relief.

But it’s not all bad news when it comes to the global climate and the Earth’s environment. Despite being a record-breaking year in terms of temperatures, 2016 was also the year that saw a dramatic drop in the amount of new coal fueled power plants being built. With cities worldwide battling poor air quality and pollution, this is certainly encouraging news.

What you might have missed

Earlier this month a BBC News crew experienced the fickle nature of volcanoes first hand. The team were visiting Mt. Etna (Sicily) to film a report on volcano monitoring, and  arrived on the Italian island to discover Europe’s most active volcano had just started to erupt again.

Etna’s slow-moving lava is not usually considered dangerous. “But about 20 minutes after arriving, a burst of white steam emerged from the lava – it didn’t make much of a noise or look especially threatening – but the guides started asking people to move. Then, moments later, there was an explosion,” writes Rebecca Morelle, one of the reporters on the team. As they ran down the mountain to safety, the team and tourists, were “pelted with deadly, hot debris.” Read the full account of their ordeal and watch a spectacular video here.

It has also been a big month for palaeontology. Up until now the shape of a dinosaur’s hip determined were along the dinosaur family tree it was placed. Lizard-hipped dinosaurs fell into one group (Saurischia), while those with a more bird-like hip configuration are known as Ornithischia. Now, a team of researchers have proposed a radically new classification system. They found that 21 other anatomical features divide the dinosaurs differently. The new tree puts theropods together with Ornithischian, indicating they probably share a common ancestor. The new theory might face an uphill struggle to debunk the long-lasting consensus on the history of dinosaurs, but many in the field agree that given the thoroughness of the study it is certainly an idea worth considering.

Scientists from the Museum and Cambridge University have proposed radical changes to the dinosaur family tree. Credit: Natural History Museum.

And while we are on the subject of dinosaurs, this brilliant interactive map of every fossil found on Earth (created by @PaleoDB) is a great resource!

Way out in space, the bounty of insights from the Rosetta mission continues. From September 2014, the mission scientists have kept a watchful eye on a 70 m-long, 1 m-wide fracture on the prominent cliff-edge subsequently named Aswan, in the Seth region of the comet, on its large lobe. A few days later, new images of the area revealed that the crack had disappeared and been replaced by a new cliff face, at the bottom of which were many new meter-sized boulders. The discovery allowed the scientists to make the link between the newly created cliff face and outbursts of dust and gas.

You might think the use of infographics to visualise data is a relatively new thing, but you’d be mistaken. This collection of 1800s educational diagrams, of scientific discoveries, from the moon’s surface to the longest rivers, is simply stunning and incredibly effective.

Emslie and Reynolds compare mountains and volcanoes, including mountains in the Alps and Andes. Featured in Geological Diagrams. Courtesy David Rumsey Historical Map Collection

Links we liked

  • Something for the weekend? Why not try your hand at baking a scientifically accurate (sort of!) cake planet?
  • New research suggests that by the middle of the century, more than half of humanity will live in water-stressed areas. Badly managed resources play a crucial role in water shortages globally
  • For a lighthearted, yet very informative, take on mass extinctions this story in The Atlantic is not to be missed
  • A German coal-mine, which has provided power for the country’s industry sector for the past half century, will get a new lease on life when it’s turned into a into a pumped-hydro-storage station, acting like a giant battery that stores solar and wind energy

The EGU story

This time of year, EGU’s biggest story is our annual General Assembly, starting only a few weeks from now. This month, we published the meeting programme, which includes some 1000 sessions and over 17,500 abstracts! On the blog, we published guides on how-to make the best of your oral, poster or PICO presentation at the General Assembly, revealed the finalists of the Communicate Your Science Video Competition, and provided tips on making the most of your time in Vienna without breaking the bank. We look forward to seeing you all in the Austrian capital in the last week of April!

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.

Imaggeo on Mondays: harnessing Earth’s inner heat

Imaggeo on Mondays: harnessing Earth’s inner heat

Iceland, the land of ice and fire, is well known for its volcanicity. Most famously, it is home to Eyjafjallajökull: the volcano which caused wide spread mayhem across European airspace when it erupted in 2010.

But not all the local volcanic activity is unwelcome. High temperature geothermal areas are a byproduct of the volcanic setting and the energy released can be used to power homes and infrastructure. Indeed, geothermal power facilities currently generate 25% of the country’s total electricity production.

“I took the photograph during a three hour walk in the Krafla area, a few kilometres away from Myvatn Lake in Northern Iceland,” explains Chiara Arrighi, a PhD student at the University of Florence in Italy, who took today’s featured image while on a two week holiday on the island.

There are 20 high-temperature areas containing steam fields with underground temperatures reaching 250°C within 1,000 m depth dotted across the country. Krafla, a caldera of about 10 km in diameter, and the wider Myvatn area is one of them. The volcano has a long history of eruptions, which drives the intrusion of magma at (geologically) shallow depths which in turn heats groundwater trapped deep underground, generating the steam field. Only a few hundred meters from the shooting location a power station of 60 MW capacity exploits high- and low-pressure steam from 18 boreholes.

Fumaroles and mud pots, like the one photographed by Chiara, are the surface expression of the geothermal activity. The discoloration of the rocks in the immediate vicinity of the bubbling mire is due to the acidic nature of the water in the pool. The steam is rich in hydrogen sulphide, which oxidises to sulphur and/or sulphuric acid as it mixes with oxygen when it reaches the surface. It deposits around the vents of fumaroles and as sulphuric acid in the stagnant waters, leading to alteration of the surrounding bedrock and soil.

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/.

Imaggeo on Mondays: a storm is coming

Imaggeo on Mondays: a storm is coming

Coastlines globally are immensely diverse: from the beautifully topical and sun kissed beaches of the Caribbean, to the wet and misty British coastline, through to the raw and wild Alaskan shores, they are home to scores of flora and fauna; rich habitats shaped by powerful forces of nature.

In stark contrast, some coastlines, (28,000 km worldwide to be precise) are dry almost barren places, where little grows. These long stretches of inhospitable seaside lands are known as hyperarid and arid coastlines. Due to the lack of protective vegetation the land is exposed to the action of winds and the sun, leaving behind pavements of bare rock, large dune formations and/or highly saline enclosed lakes (sebkhas).

The Gulf of Aqaba, in the north-western tip of Saudi Arabia, where the desert meets the Red Sea is one such place. Rivers here, which drain into the sea water, are fleeting. They appear after heavy rainfall, when flash floods deliver huge influxes of sediment to the coral-rich waters of the Red Sea.

Nadine Hoffman took today’s featured image while driving from Israel from the Red Sea. Pictured is the northern tip of Saudi Arabia, where a spring storm is coming into the desert bringing severe rain and flash floods. Eventually, the flood waters will drain into the Gulf of Aqaba.

 

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/.

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