GeoLog

Geochemistry, Mineralogy, Petrology & Volcanology

Imaggeo on Mondays: How erosion creates natural clay walls

Imaggeo on Mondays: How erosion creates natural clay walls

The badlands valley of Civita di Bagnoregio is a hidden natural gem in the province of Viterbo, Italy, just 100 kilometres from Rome. Pictured here is the ‘wall,’ one of the valley’s most peculiar features, where you can even find the wooden structural remains of a trail used for agricultural purposes in the 19th and 20th centuries.

The photograph was taken by Chiara Arrighi, a post-doc research assistant at the University of Florence (Italy), in May last year after climbing roughly 200 metres from the bottom of the Chiaro creek valley. Trails in this region are not well traced or maintained, so she had to find her own way up among the chestnut woods. Once at the top, the trail becomes narrow and unprotected. “The inhabitants of the area still do not exploit this natural beauty as a tourist attraction,” said Arrighi. “In fact, nobody was on the trail, and the silence [was] unreal.”

Badlands are a typical geological formation, where grains of sand, silt and clay are clumped together with sedimentary rock to form layers, which are then weathered down by wind and water. The terrain is characterised by erosive valleys with steep slopes, without vegetation, separated by thin ridges.

Due to the slope’s steep angle and the clay’s low permeability, little water is able enter the soil. Instead water quickly flows across the surface, removing surface clay and carving into the slopes as it does so.

The morphological evolution of the clay slopes can be very rapid (for example, rock falls can occur quite suddenly after heavy rainfall) and occurs as a result of several physical mechanisms, such as mud flows, solifluction (slow movement of wet soil towards the bottom of the valley) and sliding.

During the evolution of the badlands, peripheral portions of the terrain made up of volcanic deposits (tuff cliffs) rose up from the landscape, bordered by nearly vertical slopes (called scarps). Many towns have been built on these erected hilltops, such as Civita di Bagnoregio.

By Chiara Arrighi and Olivia Trani

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/.

Imaggeo on Mondays: Fairy chimneys in Love Valley

Imaggeo on Mondays: Fairy chimneys in Love Valley

Every year tourists from around the world flock to Love Valley in Göreme National Park in the Cappadocia region of central Turkey to marvel at the region’s peculiarly pointy geological features. These cone-shaped formations, known as ‘fairy chimneys’ or hoodoos, dominate the park’s skyline, with some rocky spires extending up to 40 metres towards the sky.

While the name ‘fairy chimney’ suggests mythical origins, these rocks began to take shape millions of years ago, when many active volcanoes dominated the region. “The deposits of [volcanic] ash, lava and basalt laid the foundations for today’s landscape,’ commented Alessandro Demarchi in the photo’s description, who captured the stunning photograph featured today. The volcanic material consolidated into a soft rock known as ‘tuff.’ Then over the years, natural weathering forces like wind and water eroded weaker parts of the rock away, leaving behind the pinnacles we see now.

Around the 4th century, during the reign of the Roman empire, many Christian pilgrims traveled to Cappodocia to flee persecution. They built their new life into the region’s rocks, carving out a network of homes and churches from the towers of tuff. If you look closely at background of the image, you can even spot remnants of their handiwork.

The region was named a UNESCO World Heritage Site in 1985, and today you can enjoy the extraordinary geological formations, as well as their cultural history, either from the ground or up in the air through hot air balloon tours.

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/.

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  

While May’s headlines may have been dominated by the Kilauea Volcano’s recent eruption in Hawaii, the science news world directed its attention to another volcanic event early this month. On June 3, Guatemala’s Volcán de Fuego erupted, sending plumes of volcanic ash several kilometres into the air. The volcano also unleashed an avalanche of hot gas and debris, otherwise known as pyroclastic flows, more than 10 kilometres down the volcano’s flanks onto the surrounding valley.

The Volcán de Fuego has been an active volcano since 2002, however, this latest event has been the volcano’s most violent eruption in more than four decades.

By 23 June, officials reported that the eruption has killed 110 people from surrounding villages, with hundreds more missing or injured.

Both Kilauea and Fuego gained international attention this year, but the two volcanoes exhibit very different behaviours by nature.

Kilauea is a shield volcano, with a relatively gradual slope and a highly fluid lava flow that can travel far distances compared to other volcanic archetypes. While the volcanic eruption’s lava, ash and haze present real threats to nearby communities, very few injuries have been reported.

“Lava flows rarely kill people,” said Paul Segall, a professor of geophysics at Stanford University, to the New York Times. “They typically move slow enough that you can walk out of the way.”

The Fuego volcano on the other hand is a stratovolcano, characterised by a cone-shaped peak built by layers of lava and ash. This type of volcano usually contains more viscous magma, meaning the hot liquid material has a sticky, thicker consistency. This type of fluid in volcanoes “clogs their plumbing and leads to dramatic explosions,” says Smithsonian Magazine.

Stratovolcanoes like Fuego also often release pyroclastic flows. These plumes can be a major threat to human health and make this kind of volcano particularly dangerous. “On its surface, a pyroclastic flow looks like a falling cloud of ash. But if you could peer into the cloud, you would find a really hot and fast-moving storm of solid rock,” reported PBS NewsHour.

Paul Rincon, a science editor for BBC News notes that pyroclastic flows can reach speeds of up to 700 kilometres per hour and are extremely hot, with temperatures between 200 to 700 degrees Celsius.

As of June 17, Guatemalan authorities have officially stopped looking for bodies and survivors. However, some local rescue workers have kept on with their search. 

What you might have missed

Meanwhile this month, in a vastly different part of the world, scientists have uncovered a wealth of new insight into Antarctica and how the region’s ice melts. Some of the discoveries made known are very foreboding while others more uplifting.

Let’s start with the bad news first. A study published this month in Nature revealed that Antarctica is melting faster than ever, and the continent’s rate of ice loss is only accelerating.

The report explains that before 2012 the Antarctic ice sheet steadily lost 76 billion tonnes of ice each year, contributing 0.2 milimetres to sea-level rise annually. However, since then, Antarctica’s rate of ice loss has increased threefold. For the last fives years the ice sheet has shed off 219 billions tonnes of ice each year. This ice loss now corresponds to a 0.6 milimetre contribution, making Antarctica one of the biggest sources of sea-level rise.

The largest iceberg ever recorded broke away from the Antarctic Peninsula in 2017. Pictured here is the iceberg’s western edge. (Credit Nathan Kurtz/NASA)

This record pace could have a devastating impact around the world, the researchers involved with the study say.

“The continent is now melting so fast, scientists say, that it will contribute six inches (15 centimeters) to sea-level rise by 2100,” reports the New York Times.

The articles continues: “’around Brooklyn you get flooding once a year or so, but if you raise sea level by 15 centimeters then that’s going to happen 20 times a year,’ said Andrew Shepherd, a professor of earth observation at the University of Leeds and the lead author of the study.”

On the other hand, one study published this month in Science offers a glimmer of hope, suggesting that a natural geologic process may help counteract some of the Earth’s sea level rise.

A team of researchers found evidence that, in response to losing ice mass, the ground underneath melting ice sheets naturally lifts up, and more substantially than scientists had previously believed. This process could help prevent further ice loss by land locking vulnerable ice sheets.

Scientists say that many ice sheets in the West Antarctic are at risk of collapsing, and furthermore contributing to sea level rise, because they are in direct contact with the ocean. The relatively warm seawater can melt these glaciers from underneath, making these giant frozen masses more at risk of losing a substantial amount of ice.

However, the new research on the West Antarctic Ice Sheet finds that as these ice masses lose weight, the ground underneath springs up, acting much like a memory-foam mattress.

“This adjustment of the land once the weight of the ice has been lifted is known as ‘glacial isostatic adjustment,’” says Carbon Brief. “It is usually thought to be a slow process, but the new data suggests the ground uplift beneath the [Amundsen Sea Embayment] area is occurring at an unprecedented rate of 41mm per year.”

A press release from Delft University of Technology in the Netherlands goes on to say that “the measured uplift rate is up to 4 times larger than expected based on the current ice melting rates.”

While this discovery offers a brighter view to the serious state of Earth’s melting ice, scientists still caution that this natural grounding process may be rendered useless in extreme cases climate change with extensive ice loss.

Links we liked 

The EGU story

For the first time, we gave participants at the annual EGU General Assembly the opportunity to offset the COemissions resulting from their travel to and from Vienna.

We are happy to report that, as a result of this initiative, we raised nearly 17,000 EUR for a carbon offsetting scheme. The Carbon Footprint project the EGU is donating to aims to reduce deforestation in Brazil and “is expected to avoid over 22 million tonnes of carbon dioxide equivalent greenhouse gas emissions over a 40 year period.”

Do you enjoy the EGU’s annual General Assembly but wish you could play a more active role in shaping the scientific programme? Now is your chance! Help shape the scientific programme of EGU 2019.

From now until 6 Sep 2018, you can suggest:

  • Sessions (with conveners and description),
  • Short Courses, or;
  • Modifications to the existing skeleton programme sessions

Plus from now until 18 January 2019, you can propose townhall meetings. It’s important to note that, for this year’s General Assembly, session proposals for Union Symposia and Great Debates are due by 15 August 2018

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: Hints of an eruption

Imaggeo on Mondays: Hints of an eruption

The photograph shows water that accumulated in a depression on the ice surface of Vatnajökull glacier in southeastern Iceland. This 700m wide and 30m deep depression [1], scientifically called an ‘ice cauldron’, is surrounded by circular crevasses on the ice surface and is located on the glacier tongue Dyngjujökull, an outlet glacier of Vatnajökull.

The photo was taken on 4 June 2016, less than 22 months after the Holuhraun eruption, which started on 29 August 2014 in the flood plain north of the Dyngjujökull glacier and this depression. The lava flow field that formed in the eruption was the largest Iceland has seen in 200 years, covering 84km2 [2] equal to the total size of Manhattan .

A number of geologic processes occurred leading up the Holuhraun eruption. For example, preceding the volcanic event, a kilometre-wide area surrounding the Bárðarbunga volcano, the source of the eruption, experienced deformation. Additionally, elevated and migrating seismicity at three to eight km beneath the glacier was observed for nearly two weeks before the eruption [3]. At the same time, seven cauldrons, like the one in this photo, were detected on the ice surface (a second water filled depression is visible in the upper right corner of the photo). They are interpreted as indicators for subglacial eruptions, since these cauldrons usually form when geothermal or volcanic activity induces ice melt at the bottom of a glacier [4].

Fracturing of the Earth’s crust led up to a small subglacial eruption at the base of the ice beneath the photographed depression on 3 September 2014. This fracturing was further suggested as the source of long-lasting ground vibrations (called volcanic tremor) [5].

My colleagues and I studied the signals that preceded and accompanied the Holuhraun eruption using GPS instruments, satellites and seismic ground vibrations recorded by an array of seismometers [2, 5]. The research was conducted through a collaboration between University College Dublin and Dublin Institute for Advanced Studies in Ireland, the Icelandic Meteorological Office and University of Iceland in Iceland, and the GeoForschungsZentrum in Germany.

The FP7-funded FutureVolc project financed the above mentioned research and further research on early-warning of eruptions and other natural hazards such as sub-glacial floods.

By Eva Eibl, researcher at the GeoForschungsZentrum

Thanks go to www.volcanoheli.is who organised this trip.

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/.