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Imaggeo

Imaggeo on Mondays: A spectacular view of moss-covered rocks

Imaggeo on Mondays: A spectacular view of moss-covered rocks

Geology has shaped the rugged landscape of the Isle of Skye – the largest island of Scotland’s Inner Hebrides archipelago. From the very old Precambrian rocks (approximately 2.8 billion years old) in the south of the island, through to the mighty glaciers which covered much of Scotland as recently as 14,700 years ago, the modestly-sized island provides a snap-shot through Earth’s dynamic history.

A far cry from its modern cold, foggy and drizzly weather, back in the Jurassic age (250 million years ago, or so), the island was part of hot and dry desert. Over time, the sea encroached the low-lying plain, depositing sands and muds, and later sandstones, as well as thin limestones and shales across the island. The best examples of these rocks are found on the western side of the island, on the Strathaird Peninsula, but they can also be found on northern and eastern coastal stretches too.

Fast-forward to the Tertiary period (approximately 60 million years ago) and the landscape changed dramatically. The calm tropical waters had made way for explosive eruptions, which vented lavas from crack’s in the Earth’s crust. The lavas blanketed large areas of the north of the island, covering the sediments deposited back in the Jurassic.

Long after the surface explosive activity ended, the cracks in the Earth’s crust continued to serves as pathways for molten magma to move below the surface. In the norther part of the island, the lava travelled sideways, pushing its way between the layers of Jurassic sedimentary rocks. The black lavas, layered between the lighter coloured limestones and sandstones (as pictured above), are in stark contrast with the present-day moss-covered cliffs.

The most spectacular examples of this layering of volcanic units atop sedimentary rocks can be seen not far from where this photograph was taken, at Kilt Rocks, in south Staffin. Visitors to the area can also enjoy Mealt waterfall, where water from Mealt Loch (the Scottish word for lake) tumbles spectacularly into the Sound of Raasay.

Marius Ulm, who captured today’s featured image, is a civil/coastal engineer meaning a totally different aspect of the geology captured his attention:

“From a coastal engineering point of view, what is interesting is the missing moss-cover at the cliff’s toe. There is a line which marks the transition where the rocks stop being covered by moss also indicates how high water regularly rises due to tides. It tells us the tidal range (difference between low and high water) reaches up to 5 m in this area.”

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: Bird’s eye view of Trebecchi Lakes

Imaggeo on Mondays: Bird’s eye view of Trebecchi Lakes

Among many other environmental impacts, human activities have introduced a range of animal and plant species to areas where they do not naturally belong. The introduction of alien species, as these translocated taxa are known, has wide ranging implications for native biota, ecosystem functioning, human health and the economy. Research published earlier this year found that during the last 200 years, the number of new established alien species has grown continuously worldwide, with 37% of all first introductions reported between 1970 and 2014. And their geographic reach is staggering too… you’ll even find them in the high peaks of the Italian Alps, as described in today’s post.

Above the tree line, small lakes punctuate the vegetated, rocky landscape of the Nivolet high plain in the Gran Paradiso National Park, Italy, at an altitude of about 2600 meters above sea level.

Geologically, this area is composed mainly of gneiss (a high-grade metamorphic rock), with relevant emergences of carbonatic rocks and extended cover of glacial deposits.

In several lakes, an alien fish (brook trout, Salvelinus fontinalis) was introduced in the sixties and seventies, drastically changing the lake ecosystems. A recent EU Life project on active ecosystem management succeeded in eradicating the alien fish in an ensemble of test lakes, restoring the original conditions. The Nivolet is now one of the pilot sites of the European H2020 Project ECOPOTENTIAL, devoted to assessing the state and changes of ecosystems and geosphere-biosphere interactions  in Protected Areas by Remote Sensing, in-situ measurements and conceptual modelling. In particular, the Nivolet watershed has now been established as an Earth Critical Zone and Ecosystem Observatory.

By, Antonello Provenzale, researcher at the Institute of Geosciences and Earth Resources in Pisa, Italy, and collaborator of the Gran Paradiso National Park.

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: Of ancient winds and sands

Imaggeo on Mondays: Of ancient winds and sands

Snippets of our planet’s ancient past are frozen in rocks around the world. By studying the information locked in formations across the globe, geoscientist unpick the history of Earth. Though the layers in today’s featured image may seem abstract to the untrained eye, Elizaveta Kovaleva (a researcher at the University of the Free State in South Africa) describes how they reveal the secrets of ancient winds and past deserts.

In summer 2016 we toured the Western US in a minivan. We visited many of the gems of Utah, Arizona, and New Mexico, such as Monument Valley, Antelope Canyon, Grand Canyon, The Arches, Bryce Canyon, White Sands Monument… But the most precious and memorable for me was Zion National Park in Utah. This canyon is a unique and special place. First, because you access it from the bottom, unlike most of the other canyons, which you observe from cliff tops, such as the Grand Canyon. Thus, as you drive along the road, leading into Zion National Park, you look upward into the magnificent cliffs and rock temples. Small hiking trails lead up to waterfalls, arches and breathtaking views.

The cliffs of Zion National Park are built of Navajo Sandstone and display aeolian deposits, which have been shaped by winds, on a massive scale. They are the remnants of an ancient fossil-bearing sand desert, one of the greatest and largest wind-shaped environments that has ever existed on Earth.

In the Early Jurassic, up to 200 million years ago, the Navajo desert covered most of the Colorado Plateau (which today includes the states of Utah, Colorado, New Mexico and Arizona). Fossils, found in these sand deposits, include ancient trees, dinosaur footprints and rare dinosaur bones.

In Zion National Park, the thickness of sand deposits reaches 762 m. Beautiful cross-beds are cross-sections through fossilized towering sand dunes. They indicate the direction of the ancient winds, which were mainly responsible for moving and accumulating the sand in the Navajo desert. On the top, the Navajo sandstone is abruptly truncated by a regional unconformity, which indicates the erosion of the overlying sediments, and is covered by Middle Jurassic sediments. In remains unknown how much of the Navajo sandstone was eroded from the top of the formation during this weathering episode. It might be that the thickness and height of the Navajo sand dunes used to be even more impressive than it is now.

The cliffs of Zion National Park. Pictured is Checkerboard Mesa (South-Eastern entrance to the Zion National Park. Credit: Credit: Elizaveta Kovaleva.

By Elizaveta Kovaleva, post-doctoral researcher at University of the Free State, in South Africa

Movement of ancient sand is one of the winners of the 2017 Imaggeo Photo Contest.

References

Ron Blakey and Wayne Ranney, Ancient Landscapes of the Colorado Plateau, Grand Canyon Association, 2008, p.156.

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: Magnetic interaction

Imaggeo on Mondays: Magnetic interaction

Space weather is a ubiquitous, but little known, natural hazard. Though not as tangible as a volcanic eruption, storm or tsunami wave, space weather has the potenital to cause huge economic losses across the globe. In Europe alone, the interaction of solar wind with our planet’s magnetosphere, ionosphere and thermosphere, could lead to disrutions to space-based telecommunications, broadcasting, weather services and navigation, as well as distributions of power and terrestrial communications.

The Sun’s magnetic field drives all solar activity, from coronal mass ejections (CMEs), to high-speed solar wind, and solar energetic particles. While not all solar activity impacts the Earth, when it does, it can cause a geomagnetic storm. The Earth’s magnetic field creates, the magnetosphere which protects us from most of the particles the Sun emits. But when a “CME or high-speed stream arrives at Earth it buffets the magnetosphere. If the arriving solar magnetic field is directed southward it interacts strongly with the oppositely oriented magnetic field of the Earth. The Earth’s magnetic field is then peeled open like an onion, allowing energetic solar wind particles to stream down the field lines to hit the atmosphere over the poles,” explains NASA.

Aurorae are the most visible effect of the sun’s activity on the Earth’s atmosphere. They usually occur 80 to 300 km above the Earth’s surface, but can extend laterally for thousands of kilometers. They most commonly occur at the Earth’s poles, meaning only those at very northern, or southern, latitudes get the chance to see them (at least regularly). However, they are a reminder of the Sun’snpower and the threat posed by space weather.

To bring aurora to those who haven’t seen them before, and raise awarness about space weather at the same time, Jean Lilensten, director of research at l’Institut de planétologie et d’astrophysique de Grenoble (IPAG) in France, created the Planeterrella; an experiment which includes two spheres, one acting as the Earth and the other acting as the Sun. It allows for auroral displays, and demonstrations of other phenomena which ocurr in the space environment, to be brought into classrooms and public outreach events.

Today’s featured image shows the Planeterrella and several space phenomena. The violet colors on the big sphere ( the “star” ) are due to N2+ (a nitrogen cation), while the redish light on the little one is due to nitrogen. Both colours are seen in actual aurorae on Earth. The red “bow” in the middle, between the two spheres, is a bow shock similar to the magnetopause between Earth and the Sun (of course not to scale). Finally, a direct magnetic reconnection between the two spheres can be seen at the bottom.

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/.