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Imaggeo on Mondays: Gothic Snow Architecture.

17 Nov

Whilst on a family holiday in Norway, Gerrit de Rooij took this incredible photograph of an ice arch. Understandably geoscience is not his top priority whilst taking photographs on holiday, however Gerrit points out that pretty much every picture of a landscape has hydrology in there somewhere”, as he goes on to describe below.

This picture was taken near Balestrand, a village along the Sognefjord in Norway (Norway’s largest fjord and the second largest in the world!). The altitude was approximately 900 m above sea level (asl), and not always does all snow vanish during summer over there (we were there in August 2013). What you can see in the picture are the remnants of a much thicker snow pack that covered the stream that trickles down. On the right hand side you can see a glimpse of the other side of the arch that  must have gradually been carved out by the stream during the snow melt season (as they call spring over there). Once a tunnel was carved out, thaw took over. The black lines of rock dust on the ridges of the snow arch presumably were left behind by water streaming down along them from the top of the melting snow cover. In the top rim the source of this material is still visible.

Gothic Snow Architecture. (Credit: Gerrit de Rooij via imaggeo.egu.eu)

Gothic Snow Architecture. (Credit: Gerrit de Rooij via imaggeo.egu.eu)

Exposed are ancient rocks, heavily eroded by several glaciations and subsequent Holocene freeze-thaw cycles and snow melt flows. The location of the picture is on the west side of Norway’s mountain range. These mountains force western winds from the Atlantic upward, which makes the air cool down and release a lot of its moisture. The very frequent rains (we had 3 rain free days out of 16) create lush vegetation at lower altitudes (the tree line is between 600 and 700 m asl) and sustain extensive moss carpets higher up, as visible in the image. In places where the rock face is too steep to support moss, lichen covers it, which is evidence of very clean air – lichen are highly sensitive to air pollution.

The stream (and many similar streams nearby) feed a small lake that supplies Balestrand with drinking water. The lake can be reached in a day from Balestrand, but hiking further requires an overnight stay, even for most Norwegians, rugged as they may be. There are no huts or any other facilities, so you need to carry your camping gear with you. We camped a little higher without seeing anybody, and from the condition of the trails it was clear that everything beyond the reach of a day trip was used very infrequently. This unperturbed state, the abundant precipitation, and the inertious rocks made the water of the lake crystal clear (several meters of visibility) and very poor in nutrients (hardly any underwater vegetation), making it an excellent source of local drinking water.

In the composition, I liked the two halves of the snow arch mirroring each other, and the fact that the lines and the slope of the large exposed rock face are similar to those in the larger snow arch. The bright green of the moss upslope adds liveliness and draws the eye. I have a relatively simple camera (you want something light when backpacking) and at the time had no software to manipulate my pictures so I had to choose my viewpoint carefully and work with the light that was there. I scooped and stood very close to the snow to create a sense of perspective and have the arch reach over the camera.

By Gerrit de Rooij, Helmholtz Centre for Environmental Research – UFZ, Halle (Saale), Germany

 

Imaggeo is the EGU’s open access geosciences image repository. Photos uploaded to Imaggeo can be used by scientists, the press and the public provided the original author is credited. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. You can submit your photos here.

Imaggeo on Mondays: Painted Hills after the storm.

10 Nov

The geological record preserved at John Day Fossil beds, in Oregon, USA, is very special. Rarely can you study a continuous succession through changing climates quite like you can at this National Park in the USA. It is a treasure trove of some 60,000 plant and animal fossil specimens that were preserved over a period of 40 million years during the Cenozoic era (which began 66 million years ago).

The geography of Oregon 45 million years ago was significantly different to present. The region received a whopping 1350 mm of annual rainfall (compare this to the approximate annual rainfall in London of 500 mm or 300 mm in Madrid) as the Cascades Mountain range had not yet formed, meaning moisture from the Pacific was not blocked. In addition, the climate was much warmer and Oregon was primarily subtropical, dominated by broad-leaved evergreen subtropical forests.

Then, 12 million years later temperatures began to lower and the climate changed from subtropical to temperate. Deciduous forests became abundant at low altitudes, whilst at higher altitudes coniferous forests dominated the landscape. Imagine a setting not dissimilar to the present day eastern USA. There were a number of active volcanic centres in the area at the time and ash, lava, and volcanic mudflows frequently spread over the region. The volcanicity culminated over a period of 11 million years during which the Columbia River Basalt Group, an extensive large igneous province, was emplaced. The current landscape was shaped during the most recent Ice Age as glaciers from the Cascade Mountains eroded their way towards the low lying terrain in central Oregon.

Painted Hills. (Credit: Daniele Penna, via imaggeo.egu.eu)

Painted Hills. (Credit: Daniele Penna, via imaggeo.egu.eu)

Photographs don’t really come any more dramatic than this one. “The conditions were prefect; I was very lucky”, says Daniele Penna, who photographed the striking Painted Hills Unit within the National Park , “I visited the area right after a storm, when the sky was partially clearing, leaving space for some light that contrasted with the remaining dark clouds in the background. The combination of atmospheric conditions made me enjoy this stunning place even more and gave me the opportunity to capture several striking images.”

During his PhD in hydrology, Daniele spent a few months at the Oregon State University, in 2007. He took the advantage of his time there by exploring the diverse natural beauties that Oregon boasts.

If, like Daniele, you are interested in photography he has some top tips for achieving a photograph as remarkable as this week’s Imaggeo On Mondays image: “Switching from a wide angle to a moderate telephoto lens can give free rein to the photographer’s creativity in playing with the colors, juxtaposed intersecting lines and interlacing forms. An extremely vivid image emerges as a result of the contrast of light and dark, yellow and red colours, and the contrasting curved and straight lines at Painted Hills. The best time for capturing images that make an impact is reserved for the late afternoon in summer and during late spring when the local park ranger service provides information over the telephone on which species are in bloom.”

Imaggeo is the EGU’s open access geosciences image repository. Photos uploaded to Imaggeo can be used by scientists, the press and the public provided the original author is credited. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. You can submit your photos here.

The known unknowns: Climate, Life, and the Solid Earth (Part V)

31 Oct

After four fascinating instalments in the known unknowns series we have (sadly) come to the final post. Since the series began in September we have explored the top questions that still remain unanswered when it comes to understanding the inner workings of the planet as well as how the interplay of a number of systems that occur at the Earth’s surface give rise to its varied landscapes. The series would not be complete without assessing the open questions on how climate and life have contributed to shape the planet and so it seems fitting that we should end the series with this topic. The geological record shows that climate is relatively stable over tectonic time-scales whereas it undergoes abrupt changes in periods ranging from decades to hundreds of thousand years. Past periods when the planet underwent extreme climate conditions may help to understand the mechanisms behind that behaviour and its significance for the evolution of the Solid Earth and for the current climate change challenge. However, we are still a long way from having all the answers…

65 Myr Climate Change (Image Source: Wikimediacommons; Image credit: Robert A. Rohde published as part of the Global Warming Art project)

Image Source: Wikimediacommons; Image credit: Robert A. Rohde published as part of the Global Warming Art project)

  1. What caused the largest carbon isotope changes in Earth? (Grotzinger et al., Nat. Geosc, 2011) How does Earth’s climate respond to elevated levels of atmospheric CO2?
  2. Was there ever a snow-ball Earth during the earliest stages of Life on Earth? 
  3. Were there also rivers and lakes on Mars? (Hand,Nature, 2012) Were there large outburst floods similar to those on Earth?
  4. What were the causes and what shaped the recovery from mass extinctions as those at the K-T boundary, the Permian-Triassic or the Late Triassic? Massive volcanism? Meteorites? Microbes? Some recent papers: (Rampino & Kaiho, Geology, 2012;  Lindström et al., Geology, 2012; Chen & Benton, Nat. GeoSci, 2012; Rothman et al.,PNAS, 2014).
  5. What triggered the extreme climatic variability during the Quaternary and the roughly coeval acceleration in continental erosion and sediment delivery to the margins? [Peizhen, Molnar et al., Nature, 2001; Herman et al., Nature, 2013) Was this related to the tectonic closure of the Central American Seaway? How do these climate events translate quantitatively into sea level changes?
  6. How do climate changes translate quantitatively into sea level changes? How do ice sheets and sea level respond to a warming climate? What controls regional patterns of precipitation, such as those associated with monsoons or El Niño?
  7. What caused the Quaternary extinction(s)? Human expansion? Climate Change? How sensitive are ecosystems and biodiversity to environmental change? Was the large fauna extinction ~13,000 yr ago a result of the Younger Dryas climatic event? Was this caused by an extraterrestrial impact? (see this article and this other article) Or may it be linked to the outburst of Lake Agassiz?
  8. How relevant are subsurface microorganisms to earth dynamics by controlling soil formation and the methane cycle? What are the origin, composition, and global significance of deep subseafloor communities? What are the limits of life in the subseafloor realm?
  9. The atmosphere is shaped by the presence of life, a powerful chemical force. The Earth’s evolution has seems to affect the evolution of life (see the Cambrian explosion of animal life, for instance; plus this recent paper on that). To what extent? And how much control has life on climate? (another recent paper). Is it possible to quantify these links to make reliable predictions that allow filling the data gaps or assessing the chances for extraterrestrial life?
  10. How much of the present climate change is anthropogenic and how much is natural? How will growing emissions from a growing global population with a growing consumption impact on climate? Computer models are in need of well documented extreme scenarios from the geological past to be properly calibrated and make reliable predictions in this field.

The 49 questions covered in this series address very specific problems and unresolved problems but there are broader difficulties that limit our understanding of how the planet works.

Not for the first time, we must acknowledge that technology continues to limit direct observation of process that might clarify the source of complex geological phenomena. For example, many processes including plate tectonics are known to be driven by the nature of the materials that make up the planet interiors, down to the smallest atomic scales, as thought for instance for the trigger of earthquakes. Answers may arrive via new devices and analytical tools working at the high pressures and temperatures of Earth’s interior.

Another issue is that of reconciling time scales. We can only make observations in the present, whilst the phenomena we try to understand occur in time scales with very different orders of magnitude. We are also limited by having to convincingly scale rates of lab experiments (e.g., mineral physics), and/or analogue models to corresponding geological scenarios. Not unreasonably, this approach does not always yield satisfactory/reliable outcomes.

Global Surface Reflectance and Sea Surface Temperature (Credit: MODIS Instrument Team, NASA Goddard Space Flight Cente).

Global Surface Reflectance and Sea Surface Temperature (Credit: MODIS Instrument Team, NASA Goddard Space Flight Cente).

Implementing Episodicity in Gradualism: For historical reasons, geology has generally underestimated the role of episodicity in nature. However, there is a growing interest driven to exceptional events and to the stochasticity of Earth’s subsystems. An example for this is the preeminence of extreme flooding events (larger than average) in erosion and surface sediment transport and during the evolution of landscape, and the importance of upscaling flood stochasticity into sediment transport models (eg., Lague, JGR, 2010). Even plate tectonics may have been episodic (during the Archean at least, (Moyen & van Hunen, Geology, 2011).  4D hyperscale data sets in geomorphology are increasingly showing the limits of smooth-process approaches. Future understanding of the Earth will benefit from incorporating the full frequency spectrum (the episodicity) in modeling natural phenomena, rather than systematically approaching these as gradual processes. 

Finally, whilst computer models help us understand whether the complexity of nature can be explained by the interplay between simple processes, can we further model the Earth as a complex system of complex systems? And when can we expect ‘compact’ explanations? 

With these last broad considerations we close the known inknowns series. Hopefully, it has achieved what it set out to do: provide an overview of what  earth scientists are up to and what the hot topics and questions in Earth sciences are. Understanding these will lead us ever closer to understand phenomena that are fundamental to societal needs such as mineral resources, global change, or waste disposal.

By Laura Roberts Artal, EGU Communications Officer, based on the article previously posted on RetosTerricolas by Daniel Garcia-Castellanos, researcher at ICTJA-CSIC, Barcelona

Imaggeo on Mondays: Polygon ponds at sunset.

27 Oct

Thinking of the Arctic conjures up images of vast expanses of white icy landscapes punctuated by towering icebergs and a few dark rocky masses; certainly not a green landscape with a series of water pools amongst rolling hills. The image below is perhaps more reminiscent of the temperate Scottish or Welsh countryside; but don’t be fooled, out Imaggeo on Monday’s image was captured by Reinhard Pienitz  (Laval University, Canada) in western Bylot Island, part of the Canadian Arctic Archipelago.

Polygon ponds at sunset. (Credit: Reinhard Pienitz, via imaggeo.egu.eu)

Polygon ponds at sunset. (Credit: Reinhard Pienitz, via imaggeo.egu.eu)

The uniqueness of Bylot Island is due to the convergence of a number of ecosystems. It lies to the north of Baffin Island and is dominated by high mountain peaks and glaciers. The southern plain of the island is at relatively low-elevations and covered by tundra vegetation. Wetlands are common in the low lying terrain where grasses, brown moss and sedges carpet the landscape. Think of them as ‘polar oasis’ which support hundreds of plant species and tens of animal and bird species. In contrast, the slopes of the hills are much drier and support shrubs, grasses and forbs.

The ground in the low-lying areas is perpetually frozen which means the drainage of water from the melted snow is hampered; it is the presence of this permafrost which allows the formation of the widespread wetlands. Year on year, organic matter accumulates, rising upwards, as the permanently wet and cold conditions mean it is very difficult for organic material to break down. As time passes, cyclic layers of peat and permafrost build up. The importance of the wetland ecosystem in the Arctic cannot be underestimated. The peat-rich soils constitute a net sink for carbon during the Holocene and are thought to store 97% of the tundra carbon reserve (Ellis et al., 2008).

Freezing over the winter months and thawing over the (slightly) warmer spring months drives the formation of the polygonal pattern seen across the wetlands of Bylot Island (and many other Arctic regions). As the ground freezes it contracts resulting in the formation of vertical cracks which penetrate the layers of peat and permafrost. The moist soils and meltwaters mean that there is plenty of water available to infiltrate the cracks, especially during spring. As the cold winter months approach the water freezes and the cracks expand, forming what are known as ice wedges, commonly connected at the surface, which give rise to the well-ordered polygonal pattern.

 

References

Ellis, C.J., et al. (2008), Paleoecological Evidence for Transitions between Contrasting Landforms in a Polygon-Patterned High Arctic Wetland, Arctic. Antarctic, und Alpine Research., 40, 4,624-637

Imaggeo is the EGU’s open access geosciences image repository. Photos uploaded to Imaggeo can be used by scientists, the press and the public provided the original author is credited. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. You can submit your photos here.

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