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Cryospheric Sciences

Imaggeo on Mondays: Rock glaciers

Imaggeo on Mondays: Rock glaciers

Picture a glacier and you probably imagine a vast, dense mass of slow moving ice; the likes of which you’d expect to see atop the planet’s high peaks and at high latitudes. Now, what if not all glaciers look like that?

Take some ice, mix in some rock, snow and maybe a little mud and the result is a rock glacier. Unlike ice glaciers (the ones we are most familiar with), rock glaciers have very little ice at the surface. Instead, the ice is locked in between the other components, or forms a solid, central structure. Looking at the rock glacier on the flanks of the Heart Peaks shield volcano in northwestern British Columbia (pictured above) you’d be forgiven for thinking this isn’t a glacier at all!

Rock glaciers move down slopes, slowly; typically at speeds which range from a few millimetres per year, up to a few meters. The movement is driven by gravity and usually due to gliding at the base of the glacier, or sometimes due to internal deformation of the ice.

How do the impressive landforms come about? The jury is still out, with the merits of a number of explanations still being debated. Some argue that they are due to geomorphic processes that result from seasonal thawing of snow in areas of permafrost; while others suggest the explanation is simpler: as a glacier wastes, it leaves behind an increasing amount of rock debris as the ice melts. It may be that rock glaciers are the result of a landslide covered glacier melting, or the mixing of a glacier with a landslide it encounters in its way down-slope…

Whatever the exact cause of the rock glacier on the flank of Hearts Peak, it remains a particularly striking example of the landform, given its unusual pink(ish) colour. The dormant volcano is characterised by steep-sided lava domes which are composed of porphyitic rhyolites  and, to a lesser extent, trachytic rocks, which give rise to the unusual colouring of this rock glacier.

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: The glacial landscape of Yosemite

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

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

Yosemite National Park, in California, is renowned for its beautiful and striking landscapes. So much so, this is the second time it has feature on the blog this summer. While our last post on the park focused on the ancient volcanic history of its landscape, in this post we fast forward to the Plesitocene (some 110,000 to 12,000 years ago) to discover more about how glaciers shaped Yosemite’s landscape. Indeed, it is the glacier carved landscape which has made the park so famous!

During the last ice age, the high peaks and valleys of the Sierra Nevada (of which Yosemite belongs to) were covered by ice.  A vast continental ice sheet spread across much of the United States and Canada. Local climate variations as well as the geographical position of Yosemite meant that the accumulation of ice in the region was particularly unique, and didn’t belong to the vast continental ice sheet. Nevertheless, glaciers dominated the landscape during this time and the scars left behind by their presence resulted in a range of landforms observable today: including chatter marks (gouges left in granite by moving glaciers), glacier polish (shiny patches of granite), exfoliation (layered cracking of rocks which resembles onions peeling), and many others.

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.

One of the best examples of glacial erratics can be seen at Olmstead Point, near Mt. Hoffmann, in Yosemite National Park, as photographed by Yuval Sadeh. Yuval reminisces about the moment he reached the spot where the boulders are strewn across the landscape:

“I remember walking on this extremely smooth scraped surface, watching the glacial erratics rocks which looks like a giant artist placed them gently on the bedrock. Although the glacier melted many years ago, out there on the glacier carved surface it seems that time is standing still ever since.”

Imaggeo on Mondays: Heavy machinery

Imaggeo on Mondays: Heavy machinery

How do you get heavy machinery, such as a drill spool onto an ice sheet? This week’s imaggeo on Mondays’ photography captures the freighting of components of a hot water drill to directly access and observe the physical and geothermal properties at the ice-bed interface. In the image, SAFIRE principal investigator Bryn Hubbard and post-doc Sam Doyle help fly in the drill spool at the start of the Summer 2014 field campaign on Store Glacier, Western Greenland.

Freighting several tons of equipment onto the Greenland Ice Sheet for the sake of science may be slightly intense, but in doing so, it reveals an environment that is complex in history and dynamics.

The Greenland Ice Sheet is losing mass at an increasing rate, and since 2010 has contributed 1 mm/year to global sea level rise. The large majority of changes occur within the drainage basins of marine-terminating glaciers (those which end at the lands edge and drain into the sea), which flow rapidly and drain 88% of the ice sheet. While the surface melt processes of glaciers has been well-studied and quantified, very little is known about what happens below the glacier surface, especially where the ice meets the bedrock.

Recent studies from Greenlandic outlet glaciers have emphasized meltwater-enhanced basal lubrication as an increasingly important mechanism to explain the flow of ice down a glacier. In essence, meltwater generated at the glacier surface will eventually find its way down to the glacier bed through crevasses that connect these two systems. The sudden influx of water increases the pressure within the environment, causing the glacier to “lift” off the bed and flow faster. However, the mechanism is largely an untested theory, and its specifics at the ice-bed interface are still largely unknown, especially on fast-flowing outlet glaciers. In order to achieve accurate predictions of sea level rise in the near future, we need to fully understand the dynamics occurring at the ice-bed interface and its complex response to climate-induced ice melt.
Obviously, a great method to tackle this research question is to air freight tons of heavy machinery onto the Greenland Ice Sheet, and to gain access to the bed of the ice sheet by drilling a 600-metre tunnel with hot water. This is part of the Subglacial Access and Fast Ice Research Experiment (SAFIRE), a collaboration between the Scott Polar Research Institute at the University of Cambridge and Aberystwyth University in Wales.

The SAFIRE project has two specific goals: 1. to identify and characterise the mechanical and hydrological conditions at the base of a large outlet glacier in Greenland, using instruments installed in boreholes drilled to the bed; and 2. to determine the role of basal processes in governing ice flow and iceberg calving. With no previous observation ever made in a subglacial environment of this type of glacier, this project breaks new ground, and from the unique datasets acquired from instruments deployed in boreholes and on the glacier’s surface, higher order numerical ice-flow models can be written and constrained.

Our work is mainly on Store Glacier, which is a large tidewater glacier in the Uummannaq region of northwestern Greenland. Store has a large drainage basin (35,000 km2) and flows up to 5 km/year at the glacier terminus, discharging extremely large volumes of ice into the ocean every day. Since 2014, we have been working on-site at a campsite ~30 km from the terminus, and our results characterise an extremely dynamic and warm basal environment over a deformable sediment bed. A detailed analysis of these unexpected results will be forthcoming in the near future.

By TJ Young, Scott Polar Research Institute / British Antarctic Survey 

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: Moving images – Photo Contest 2016

Since 2010, the European Geosciences Union (EGU) has been holding an annual photo competition and exhibit in association with its General Assembly and with Imaggeo – the EGU’s open access image repository.

In addition to the still photographs, imaggeo also accepts moving images – short videos – which are also a part of the annual photo contest. However, 20 or more images have to be submitted to the moving image competition for an award to be granted by the judges.

This year saw seven interesting, beautiful and informative moving images entered into the competition. Despite the entries not meeting the required number of submissions for the best moving image prize to be awarded, three were highly ranked by the photo contest judges. We showcase them in today’s imaggeo on Mondays post and hope they serves as inspiration to encourage you to take short clips for submission to the imaggeo database in the future!


Aerial footage of an explosion at Santiaguito volcano, Guatemala. Credit: Felix von Aulock (distributed via imaggeo.egu.eu)

During a flight over the Caliente dome of Santiaguito volcano to collect images for photogrammetry, this explosion happened. At this distance, you can clearly see the faults along which the explosion initiates, although the little unmanned aerial vehicle is shaken quite a bit by the blast.


Undulatus asperitus clouds over Disko Bay, West Greenland. Credit: Laurence Dyke(distributed via imaggeo.egu.eu)

Timelapse video of Undulatus asperitus clouds over Disko Bay, West Greenland. This rare formation appeared in mid-August at the tail end of a large storm system that brought strong winds and exceptional rainfall. The texture of the cloud base is caused by turbulence as the storm passed over the Greenland Ice Sheet. The status of Undulatus asperitus is currently being reviewed by the World Meteorological Organisation. If accepted, it will be the first new cloud type since 1951. Camera and settings: Sony PMW-EX1, interval recording mode, 1 fps, 1080p. Music: Tycho – A Walk.

Lahar front at Semeru volcano, Indonesia. Credit: Franck Lavigne (distributed via imaggeo.egu.eu)

Progression of the 19 January 2002 lahar front in the Curah Lengkong river, Semeru volcano, Indonesia. Channel is 25 m across. For further information, please contact me (franck.lavigne@univ-paris1.fr)

 

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