Archive | Cryospheric Sciences RSS feed for this section

Imaggeo on Mondays: Pitter-patter of little paws in Patomsky crater

10 Feb

This week’s Imaggeo on Mondays is brought to you by Dmitry Demezhko, who describes how Patomsky crater may have formed and why it keeps scientists puzzling…

Patomsky crater, also known as Patomskiy crater or the Patom cone, sits in the Irkutsk Region of Eastern Siberia. The site is a curious cone with a crater at the top and a small mound in the center. The cone totals some 39 metres in height and stretches more than 100 metres in diameter (at the base of the cone).

Patomsky crater – view from a helicopter. (Credit: Dmitry Semenov)

Patomsky crater – view from a helicopter. (Credit: Dmitry Semenov)

The crater was discovered in 1949 by Russian geologist Vadim Kolpakov and for a long time it was considered to be an impact structure with a meteoric origin. Later, Viktor Antipin suggested it could be a nascent volcano. But neither meteoritic nor volcanic matter was found there. The crater consists of proterozoic limestone and sandstone debris and, to date, there is no consensus among scientists regarding the crater’s origin.

View from the crater. (Credit: Dmitry Demezhko, distributed via imaggeo.egu.eu)

View from the crater. (Credit: Dmitry Demezhko, distributed via imaggeo.egu.eu)

During a short expedition in August 2010 we conducted a gravimetric survey at the crater and surrounding area, aiming to evaluate its internal structure. The gravity field shows that surface negative anomalies, where the gravity is unusually low, have deep “roots” and a joint source at depth. But the crater’s gravity field differs greatly from the fields of other well-known impact structures, suggesting that it may not have formed during a meteoric impact.

Downward continuation of the Patomsky crater (left) and Popigay impact structure gravity fields (right). (Credit: Demezhko et al., 2011)

Downward continuation of the Patomsky crater (left) and Popigay impact structure gravity fields (right), (click for larger). (Credit: Demezhko et al., 2011)

We suggest this structure formed in two stages. During the first stage tectonic processes similar to mud volcanism created a porous vertical channel. In the second stage, cryogenic processes would have played an important role in breaking apart the rocks to form the cone and crater.

There is a lot of mysticism and superstition surrounding Patomsky. Local residents call the crater “a fabulous Eagle’s Nest” and say that both people and animals bypass it. We didn’t sense anything mystical while working in the crater though – and this cute little animal lives quite comfortably there.

Downward continuation of the Patomsky crater (left) and Popigay impact structure gravity fields (right). (Credit: Demezhko et al., 2011)

“Inside Patomsky crater: a chipmunk” by Dmitry Demezhko. This image is distributed via imaggeo.egu.eu.

By Dmitry Demezhko, Institute of Geophysics UB RAS, Yekaterinburg

References:

Alekseyev, V. R.  Cryovolcanism and the mystery of the Patom Cone, Geodynamics and Tectonophysics, 3, 289-307, 2012 (in Russian)

Demezhko D.Y., Ugryumov I.A., Bychkov S.G.: Gravimetric studies of Patom Crater. In: Patom Crater. Research in the 21st Century. Publishing House of the Irkutsk State University, Irkutsk, p. 42–50, 2011 (in Russian)

If you are pre-registered for the 2014 General Assembly (Vienna, 27 April – 2 May), you can take part in our annual photo competition! Up until 1 March, every participant pre-registered for the General Assembly can submit up three original photos and one moving image on any broad theme 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: Moulding Malaspina’s moraines

6 Jan

There are many different types of glaciers, each defined by where they’re located and how they terminate. Piedmont glaciers are those that flow out from a confining valley and spill out into the open, forming wide lobes. This one is Malaspina Glacier, which spreads out over the Seward Ice Field.

“Mt St Elias and Malaspina” by Jean-Daniel Champagnac, distributed by the EGU under a Creative Commons licence.

“Mt St Elias and Malaspina” by Jean-Daniel Champagnac, distributed by the EGU under a Creative Commons licence.

Stretching 45 kilometres over the lowlands towards the sea, and spanning some 65 kilometres across, Malaspina is the world’s largest piedmont glacier and the classic example of its kind. Here’s how it would look face on:

Malaspina Glacier is created by the junction of several powerful glaciers from the North including Agassiz Glacier (left) and Seward Glacier (right). (Credit: SRTM Team NASA/JPL/NIMA)

Malaspina Glacier is created by the junction of several powerful glaciers from the North including Agassiz Glacier (left) and Seward Glacier (right). (Credit: SRTM Team NASA/JPL/NIMA)

Ahead of the glacier are a number of folded moraines. Moraines are piles of unconsolidated sediment and rocky debris that have been eroded from the glacier valley walls and deposited by the glacier. Malaspina’s moraines have been folded by the force of ice pressing in from behind.

The striations in Champagnac’s photo are the remnants of glacier moraines. A number of tributary glaciers coalesce to form Malaspina, and as they enter the flow of this glacier, their debris is folded into the moving mass of ice. As this glacier flows, the debris flows with it, producing the striking striations on the glacier surface.

References:

National Snow and Ice Data Center (NSIDC): What types of glaciers are there?, accessed December 2013

NASA Earth Observatory, accessed December 2013

The EGU’s open access geoscience image repository has a new and improved home at http://imaggeo.egu.eu! We’ve redesigned the website to give the database a more modern, image-based layout and have implemented a fully responsive page design. This means the new website adapts to the visitor’s screen size and looks good whether you’re using a smartphone, tablet or laptop.

Photos uploaded to Imaggeo are licensed under Creative Commons, meaning they can be used by scientists, the public, and even the press, provided the original author is credited. Further, you can now choose how you would like to licence your work. Users can also connect to Imaggeo through their social media accounts too! Find out more about the relaunch on the EGU website. 

Imaggeo on Mondays: A feast of pancakes

30 Dec

The thought of pancake ice always makes me a little hungry – I just can’t help thinking about stacks of syrup-drowned pancakes, or crepes covered wish sugar and doused with lemon juice – but the science of pancake ice is quite a tempting topic too!

Pancake ice occurs in areas where ice formation is repeatedly disturbed by water movement. In the Southern Ocean, the water extremely open and the swell of the waves causes a large soupy mixture of saltwater and needle-like ice crystals (frazil) to form. This slushy mixture is known as grease ice. Cyclical movement of the slush causes crystals to be compressed and begin to form cakes. Over time, the ice crystals stick together to form thin pancakes that are roughly 30 centimetres to 3 metres in diameter, like these:

Pancake ice in Drake Passage, the Southern Ocean by Kenneth Mankoff. This photo is distributed by the EGU under a Creative Commons licence.

Pancake ice in Drake Passage, the Southern Ocean” by Kenneth Mankoff. This photo is distributed by the EGU under a Creative Commons licence.

This field of ice pancakes in the Southern Ocean is constantly moving as waves cause them to jostle and bump on the water’s surface. The bumping causes the soupy grease ice to be sloshed up onto the edges of each pancake. As the water drains away, a raised lip of ice crystals is left behind – the feature that gives pancake ice its wonderful pancake-like texture.

In the Northern Hemisphere, pancake ice may become more common as the decline in inter-annual sea ice cover frees up larger expanses of water and allows it to swell. Pancake ice isn’t exclusive to the oceans though – it can also form on rivers when temperatures are close to freezing point – enough to form ice crystals, but not so low that the whole river freezes over.

By Sara Mynott, EGU Communications Officer

References:

Linder, C. A.: Sea Ice Glossary. Woods Hole Oceanographic Institution, 2003 (accessed November 2013)

Wadhams, P.: How Does Arctic Sea Ice Form and Decay? NOAA, 2003 (accessed November 2013)

Wilkinson, J. P., DeCarolis, G. Ehlert, I et al.: Ice Tank Experiments Highlight Changes in Sea Ice Types, EOS Transactions, American Geophysical Union, 90, 81-82, 2009

The EGU’s open access geoscience image repository has a new and improved home at http://imaggeo.egu.eu! We’ve redesigned the website to give the database a more modern, image-based layout and have implemented a fully responsive page design. This means the new website adapts to the visitor’s screen size and looks good whether you’re using a smartphone, tablet or laptop.

Photos uploaded to Imaggeo are licensed under Creative Commons, meaning they can be used by scientists, the public, and even the press, provided the original author is credited. Further, you can now choose how you would like to licence your work. Users can also connect to Imaggeo through their social media accounts too! Find out more about the relaunch on the EGU website. 

Imaggeo on Mondays: Carving polar canyons

23 Dec

This week Ian Joughin, a research scientist from the Polar Science Center at the University of Washington, takes us on the polar express to put glacial processes into perspective and find out what makes a moulin…

“Water filled canyon” by Ian Joughin, distributed by the EGU under a Creative Commons licence.

“Water filled canyon” by Ian Joughin, distributed by the EGU under a Creative Commons licence.

This canyon formed when a melt lake on the surface of the Greenland Ice Sheet overflowed and created a stream that extended out toward a crevasse field. This outflow stream filled a crevasse, causing it to fracture under the pressure of the liquid, creating a hydrofracture that ran through the full thickness of the ice sheet. This fracture created a conduit to the base of the ice sheet, known as a moulin, through which the surface water drained to the bed.

Surface water entering a moulin on Athabasca Glacier (a much smaller Moulin than the one what would have drained the Greenland lake). (Credit: Wikimedia Commons user China Crisis)

Surface water entering a moulin on Athabasca Glacier. (Credit: Wikimedia Commons user China Crisis)

Over the course of several years, the turbulent overflow stream melted the ice down to create this canyon. By the time this photo was taken, snow had dammed canyon near the lake outlet, meaning it no longer actively drained the lake.

Most of the water in the photo is from melt at the sides of the canyon. The ice is flowing at approximately 100 m/yr, slowly moving the stream outlet toward higher ground so it is unlikely that the lake will overflow at this location again. And instead, we have found a new canyon forming in a lower part of the lake basin.

By Ian Joughin, University of Washington

The EGU’s open access geoscience image repository has a new and improved home at http://imaggeo.egu.eu! We’ve redesigned the website to give the database a more modern, image-based layout and have implemented a fully responsive page design. This means the new website adapts to the visitor’s screen size and looks good whether you’re using a smartphone, tablet or laptop.

Photos uploaded to Imaggeo are licensed under Creative Commons, meaning they can be used by scientists, the public, and even the press, provided the original author is credited. Further, you can now choose how you would like to licence your work. Users can also connect to Imaggeo through their social media accounts too! Find out more about the relaunch on the EGU website. 

Follow

Get every new post on this blog delivered to your Inbox.

Join other followers: