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Tuesday, 10 July 2012

Ice-carved Pinnacles at sea-level

Top: Rock pinnacles on the coast of SE Greenland (Chris Sugden).  Middle: Una's Tits and adjacent coastline in the Lamaire Channel, Antarctic Peninsula (Liam Quinn).  Bottom: Lofoten Islands, Norway (Mike Mallinger)

I was looking at one of Chris's Greenland films when I spotted a splendid image of rock pinnacles or buttresses apparently surrounded by sea water on the coast of SE Greenland, south of Scoresbysund.  It struck me that such features are comparatively rare at sea-level but quite common high in the mountains where a ridge between adjacent glaciers is gradually being whittled away by glacial processes and frost shattering.  (cf my posts of Torres del Paine etc).

What these features suggest is very active erosion by outlet glaciers to a level well below present sea-level.  That means either that relative sea-level was very low indeed at the time these features were created, or else that the ice streams responsible were so thick and dynamic that sea-level actually didn't matter very much -- with glaciers remaining grounded and eroding actively while other thinner glaciers might have had floating snouts.

I haven't examined the precise glacial history of the three locations mentioned above -- but what we have is very magnificent coastal scenery.......

By the way, in case anybody is offended / excited by the name of those twin peaks in Antarctica,  I can assure you that it's all official.  Here is the Wikipedia entry:

Una's Tits, also known as Cape Renard Towers, are two towers of basalt, each topped by a cap of ice, guarding the northern entrance to the Lemaire Channel on the Antarctic Peninsula. With the highest summit at 747 metres (2,451 ft), they are officially named "Una's Tits" and are identified as such on navigation charts. The peaks appear on a British Antarctic Territory stamp although they are not identified as such. The individual towers are referred to as "buttresses".

Una was a woman living in Stanley, Falkland Islands who was working for what is now the British Antarctic Survey.  The tallest tower has only been summited once; this was by a German team in 1999.

In case you wondered, Una's Tits are the ones on the left of the image, each one capped by a miniature ice cap.  If you want to look at other images, just do a search on Google.....





2 comments:

Anonymous said...

It would appear, then that Una was one foxy lady (think about it, there's a French Connection)

Monsieur Dave Attenborough

BRIAN JOHN said...

Could well have been. I never met the good lady myself, but to give her name to such spectacular features she must have been a very impressive -- if not statuesque -- lady. She had left BAS / FIDS by the time I passed through Port Stanley, no doubt with a wondrous reputation and a nice government pension.....