rewshearer 2006-09-18 20:16
I would be interested in learning more about the geological history of this, as I have heard the name but never seen any pictures of it.
The POV you chose works well for the rocks but not for the sky, it is overexposed - a filter such as a polarizer may have helped here - or crop it more to eliminate some of the sky? Your composition has already shaved a little off the top of the formation, so a little more is probably no big deal.
(To be honest, overexposed skies are a constant struggle for me so I don't have any easy answers.)
Thanks for sharing
Rew
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#1
09-19-2006, 06:04 AM
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To rewshearer: Giants causeway geology
Hi Rew,
Nice to see someone out there interested in geology. The structure seen at the Giant's causeway is called columnar jointing. This occurs when thick flows of basalt (a volcanic rock, basic in chemistry, meaning rich in iron and magnesium as opposed to acidic rocks which are rich in sodium and potassium)cool in adequate conditions (ie flow motion has stopped). When the cooling occurs, the rock cracks as it shrinks. It is basically the same kind of shrinking phenomenon that one can observe when the clay-rich bottom of a shallow pool of water dries out; hexagonal chip-like structures in the clay then develop. Similarily, if you look at the columnar joints from above, you will see that they form hexagons. Hope this helps. Richard 
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#2
09-19-2006, 11:21 AM
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Re: To rewshearer: Giants causeway geology
Very useful! Thanks! I now know how the causeway was caused!
Rew
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