Further to our earlier posts on Flat Holm, I found this new satellite image from Bing which shows Flat Holm at low tide -- with the roche moutonnee form even more clearly displayed. If the island had been created or influenced by coastal processes alone, we would expect there to be sea cliffs on the exposed western flank, with a lower sloping coast on the eastern side. What we see is the opposite of that, with a long rising slope to the west and a higher and steeper coast with sea cliffs to the east -- on the lee flank of an old hill summit affected by eastward-flowing ice on several occasions during the Ice Age.
4 comments:
How has it been determined that there was ice flowing in an easterly direction ON SEVERAL OCCASIONS? Also, do we deduce from this that signs of glacial activity in the vicinity of approximately Portishead/Easton - in - Gordano was part of a general easterly trend? Apologies if I am asking you to re - state previous Posts, but I'd have thought some of our newer visitors to the Blog might not know too much about this.
Yes, I'm increasingly convinced that there were several large glaciations in which ice pressed eastwards up the Bristol Channel, partly influenced by the work on Svalbard: https://www.blogger.com/blog/post/edit/1228690739485734684/2998911164645505016
Also the evidence for multiple glaciations on the eastern flank of the British Isles is now very powerful, as pointed out by Phil Gibbard and others in a series of papers. Is is inconceivable that extensive ice "pulses" in Yorkshire, Lincolnshire and east Anglia will not have been matched by similar pulses involving the growth and recession of the Irish Sea Ice Stream and the Welsh Ice Cap. The problem is that the most recent pulses, in areas of glacial erosion (such as western Britain), eliminate most of the evidence of earlier pulses. The evidence of deposits on the ground is very sparse, but my best guess at the moment is that the ice has overridden Flat Holm on at least three occasions.
Full reference:
Jonathan R. Lee, James Rose, Richard J.O. Hamblin, Brian S.P. Moorlock, James B. Riding, Emrys Phillips, René W. Barendregt and Ian Candy, The Glacial History of the British Isles during the Early and Middle Pleistocene: Implications for the long-term development of the British Ice Sheet. In J. Ehlers, P.L. Gibbard and P.D. Hughes, editors: Developments in Quaternary Science, Vol. 15, Amsterdam, The Netherlands, 2011, pp. 59-74. ISBN: 978-0-444-53447-7
The biggest mystery still relates to the Wolstonian Glaciation.......
There is a lot of confusion out there, as described in this article last year from Batchelor et al:
https://doi.org/10.1038/s41467-019-11601-2
This was all discussed in my post of last March:
https://brian-mountainman.blogspot.com/2020/03/glacial-intensity-map.html
I bought a little booklet (undated but not very old) by Isobel Geddes published by the Bradford on Avon Museum and titled "Geology, Landscape and Building Stone around Bradford - on - Avon. It has her own musings on the effect of the various Ice Ages upon Bradford and beyond e.g Malmesbury, Swindon as well as west of Bath, Portishead and also the Wye Valley etc. I'll send it to you for a perusal, Brian. Has an excellent series of coloured sections and maps.
Post a Comment