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The new Ballyknockan Island.

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  • 29-10-2013 12:28am
    #1
    Coles
    Registered Users Posts: 1,020 ✭✭✭


    During the summer months the level of the Blessington Reservoir dropped to such a degree that areas of the old fields and bogs become visible again. The level stayed quite low for a prolonged period, and now that the level has risen to more normal levels one of the 'islands' remains visible.

    The area where the 'island' is located used to be bog land, and I can only guess that over the summer a portion of 'revealed' bog dried out and was buoyant enough to become detached from the rock or subsoil beneath when the water rose.

    The area of the 'island' looks to be about half an acre, perhaps less, and is in two bits with a rough circular shape in the middle. I have been expecting the 'island' to sink beneath the surface but it's been there a few months now.

    Maybe there is another explanation, and I would be interested in hearing any other opinions.

    This is the approximate location on the old maps.

    http://maps.osi.ie/publicviewer/#V1,700166,708062,7,9


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    #2
    slowburner
    Moderators, Science, Health & Environment Moderators Posts: 5,219 Mod ✭✭✭✭slowburner


    Obvious question: are the levels back up to normal yet?


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    #3
    Coles
    Registered Users Posts: 1,020 ✭✭✭Coles


    Yes, the levels are back to their normal range. I'll take a photo of the 'island' later and post it up. It'll be just my luck now if it has disappeared beneath the waves.


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    #4
    Coles
    Registered Users Posts: 1,020 ✭✭✭Coles


    It's still there.

    BallyknockanIsland_zpsc535d4cf.jpg

    I got a couple of sight lines of it from around the lake and this is a fairly accurate guess of it's location on the old maps...

    http://maps.osi.ie/publicviewer/#V1,699797,708008,7,9


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    #5
    slowburner
    Moderators, Science, Health & Environment Moderators Posts: 5,219 Mod ✭✭✭✭slowburner


    This is a right old puzzle.
    All I can think of is that water levels are not yet up to normal. That might be supported by the fact that tree stumps (?) are still peeking above the water surface between the island and the shore.
    Is there any chance that the apparent height of the island might be a product of vegetation?
    Levels were low since last spring and there may have been enough time for plants to gain a foothold. Probably a long shot theory because to the best of my knowledge, little soil survives on the bed of the lake and what does survive seems to be fairly well compressed into a clayey, dense matter.
    I was involved in an archaeological survey around the lakeshore before levels started to creep back up. One of the striking things about the underwater topography was that soil seems to have survived only in or around areas of habitation. This may be due to compression from years of traffic of various kinds.
    There is very little intact peat/turf surviving, so much so that previously boggy areas can almost be identified by the presence of bog iron deposits - good sized lumps of it. So you would expect that little turf survives on the island, unless its height softened the effects of underwater currents.

    By the way, is the photo looking to the NW?


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    #6
    Coles
    Registered Users Posts: 1,020 ✭✭✭Coles


    It is a bit of a puzzle alright, and I can assure you that the water levels are back to normal. The water level at the location where the 'island' is would be about 10-15ft now. It's entirely possible that the ground at this location was not revealed by the low summer levels and rather this object/'island' has been growing there since then.

    It might be completely unrelated, but I wonder if it might be an organic growth of some sort and related to the difficulties in the Ballymore Eustace plant?

    As an aside, around the lake shore there is very little organic material left after years of scouring by the lapping waves, but once you go out a bit I thought the old soil and peat was buried in a layer of silt and mud?

    And yes, the picture was taken while standing on the lion's head and looking directly northwest.


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    #7
    dogmatix
    Registered Users Posts: 1,404 ✭✭✭dogmatix


    slowburner wrote: »
    This is a right old puzzle.
    All I can think of is that water levels are not yet up to normal. That might be supported by the fact that tree stumps (?) are still peeking above the water surface between the island and the shore.

    They look more like birds resting on the wire - there is a telephone pole thingy in the lower right of the pic...


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    #8
    Rackstar
    Registered Users Posts: 1,347 ✭✭✭Rackstar


    Is this the same island in 2011?

    Pic at bottom of page http://www.poulaphuca.com


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    #9
    Coles
    Registered Users Posts: 1,020 ✭✭✭Coles


    Rackstar wrote: »
    Is this the same island in 2011?

    Pic at bottom of page http://www.poulaphuca.com
    Yes, I think so. 'Ballyknockan West' as some wags called it. The water level is getting fairly low now but no sign of it yet.


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    #10
    Rackstar
    Registered Users Posts: 1,347 ✭✭✭Rackstar


    Yeah I noticed how low the lake is this evening on my way home. Good to see a stretch in the evenings. :-D


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