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River Blackwater Puzzle

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  • 05-06-2016 3:43am
    #1
    JupiterKid
    Moderators, Social & Fun Moderators Posts: 12,620 Mod ✭✭✭✭


    When I was a geography student in college 20 years ago, our Geomorphology lecturer pointed out to us that the course of the River Blackwater was an enduring puzzle.

    For most of its length, it runs from west to east, but then at Cappoquin in Waterford it turns abruptly south to enter the sea at Youghal. Our lecturer said that this didn't make geologic sense as the river had to cut through harder sandstone rock units in its southwards course.

    I'm intrigued by this puzzle. In the past two decades, has it been solved? Or does it remain a mystery?


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    #2
    Coles
    Registered Users Posts: 1,020 ✭✭✭Coles


    My understanding was that the ancient north/south river existed on a limestone landscape above the sandstone outcrop. As the land rebounded (or was forced upwards by some other process) the limestone eroded away and revealed the sandstone at this location. The flow of the river was sufficient to erode away the sandstone and the river maintained it's course.


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    #3
    tabbey
    Registered Users Posts: 1,943 ✭✭✭tabbey


    If it did not turn south, it would meet the Comeragh mountains, and have to turn towards the sea sooner or later.
    A river will always seek the lowest terrain, it cannot ignore the law of gravity.


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


    Frank Mitchell discusses it a bit in 'Reading the Irish Landscape'.

    This page also touches on it.

    http://www.askaboutireland.ie/reading-room/environment-geography/physical-landscape/Irelands-physical-landsca/the-formation-of-the-phys/a-mystery-of-irish-landsc/


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    #5
    Fathom
    Moderators, Category Moderators, Science, Health & Environment Moderators, Society & Culture Moderators, Regional East Moderators, Regional Midlands Moderators, Regional Midwest Moderators, Regional Abroad Moderators, Regional North Mods, Regional West Moderators, Regional South East Moderators, Regional North East Moderators, Regional North West Moderators, Regional South Moderators Posts: 9,034 CMod ✭✭✭✭Fathom


    Plate tectonics. Uplift. Erosion.


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    #6
    Rebel_Kn1ght
    Registered Users Posts: 244 ✭✭Rebel_Kn1ght


    According to Geoffrey Keating (Seathrún Céitinn), in late March 830 there was a "great convulsion of nature" in the province of Munster. This changed the flow of the River Blackwater moving its mouth from Whiting Bay and forming the harbour of Youghal.

    I've seen this on Wiki and a few other places but have never seen any proof. Plus I live in Youghal and the mouth of the river is too wide to have been created just 1200 years ago


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    #7
    joebloggs32
    Registered Users Posts: 1,596 ✭✭✭joebloggs32


    A process known as river capture would have diverted the course of the river. Its linked to a change in a river's base level due to isostatic rebouond, causing river rejuvenation.


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    #8
    Coles
    Registered Users Posts: 1,020 ✭✭✭Coles


    Rebel_Kn1ght wrote: »
    According to Geoffrey Keating (Seathrún Céitinn), in late March 830 there was a "great convulsion of nature" in the province of Munster. This changed the flow of the River Blackwater moving its mouth from Whiting Bay and forming the harbour of Youghal.

    I've seen this on Wiki and a few other places but have never seen any proof. Plus I live in Youghal and the mouth of the river is too wide to have been created just 1200 years ago
    Very interesting, but isn't that really just a change in the river's course as it enters the ocean?

    http://kinsalebeg.com/chapters/ferrypoint/ferrypoint.html


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