Pwysigrwydd llofnod cemegol lludw folcanig o Wlad yr Iâ: Teffra “Grákolla” o losgfynydd Torfajökull


Pwysigrwydd llofnod cemegol lludw folcanig o Wlad yr Iâ: Teffra “Grákolla” o losgfynydd Torfajökull
Rhian Meara

Mae astudiaethau teffrocronoleg yn rhanbarth Gogledd yr Iwerydd ar y cyfan yn canolbwyntio ar gynhyrchion echdoriadau mawr e.e. Askja 1875, Hekla 1104 ac Öræfajökull 1362. Serch hynny, mae echdoriadau llai o faint o Wlad yr Iâ yn dechrau dod yn fwy pwysig o ran sicrhau dyddiadau mewn meysydd eraill ac mae’n bosibl eu bod yn berthnasol dros bellterau ehangach e.e. echdoriad Eyjafjallajökull yn 2010. Mae teffra Grákolla, sy’n tarddu o losgfynydd Torfajökull yn un enghraifft. Os defnyddir data’r prif elfennau yn unig, mae’r teffra yn dangos ôl bys cemegol yr un fath a theffra Landnám, sy’n tarddu o’r un system. Ond o ddefnyddio data’r elfennau hybrin, mae’n bosibl gwahaniaethu rhwng yr haenau hyn er bod ychydig o orgyffwrdd yn parhau yn y data. Wrth ddefnyddio’r wybodaeth hon i ailystyried astudiaeth flaenorol o fudo ac anheddu yn Ynysoedd Ffaröe, nodir bod perygl camddyddio digwyddiadau os yw’r broses o adnabod teffra yn dibynnu ar ddata’r prif elfennau yn unig. Mae hyd at 600 mlynedd rhwng y ddau deffra, ac er bod hwn yn gyfnod byr iawn o ran digwyddiadau daearegol, y mae’n gyfnod hir o ran camddyddio digwyddiadau dynol.


Cyfeiriad:

 
  	Rhian Meara, 'Pwysigrwydd llofnod cemegol lludw folcanig o Wlad yr Iâ: Teffra “Grákolla” o losgfynydd Torfajökull', Gwerddon, 13, Chwefror 2013, 66-77.
   

Allweddeiriau

 
    Torfajökull, Grákolla, Domadalshraun, teffra, Landnám.
    

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