{"id":6130,"date":"2026-10-19T09:48:30","date_gmt":"2026-10-19T09:48:30","guid":{"rendered":"https:\/\/phd.hi.is\/doktorsvorn\/doktorsvorn-i-jardfraedi-robert-alexander-askew\/"},"modified":"2026-10-19T09:48:30","modified_gmt":"2026-10-19T09:48:30","slug":"doktorsvorn-i-jardfraedi-robert-alexander-askew","status":"publish","type":"phd_defence","link":"https:\/\/phd.hi.is\/en\/doktorsvorn\/doktorsvorn-i-jardfraedi-robert-alexander-askew\/","title":{"rendered":"Doktorsv\u00f6rn \u00ed jar\u00f0fr\u00e6\u00f0i – Robert Alexander Askew"},"content":{"rendered":"
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Doktorsefni:<\/strong>\u00a0Robert Alexander Askew<\/p>\n

Heiti ritger\u00f0ar:<\/strong>\u00a0Brei\u00f0dalseldst\u00f6\u00f0varkerfi\u00f0. Hvort kom fyrst: megineldst\u00f6\u00f0in e\u00f0a sprungusveimurinn?<\/p>\n

Andm\u00e6lendur<\/strong>: <\/strong>Dr. Valentin Rudolf Troll, pr\u00f3fessor \u00ed bergfr\u00e6\u00f0i vi\u00f0 Jar\u00f0v\u00edsindadeild Uppsalah\u00e1sk\u00f3la \u00ed Sv\u00ed\u00fej\u00f3\u00f0.
Dr. Brian Bell, lektor vi\u00f0 land- og jar\u00f0v\u00edsindasvi\u00f0 H\u00e1sk\u00f3lans \u00ed Glasgow, Skotlandi.<\/p>\n

Lei\u00f0beinandi:<\/strong>\u00a0Dr. \u00deorvaldur \u00de\u00f3r\u00f0arson, pr\u00f3fessor \u00ed eldfjalla- og bergfr\u00e6\u00f0i vi\u00f0 Jar\u00f0v\u00edsindadeild H\u00e1sk\u00f3la \u00cdslands.<\/p>\n

Einnig \u00ed doktorsnefnd:<\/strong> Dr. \u00c1rmann H\u00f6skuldsson, ranns\u00f3knarpr\u00f3fessor \u00ed eldfjallafr\u00e6\u00f0i vi\u00f0 Jar\u00f0v\u00edsindastofnun H\u00e1sk\u00f3lans.<\/p>\n

Dr. Phillip Gans, pr\u00f3fessor \u00ed str\u00fakt\u00farjar\u00f0fr\u00e6\u00f0i vi\u00f0 Jar\u00f0v\u00edsindadeild University of California Santa Barbara, Bandar\u00edkjunum.<\/p>\n

Doktorsv\u00f6rn st\u00fdrir:<\/strong>\u00a0Dr. Magn\u00fas Tumi Gu\u00f0mundsson, pr\u00f3fessor og deildarforseti Jar\u00f0v\u00edsindadeildar H\u00e1sk\u00f3la \u00cdslands.<\/p>\n

\u00c1grip<\/strong><\/p>\n

Eldst\u00f6\u00f0vakerfi\u00f0 sem er kennt vi\u00f0 Brei\u00f0dal \u00e1 Austurlandi samanstendur af c.a. 600 km\u00b3 megineldst\u00f6\u00f0, me\u00f0 r\u00famm\u00e1l meti\u00f0 upp \u00e1, og 30-40 km l\u00f6ngum gangasveim sem framleiddi ofan og umliggjandi fl\u00e6\u00f0ibasalthraun. Eldst\u00f6\u00f0vakerfi\u00f0 var virkt \u00e1 t\u00edmabilinu fr\u00e1 10,1 til 7,8 millj\u00f3num \u00e1ra (Ma), megineldst\u00f6\u00f0in fr\u00e1 10,1 til 9,1 Ma. Gangasveimurinn byrja\u00f0i a\u00f0 myndast fyrir c.a. 9.9 Ma og var virkur n\u00e6stu 2,3 millj\u00f3nir \u00e1r. Megineldst\u00f6\u00f0in er a\u00f0 mestu ger\u00f0 \u00far basalthraunum fr\u00e1 gosum \u00e1 t\u00edmabilinu 10.1 Ma til c.a. 9,6 Ma sem hl\u00f3\u00f0u upp ytri hl\u00ed\u00f0ar fjallsins. \u00der\u00f3a\u00f0ri hraun \u00far basalt\u00edsku \u00edsland\u00edti og \u00edsland\u00edti myndu\u00f0ust einnig \u00e1 \u00feessum t\u00edma og \u00fe\u00e1 einkum \u00e1 t\u00edmabilinu 9,9-9,7 Ma \u00feegar 400 m \u00feykk syrpa af \u00edsland\u00edthraunum stafla\u00f0ist upp \u00ed su\u00f0austurhl\u00ed\u00f0um fjallsins. \u00deessar \u00eds\u00faru kvikur myndu\u00f0ust sennilega vi\u00f0 hlutkrist\u00f6llun \u00e1 kvikunni sem lag\u00f0i til bas\u00edsku hraunin \u00ed \u00e1rdaga eldst\u00f6\u00f0varinnar og benda til \u00feess a\u00f0 einhvers konar kvikugeymsla (kvikuh\u00f3lf?) hafi \u00fe\u00e1 \u00feegar myndast undir megineldst\u00f6\u00f0inni.<\/p>\n

R\u00fd\u00f3l\u00edt-eldvirkni h\u00f3fst \u00ed Brei\u00f0dalsmegineldst\u00f6\u00f0inni fyrir um 9,6-9,5 Ma sem leiddi af s\u00e9r myndun \u00f6skju \u00ed toppi fjallsins. Askjan, sem er a\u00f0 st\u00f3rum hluta fyllt af vikurbrex\u00edu, h\u00e9lt \u00e1fram a\u00f0 \u00fer\u00f3ast \u00ed \u00feeim eldgosum sem fylgdu \u00ed kj\u00f6lfari\u00f0. R\u00fd\u00f3l\u00edt-kvikur Brei\u00f0dalseldst\u00f6\u00f0varinnar vir\u00f0ast hafa myndast vi\u00f0 hlutbr\u00e1\u00f0nun \u00e1 vatna\u00f0ri basaltskorpu og drifu \u00e1fram sprengigosavirknina \u00ed eldst\u00f6\u00f0inni. Askjan \u00ed Brei\u00f0dalseldst\u00f6\u00f0inni var 8-10 km \u00ed \u00feverm\u00e1l og allt a\u00f0 500 m dj\u00fap og er fyllt af gosmyndunum s\u00farra sprengigosa og hraungosa \u00e1samt seint tilkomnum bas\u00edskum og \u00eds\u00farum innskotum. Gj\u00f3skumyndanirnar \u00ed \u00f6skjufyllunni ur\u00f0u \u00e1 \u00feessum t\u00edma fyrir verulegu rofi og endurflutningi, sennilega a\u00f0 mestu vegna \u00farkomu. Um t\u00edma voru l\u00edtil \u201e\u00f6skjuv\u00f6tn\u201c inni \u00ed \u00f6skjunni og seti\u00f0 \u00ed \u00f6\u00f0ru \u00feeirra hefur var\u00f0veitt steinrunnin f\u00f6r eftir vatnal\u00edfverur. Ofan \u00e1 gosmyndanir \u00f6skunnar leggst \u201eToppmyndunin\u201c (e. Summit Group), sem er syrpa af l\u00e1r\u00e9tt liggjandi stafla sem er bygg\u00f0ur upp af hraunum, gj\u00f3skuhlaupaseti, og gj\u00f3sku sem myndu\u00f0ust \u00ed eldgosum \u00ed kringum 9,3 Ma og inniheldur \u00ed minna m\u00e6li setlagamyndanir. \u00c1 svipu\u00f0um t\u00edma myndu\u00f0ust r\u00fd\u00f3l\u00edthraun \u00ed hraungosum \u00e1 ytri hl\u00ed\u00f0um eldst\u00f6\u00f0varinnar og \u00fear eru mest \u00e1berandi Su\u00f0austur-R\u00fd\u00f3l\u00edt-Hraunasyrpan (e. South East Rhyolite Group) sem kr\u00fdnir fjallagar\u00f0inn sem skilur a\u00f0 Berufj\u00f6r\u00f0 og Brei\u00f0dal og s\u00ed\u00f0an samsetta hrauni\u00f0 (e. composite lava) ne\u00f0arlega \u00ed su\u00f0urhl\u00ed\u00f0um eldst\u00f6\u00f0varinnar og rekja m\u00e1 me\u00f0 Foss\u00e1rfjalli og yfir \u00ed Foss\u00e1rdal. \u00deessi r\u00fd\u00f3l\u00edt-eldvirkni var \u00f6ll um 9.1 Ma.<\/p>\n

Gangasveimurinn byrja\u00f0i a\u00f0 myndast tv\u00f6 hundru\u00f0 \u00fe\u00fasund \u00e1rum seinna en megineldst\u00f6\u00f0in og var virkur fr\u00e1 9.8 Ma til 7,8 Ma. Berggangarnir eru a\u00f0 mestu bas\u00edskir og eflaust tengist myndun sumra \u00feeirra myndun fl\u00e6\u00f0ibasalthraunanna sem umlykja og leggjast ofan \u00e1 Brei\u00f0dalseldst\u00f6\u00f0ina. Eldst\u00f6\u00f0in gr\u00f3fst \u00ed hraun \u00e1 nokkrum hundra\u00f0 \u00fe\u00fasund \u00e1rum og virkni logna\u00f0ist \u00fat af \u00ed Brei\u00f0dal fyrir um 7,8 Ma.<\/p>\n

Kulnu\u00f0u eldst\u00f6\u00f0varkerfin \u00deingm\u00fali, Brei\u00f0dalur og \u00c1lftafj\u00f6r\u00f0ur voru \u00f6ll virk \u00e1 svipu\u00f0um t\u00edma, e\u00f0a \u00e1 t\u00edmabilinu 11 Ma til 8 Ma og me\u00f0 til hl\u00fd\u00f0andi sk\u00f6run \u00ed eldvirkninni. Kerfin sem eru kennd vi\u00f0 Rey\u00f0arfj\u00f6r\u00f0 og Streitishvarf eru eldri, e\u00f0a um 12-11 Ma. \u00d6ll kerfin eru \u00fe\u00f3lei\u00edt\u00edsk og framleiddu kvikur sem eru heldur au\u00f0ugri af utangar\u00f0sefnum en d\u00e6miger\u00f0ar \u00fathafshryggja kvikur (\u00fe.e. MORB). Sams\u00e6tugreiningar \u00e1 s\u00fdnum sem var safna\u00f0 innan \u00feessara kerfa s\u00fdna a\u00f0 Brei\u00f0dals-, \u00deingm\u00fala- og Streitishvarfskerfin eru \u00f3a\u00f0greinanleg, sem bendir til \u00feess a\u00f0 basaltkvikur \u00feessara kerfa eigi r\u00e6tur s\u00ednar a\u00f0 rekja til upptaka me\u00f0 s\u00f6mu samsetningu og \u00fea\u00f0 \u00fer\u00e1tt fyrir aldursmuninn \u00e1 s\u00ed\u00f0astnefnda og hinum tveimur fyrrnefndu kerfum. Basaltkvikur Rey\u00f0arfjar\u00f0arkerfisins, sem liggur nyrst af \u00feessum kerfum, vir\u00f0ast komnar fr\u00e1 uppt\u00f6kum sem eru heldur snau\u00f0ari \u00ed utangar\u00f0sefnum, \u00e1 me\u00f0an basaltkvikur sy\u00f0sta kerfisins, sem er kennt vi\u00f0 \u00c1lftafj\u00f6r\u00f0, er heldur au\u00f0ugari \u00ed utangar\u00f0sefnum. \u00deessar ni\u00f0urst\u00f6\u00f0ur benda til \u00feess a\u00f0 \u00fea\u00f0 s\u00e9 sta\u00f0bundinn munur \u00e1 sams\u00e6tusamsetningu upptakasv\u00e6\u00f0a kvikunnar sem komu upp \u00ed \u00feessum eldst\u00f6\u00f0varkerfum \u00e1 s\u00ednum t\u00edma, ekki \u00f3svipa\u00f0 \u00feeim mun sem er til sta\u00f0ar \u00ed dag innan virkra gosbelta \u00e1 \u00cdslandi. Einnig fylgir me\u00f0 uppf\u00e6rt jafnaldurkort af Austfjar\u00f0arstaflanum og kort sem s\u00fdna sv\u00e6\u00f0isbundnar breytingar \u00ed efnasamsetningu hraunlagastaflans.<\/p>\n

Um doktorsefni\u00f0<\/strong><\/p>\n

Robert Askew er f\u00e6ddur 1989 og uppalinn \u00ed Nor\u00f0austur-Englandi. Hann flutti til Skotlands \u00feegar kom a\u00f0 h\u00e1sk\u00f3lan\u00e1mi \u00fear sem hann hlaut meistaragr\u00e1\u00f0u \u00ed jar\u00f0v\u00edsindum fr\u00e1 Edinborgarh\u00e1sk\u00f3la \u00e1\u00f0ur en hann f\u00e6r\u00f0i sig um set til \u00cdslands til \u00feess a\u00f0 hefja sitt doktorsn\u00e1m. Robert starfar hj\u00e1 N\u00e1tt\u00farufr\u00e6\u00f0istofnun.
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