{"id":6120,"date":"2026-10-19T09:48:29","date_gmt":"2026-10-19T09:48:29","guid":{"rendered":"https:\/\/phd.hi.is\/doktorsvorn\/doktorsvorn-i-jardfraedi-jonas-gudnason\/"},"modified":"2026-10-19T09:48:29","modified_gmt":"2026-10-19T09:48:29","slug":"doktorsvorn-i-jardfraedi-jonas-gudnason","status":"publish","type":"phd_defence","link":"https:\/\/phd.hi.is\/en\/doktorsvorn\/doktorsvorn-i-jardfraedi-jonas-gudnason\/","title":{"rendered":"Doktorsv\u00f6rn \u00ed jar\u00f0fr\u00e6\u00f0i – J\u00f3nas Gu\u00f0nason"},"content":{"rendered":"
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Mi\u00f0vikudaginn 12. j\u00fal\u00ed<\/strong> ver J\u00f3nas Gu\u00f0nason doktorsritger\u00f0 s\u00edna vi\u00f0 Jar\u00f0v\u00edsindadeild H\u00e1sk\u00f3la \u00cdslands.<\/strong> Ritger\u00f0in ber heiti\u00f0:\u00a0<\/span>Sundrun kviku og gj\u00f3skufall \u00ed \u00feeytigosum: Eldgosin \u00ed Heklu \u00e1rin 1991 og 1845 (e. Magma fragmentation and tephra dispersal in explosive eruptions: The 1991 and 1845 Hekla eruptions). <\/em><\/p>\n

Andm\u00e6lendur <\/strong>eru dr. Dave McGarvie, lektor vi\u00f0 Opna H\u00e1sk\u00f3lann \u00ed Bretlandi og dr. Eliza Calder, lektor \u00ed eldfjallafr\u00e6\u00f0i vi\u00f0 H\u00e1sk\u00f3lann \u00ed Edinborg.<\/p>\n

Lei\u00f0beinandi<\/strong> er dr. \u00deorvaldur \u00de\u00f3r\u00f0arson, pr\u00f3fessor \u00ed eldfjalla- og bergfr\u00e6\u00f0i vi\u00f0 Jar\u00f0v\u00edsindadeild H\u00e1sk\u00f3la \u00cdslands. A\u00f0rir \u00ed doktorsnefnd eru dr. Bruce F. Houghton, pr\u00f3fessor \u00ed eldfjallafr\u00e6\u00f0i vi\u00f0 Jar\u00f0v\u00edsindadeild H\u00e1sk\u00f3lans \u00e1 Hawaii \u00ed M\u0101noa og Gu\u00f0r\u00fan Larsen, v\u00edsindama\u00f0ur emeritus vi\u00f0 Jar\u00f0v\u00edsindastofnun H\u00e1sk\u00f3la \u00cdslands.<\/p>\n

Magn\u00fas Tumi Gu\u00f0mundsson,<\/strong> deildarforseti og pr\u00f3fessor vi\u00f0 Jar\u00f0v\u00edsindadeild H\u00e1sk\u00f3la \u00cdslands st\u00fdrir v\u00f6rn.<\/p>\n

\u00c1grip af ranns\u00f3kn<\/strong><\/p>\n

V\u00e1 vegna eldgosa er vel \u00feekkt \u00e1 \u00cdslandi. Gosv\u00e1 vegna Heklu er einna best \u00feekkt, \u00fear sem r\u00e6ktarl\u00f6nd, \u00fathagar og vatnsb\u00f3l geta spillst vegna gj\u00f3skufalls. Me\u00f0 aukinni flugumfer\u00f0 \u00e1 N-Atlantshafssv\u00e6\u00f0inu og \u00ed Evr\u00f3pu geta jafnvel l\u00edtil til mi\u00f0lungs st\u00f3r eldgos valdi\u00f0 alvarlegum truflunum utan landsteinanna. H\u00e1 gost\u00ed\u00f0ni \u00ed Heklu, stuttur vi\u00f0v\u00f6runart\u00edmi og sprengivirkni veldur \u00fev\u00ed a\u00f0 Hekla er eitt \u00feeirra \u00edslensku eldfjalla sem hva\u00f0 best er fylgst me\u00f0. Markmi\u00f0 \u00feessarar ritger\u00f0ar er a\u00f0 b\u00e6ta vi\u00f0 \u00f6rt vaxandi \u00feekkingu \u00e1 \u00edslenskum \u00feeytigosum, me\u00f0 ranns\u00f3kn \u00e1 opnunarfasa Heklugosanna \u00e1rin 1991 og 1845 og skilgreiningu \u00e1 kennist\u00e6r\u00f0um \u00feeirra (\u00fe.e. eruption source parameters). \u00deeim eru ger\u00f0 skil \u00ed \u00ferem greinum.<\/p>\n

\u00cd Heklu gosinu \u00e1ri\u00f0 1991 reis gosm\u00f6kkurinn \u00e1 10 m\u00edn\u00fatum upp \u00ed um 11.5 km h\u00e6\u00f0 (yfir sj\u00f3), heildarr\u00famm\u00e1l gj\u00f3skunnar var 0.017 km3 (0.003 km3 \u00fe\u00e9tt berg), framlei\u00f0nin var a\u00f0 me\u00f0altali 2.6 x 106 kg s-1 og heildarmassi gj\u00f3skunnar 8.6 x 109 kg. Heildarkornast\u00e6r\u00f0 gj\u00f3skunnar er tv\u00edtoppa en f\u00ednefni er l\u00edti\u00f0. Gj\u00f3skufall var til NNA og breyting \u00ed kornast\u00e6r\u00f0ardreifingu gj\u00f3skunnar er hva\u00f0 mest fyrstu 65 km \u00fear sem st\u00e6rstu gj\u00f3sku kornin f\u00e9llu hratt \u00far gosmekkinum. Lengra fr\u00e1 Heklu var\u00f0 kornast\u00e6r\u00f0 gj\u00f3skunnar st\u00f6\u00f0ug, a\u00f0eins var\u00f0 breyting \u00e1 massa af gj\u00f3sku sem f\u00e9ll \u00e1 flatareiningu. Breytingar \u00ed kornast\u00e6r\u00f0 me\u00f0 t\u00edma og bl\u00f6\u00f0ruinnihald gj\u00f3skunnar benda til \u00feess a\u00f0 opnunarfasi Heklugossins 1991 hafi veri\u00f0 \u00f3st\u00f6\u00f0ugur og komi\u00f0 \u00ed tveim hrinum, s\u00fa s\u00ed\u00f0ari var kraftmesti \u00fe\u00e1ttur gossins \u00ed Heklu \u00e1ri\u00f0 1991.<\/p>\n

Opnunar fasi gossins \u00ed Heklu \u00e1ri\u00f0 1845 var um 1 klukkustund. Heildar r\u00famm\u00e1l gj\u00f3skunnar var 0.13 km3 (0.03 km3 \u00fe\u00e9tt berg), framlei\u00f0nin var 2.1 x 107 kg s-1, heildarmassinn 7.5 x 1010 kg og h\u00e6\u00f0 gosmakkarins um 19 km (yfir sj\u00f3). Gj\u00f3skufall var til ASA. \u00deess var\u00f0 vart \u00e1 skipum og eyjum 700\u20131100 km fr\u00e1 Heklu og barst \u00fea\u00f0 \u00feanga\u00f0 me\u00f0 hra\u00f0anum 16\u201319 m s-1. Opnunarfasinn \u00e1ri\u00f0 1845 n\u00e1\u00f0i h\u00e1marki \u00ed framlei\u00f0ni sk\u00f6mmu eftir upphaf gossins, \u00e1kvar\u00f0a\u00f0 \u00fat fr\u00e1 l\u00f3\u00f0greiningu gj\u00f3sku \u00ed n\u00e1grenni Heklu og breytingu \u00ed bl\u00f6\u00f0ruinnihaldi gj\u00f3skunnar me\u00f0 t\u00edma. Heildarkornast\u00e6r\u00f0in er tv\u00edtoppa. Kornast\u00e6r\u00f0argreiningar s\u00fdna a\u00f0 tveir ferlar voru r\u00e1\u00f0andi \u00feegar gj\u00f3ska f\u00e9ll \u00far mekkinum. Gr\u00f3fara gj\u00f3sku-fylki\u00f0 s\u00fdnir a\u00f0 st\u00e6rstu korn falla hratt \u00far gosmekkinum me\u00f0 flutningi. F\u00ednna gj\u00f3sku-fylki\u00f0 s\u00fdnir mj\u00f6g st\u00f6\u00f0uga st\u00e6r\u00f0ardreifingu \u00f3h\u00e1\u00f0 fjarl\u00e6g\u00f0 fr\u00e1 uppt\u00f6kum og er best sk\u00fdrt me\u00f0 samlo\u00f0un f\u00ednna \u00f6skukorna. Sl\u00edkt samsafn agna fellur fyrr og jafnar til jar\u00f0ar en ella.<\/p>\n

Bl\u00f6\u00f0rust\u00e6r\u00f0ar greiningar \u00e1 gj\u00f3skunni bendir til a\u00f0 \u00ed opnunarfasa beggja gosanna f\u00e6kkar bl\u00f6\u00f0rum og \u00fe\u00e6r st\u00e6kka me\u00f0 t\u00edma. \u00cd gosinu 1845 f\u00e6kkar bl\u00f6\u00f0rum og \u00fe\u00e6r st\u00e6kka til ja\u00f0ranna \u00ed gosr\u00e1sinni. \u00deetta s\u00fdnir a\u00f0 gasi\u00f0 skilur sig hra\u00f0ar fr\u00e1 kvikunni \u00feegar uppstreymishra\u00f0inn minnkar og ver\u00f0ur til \u00feess a\u00f0 gas fer a\u00f0 r\u00edsa upp \u00ed gegnum kvikuna, sem a\u00f0 lokum lei\u00f0ir til tveggja fasa fl\u00e6\u00f0is og breytingar fr\u00e1 \u00feeytigosi yfir \u00ed fl\u00e6\u00f0igos.<\/p>\n

Ni\u00f0urst\u00f6\u00f0ur ranns\u00f3knanna b\u00e6ta vi\u00f0 \u00fe\u00e1 \u00feekkingu sem n\u00fa er til sta\u00f0ar um bl\u00f6\u00f0rumyndun og sundrun kviku \u00ed \u00feeytigosum \u00ed Heklu og skilgreint magnbundi\u00f0 lykil kennist\u00e6r\u00f0ir \u00feessara gosa. Breytingar \u00ed kornast\u00e6r\u00f0 me\u00f0 flutningi fr\u00e1 eldfjallinu og greining \u00e1 heildarkornast\u00e6r\u00f0ardreifingu gj\u00f3skunnar munu n\u00fdtast vi\u00f0 ger\u00f0 l\u00edkana \u00e1 gj\u00f3skudreifingu og b\u00e6ta mat \u00e1 v\u00e1 fr\u00e1 \u00feeytigosum.<\/p>\n

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

\"J\u00f3nas<\/strong><\/p>\n

J\u00f3nas Gu\u00f0nason er f\u00e6ddur \u00ed Danm\u00f6rku \u00e1ri\u00f0 1982. J\u00f3nas er giftur El\u00edsu \u00d3lafsd\u00f3ttur og eiga \u00feau tvo syni Emil \u00d3la og Vigg\u00f3 Gu\u00f0na. J\u00f3nas h\u00f3f n\u00e1m \u00ed Jar\u00f0fr\u00e6\u00f0i vi\u00f0 H\u00e1sk\u00f3la \u00cdslands \u00e1ri\u00f0 2004 og lauk \u00fea\u00f0an BS pr\u00f3fi \u00fear sem J\u00f3nas sko\u00f0a\u00f0i brennisteins afg\u00f6sun \u00ed t\u00e6tigosum og mat ve\u00f0urfars\u00e1hrif fr\u00e1 \u00feeim. Fr\u00e1 \u00cdslandi l\u00e1 lei\u00f0in \u00ed meistaran\u00e1m vi\u00f0 Kaupmannahafnar H\u00e1sk\u00f3la \u00fear sem meistararitger\u00f0in fjalla\u00f0i um aldursgreiningar \u00e1 Argent\u00ednsku gosbergi. Fr\u00e1 Kaupmannah\u00f6fn l\u00e1 lei\u00f0in \u00ed doktorsn\u00e1m vi\u00f0 H\u00e1sk\u00f3la \u00cdslands, me\u00f0 \u00e1herslu \u00e1 \u00feeytigos \u00ed Heklu.<\/p>\n

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