Náttúrufræðingurinn - 2013, Síða 17

125
Tímarit Hins íslenska náttúrufræðifélags
eruption frequency of each volcanic sys-
tem was estimated; Grímsvötn has been
the most active with an average of ~7
eruptions/100 years (range 4–14) during
prehistoric time (before ~870 AD);
Bárdarbunga has been the second most
active with ~5 eruptions/100 years
(range 1–8); and Kverkfjöll has remained
essentially calm with 0–3 eruptions/100
years but showing periodic activity with
repose times of >1000 years. A lull in ac-
tivity from 5 ka to 2 ka, referred to as the
“Mid-Holocene low,” is observed in all
three volcanic systems. It appears to
have resulted from a decrease in magma
generation and delivery from the mantle
plume rather than from changes in ice-
load/glacier thickness. In prehistoric
time, there was a time lag of 1000–3000
years between a peak of activity at vol-
canoes directly above the mantle plume
versus volcanoes located in the non-rift-
ing part of the Eastern Volcanic Zone,
closer to the periphery of the island.
This time-space relationship suggests
that a significant future increase in vol-
canism can be expected there, following
increased levels of volcanism above the
plume.48
Þakkir
Grein þessi er byggð á doktorsverkefni unnu á árunum 2005–2009 við Há-
skóla Íslands og Université Blaise Pascal í Clermont-Ferrand í Frakklandi
og grein sem birtist í tímaritinu Bulletin of Volcanology árið 2011. Verkið
var fjármagnað af Rannís, Landsvirkjun, Háskólasjóði Eimskipafélagsins,
Rannsóknarsjóði Háskólans, Franska sendiráðinu og fransk-íslenska sam-
starfssjóðnum Jules Vernes. Jean-Luc Devidal fær sérstakar þakkir fyrir að-
stoð við efnagreiningar og hjálplegar umræður þeim tengdar, eins þökkum
við Þorvaldi Þórðarsyni yfirlestur frumhandrits, Magnúsi Tuma Guð-
mundssyni og ónafngreindum yfirlesara fyrir góðar ábendingar. Einnig
þökkum við öllum þeim sem aðstoðuðu á einn eða annan hátt við feltvinnu
eða veittu aðgang að feltgögnum og sýnum, Elsu G. Vilmundardóttur, Jóni
Eiríkssyni, Óskari Knudsen, Aðalsteini Eiríkssyni og síðast en ekki síst Guð-
mundi Óla Sigurgeirssyni og Ester Önnu Ingólfsdóttur.
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