Náttúrufræðingurinn - 1978, Side 15

heimilisfólkinu á Snorrastöðum fyrir
einstaka gestrisni. Sérstakar þakkir
eru færðar fræðimanninum Kristjáni
Jónssyni á Snorrastöðum fyrir marg-
víslegar upplýsingar. Einnig ber að
þakka Sigmundi Einarssyni fyrir að-
stoð við öskulagaathuganirnar og
honum og Jóni Eiríkssyni fyrir yfir-
lestur handrits.
HEIMILDIR
Askelsson, Jóhannes, 1955: „Þar var bær-
inn, sem nú er borgin". Náttúrufr.
25: 122-132.
Brynjólfsson, Ari, 1957: Studies of reman-
ent magnetism in the basalts of Ice-
land. Adv. Physics, 6: 247—254.
Doell, R. ]{., 1972: Palaeomagnetic stu-
dies of Icelandic lava flows. Geophys.
J. G. astr. Soc., 26: 459—479.
Einarsson, Þorleifur, 1960: Geologie von
Hellisheiði. Sonderveröff. Geol. Inst.
Univ. Köln, 5: 55 bls.
— 1970: Þættir um jarðfræði Hnappa-
dalssýslu. Árbók F.Í.: 105—123.
— 1974: Jarðfræði Reykjavíkur og ná-
grennis. í Reykjavík í ellefu hundruð
ár. Safn til sögu Reykjavíkur: 33—52.
Jónsson, Jón, 1977: Reykjafellsgígir og
Skarðsmýrarhraun á Hellisheiði.
Náttúrufr., 47: 17-26.
Landnámabók. Gefin út af Jakobi Bene-
diktssyni á vegum H i ns íslenzka forn-
ritafélags árið 1968. Reykjavík.
Lárusson, Ólafur, 1945: Snæfellsnes I,
Landnám á Snæfellsnesi. 197 bls.
Reykjavík.
Sœmundsson, Kristján, 1966: Zwei neue
C14-Datierungen islándischer Vulkan-
ausbriiche. Eiszeitalter und Gegen-
wart, 17: 85-86.
Thoroddsen, Þorvaldur, 1911: Lýsing ís-
Iands. II. 673 bls. Kaupmannahöfn.
Þórarinsson, SigurÖur, 1951: Laxárgljúfur
and Laxárhraun, a tephrochronologi-
cal study. Geografiska Annaler, 1—2:
0-88.
— 1956: Mórinn í Seltjörn. Náttúrufr.,
26: 179-193.
S U M M A R Y
The age of two recent lava flows
in Hnappadalur, W-Iceland
by Dr. Haukur Jóhannesson,
National Etiergy Authority,
Laugavegur 116, Reykjavik, Iceland.
The Eldborg and Rauðhálsar lava flows
in Hnappadalur W-Iceland are describ-
ed. They are both basaltic in composi-
tion. The Eldborg lava flow was formed
in a single eruption but not in two as
Áskelsson (1955) suggested. The eruption
took place when sea-level was at least
2 m lower than at present. The country
covered by the lava flow was barren at
tlie time of the eruption. This suggests
an age of 5000 to 9000 years and the
higher age is more likely. Rauðhálsar
lava flow is the freshest-looking flow in
Hnappadalur and it was eruptcd from
the Rauðhálsar cinder cone. Unlike the
Eldborg eruption, the Rauðhálsar erup-
tion included an early phreatic phase.The
ash produced can be traced in the wet-
lands south of Rauðhálsar. In soil pro-
files the dark peat below the ashlayer
changes to brown above it. This cliange
in colour has been attributed to soil ero-
sion soon after the settlement of Iceland.
The Rauðhálsar eruption thus appears to
have taken place during, or shortly after,
the settlement period (874—930 A.D.).
Landnámabók (the Book of Settlement),
written in the eleventh century, refers to a
volcanic eruption in Eldborg in the ninth
century but the present study has shown
that the Eldborg lava flow is much older
and may therefore have been confused
with the Rauðhálsar eruption. A study of
the Landnámabók indicates that the erup-
tion may have taken place in 950—970
A.D.
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