Árbók Hins íslenzka fornleifafélags - 01.01.1976, Blaðsíða 33

GJÓSKULÖG OG GAMLAR RÚSTIR
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beitingu gjóskutímatals og geislakolsmælinga, því aðferðirnar bæta
hvor aðra upp.
Æskilegt væri að kanna kerfisbundið aldur eyðibýla í heilum
héruðum þar sem gjóskulög henta best til aldursákvörðunar. Hér
yrði ekki um uppgröft að ræða að hætti fornleifafræðinga, og væri
skynsamlegt að fara sér hægt um hann þar til búið væri að
kanna með áðurgreindum hætti allstór svæði, en sú könnun myndi
leiða í ljós hvar æskilegast væri að bera niður um fornleifarann-
sóknir í venjulegum skilningi. Ég hygg að það væri ekki neitt óskap-
legt verk, hvorki um tíma né kostnað, að framkvæma áðurgreinda
könnun, og ég ætla að hún myndi meðal annars varpa nokkru ljósi
á sambúð Islands og Islendinga fyrstu aldirnar.
S U M M A R Y
Tephra layers and old farm ruins.
Settlement changes in Iceland since the beginning' of the Nordic colonization
eleven centuries ago follow, especially in North and Northeast Iceland, a similar
pattern. This pattern is here illustrated with an example from Northeast Ice-
land, the Vopnafjörður and Jökuldalur valleys, and the highland area between
them (Figs. 3—5). The position of the settlement frontier towards the interior
has not been stable. When the first general census was taken in 1703 the fron-
tier had receded considerably from an advanced stage reached much earlier.
About the middle of the 19th century the frontier had again advanced towards
the old stage of maximum advance. During the 20th century and especially
since the First World War it has, on the whole, greatly retreated. The question
arises: When did the settlemc-nt frontier reach its stage of maximum advance
towards the interior?
Tephrochronology has proved an effective method for a rapid, rough, age
determination, and in some cases a rather exact one, of old farm ruins. In
Northeast Iceland the light, acicl tephra layers Hekla 1104 and Öræfajökull 1362
are very useful for this purpose (Figs. 6 and 7). A dark basalt tephra layer, „a“,
found all over Northeast Icelar.d (Fig. 12), was deposited in the 15th century,
probably by an eruption in the Kverkfjöll area in northern Vatnajökull in 1477.
Ci‘i-datings supplement the tephrochronological ones.
The writer has visited some abandoned border settlements together with
Jón Sigurgeirsson from Helluvað near Mývatn, a skilful driver with a thorough
knowledge of the interior of North Iceland. The dated farm ruins and other
remainders of human activity mentioned in the paper are the following (height
in m above sea level):
Heap of charred sheep bones at Þórisstaðir in Hrafnkelsdalur (Figs. 8
and 9) 410 m. The bones are much older than H 1104 and most likely date back
to Settlement Time.