Jökull - 01.01.2012, Page 12

S. Steinþórsson
Figure 5. Cross sections, taken 15 km away from Hekla, showing thickness of tephra layers from 14 eruptions,
from 1104 to 1947. – Þykkt gjóskulaga úr 14 gosum, frá 1104 til 1947, í sniðum 15 km frá Heklu.
This unraveling of the tephrochronology of one of Ice-
land’s most fateful volcanoes was to open new possi-
bilities in the volcanology and archaeology of the re-
gion.
In 1956 three companion papers appeared in Nátt-
úrufræðingurinn on sea-logged peat bogs by Reyk-
javík. Sigurður himself wrote about tephra layers in
the soil and two other geologists treated the diatoms
and pollen, respectively. The evidence showed, ac-
cording to Sigurður, that the sea level has risen "at
least some few meters" since 3000 years ago and that
this must be due to isostatic sinking of the land. And
in 1958 appeared a 100-page article of his about the
1362-eruption in Öræfajökull which had temporarily
devastated the region around the volcano. The vol-
ume of the tephra layer, which Sigurður and Hákon
Bjarnason had mapped in the 1930s and attributed to
the 1727-eruption, he estimated to be 10 cubic kilo-
meters and the eruption the largest in Iceland in his-
torical time.
When Sigurður started examining Icelandic
marsh-soils in 1934, amongst his main aims was to
study the history of wind-ablation in the country. In
1961 he published an article on that subject in which
tephra layers were used to measure the rate of soil
thickening, and hence of ablation, as function of time
10 JÖKULL No. 62, 2012