Holocene glacier fluctuations around Eyjafjallajökull, south Iceland : a tephrochronological study
Stratigraphic studies of layers of volcanic ash, or tephra, in buried soils have been used to date accurately Holocene glacier fluctuations in Southern Iceland. 132 stratigraphic sections up to 11m deep, and containing up to 78 tephra layers, were logged to a resolution of 0.25cm. The chronological framework was completed with 12 radiocarbon dates, and by examing the association of the tephra stratigraphy with moraines representing former ice margins, a chronology of Holocene glacier fluctuations was constructed. The forelands of five glaciers were studied: Seljavallajokull, Gigjokull and Steinholtsjokull (outlets of Eyjafjallajokull) and Solheimajokull and Klifurarjokull (outlets of Myrdalsjokull). This study has shown for the first time that large glaciers existed in mid-Holocene Iceland because after 700 BP and before 4500 BP Solheimajokull extended at least 4km beyond its present limits, and terminated at less than 100m above sea level. Other major advances of this glacier culminated before 3100 BP, and between 1400-1200 BP. In the tenth century AD Solheimajokull was also longer than during the late Little Ice Age (1700-1900 AD). In contrast, Klifurarjokull and all the outlets of Eyjafjallajokull reached a maximum Holocene extent during the late Little Ice Age. It is proposed that the anomalous behaviour of Solheimajokull may be explained as a result of catchment changes caused by the growth of the Myrdalsjokull ice cap. The great human impact on the landscape since the Norse Settlement (c870-930 AD) has also been assessed as a result of the extensive study of the aeolian sediments lying between numerous, accurately dated tephra layers. These studies show that a zone of chronic soil erosion developed in the natural upland pastures immediately after the Norse Settlement and slowly swept down hill to reach lowlying areas during the last 400 years.