Tephrochronology, Environmental Change and the Norse Settlement of Iceland

Abstract

The first human impacts on the Icelandic environment came with the Norse colonisation or Landnám of the ninth century AD. The colonisation represents a fundamental environmental change that is both rapid and profound. In this paper we assess geomorphological dimensions of the initial settlement period using a tephrochronology that includes the Landnám Tephra, erupted ca. 870 AD, two tenth century AD tephras KR 920 and E 935, and 11 other well dated tephra layers. We report a new 14C age of 1676 ±12 14C yr BP (cal AD 345 (400) 419) for the tephra SILK-YN which forms a key prehistoric marker horizon that constrains rates of environmental change in the centuries before Norse Settlement. Aeolian sediment accumulation rates show five geomorphological responses to settlement that differ in the rate and trajectory of change. These distinct anthropogenic signals are the result of spatially variable sensitivity to grazing and deforestation, and reflect the extent of local soil erosion. This critical erosion threshold is variable in space and time.