Last millennium dispersal of air-fall tephra and ocean-rafted pumice towards the north Icelandic shelf and the Nordic seas

Abstract

Abstract The paper focuses on dispersal of airborne tephra that may have reached the marine environment north of Iceland during the last millennium, particularly the shelf off north Iceland. Many of these tephra horizons may extend into the Nordic Seas and the Arctic. The tephrochronology of Iceland after the settlement in the late ninth century AD relates to volcanic events that have been dated with documentary records as well as ice cores. The relevant eruptions for long-distance transport of tephra have been explosive or partly explosive, and mostly deposited from volcanic plumes. However, other methods of transport into the area north of Iceland are also considered. These include rafting of pumice from offshore eruptions elsewhere around Iceland, leading to instantaneous flotation of tephra, and river-rafted pumice from inland areas of heavy tephra fall, as well as potential contributions from volcanogenic glacial bursts. Airborne tephra in 25–30 explosive and partly explosive eruptions had the potential to reach the north Icelandic shelf and beyond during the time slice considered here. Four instances of ocean-rafted pumice off the north coast are known. Tephra from 15 of these eruptions has been identified in marine cores from the north Icelandic shelf and eastern Norwegian sea.