Jökulhlaup deposits at Ásbyrgi, northern Iceland: sedimentology and implications for flow type

Knudsen, Ó; Russell, AJ

Jökulhlaup deposits at Ásbyrgi, northern Iceland: sedimentology and implications for flow type

Lookup NU author(s): Professor Andrew Russell ORCiD

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Abstract

Most research into the impact of Icelandic jökulhlaups has concentrated on large relatively unconfined outwash plains in the south of Iceland. By contrast, here is only a limited picture of the magnitude, rheology, geomorphic impact and sedimentology of floods draining to the north from Vatnajökull glacier. This paper presents sedimentary evidence of jökulhlaup deposits at Ásbyrgi. The sedimentary succession consists of large-scale sandy trough cross-bedded units capped by a boulder-rich unit. These deposits are interpreted as the product of a hyperconcentrated flow. The location of the pit and the boulder surface suggests these flows emanated from the present river course of the Jökulsá á Fjöllum. The last period of jökulhlaup activity within the Jökulsá á Fjöllum was in the early-mid eighteenth century when a series of jökulhlaups inundated the lowlands north of Ásbyrgi. The fact that the historical floods within the Jökulsá á Fjöllum were hyperconcentrated suggests that these floods may have had a subglacial volcanic origin.