Timeline reconstruction of Holocene jökulhlaups along the Jökulsá á Fjöllum channel, Iceland
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The Jökulsá á Fjöllum is Iceland’s second longest river, draining from the Vatnajökull ice cap and winding for over 200 km through the eastern highlands before emptying into the Arctic Ocean. Hydrothermal activity and subglacial eruptions beneath Vatnajökull generate enormous quantities of meltwater, which can drain catastrophically in outburst floods, known as jökulhlaups. Jökulhlaups have flowed through the Jökulsá á Fjöllum channel throughout the Holocene, but intense debate exists over their timing and magnitude. While previous studies report a peak flood discharge of 0.9 x 106 m3 s-1, Howard et al. (2012) found evidence of a peak discharge of 2.2 x 107 m3 s-1, which would make this the largest known flood on Earth. This project seeks to test Howard et al.’s (2012) hypothesis and, more broadly, to reconstruct a timeline of Holocene jökulhlaups along the Jökulsá á Fjöllum. First, it reviews current literature and research on Icelandic geology and megafloods; second, it reviews and critiques previous research methods and evidence of Holocene jökulhlaups along the channel, while also presenting new geomorphologic and geochronological evidence from field work in August 2015; and finally, it sets up a framework for future research and explores unanswered questions regarding the history of Holocene jökulhlaups along the Jökulsá á Fjöllum.