Evidence of a large explosive silicic eruption on Skye

An article recently published in Nature Communications has suggested a connection between the Sgúrr of Eigg and a distant rocky outcrop Òigh-sgeir, with a major volcanic eruption on the island of Skye and a significant climate event 55 million years ago, the Palaeocene-Eocene Thermal Maximum (PETM).

Valentine R. Troll et al compared mineralogy and isotope geochemistry of the pitchstone on Eigg and Òigh-sgeir, and the results suggest that the two outcrops represent a single, pyroclastic deposit. Prior to this study, David Brown and Brian Bell (in a paper published in 2013) had suggested a connection between the outcrops and an volcanic eruption on Skye – the new paper confirms these results and proposes a connection with the PETM.

The magnitude of the Skye volcanic eruption was estimated to 3.9- 15 km3 DRE (dense-rock equivalent) and a 5-6 on the Volcanic Explosivity Index scale, which compares with historical examples such as the 1991 Pinatubo eruption ( ~ 5 km3 DRE). The results imply that large-scale explosive silicic eruptions have likely been common during the opening of the North Atlantic. This paints a more violent picture of the rift to drift transition of the North-Atlantic region between 61 and 56 million years ago than previously assumed.

Source and run-out distances of the proposed Skye volcanic event, Troll et al. 2019

You can read more about the Sgúrr of Eigg and different ideas proposed in the past to explain its formation by some of Scotland’s well-known geologists (including Hugh Miller and Archibald Geikie) in the Geology of Eigg (2016), by John D Hudson, Angus D Miller and Ann Allwright, published by the Edinburgh Geological Society.

Valentin R. Troll, C. Henry Emeleus, Graeme R. Nicoll, Tobias Mattsson, Robert M. Ellam, Colin H. Donaldson & Chris Harris: “A large explosive silicic eruption in the British Palaeogene Igneous Province”. Scientific Reports volume 9, Article number: 494 (2019) Published in Nature

A summary of the article was included in the BBC news website

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