The Lifecycle of Caldera-Forming Volcanoes in the Main Ethiopian Rift: Insights from Aluto Volcano

Mather, T.A., Hutchison, W., Yirgu, G., Biggs, J., Cohen, B.E. , Barfod, D.N. , Lewi, E. and Pyle, D.M. (2015) The Lifecycle of Caldera-Forming Volcanoes in the Main Ethiopian Rift: Insights from Aluto Volcano. AGU Fall Meeting, San Francisco, CA, USA, 14-18 Dec 2015.

Abstract

The silicic peralkaline volcanoes of the East African Rift are some of the least studied and yet potentially most dangerous volcanoes in the world. We present the first detailed account of the eruptive history of Aluto, a restless silicic volcano located in the Main Ethiopian Rift, using newconstraints from fieldwork, remote sensing, 40Ar/39Ar geochronology and geochemistry. Prior to the growth of the Aluto volcanic complex (before 500 ka) the region was characterized by a significant period of fault development and mafic fissure eruptions. The earliest volcanism at Aluto built up a trachytic complex over 8 km in diameter. Aluto then underwent large-volume ignimbrite eruptions at ca. 300 ka developing a ~42 km2 collapse structure. After a hiatus of ~250 kyr, a phase of post-caldera volcanism began.Since ca. 60 ka, highly-evolved peralkaline rhyolite lavas, ignimbrites and pumice fall deposits have erupted from vents across the complex. The age of the youngest volcanism is not well known. Geochemical modelling is consistent with rhyolite genesis from protracted fractionation (>80 %) of typical rift basalt. Based on the field stratigraphy and the number, style and volume of recent eruptions we suggest that silicic eruptions occur at an average rate of 1 per 1000 years, and that future eruptions of Aluto will involve explosive emplacement oflocalised pumice cones and effusive obsidian coulees of volumes between 1100 106 m3. Comparisons with other caldera volcanoes in this section of the rift suggest that there may be parallels between Alutos behaviour and that of other volcanic centres, both in terms of the volcanic lifecycle, and broad timings of caldera collapse events.

• Item Type: Conference or Workshop Item
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Barfod, Dr Dan and Cohen, Dr Benjamin
• Authors: Mather, T.A., Hutchison, W., Yirgu, G., Biggs, J., Cohen, B.E., Barfod, D.N., Lewi, E., and Pyle, D.M.
• College/School: College of Science and Engineering > School of Geographical and Earth Sciences

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