Fluidal pyroclasts reveal the intensity of peralkaline rhyolite pumice cone eruptions

Ben Clarke, Eliza Calder, Firawalin Dessalegn, Karen Fontijn, JOAQUIN ALBERTO CORTES CARRILLO, Mark Naylor, Ian Butler, William Hutchinson, Gezahen Yirgu

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Abstract

Peralkaline rhyolites are medium to low viscosity, volatile-rich magmas typically associated with rift zones and extensional settings. The dynamics of peralkaline rhyolite eruptions remain elusive with no direct observations recorded, significantly hindering the assessment of hazard and risk. Here we describe uniquely-preserved, fluidal-shaped pyroclasts found within pumice cone deposits at Aluto, a peralkaline rhyolite caldera in the Main Ethiopian Rift. We
use a combination of field-observations, geochemistry, X-ray computed microtomography (XCT) and thermal-modelling to investigate how these pyroclasts are formed. We find that they deform during flight and, depending on size, quench prior to deposition or continue to inflate then quench in-situ. These findings reveal important characteristics of the eruptions that gave rise to them: that despite the relatively low viscosity of these magmas, and similarities to basaltic scoria-cone deposits, moderate to intense, unstable, eruption columns are developed; meaning that such eruptions can generate extensive tephra-fall and pyroclastic density currents.
Original languageEnglish
JournalNature Communications
Early online date1 May 2019
DOIs
Publication statusPublished - 1 May 2019

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pumice
rhyolite
Viscosity
volcanic eruptions
Cones
cones
Deposits
X-Ray Microtomography
Geochemistry
Hazards
Current density
Hot Temperature
deposits
viscosity
X rays
calderas
geochemistry
hazards
flight
current density

Keywords

  • Natural Hazards
  • Volcanology

Cite this

Clarke, Ben ; Calder, Eliza ; Dessalegn, Firawalin ; Fontijn, Karen ; CORTES CARRILLO, JOAQUIN ALBERTO ; Naylor, Mark ; Butler, Ian ; Hutchinson, William ; Yirgu, Gezahen. / Fluidal pyroclasts reveal the intensity of peralkaline rhyolite pumice cone eruptions. In: Nature Communications. 2019.
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abstract = "Peralkaline rhyolites are medium to low viscosity, volatile-rich magmas typically associated with rift zones and extensional settings. The dynamics of peralkaline rhyolite eruptions remain elusive with no direct observations recorded, significantly hindering the assessment of hazard and risk. Here we describe uniquely-preserved, fluidal-shaped pyroclasts found within pumice cone deposits at Aluto, a peralkaline rhyolite caldera in the Main Ethiopian Rift. Weuse a combination of field-observations, geochemistry, X-ray computed microtomography (XCT) and thermal-modelling to investigate how these pyroclasts are formed. We find that they deform during flight and, depending on size, quench prior to deposition or continue to inflate then quench in-situ. These findings reveal important characteristics of the eruptions that gave rise to them: that despite the relatively low viscosity of these magmas, and similarities to basaltic scoria-cone deposits, moderate to intense, unstable, eruption columns are developed; meaning that such eruptions can generate extensive tephra-fall and pyroclastic density currents.",
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Fluidal pyroclasts reveal the intensity of peralkaline rhyolite pumice cone eruptions. / Clarke, Ben; Calder, Eliza; Dessalegn, Firawalin; Fontijn, Karen; CORTES CARRILLO, JOAQUIN ALBERTO; Naylor, Mark; Butler, Ian ; Hutchinson, William; Yirgu, Gezahen.

In: Nature Communications, 01.05.2019.

Research output: Contribution to journalArticle

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AU - Clarke, Ben

AU - Calder, Eliza

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AU - CORTES CARRILLO, JOAQUIN ALBERTO

AU - Naylor, Mark

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AU - Hutchinson, William

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