The 0.57 Ma plinian eruption of the Granadilla Member, Tenerife (Canary Islands): an example of complexity in eruption dynamics and evolution

Bryan, S. E., Cas, R. A. F. and Marti, J. (2000) The 0.57 Ma plinian eruption of the Granadilla Member, Tenerife (Canary Islands): an example of complexity in eruption dynamics and evolution. Journal of Volcanology and Geothermal Research, 103 1-4: 209-238. doi:10.1016/S0377-0273(00)00225-0

Author Bryan, S. E.
Cas, R. A. F.
Marti, J.
Title The 0.57 Ma plinian eruption of the Granadilla Member, Tenerife (Canary Islands): an example of complexity in eruption dynamics and evolution
Journal name Journal of Volcanology and Geothermal Research   Check publisher's open access policy
ISSN 0377-0273
Publication date 2000-12
Sub-type Article (original research)
DOI 10.1016/S0377-0273(00)00225-0
Volume 103
Issue 1-4
Start page 209
End page 238
Total pages 30
Editor Y. Ida et al
Place of publication Amsterdam
Publisher Elsevier Science
Collection year 2001
Language eng
Subject C1
260103 Vulcanology
780104 Earth sciences
Abstract The Granadilla Member is one of the most widely dispersed and largest volume pyroclastic units at Tenerife (Canary Islands) and represents the culminating eruption to a second cycle of explosive volcanism of the Las Canadas edifice. The member, dared at 0.57 Ma, comprises a plinian fall deposit. the Granadilla pumice, which is overlain by ignimbrite up to 30 m thick. The Granadilla pumice is up to 9 m thick approximately 10 km from sourer (Pyle b(t) value is 5.35 km), and is subdivided into four Fail units. Unit 1 is up to 1.2 m thick and is further divisible into another four pumice fall subunits, based on bedding and grainsize differences. Unit 2 is a thin but distinctive ash layer (similar to2 cm thick), and its wide dispersal (>550 km(2)), constant thickness. planar laminations and ash aggregate textures collectively indicate a phreatoplinian fall origin. The lithic-rich nature and abundance of unaltered lithic fragments reflect magma interaction with aquifer-derived water at depth. Unit 3 (less than or equal to1.8 m thick), records a reversal to dry plinian eruptive activity. Unit 4, the thickest of the fall units (up to 6.3 m thick), records the maximum dispersal and intensity of the eruption (Pyle b(t) and b(c) values are 5.7 and 6.3 km, respectively), best illustrated by the presence of large pumice bombs up to 30 cm diameter (at distances up to 20 km from vent). and reverse grading of lithic and pumice clasts. The widespread (>500 km(2)), nonwelded and pumice-rich Granadilla ignimbrite (unit 5) records the collapse of the plinian eruption column. The ignimbrite has a simple sheet-like geometry. but exhibits a complex internal stratigraphy. The base of the ignimbrite locally cuts down through the underlying Granadilla pumice removing it entirely, indicating up to 9 m of erosion by the pyroclastic flows. A coarse, vent-derived lithic breccia horizon towards the top of the ignimbrite is interpreted to record the onset of caldera collapse late in the eruption. Minimum volume estimates for the Granadilla pumice and ignimbrite are 5.2 and 5 km(3), respectively. The dispersal area, deposit characteristics. and exponential thickness and clast size decay relationships with (isopach area)(1/2) are consistent with dispersal and fallout from the umbrella region of a moderately high (similar to 17 to greater than or equal to 25 km) plinian column. We propose that the eruption involved two vents, probably aligned along a NE-SW fissure within the Las Canadas caldera. (C) 2000 Elsevier Science B.V. All rights reserved.
Keyword Geosciences, Multidisciplinary
Granadilla Pumice
Eruption Dynamics
Tephra Fall Deposits
Explosive Eruptions
Pyroclastic Deposits
Phreatoplinian Ashes
Nepheline Syenite
Volcanic Plumes
Q-Index Code C1

Document type: Journal Article
Sub-type: Article (original research)
Collection: School of Earth Sciences Publications
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Created: Tue, 10 Jun 2008, 16:04:22 EST