Onset of a basaltic explosive eruption from Kīlauea’s summit in 2008: Chapter 19

Geophysical Monograph - 19
By: , and 
Edited by: Rebecca CareyValérie CayolMichael P. Poland, and Dominique Weis



The onset of a basaltic eruption at the summit of Kīlauea volcano in 2008 is recorded in the products generated during the first three weeks of the eruption and suggests an evolution of both the physical properties of the magma and also lava lake levels and vent wall stability. Ash componentry and the microtextures of the early erupted lapilli products reveal that the magma was largely outgassed, perhaps in the preceding weeks to months. An increase in the juvenile:lithic ratio and size of ash collected from March 23 to April 3 records an increasing level of the magma within the conduit. After April 3 until the explosive eruption of April 9, a trend of decreasing juvenile:lithic ratio suggests that vent wall collapses were more frequent, possibly because lava level increased and destabilized the overhanging wall [Orr et al. 2013]. Despite increasing lake height, the microtextural characteristics of the lapilli suggest that the outgassed end-member was still being tapped between March 26 and April 8. The April 9 rockfall triggered an explosive eruption that produced a new component in the eruption deposits not seen in the preceding weeks; microvesicular juvenile lapilli, the first evidence of an actively vesiculating magma. Two additional dense end-member pyroclast types were also erupted during the April 9 explosion, likely related to outgassed magma with longer residence times than the microvesicular magma. We link these pyroclasts to a stagnant viscous crust at the top of the magma column or to convecting, downwelling magma. Our study of ash componentry and the textures of juvenile lapilli suggests that the April 9 explosive event effectively cleared the conduit of largely outgassed magma. The degassing processes during this eruption are complex and varied: in the period of persistent degassing during March 26-April 8 small resident bubbles at shallow levels in the lava lake were coupled to the magma whereas large bubbles ascended, expanded and fragmented. During the rockfall- triggered explosion of April 9, all bubbles were coupled to the host magma on the timescale of decompression, but additional exsolution, decompression and expansion of deeper, more gas-rich resident magma likely occurred [cf. Carey et al. 2012]. Where external conditions play a significant role in eruption dynamics, e.g., by triggering eruptions, vesiculation and degassing dynamics can be expected to be complex.

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Additional publication details

Publication type Book chapter
Publication Subtype Book Chapter
Title Onset of a basaltic explosive eruption from Kīlauea’s summit in 2008: Chapter 19
Series title Geophysical Monograph
Chapter 19
ISBN 978-1-118-87204-8
DOI 10.1002/9781118872079.ch19
Volume 208
Year Published 2015
Language English
Publisher American Geophysical Union; John Wiley & Sons
Publisher location Washington, D.C.
Contributing office(s) Volcano Science Center
Description 17 p.
Larger Work Type Book
Larger Work Subtype Monograph
Larger Work Title Hawaiian volcanoes: From source to surface
First page 421
Last page 437
Conference Title AGU Chapman Conference
Conference Location Waikoloa, Hawai'i
Conference Date August 20-24, 2012
Country United States
State Hawai'i
Other Geospatial Kīlauea