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Explosive eruptions at the summit of Mauna Loa; lithology, modeling and dating

Frank A. Trusdell, Jefferson D. G. Hungerford, John O. Stone, Keith Fifield, Kaitlin McCann, Harold Wershow, Shikma Zaarur and Melissa Dimeo Boyd
Explosive eruptions at the summit of Mauna Loa; lithology, modeling and dating (in Field volcanology; a tribute to the distinguished career of Don Swanson, Michael P. Poland, Michael O. Garcia, Victor E. Camp and Anita L. Grunder)
Special Paper - Geological Society of America (February 2019) 538: 325-349

Abstract

Near Moku'aweoweo, Mauna Loa's summit caldera, there are three fans of explosive deposits. The fans, located to the west, northwest, and east, are strongly arcuate in map view. Along Ainapo Trail, 2.8-3.5 km southeast of the caldera, there are several small kipuka that expose a fourth explosive deposit. Although these explosive deposits have been known for some time, no study bearing on the nature of the explosive activity that formed them has been done. By analyzing cosmogenic exposure age data and the physical properties of the debris fans-lithology, size distributions, and clast dispersal-we conclude that the lithic deposits are the result of five separate phreatic events. The lithic ejecta consist of fragments of ponded lavas, pahoehoe, gabbroic xenoliths, and "bread-crust" fragments. The exposure ages indicate that the explosive deposit on the west caldera rim was erupted 868+ or -57 yr B.P.; for the northwest fan, the age determination is 829+ or -51 yr B.P.; and on the east rim, ejecta deposits are younger, with ages of 150+ or -20 and 220+ or -20 yr B.P. Lavas underlying these deposits have exposure ages of 960-1020 yr B.P., consistent with the stratigraphy. Near Ainapo Trail, the explosive deposit is much older, overlain by flows dated with a pooled mean age of 1507+ or -19 yr B.P. From the cosmogenic dating, we have three reliable and unambiguous dates. At a much earlier time, a fourth explosive eruption created the Ainapo Trail deposit. We conclude there were at least five explosive episodes around the summit caldera. These deposits, along with recent work done on Kilauea's explosive activity, further discredit the notion that Hawaiian volcanoes are strictly effusive in nature. The evidence from the summit of Mauna Loa indicates that it, too, has erupted explosively in recent history.


ISSN: 0072-1077
EISSN: 2331-219X
Coden: GSAPAZ
Serial Title: Special Paper - Geological Society of America
Serial Volume: 538
Title: Explosive eruptions at the summit of Mauna Loa; lithology, modeling and dating
Title: Field volcanology; a tribute to the distinguished career of Don Swanson
Author(s): Trusdell, Frank A.Hungerford, Jefferson D. G.Stone, John O.Fifield, KeithMcCann, KaitlinWershow, HaroldZaarur, ShikmaBoyd, Melissa Dimeo
Author(s): Poland, Michael P.
Author(s): Garcia, Michael O.
Author(s): Camp, Victor E.
Author(s): Grunder, Anita L.
Affiliation: U. S. Geological Survey, United States
Affiliation: U. S. Geological Survey, Cascades Volcano Observatory, Vancouver, WA, United States
Pages: 325-349
Published: 20190207
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
ISBN: 9780813795386
References: 31
Accession Number: 2020-016571
Categories: Quaternary geology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 tables, sketch maps
N19°25'60" - N19°28'00", W155°35'60" - W155°34'00"
Secondary Affiliation: National Park Service, USA, United StatesUniversity of Washington, USA, United StatesAustralia National University, AUS, AustraliaGZA GeoEnvironmental, USA, United StatesEverett Community College, USA, United StatesHebrew University, ISR, IsraelYeh and Associates, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2020, American Geosciences Institute.
Update Code: 2020
Program Name: USGSOPNon-USGS publications with USGS authors
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