Strombolian explosive styles and source conditions: insights from thermal (FLIR) video |
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| Authors: | Matthew R Patrick Andrew J L Harris Maurizio Ripepe Jonathan Dehn David A Rothery Sonia Calvari |
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| Institution: | 1.Hawaii Institute of Geophysics and Planetology, School of Ocean and Earth Science and Technology,University of Hawaii Manoa,Honolulu,USA;2.Department of Earth Sciences,The Open University,Milton Keynes,UK;3.Dipartimento di Scienze della Terra,Universita di Firenze,Firenze,Italy;4.Alaska Volcano Observatory, Geophysical Institute,University of Alaska Fairbanks,Fairbanks,USA;5.Istituto Nazionale di Geofisica e Vulcanologia,Catania,Italy;6.Department of Geological and Mining Engineering and Sciences,Michigan Technological University,Houghton,USA |
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| Abstract: | Forward Looking Infrared Radiometer (FLIR) cameras offer a unique view of explosive volcanism by providing an image of calibrated
temperatures. In this study, 344 eruptive events at Stromboli volcano, Italy, were imaged in 2001–2004 with a FLIR camera
operating at up to 30 Hz. The FLIR was effective at revealing both ash plumes and coarse ballistic scoria, and a wide range
of eruption styles was recorded. Eruptions at Stromboli can generally be classified into two groups: Type 1 eruptions, which
are dominated by coarse ballistic particles, and Type 2 eruptions, which consist of an optically-thick, ash-rich plume, with
(Type 2a) or without (Type 2b) large numbers of ballistic particles. Furthermore, Type 2a plumes exhibited gas thrust velocities
(>15 m s−1) while Type 2b plumes were limited to buoyant velocities (<15 m s−1) above the crater rim. A given vent would normally maintain a particular gross eruption style (Type 1 vs. 2) for days to
weeks, indicating stability of the uppermost conduit on these timescales. Velocities at the crater rim had a range of 3–101 m
s−1, with an overall mean value of 24 m s−1. Mean crater rim velocities by eruption style were: Type 1 = 34 m s−1, Type 2a = 31 m s−1, Type 2b = 7 m s−1. Eruption durations had a range of 6–41 s, with a mean of 15 s, similar among eruption styles. The ash in Type 2 eruptions
originates from either backfilled material (crater wall slumping or ejecta rollback) or rheological changes in the uppermost
magma column. Type 2a and 2b behaviors are shown to be a function of the overpressure of the bursting slug. In general, our
imaging data support a broadening of the current paradigm for strombolian behavior, incorporating an uppermost conduit that
can be more variable than is commonly considered. |
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| Keywords: | FLIR Stromboli volcano Monitoring Thermal imaging Eruption dynamics |
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