The transition from explosive to effusive eruptive regime: The example of the 1912 Novarupta eruption, Alaska

Research Article| May 01, 2006 The transition from explosive to effusive eruptive regime: The example of the 1912 Novarupta eruption, Alaska Nancy K. Adams; Nancy K. Adams 1Department of Geology and Geophysics, University of Hawaii, 1680 East-West Road, Honolulu, Hawaii 96822, USA Search for other works by this author on: GSW Google Scholar Bruce F. Houghton; Bruce F. Houghton 1Department of Geology and Geophysics, University of Hawaii, 1680 East-West Road, Honolulu, Hawaii 96822, USA Search for other works by this author on: GSW Google Scholar Sarah A. Fagents; Sarah A. Fagents 1Department of Geology and Geophysics, University of Hawaii, 1680 East-West Road, Honolulu, Hawaii 96822, USA Search for other works by this author on: GSW Google Scholar Wes Hildreth Wes Hildreth 2Volcano Hazards Program, U.S. Geological Survey, Middlefield Road, Menlo Park, California 94025, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Nancy K. Adams 1Department of Geology and Geophysics, University of Hawaii, 1680 East-West Road, Honolulu, Hawaii 96822, USA Bruce F. Houghton 1Department of Geology and Geophysics, University of Hawaii, 1680 East-West Road, Honolulu, Hawaii 96822, USA Sarah A. Fagents 1Department of Geology and Geophysics, University of Hawaii, 1680 East-West Road, Honolulu, Hawaii 96822, USA Wes Hildreth 2Volcano Hazards Program, U.S. Geological Survey, Middlefield Road, Menlo Park, California 94025, USA Publisher: Geological Society of America Received: 30 Nov 2004 Revision Received: 28 Aug 2005 Accepted: 21 Sep 2005 First Online: 08 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (2006) 118 (5-6): 620–634. https://doi.org/10.1130/B25768.1 Article history Received: 30 Nov 2004 Revision Received: 28 Aug 2005 Accepted: 21 Sep 2005 First Online: 08 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Nancy K. Adams, Bruce F. Houghton, Sarah A. Fagents, Wes Hildreth; The transition from explosive to effusive eruptive regime: The example of the 1912 Novarupta eruption, Alaska. GSA Bulletin 2006;; 118 (5-6): 620–634. doi: https://doi.org/10.1130/B25768.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The shift from explosive to effusive silicic volcanism seen in many historical eruptions reflects a change in the style of degassing of erupted magma. This paper focuses on such a transition during the largest eruption of the twentieth century, the 1912 eruption of Novarupta. The transition is recorded in a dacite block bed, which covers an elliptical area of 4 km2 around the vent. Approximately 700 studied blocks fall into four main lithologic categories: (1) pumiceous, (2) dense, (3) flow-banded dacites, and (4) welded breccias. Textural analyses of the blocks indicate portions of the melt underwent highly variable degrees of outgassing. Vesicle populations show features characteristic of bubble coalescence and collapse. A decrease in measured vesicularity and increased evidence for bubble collapse compared with pumice from earlier Plinian episodes mark the transition from closed- to open-system degassing. Block morphology and textures strongly suggest the magma was first erupted as a relatively gas-rich lava dome/plug, but incomplete out-gassing led to explosive disruption. Heterogeneous degassing of ascending magma began in Plinian Episode III and resulted in instability during Episode IV dome growth and a (series of) Vulcanian explosion(s). Modeling of the dynamics of explosion initiation and ejecta dispersal indicates that a significant concentration in gas is required to produce the explosions responsible for the observed block field dispersal. The amount of gas available in the hot pumiceous dome material appears to have been inadequate to drive the explosion(s); therefore, external water most likely contributed to the destruction. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.