Duration of large-magnitude explosive eruptions deduced from graded bedding in deep-sea ash layers

Abstract

Research Article| May 01, 1979 Duration of large-magnitude explosive eruptions deduced from graded bedding in deep-sea ash layers Michael T. Ledbetter; Michael T. Ledbetter 1Department of Geology, University of Georgia, Athens, Georgia 30602 Search for other works by this author on: GSW Google Scholar R.S.J. Sparks R.S.J. Sparks 2Graduate School of Oceanography, University of Rhode Island, Kingston, Rhode Island 02881 Search for other works by this author on: GSW Google Scholar Author and Article Information Michael T. Ledbetter 1Department of Geology, University of Georgia, Athens, Georgia 30602 R.S.J. Sparks 2Graduate School of Oceanography, University of Rhode Island, Kingston, Rhode Island 02881 Publisher: Geological Society of America First Online: 02 Jun 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (1979) 7 (5): 240–244. https://doi.org/10.1130/0091-7613(1979)7<240:DOLEED>2.0.CO;2 Article history First Online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Michael T. Ledbetter, R.S.J. Sparks; Duration of large-magnitude explosive eruptions deduced from graded bedding in deep-sea ash layers. Geology 1979;; 7 (5): 240–244. doi: https://doi.org/10.1130/0091-7613(1979)7<240:DOLEED>2.0.CO;2 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 SocietyGeology Search Advanced Search Abstract Thick silicic volcanic ash layers commonly observed hundreds of kilometres from potential source areas have resulted from large-magnitude explosive eruptions that have no historical equivalents. We have developed a model that predicts the duration of these eruptions from the vertical size grading of feldspar phenocrysts near the base of deep-sea tephra layers. The size grading is a function of the release time of the particles, their settling velocity, the water depth at the site of the ash layer, and the duration of the eruption. The model has been tested on two layers of the Worzel D ash in the eastern equatorial Pacific. This ash layer is the distal counterpart of the rhyolitic Los Chocoyos ash-flow tuff and H-tephra layer associated with the formation of the Lake Atitlán caldera in Guatemala. The estimated duration of the eruption is 20 to 27 d. Calculations using published estimates of the volume of erupted material yield an average magma-discharge rate of about 240,000 m3/s. This rate is approximately equivalent to that recorded in the 1956 eruption of Bezymianny and the 1912 eruption of Katmai. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.