Temporal variations in column height and magma discharge rate during the 79 A.D. eruption of Vesuvius

Abstract

Research Article| August 01, 1987 Temporal variations in column height and magma discharge rate during the 79 A.D. eruption of Vesuvius STEVEN CAREY; STEVEN CAREY 1Graduate School of Oceanography, University of Rhode Island, Kingston, Rhode Island 02881 Search for other works by this author on: GSW Google Scholar HARALDUR SIGURDSSON HARALDUR SIGURDSSON 1Graduate School of Oceanography, University of Rhode Island, Kingston, Rhode Island 02881 Search for other works by this author on: GSW Google Scholar GSA Bulletin (1987) 99 (2): 303–314. https://doi.org/10.1130/0016-7606(1987)99<303:TVICHA>2.0.CO;2 Article history first online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation STEVEN CAREY, HARALDUR SIGURDSSON; Temporal variations in column height and magma discharge rate during the 79 A.D. eruption of Vesuvius. GSA Bulletin 1987;; 99 (2): 303–314. doi: https://doi.org/10.1130/0016-7606(1987)99<303:TVICHA>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 SocietyGSA Bulletin Search Advanced Search Abstract The 79 A.D. plinian eruption of Vesuvius ejected ∼4 km3 (ORE) of phonolitic magma over a period of ∼19 hr. A change in magma composition during the eruption is marked by a sharp transition from white, evolved phonolitic pumice to denser, overlying gray pumice, at mid-level within the fall deposit. Deposition of the upper, gray pumice fall was interrupted six times by the emplacement of pyroclastic surges and flows. Reverse size grading is conspicuous in the fall deposit. Measurements of maximum pumice and lithic diameters have been used to construct isopleths for eight chronostratigraphic levels within the fall deposit. The temporal evolution of eruption column height and magma discharge rate have been evaluated from these isopleths, using a theoretical model of pyroclast dispersal from explosive eruptions. During ejection of the white pumice, the column height rose from 14 to 26 km, as the magma discharge rate increased to 7.7 × 107 kg/s. Shortly after onset of the gray pumice fall, the column reached its maximum altitude of 32 km, with a discharge rate of 1.5 × 108 kg/s. Subsequent generation of surges and pyroclastic flows was associated with fluctuations in column height, supporting an origin by column collapse. At the white-gray boundary in the fall deposit, pumice density increases abruptly from 0.60 g/cm3 in the white pumice to 1.10 g/cm3 at the base of the gray pumice. Higher in the gray fall, the density decreases continuously to 0.60 g/cm3. The variation in pumice density is attributed primarily to differences in volatile content of two magmas which were tapped and mixed in varying proportions during ascent and eruption. This content is PDF only. Please click on the PDF icon to access. 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.