Two Plinian Pumice-Fall Deposits from Somma-Vesuvius, Italy

Research Article| March 01, 1973 Two Plinian Pumice-Fall Deposits from Somma-Vesuvius, Italy LUCIO LIRER; LUCIO LIRER 1Istituto di Mineralogia, Universita di Napoli, 80134 Napoli Search for other works by this author on: GSW Google Scholar TULLIO PESCATORE; TULLIO PESCATORE 2Istituto di Geologia, Universita di Napoli, 80138 Napoli Search for other works by this author on: GSW Google Scholar BASIL BOOTH; BASIL BOOTH 3Department of Geology, Imperial College of Science and Technology, London SW7 2BP, England Search for other works by this author on: GSW Google Scholar GEORGE P. L. WALKER GEORGE P. L. WALKER 3Department of Geology, Imperial College of Science and Technology, London SW7 2BP, England Search for other works by this author on: GSW Google Scholar Author and Article Information LUCIO LIRER 1Istituto di Mineralogia, Universita di Napoli, 80134 Napoli TULLIO PESCATORE 2Istituto di Geologia, Universita di Napoli, 80138 Napoli BASIL BOOTH 3Department of Geology, Imperial College of Science and Technology, London SW7 2BP, England GEORGE P. L. WALKER 3Department of Geology, Imperial College of Science and Technology, London SW7 2BP, England Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1973) 84 (3): 759–772. https://doi.org/10.1130/0016-7606(1973)842.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation LUCIO LIRER, TULLIO PESCATORE, BASIL BOOTH, GEORGE P. L. WALKER; Two Plinian Pumice-Fall Deposits from Somma-Vesuvius, Italy. GSA Bulletin 1973;; 84 (3): 759–772. doi: https://doi.org/10.1130/0016-7606(1973)842.0.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 Two of the major pumice-fall deposits of Somma-Vesuvius are described. One, the Pompei Pumice, resulted from the classic eruption of A.D. 79, which is taken as the type example of a Plinian eruption. The Pompei Pumice is dispersed south and southeast of the volcano and has been traced to a distance of 72 km. The other, the Avellino Pumice, is probably a thousand years older. It is dispersed to the east and northeast and has been traced to a distance of 50 km. The two deposits are remarkably similar in character, each consisting of a lower part of white pumice and an upper part of mafic gray pumice having a similar grain-size distribution. The distinction between the two deposits is based on (a) the differing proportions of felsic crystals, mafic crystals, and lithic fragments in selected sieve grades; (b) the abundance of nepheline crystals in the Avellino Pumice and their absence from the Pompei; and (c) the greater abundance of crystals in the Avellino Pumice and of lithic debris in the Pompei. The change in composition of the erupting magmas was accompanied by an increase in the vigor of each eruption, as shown by an increase in the density and size of the pumice, in the content and size of lithic fragments, and in the area of dispersal. This is correlated with an increasing depth of origin in a compositionally zoned magma chamber. Granulometric analyses of some ninety samples show that the deposits are well sorted, the sorting improving slightly with increasing distance from the source. Maps showing the median terminal fall velocity, based on the grain-size data, enable limiting values to be derived for the height of the eruptive column and the wind strength. The volume of each deposit has been estimated from the isopach maps, namely, 2.6 km3 for the Pompei Pumice and 2.1 km2 for the Avellino Pumice. 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.