The Eruption of Vesuvius in A.D. 79: Reconstruction from Historical and Volcanological Evidence

Abstract

Reinterpretation of the volcanological and historical evidence shows that the eruption of Vesuvius in A.D. 79 consisted of two main phases. initial 18 to 20hour Plinian phase caused extensive pumice-fall south of the volcano, resulting in the slow accumulation of a pumice layer up to 2.8 m. thick over Pompeii and other regions to the south. Much of the population fled the area during this non-lethal phase. On the second day of activity the Pelkan phase occurred, when a series of nudes ardentes or hot ash-avalanches swept down the south and west flanks of the volcano, affecting the region as far as Misenum, 30 km. to the west. first of two nudes ardentes which inundated Pompeii overwhelmed and asphyxiated those who remained above ground in the city and their bodies were immediately interred in the fine-grained deposit. effects of the Pelkan activity were even more severe west and northwest of Pompeii, resulting in burial of the cities of Oplontis and Herculaneum by a series of nue A. Maiuri, Herculaneum (Rome 1977) 13. 2 S.R.J. Sparks and G.P.L. Walker, The Ground Surge Deposit: a Third Type of Pyroclastic Rock, Nature 241 (1973) 62-64; S.R.J. Sparks, S. Self and G.P.L. Walker, Geology 1 (1973) 115-18; S.R.J. Sparks, Dusts of Destruction, New Scientist (1973) 134-36. 3A. Rittmann, Vulkane und ihre Tiitigkeit (Stuttgart 1960) 48. 4 Maiuri 1958 (supra n. 1) 69. 5G.A. Macdonald, Volcanoes (Englewood Cliffs 1972) 234; F.M. Bullard, Volcanoes of the Earth (Austin 1976) 200; P. Francis, Volcanoes (New York 1976) 63. 6 A. Helprin, Mont Pelke and the Tragedy of Martinique (New York 1903) 120; E.T. Merrill, Notes on the Eruption of Vesuvius in 79 A.D., AJA 22 (1918) 304-309; E.T. Merrill, Further Note on the Eruption of Vesuvius in 79 A.D., AJA 24 (1920) 262-68. This content downloaded from 157.55.39.35 on Mon, 29 Aug 2016 05:31:16 UTC All use subject to http://about.jstor.org/terms 40 H. SIGURDSSON, S. CASHDOLLAR AND S.R.J. SPARKS [AJA 86 after the disastrous nu&e ardente eruption of Mt. Pel&e in 1902, and later revived by Sparks and Walker,7 and Lirer et al.8 VOLCANOLOGICAL EVIDENCE Products of the eruption of Vesuvius in A.D. 79 form distinct deposits on the southwestern and southern slopes of the volcano and on the Sarno plain as far south as Castellammare (ill. 1). We r. Air-fall deposits accumulate gradually during the explosive phase of a volcanic eruption and characteristically mantle the topography with a wellbedded, uniform pumice layer which shows an exponential decrease in thickness with increasing distance from the volcano. Their distribution is entirely controlled by the effect of the prevailing wind direction on the vertical eruption column, which may reach a height of tens of kilometers above the vol-