On boron content in products of explosive volcanism.

Pumice from Vesuvius, Vulcano, Lipari and Santorini, as well as finer pyroclastic products and lavas from the same areas, have been investigated with the aim of detecting any peculiarity of boron distribution which could be correlated with the stages of volcanic activity. At Vesuvius, relatively high mean B content of 20 ppm for pumices of the 'Pompei' eruption (79 A.D.) can be correlated with a long repose time after the 'Avellino' event (3500 B.C.); for the 'Pollena' eruption (472 A.D.) the shorter interval can explain the lower value of 8 ppm as well. The low values (2.9 ppm) observed at Vulcano could also correspond with the ages of recorded activity. By contrast, the development of soil horizons in the cases of Lipari and Santorini show that long gaps occurred between eruptions. -J.M.H.