The “Lorenzo pumice” (LP) fallout was produced by a Plinian (VEI = 4) eruption of Popocatépetl volcano ∼40 cal BCE during the Terminal Preclassic period. It is part of a pyroclastic sequence that consists in stratigraphic order of fall, pyroclastic density current, and lahar deposits, which in turn are partly covered by the 70 km2 andesitic-dacitic “Pedregal de Nealtican” lava flow field on the eastern slope of the volcano.The composition of the pumice varies insignificantly (SiO2 = 61.0 to 63.5 wt%) with phenocrysts of euhedral plagioclase > orthopyroxene > clinopyroxene ± olivine ± hornblende ± opaques.Sizes of lithics and the isopach map indicate an eruption column height of ∼28 km and a dispersal axis toward the ENE, where an area of ∼600 km2 that included pre-Hispanic dispersed villages was buried under >10 cm of pumice. The minimum volume for the LP fallout was calculated at ∼0.6 km3 corresponding to ∼0.2 km3 of dense rock equivalent (DRE).The short Plinian phase ended when the column collapsed abruptly, generating lethal pyroclastic density currents that were emplaced around the volcano. It was followed by periodic flooding by rain lahars that originated from the slopes of Popocatépetl and from neighboring Iztaccíhuatl, severely affecting ravines and large portions of the plains of Puebla in the east.After the cataclysmic phase, the El Ombligo vent alignment opened at ∼4000 m a.s.l. on Popocatépetl's NE upper slope from which the lavas that form the Nealtican lava flow field emanated, an effusive activity that lasted >30 years. Paleomagnetic data for these lavas and stratigraphic evidence indicate that the lava flows with a total volume of 4.2 km3 were emplaced shortly after the explosive Plinian phase and represent the degassed portion of the LP magma.This eruption had a considerable impact on pre-Hispanic settlements around the volcano, whose population exodus and relocation probably contributed to the rise of important cities in central Mexico, such as Teotihuacán, Cholula, and Cantona.